UNIVERSITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA A STUDY OF SIDEDRAFT AND TRACTOR HITCHES BY ARTHUR H. HOFFMAN BULLETIN No. 349 October, 1922 UNIVERSITY OF CALIFORNIA PRESS BERKELEY, CALIFORNIA 1922 David P. Barrows, President of the University. EXPERIMENT STATION STAFF HEADS OF DIVISIONS Thomas Forsyth Hunt, Dean. Edward J. Wickson, Horticulture (Emeritus). , Director of Resident Instruction. , C. M. Haring, Veterinary Science, Director of Agricultural Experiment Station. B. H. Crocheron, Director of Agricultural Extension. C. B. Hutchison, Plant Breeding, Director of the Branch of the College of Agriculture at Davis. H. J. Webber, Sub-tropical Horticulture, Director of Citrus Experiment Station. William A. Setchell, Botany. Myer E. Jaffa, Nutrition. Ralph E. Smith, Plant Pathology. John W. Gilmore, Agronomy. Charles F. Shaw, Soil Technology. John W. Gregg, Landscape Gardening and Floriculture. Frederic T. Bioletti, Viticulture and Fruit Products. Warren T. Clarke, Agricultural Extension. Ernest B. Babcock, Genetics. Gordon H. True, Animal Husbandry. Walter Mulford, Forestry. James T. Barrett, Plant Pathology. Fritz W. Woll, Animal Nutrition. W. P. Kelley, Agricultural Chemistry. H. J. Quayle, Entomology. Elwood Mead, Rural Institutions. H. S. Reed, Plant Physiology. L. D. Batchelor, Orchard Management. W. L. Howard, Pomology. *Frank Adams, Irrigation Investigations. C. L. Roadhouse, Dairy Industry. R. L. Adams, Farm Management. W. B. Herms, Entomology and Parasitology. John E. Dougherty, Poultry Husbandry. D. R. Hoagland, Plant Nutrition. G. H. Hart, Veterinary Science. L. J. Fletcher, Agricultural Engineering. Edwin C. Voorhies, Assistant to the Dean. DIVISION OF AGRICULTURAL ENGINEERING L. J. Fletcher J. Koeber A. H. Hoffman E. G. McKibben B. D. Moses J. D. Long R. R. Thomson W. L. Zink H. L. Belton * In cooperation with Division of Agricultural Engineering, Bureau of Public Roads, U. S. Department of Agriculture. A STUDY OF SIDEDRAFT AND TRACTOR HITCHES By AETHUR H. HOFFMAN INTRODUCTION This bulletin has been prepared mainly to enable more complete answer to numerous requests made by farmers for information on various phases of tractor hitching. Fig. l Sidedraft is the sidewise pull on the rear end of a tractor when it draws a machine that does not trail straight behind. It is impossible to utilize animal or mechanical power in agricul- tural field work unless it be applied to an implement. In applying power certain mechanical principles govern. These have long been known and applied by engineers. In the use of agricultural machinery, however, their correct application has often been lacking. * For valuable assistance received in the preparation of this work, grateful acknowledgment is hereby extended to L. J. Fletcher and others. 114 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Sidedraft. — Draft means pull or force. Sidedraft means sidewise force present in a tractor when it is drawing some load which does not trail straight back from the center of pull of the tractor, but pulls off to one side, as does the chain in the frontispiece (Fig. 1). (Sidedraft may also be present in the implement, as later explained. ) This means that the rear end of the tractor is pulled bodily to the side against the hubs of the drive wheels (against sprockets in track type). The drivers in turn press with a sidewise force against the soil under them. The soil resists being pushed over and, if firm enough, enables the tractor to go straight forward. Sometimes the side-force is so great that the soil is pushed over, allowing the tractor to skid to one side, one driver in some cases dropping into the furrow. Effects of sidedraft. — Sidedraft causes increased friction, especially on the tractor wheel bearings. This means rapid wear, more repairs, and shorter life for the tractor. It makes the tractor less able to pull its full load because a larger part of the power developed in the engine is needed just to move the tractor itself. This means more fuel to do the same work and less work done per hour. Sidedraft makes the tractor harder to steer. In some cases it is found absolutely im- possible to turn the tractor, except in the direction of the sidedraft, without first removing the load (lifting out plows, for example). The result is crooked furrows and, in general, poor, uneven work. Side- draft effects are practically the same for wheel type and track type tractors. Sidedraft illustrated. — Sidedraft is present in a tractor whenever the direction of the pull on the implement is not parallel to the direc- tion in which the implement is moving (considering only the horizontal plane). To illustrate, take the case of a team hitched by a ten-foot chain to the side of a box car to move it along a switchyard track. The horses are at a great disadvantage and must sidestep in order to keep pulling. The sidewise pull crowds the wheel flanges against the rail on the side next to the team, greatly increasing friction. If the team could be hitched to the car drawbar head and could walk between the rails they could move the car much more easily and comfortably. Similarly, when a small tractor running with both drivers on the unplowed land is pulling a two or three bottom plow, the center of resistance in the plow moves in a line considerably offset from the line in which the drawbar center moves. The farther from the furrow wall the tractor runs, the greater will be the amount of offset. Hence, if an inexperienced plowman in order to make his plow cut full width, drives his tractor or team farther over on the land instead of adjust- ing the hitch bars on his plow, he is increasing sidedraft unnecessarily. Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 115 Not only is the tractor affected, but the side strains and wear on the plow are greatly increased as a result of such mis- adjustment. The plow will also pull as much as 20 per cent harder in some cases and the work done will not be so good. When sidedraft is unnecessary. — There is no excuse for sidedraft when the load is such that it can just as well trail straight back from the center of the drawbar ; for example, in most scraping, leveling, disking, dragging, packing, seeding, cultivating, hauling, etc. There Fig. 2 More sidedraft than necessary. When the tractor is run farther over on the land to make 'the plow take full cut, sidedraft is unneces- sarily increased. need be no sidedraft in any of these cases if the hitch is to the drawbar center. Offsetting the hitch on the tractor drawbar will make one driver pull more of the load than is carried by the other, but will not cause sidedraft in the implement pulled, provided the line of pull is straight forward ; nor on the tractor, unless the load is so great that the front wheels are skidded to one side by the un- equal loading effects, as later explained. Fig. 3 No sidedraft where the tool is hitched to drawbar center and trails straight back. Examples: scrapers and levelers, narrows, culti- vators, rollers. Unavoidable sidedraft. — Whenever the path of the tractor is lim- ited, for example, by the edge of furrow wall or of standing grain or grass, or by rows of trees or vines, sidedraft is practically unavoidable in many cases, though, as will be shown later, it may be reduced so as to do little harm. Binders and mowers do not usually produce much 116 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION injurious sidedraft because the force required to pull them is relatively small. When the center lines of tractor and load are offset and the forces needed are very large, as in plowing, sidedraft needs to be looked after very carefully. At least 90 per cent of sidedraft troubles occur in plowing. Small tractors able to pull only two or three plow bottoms have more difficulty than larger outfits. If the tractor has power enough to plow out its own width or more at the required depth, the hitch can be made central, the pull straight forward, and sidedraft thus be avoided. How to detect sidedraft. — A rope, chain, hook, loose clevis, or any other object capable of trans- mitting a pull, will, if free to swivel at both ends, set itself in the direc- tion of the force it is transmitting. Hence, if there is somewhere be- tween the tractor drawbar and the plow a link or clevis free to turn at both ends, its position when the force is applied will show the direc- tion of the force. Whenever such a free link is not parallel to the direc- tion of motion but makes an angle r§^ \\ %^S^$( fJ %P with it (in the horizontal plane), there is sidedraft. See clevises in Fig. 4 Test for sidedraft. If a free link in the hitch (the chain of Fig. 1 ; the clevises, Fig. 4) makes an angle with the direction of motion, there is sidedraft. figure 4 and chain in figure 1. Sometimes there is in the hitch no link free at both ends, as figure 5. A link or two of chain or a clevis may be inserted temporarily and by its direction the presence or absence of sidedraft be shown. This test applied to patented hitches said to prevent sidedraft even when center lines of tractor and of plow are offset and the hitch is to drawbar center, will prove the truth or falsity of such claims. How to prevent or reduce sidedraft. — A study of the underlying principles shows clearly how we may reduce or even entirely prevent Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 117 sidedraft. Assuming a rear drive four-wheel tractor and the hitch to drawbar center unless otherwise specified : 1. Reduce the angle of offset to nothing, and there iv'ill be no side- draft. 2. Make the angle of offset very small, and the sidedraft will be c o rrespon ding ly s mall. 3. Reduce the total draft required, and the sidedraft will be reduced in the same proportion. The angle of offset may be reduced in three ways: a) By running one driver in the furrow; b ) By running very close to the furrow ; c) By lengthening the hitch. Fig. 5 No free link. Sometimes, as here, there is in the hitch no link free at both ends. A link or two of chain or a clevis may be inserted to make the test for sidedraft. If we run one driver in the furrow, as in figure 6, and adjust the plow hitch-bars properly, the pull on the plow may be straight forward or even slightly toward the plowed land, which is some advantage, as later explained. Several difficulties are encountered. Unless especially designed for such use the tractor will be badly tilted and throw its weight against the wheel bearings, causing excessive friction and wear, possibly even worse than the effects of sidedraft which we are trying to avoid. This tilting will affect the oiling system in some tractors, and cause bearings to be " burned out. ' ' Also the tilted position makes driving a rather uncomfortable job for the operator. At least two tractors are designed for such running: one, the Moline, levels up by raising the drive wheel that runs on the land; the other, the Bean (no longer manufactured), which had one central track- type driver and two supporting wheels, leveled up by lowering one supporting wheel 118 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION into the furrow. Another objection to running a wheel in the furrow is that under certain conditions of soil and kind of crop the resultant packing of the subsoil might injure the crop. We may reduce sidedraft by running the tractor as close to the furrow mall as the firmness of the soil will permit and then adjusting the plow hitch-bars so that the plow will just take full width. We may lengthen the hitch. With twenty feet of chain be- tween plow and tractor the angle of offset would be made very small, even if the actual offset in inches were fairly large. Such an arrangement would not be practical for several reasons, chief among them being the very wide headland that would be needed for turning. However, lengthening a hitch by one, two, three, or even four feet would in many cases be practicable and would greatly reduce the injur- ious effects of sidedraft. It is Tig. 6 Running one driver in the furrow removes left sidedraft from the plow and may even, as here, cause pull to be slightly toward the plowed land. This makes less draft by reducing friction between landside and furrow wall. Disadvantages are packing of subsoil and troubles due to tilting of tractor. often said that a long hitch makes a machine pull harder. Careful tests show that, other conditions being the same, this is not the case. A long series of tests at the University Farm, Davis, indicates that when the pull is level (that is to say, when the hitch point on the object pulled is at the same height above ground as the point of attachment on the drawbar or on the hame), the difference between the average of pulls with close hitch and the average of pulls with fifty feet of cable between is less than one per cent. When, however, the pull is not level, the angle that the hitch makes with the horizontal is changed when the length of hitch is changed. Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 119 This affects the draft due to the fact that the lifting effect on the front end of the object is greater for a large angle of trace (hitch short and low on the object) than it is where the pull is level (angle of trace equal to zero). If the hitch point on the object is higher than the point of attach- ment on the hame, there will be a downward force on the front of the object, tending to press it into the soil and so to increase draft. Fig. 7 Sidedraft reduced by running tractor as close as possible to furrow wall, the plow hitch-bars being ad- justed to take just full cut. Fig. 8 Sidedraft further reduced by lengthening the hitch by three feet of chain and readjusting plow hitch-bars to take full cut. A chain hitch does not permit of backing plow to clear out accumulated trash. Reducing sidedraft by in- creasing effective length of hitch. —The effective length of hitch between tractor and implement may be increased and yet the implement be kept as close to the tractor as before. This is done by attaching a chain or swinging drawbar underneath the tractor ahead of the regular drawbar. In this way the angle of offset, and hence the sidedraft, is reduced. 120 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION This arrangement also helps materially in turning with such loads as disks and cultivators. (See figs. 9 and 10). In making such an attachment care should be taken that the parts of the tractor to which attachment is made are strong enough to bear the force that will come upon them when the tractor is pulling. Fig. 9 Sidedraft reduced by lengthening hitch by use of an extra draw- bar swinging between horizontal guides attached (in effect) well forward under tractor. If pinned rigidly this arrangement increases sidedraft effects because it extends a rigid drawbar farther behind the rear axle. Fig. 10 Details of extra swinging drawbar. Frame bolted to regular drawbar at rear and carried in front by two rods attached at either side to tractor crank case. Reducing the total draft required for the plow will reduce side- draft in the same proportion. We may do this by having the shares sharp and the friction surfaces of share and moldboard scouring well, the bearings in good condition and well lubricated, and all parts of the plow in good adjustment. Bulletin 349] A study of sidedraft and tractor hitches 121 Dividing the sidedraft between tractor and plow. — By offsetting the point of hitch on the tractor drawbar we may take off of the plow much, if not all, of the sidedraft due to the pull of the tractor. This, however, causes the load to be heavier on the driver nearer the point of hitch. The wheel carrying the larger load will slip more easily than the other. Thus we see, in the extreme case, the more lightly loaded driver tending to run in a circle around the more heavily loaded one, shoving over the front of the tractor toward the furrow. This means a side force on the front wheels. Whenever the steering wheels must be held turned toward the land (fig. 11) to make the tractor go straight forward there will be strong forces pressing the axle collars against the front wheel hubs. More power is therefore needed just to move the tractor and less left to do the plowing. If circumstances compel us to have the center lines of tractor and plow offset, we may divide the bad effects between tractor and plow by hitching slightly (two to six inches) off Fig. 11 Offsetting the hitch makes steer- ing harder. When steering wheels must be held at a considerable angle to make the tractor go straight for- ward, wear will be rapid and effici- ency low. Sometimes, as here, the whole tractor runs askew, due to poor hitch arrangement. rJIfcv 'ti&Bt'*- center on the tractor drawbar and adjusting the hitch bars of the plow so that the pull of the tractor will make a small angle with the direc- tion of motion, as shown in figures 1 and 7. As explained on pages 143-144, "dividing the sidedraft" may balance the side forces on the front axles in the case of certain tractors, thus making steering easier. How a moldboard plow works. — A moldboard plow is a sort of double wedge which in being pulled forward slides between the furrow slice and the furrow wall forcing the slice over, and at the same time slides under the furrow slice forcing it up. Everyone is familiar with the fact that we cannot successfully move or lift a heavy object unless we can stand on something solid, some- thing able to resist the tendency of our feet to move in the opposite direction. Likewise we find it much easier to push over a heavy box if we have a solid wall against which to brace ourselves. The Avail gives a reaction force which enables us to push on the box and still maintain our position. In the same way, when the plow wedge is 122 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION pushed in between furrow slice and furrow wall, the furrow wall must press against the land-side of the plow with a force equal to that needed to separate the slice and to push it over bodily, say fourteen inches. If the land-side hits a soft spot unable to give the required force, the partly loosened slice will push the plow over bodily into the soft spot and the furrow will not be straight. It is common experience that it is very hard to make a plow, especially a single bottom one, turn a straight furrow in making the last round to finish a "land." The reason is that there is no solid soil left to furnish the necessary sidewise force to enable the plow to push over the furrow slice, so the slice itself pushes the plow over. It is like a man in a light row boat trying to push aside a heavy floating log ; the log moves scarcely at all ; instead the man and his boat move back. Similarly when the plow wedge slides under the slice, the force needed to separate the slice from the furrow bottom and lift it cannot operate unless the plow has a firm footing on which to stand. That is to say, the furrow bottom must resist the tendency of the plow to sink down into it. In the old-fashioned walking plow these forces supplied by furrow wall and furrow bottom cause a large amount of friction between land- side and sole and the earth. In modern plows, one or more wheels are used to supply these necessary sidewise and upward forces and to sub- stitute the lesser friction of well-lubricated wheel bearings for the friction between iron or steel and earth. Side force always present in plowing. — It will be seen from the foregoing that sidewise forces and upward forces are always and necessarily present in the use of a moldboard plow. Plow designers provide for these side forces by making the rjms of the carrying wheel of "nonskid" shape, and often in the case of the rear wheel (some- times the front furrow wheel also) by setting it to run at an angle in the corner between wall and bottom of the furrow, as in figure 1. This placing enables the wheels to supply both side force and up force for moving the furrow slice, without much endwise force being present in the bearings. It is possible, though perhaps not practical, to take these side forces entirely off the front wheels of the plow and supply them from the pull of the tractor by driving the tractor with one wheel in the furrow, as in figure 6, or even on the plowed ground, and adjusting the hitch- bars of the plow so as to make it run in the desired direction. The pull would then be obliquely toward the plowed, instead of, as is usual, toward the unplowed land. The plow would then run lighter, but not enough so to offset the great disadvantage of running one driver on the BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 123 plowed ground. When the tractor pulls obliquely toward the unplowed land, the front wheels of the plow not only must supply their part of the force for pushing the furrow slice sidewise, but must in addition bear the sidewise part of the tractor's pull. This accounts for the before mentioned very rapid wear in the wheel bearings of plows that occurs when the pull of the tractor is at a considerable angle with the direction of motion. How a disk plow works. — In general, the same principles of force apply to both disk and moldboard type plows. The disk plow, however, lifts the furrow slice somewhat less than the moldboard. Hence the upward forces and downward reactions will usually be slight in a disk plow, while the sidewise forces and reactions will be similar to those of a moldboard plow cutting the same average width and depth. Plow adjustments. — Every man experienced in the use of the old- fashioned walking plow knows that if he hitches at the top of the vertical adjustment on the front end of the plow beam, the plow tends to run down and plow deep. Likewise, by lifting up on the plow handles the plowman can make the plow run still deeper. By a low hitch and by putting weight on the plow handles one can make the implement plow shallow or even run entirely out of the ground. Similarly, by hitching toward the right end of the horizontal adjustment at the front end of the beam, the plow is made to 'Hake more land" (assuming a right-hand plow) ; that is to say, to travel in a line offset to the left; and by hitching to the left end the offset is increased to the right, thereby making it take less land. Each plow in a gang has the same tendency to follow its hitch that it would have if it were unbolted from its place in the gang and made a walking plow without any wheels. The wheels of a gang plow, together with the weight of the plow itself, compel a given depth and offset almost regardless of the height and angular direction of the pull on the gang. It is therefore a relatively easy matter to make the mistake of hitching in such a way that each plow is forced by the wheels to run where it does not want to go. It resists as much as it can, with consequent harder pulling and more rapid wear on the bearings. In extreme cases the plows will tear or root along instead of cutting cleanly as they should. In some cases of extremely bad adjustment the draft may be lighter than when adjustment is correct, because the work done may be much less. Thus in figure 12 where the hitch is too high on the plow so that it ' ' runs on its nose, ' ' the draft was found to be 353 pounds less than the 2071 pounds required for the same plow properly adjusted. The two sets of eight 50-foot test runs each for good and bad adjustment 124 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION were taken in the same field, in adjacent rounds of the gang plow, and the pairs of individual runs in both sets as nearly as possible side by side. Careful reading and following of directions for making adjust- ments, to be found in the manual for the particular plow, will pay good dividends in saving of time and expense. Nearly all the implement manufacturers publish such manuals. The buyer should insist on getting a copy with the implement purchased. Adjusting tractor moldboard plows by trial. — See that the plows of the gang are properly put together; that all beams are parallel; that all bolts are tight, the shares sharp, and the coulters sharp and properly set. Fio-. 12 Extremely bad adjustment sometimes makes draft lighter. This may be due to the fact that the plow may be taking a smaller cut or be pulverizing less effectively. Here, too high a hitch runs the plow on its nose, making the rear bottom cut less than full depth. The draft here is 1718 lbs. as against 2071 lbs. with proper adjustment. A coulter should be set far enough to landward of the shin to give proper clearance between the plow and the upper part of the furrow wall. This distance varies between one-quarter and three-quarters of an inch, depending on the construction of the plow and on plowing conditions. The distance forward of the shin that the coulter should be set depends in part on the nature of the soil. It should be just far enough forward that the furrow slice will be cut cleanly from the furrow wall, with no tendency for it to break or tear away ahead of the Coulter. This holds when the soil is moist enough to plow well. In very hard and dry soil, a coulter set too far forward will tend to act as a depth gauge wheel and to prevent the plow from going down to the proper depth. A rolling coulter should never be set close enough to rub on the shin of the plow. If there is much trash on the ground a BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 125 coulter set too deep will push it forward instead of cutting it cleanly. The best depth depends on the character of soil and trash, and can be determined only by trial. See that the friction surfaces of the share, moldboard, and land-side are smooth enough to scour well, and that there is sufficient " lead-to land," figure 13, and vertical suction, figure 14, on the point of each Fig. 13 "Lead to land" or horizontal suction. The point of the share should curve out slightly toward the unplowed land to lessen fric- tion. The amount varies from about % inch to % inch in new shares. It is measured by the width of the gap at x in this figure. Fig. 14 1 'Suck' ' or vertical suction. This keeps the plow in the ground. It should be % inch to % inch in a new share measured at the widest gap (as indicated) when the plow bottom is laid on a level surface. share of the gang. Figures 15 and 16 show a steel share badly worn and ready to be reforged. It is good economy to keep an extra unworn share to be used by the blacksmith as a model to enable him to restore very nearly the original shape. Without such a guide the smith will be compelled to follow his own ideas, which may or may not give good results when the share gets into the soil. 126 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Hitch to center of tractor drawbar or to a swinging drawbar free between horizontal guides. By means of levers lower the plows into the soil until they run level and at the depth desired, with the hitch on the beam about halfway up. If they will not run deep enough that way or if there is not weight enough on the power-lift traction wheel Fi 15 Ready to reforge to restore shape. Bottom view of badly worn share. The "lead-to-land" is all gone and in its stead there is a reverse lead. Fig. 16 Ready to reforge. Landside view of the share of figure 15. The vertical suction is all gone and instead there is an upward trend at the bottom of the point. A plow with such a share is very hard to keep in the soil. to prevent its slipping when used, raise the hitch little by little on the beam. Lowering the hitch at the tractor will have much the same effect. If the tractor drawbar is higher than the hitch point on the plow frame, as it should be, lengthening the hitch will also tend to make the shares run deeper. For very hard soil the final resort is to load at the plow beams with sacks of earth or other weight to keep the shares in at the required depth. See that the plow is adjusted to run level, so that it cuts the same depth right and left and front and rear. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 127 Driving the tractor as close to the furrow as the firmness of the soil will permit, observe whether the plow takes just enough, too much, or too little land. If too little, assuming a right-hand plow, shorten the right hitch-bar or lengthen the left one ; if too much, do the opposite until the plow just cuts out. Some hitch -bars are not adjustable as to length, but may be adjusted by moving sidewise and fastening in different holes either in the bar or on the front end of the plow-frame proper. Next, after driving the tractor a short distance, apply the "test for sidedraft" (page 116). If there is a considerable angle be- tween the clevis or chain and the direction of motion, lengthen the hitch, if feasible ; otherwise try "dividing the sidedraft between tractor and plow" (page 143) by moving the point of hitch on the tractor drawbar over one hole toward the furrow. Be sure next to readjust the plow hitch-bars to take more land, if necessary, in order to enable the tractor to run close to the furrow wall. The best results are obtained by hitching as near as may be to drawbar center, running tractor as close as possible to furrow wall, hitching as low as we can on plow frame, using as long a hitch as is practical. Adjusting disk plows. — The instruction manual for the particular make should be followed closely. In very hard ground each disk of a disk plow tends to roll out of the soil and run along like a wheel on top of the ground. This is .especially noticeable when the disk support arms are set so that the plane of the disk edge is too nearly parallel to the direction of motion of the plow. Setting each support arm or bracket so that the disk is somewhat more nearly crosswise of the direction of motion, will make it dig in like a hoe. Up- and downdraft on plow and tractor. — How may we transfer from the small and easily overloaded front-wheel bearings of the plow to the large and strong driver bearings of the tractor some of the force needed to hold up the front end of the plow wedge when it is lifting the furrow slice ? As an example of "how not to do it." let us take an old-fashioned horse-drawn walking plow, and suppose an inexperienced plowman has hitched as high as possible on the plow beam end, yet he wants to plow shallow. If he were a heavy man and strong-armed, he might, possibly, by constantly putting his weight on the plow handles, lift the front end of the beam enough to plow the depth he wanted; but he would be a marvel of strength and endurance if he lasted a half- day on the job. Suppose that we put a depth-gauge wheel on the same plow and hitch to a tractor by a short chain attached as high as possible on the plow and as low as possible on the tractor and set the depth 128 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION wheel to plow very shallow, as figure 17. In this arrangement not only does the pull of the tractor fail to furnish any of the upward force needed by the plow wedge, but it actually pulls downward on the plow beam. The tractor is in reality resting some of its weight on the depth wheel of the plow. The depth wheel does the best it can to prevent the plow running down very deep, but is not equal to the task and is pressed deeply into the soil. Its bearings wear out quickly under the over- load and the pull required for the plow may be increased appreciably. At the same time we have by taking some weight off the tractor drivers increased their tendency to slip. If we hitch as shown by the dotted line in the same figure, we take the down force off the depth wheel and put it on the drive wheels of the tractor where it will add little to the Fig. 17 * Tractor "riding" on the plow. Tractor pu'ls downward on plow, pressing depth gauge wheel into soil, thereby increasing draft. The hitch shown by dotted line would be much better. wear of the large bearings and where it may be needed to increase traction by preventing slipping. Of course, a single plow would pro- duce no noticeable effect on a large tractor ; but if the hitch were made in a similar manner to a gang plow having about as many bottoms as the tractor could pull, taking some of the weight off the drivers would reduce the pulling capacity. Very often one sees, as in figure 1, plow beams loaded down with heavy weights to keep the plow at the required depth in hard soil. Usually the failure to plow deeply enough is due to share points worn so badly that all the downward "suction" is gone (figures 14 and 16). A better remedy than loading down is to have the "suction" restored by reforging, if a steel share, or by replacing with a new one if a chilled cast share is used. Some steel shares can be reshaped by hammering cold. Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 129 Tongue trucks (fore carriages) are generally designed to relieve horses' necks of excessive weight and jerking. When the machine is to be drawn by a tractor it is usually better to remove the truck entirely and connect by stub pole and clevis. When used as shown, figure 18, the downward pull presses the truck wheels into the soil, increasing draft and causing rapid wear. When the truck is removed, as in lf^^% Fig. 18 Tongue trucks are designed to relieve horses' necks of weight and jerking. If used with low drawbar tractor the pull is down- ward on the truck, causing heavy draft and rapid wear. Fig. 19 Tongue truck removed. The extra weight on the rear axles of the tractor will do more good than harm. The pull will be lighter. figure 19, the extra weight rests on the rear wheels of the tractor where it does little or no harm and may do good by increasing traction. If a long hitch is necessary (for example, when several grain drills are drawn by the same tractor), the truck may be needed. The longer hitch lessens the downward angle and hence lessens also the downward pull on the truck. In some machines designed for tractor operation, 130 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION for instance, the leveler shown in figure 20, a tongue truck is used to give steadiness of pull without which it is not possible to get satisfac- tory results, especially with a track-type tractor on uneven ground. The truck shown is too high for the drawbar of the tractor with which it is here used. The truck wheels are pulled clown into the soil increas- ing the draft unnecessarily. Length of hitch affects up- and downdraft. — If the tractor draw- bar is higher than the level of hitch on the plow frame proper, lengthening the hitch will decrease the lifting effect on the plow. Heuce, if we lengthen the hitch to decrease sidedraft we should also Fig. 20 Tongue truck designed for tractor operation. Having A long and B short reduces vertical motion of tractor drawbar to enable leveler to do smooth work on rough ground. The pull on the truck should be level, or slightly up instead of down. lower the hitch on the plow or raise it on the tractor if we wish to plow the same depth as before and avoid excessive downward force on the plow wheels. Center of resistance and true line of draft in a moldooard plow. — When a single bottom general-purpose type walking plow is turning a furrow slice fourteen inches wide and seven inches deep in uniform soil, the center of resistance is at a point (X, fig. 21) on the moldboard, about three inches from the landside surface, about three inches above the bottom level and about fourteen inches back from the share point. For other widths of bottom and depths of cut, the center of resistance has about the same relative position. If the soil has a tough sod, the center of resistance will be relatively higher; if we are turning up a hard plow pan, it will be relatively lower. Its position will also be influenced slightly by the shape of the plow, particularly as to mold- board and share. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 131 A line from the point of hitch on the plow beam end to the center of resistance, shows the actual direction of the pull on the plow before specified when it is working freely. This is the line of draft. The center of resistance and the line of draft may be located by pulling the plow at its proper depth using a short piece of chain to attach it to the tractor drawbar or to the doubletree, figures 22 and 22a. By the direction it takes when the pull is on, the chain will point backward Fig. 21 The center of resistance in a 14-inch moldboard plow is at a point x on the moldboard, about 3 inches from the landside surface, about 3 inches above the bottom level, and about 14 inches back from the share point. It varies with depth of plowing and with character of soil (sod, hardpan, etc.). Fig. 22 True line of draft. When a walking plow without depth-gauge wheel is working freely, the traces drawing it take the direction of the true line of draft and point back (along line shown dotted) to the true center of resistance. and downward to the true center of resistance along the true line of draft. It will be noted that practically all of the true line of draft lies below the plow beam and not parallel to the straight part of the beam. If the plow has a depth-gauge wheel, it must be removed or raised off the ground before making this test. Wheeled plows cannot be tested in this way since the wheels are designed to compel the plow bottoms to move parallel to their land- 132 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION sides, even when the pull of the tractor is oblique, and to plow at a certain depth, even though a high hitch on the beam tends to make them run much deeper. For such plows we may estimate the true line of draft closely enough as follows: let us mark on the middle (one or) two moldboards the spots we estimate as their centers of resistance ; then, for a two-bottom or four-bottom gang the common center of resistance would be at a point midway between the two marked points ; for a three-bottom or a five-bottom gang it would be at the center of resistance of the middle bottom. To get in the wheeled gang plow the point corresponding to the hitch at the front end of the beam in the walking plow, we must go to the two pins (bolts, or other device) by which the plow proper is attached to the plow hitch-bars. The point sought will be in or near the line through the two pins but not neces- sarily midway between them. In a three- or a five-bottom fourteen-inch gang it should be about three inches to the right of the front end of the middle plow beam ; that is to say, it is almost the same as that of the middle plow of the gang if it were detached and used alone Fig. 22a True line of draft. Line-up of clevises shows line of draft. Dotted line points back toward center of resistance of moldboard plow. The horizontal adjustment position used will affect position of the line. as a walking plow ; in two- or four-bottom gangs it should be a point three inches to the right of a point midway between the front ends of the middle beams, assuming right-hand plows. Evidently when we adjust the point of hitch up and down and sidewise on the front end of the gang frame to get the depth and running position desired, or adjust the lengths of the ' ' A " hitch bars, we change the direction of the line of draft. The center of resistance cannot be changed much in a given gang, though it will be varied some by depth of plowing and by soil conditions as previously stated. The point of hitch on the tractor should be chosen as nearly as possible in the same straight line with the line of draft of the plow. That is to say, the most satisfactory plow hitch is that in which the tractor's pull is as nearly as may be, BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 133 not only parallel to but also in the same straight line with the plow's true line of draft for the desired depth. Such hitching means easier running, less wear, and better work. MODEL FOR STUDYING SIDEDRAFT EFFECTS Sidedraft effects may be studied and illustrated conveniently by the use of a few spring balances and a frame representing the chassis of a tractor as shown in figure 23. The pull on balance A represents the forward pull of the tractor, that on B represents the resistance of the implement drawn, that on C is numerically equal to the sidedraft and represents the resistance of the soil enabling the rear wheels of the tractor to go straight forward in spite of the side- draft. The tension on C is adjusted until the frame lines up parallel to A. In the figure, vox shows the position of the front axle and yz that of the rear axle ; uv is midway between front and rear axles and is designed for attachment of swinging drawbars. •Fig. 23 Model for studying sidedraft effects. The frame, wxzy, represents chassis of tractor, A the tractor's pull, B the implement's resist- ance, C the sidedraft. M is an extra rear- vvardly extending drawbar which may be at- tached. When C reads zero there is no side- draft. The figure shows the simplest case— that of a tractor having its drawbar in line with the rear axle and the point of attachment at the drawbar center. It is equivalent to the draw-bar shown in figure 23a. M is an attachment which may be bolted on to the frame to represent the common case of tractors having drawbar located back of the rear axle. When the drawbar to which attachment is made is either for- ward of or to rear of the rear axle, or when hitch is not to drawbar center, it is necessary to use a fourth spring balance to counteract the sidewise forces on the front axle. Whenever balance C reads zero, sidedraft is absent at the rear axle. 134 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION DRAWBARS* True point of hitch on a tractor. — A hitch as here used means the connecting member between tractor and implement by which the imple- ment is pulled, beginning where flexibility begins as we go from tractor toward implement and ending where flexibility ends in solid attach- ment to the implement. It may consist of a bolt or pin, a clevis, a rope, cable, chain, or set of chains, a straight bar, a bent bar, or any combination of the foregoing. By true point of hitch on a tractor is meant that point on the end of the hitch toward the tractor where freedom of motion up, down, and sidewise ceases and the hitch becomes rigid with the tractor frame. Fig. 23a Drawbar in line with the rear axle. Sidedraft, if any, is all carried by the rear wheels. (Note: This tractor is no longer manufactured.) The position of this true point of hitch is a matter of great importance, especially when the pull is heavy, since in a very large measure it determines how the tractor will act under given circumstances. To make this matter clear a number of drawbar arrangements will be shown and discussed. Illustrations : Let us consider first a hitch, figure 24, consisting of a heavy steel bar having an eye at the rear end and a ball at the for- ward end, the ball forming part of a tall-and-socket joint attached to the under side of the tractor frame somewhere between the front and rear axles. Let us suppose that there are no guides at the rear, leaving the hitch-bar free through a wide range to swing radially from the * Several years ago the American Society of Agricultural Engineers made up a list of recommended specifications for tractor drawbar heights and offset adjust- ments. Because of much adverse criticism, however, these are not to be announced as il standards of the Society." The list is therefore omitted from this bulletin. Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 135 ball joint. It might be designated as a radially swinging drawbar. The true point of hitch in this case would be the center of the ball-and- socket joint. Such, a drawbar gives the hitch freedom to take its best direction. Being long, it reduces sidedraft effects when the implement runs offset. It makes steering easier, greatly facilitating turning with Fig. 24 Radially swinging drawbar. A rigid bar pivoted by a ball-and-socket joint at its forward end and having no guide of any kind at or near the rear end. If the ball-joint is placed far forward it tends to increase trac- tion in track type tractors by holding down the front end of the tractor. This is valuable, especially on the soft soils of the rice fields. such loads as disk harrows, pulverizers, drags, etc. By its use the front ends of the tracks in track-type tractors are held down, giving better contact, hence better traction, especially on soft soils, as for, example in the rice fields. If the location of the ball joint is central between front and rear axles, sidedraft effects, if any, are divided equally between front and rear wheels. This, other things being equal, would tend to reduce strains in the frame. Further, as in every case where the true point of hitch is in the central vertical plane lengthwise of the tractor, the draft is furnished equally by both drivers. One dis- advantage of the radially swinging drawbar is that it is not well adapted for backing. Fig. 25 Pinning a drawbar. If the radi- ally swinging drawbar of figure 24 is bolted to the tractor as in figure 25, the true point of hitch becomes the eye at the rear end of the drawbar. The chief advantages of the swinging drawbar are lost by pinning. Figure 25 shows the same drawbar as figure 24, but with the addi- tion of a stationary guide-bar to which the swinging drawbar is bolted. The true point of hitch now becomes the eye at the extreme rear of the drawbar. It is no longer correct to call it a swinging drawbar. A similar case is shown in figure 26. Such an arrangement is in its effects practically the same as if we had hitched to a hole in a station- ary drawbar the same distance out from the rear axle of the tractor. 136 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 26 Pinned drawbar. For all effects this drawbar is the same as a station- ary drawbar extending out the same distance from the rear axle. Fig. 27 Stationary drawbar extending back of the rear axle. This type by its lever action increases the sidedraft effects, if any, on the rear wheels. Fig. 28 Drawbar passing over rear axle and attaching rigidly to forward part of frame. Effects are the same as for a drawbar consisting of the frame itself extended back the same distance. (Note: This drawbar is no longer furnished with the tractor shown.) ~T— | J 1w-ffi5r/^ -^""*"*S!f l ^ff ' 1 . 1 Fig. 29 Drawbar passing under rear axle and attaching rigidly to forward part of frame. If pinned in one of the notches shown, it becomes in effect the same as a stationary drawbar consist- ing of the frame itself extended back the same distance. It matters not at all so far as draft purposes are concerned, pro- vided only that the parts are made strong enough to withstand the forces they are to transmit, whether a stationary drawbar is attached directly to the rear end of the tractor frame, as in Figure 27, or goes over the rear axle, as in figure 28, or under it, as in figure 29, and attaches rigidly to a forward part of the frame. Going from tractor toward implement we find the true point of hitch where rigidity ceases. If a drawbar is free to swing between horizontal guides, as is the upper bar in figure 30, it has, within the limits set by the guides, all the advantages of the radially swinging drawbar as regards sidedraft effects, and for all horizontal effects the true point of hitch would be Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 137 Fig. 30 Multiple drawbar. The lower draw- bar is a radially swinging drawbar within the limits set by the support- ing chain. The upper drawbar is swinging between horizontal guides within the limits set by the stops, provided it is not pinned. Fig. 30a Multiple drawbar. A stationary drawbar and a drawbar swinging between horizontal guides. Fig. 30& Multiple drawbar. A stationary (loop) drawbar and a swinging bar drawbar supported by two rods and by two chains of adjustable length. Fig. 31 Adjustable drawbar. Adjustable vertically and swinging between hor- izontal guides unless pinned. the front end of the bar. But for up-and-down effects the true point of hitch is the rear end of the bar. In the same figure, the lower bar has the true point of hitch at the front end for both horizontal and vertical effects so long as it has not reached the limits set by the chain and the guides. Beyond those limits, the rear end becomes the true point of hitch. In figure 31 the drawbar is equivalent to a swinging drawbar (unless pinned) for horizontal effects and to a stationary but adjust- able drawbar for vertical effects. If the motion of a swinging drawbar between horizontal guides is limited by pins set in the guides (a very common arrangement), the 138 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 32 Horizontally adjustable drawbar. The lever furnishes a quick means of adjusting the amount of offset. By removing the connecting bar this drawbar may be made swinging be- tween horizontal guides. Fig. 33 Adjustable drawbar. Vertical adjustability is secured by use of the turnbuckle, and horizontal adjust- ability by offsetting to the several holes. front end of the bar is the true point of hitch whenever the bar does not touch the pins. Whenever the bar is against a pin, the rear end of the bar becomes the true point of hitch. Thus one of the big advantages of a swinging drawbar, namely, reduction of sidedraft by lengthening the hitch, may be lost if the drawbar is prevented from swinging. A drawbar is often pinned during the turn to prevent a close-hitched implement from getting foul of a tractor drive wheel. After the turn the pin should be withdrawn. Especially in the smaller size tractors adjustability of the true point of hitch on the tractor is of advantage in that it furnishes a ready means of adapting the tractor to implements differing widely as to the height of hitch they require and the amount of offset at which they must run. It may also aid in turning. Many different devices are used to obtain adjustability. Figures 31, 32, and 33 show a few such devices. The curved drawbar with or without a roller approaches the swing- ing drawbar rather closely in its effects. (See figures 34 and 34a.) Within the limits set by the clamps, the drawbar of figure 34 is equiva- lent to a swinging drawbar for horizontal effects with true hitch point, in effect, the center of curvature of the curved drawbar. For vertical effects it is swinging also, but with the center line of the curved bar itself as the location of the true point of hitch. Bulletin 349 A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 139 Fig. 34 Arc and roller type drawbar. Within the limits set by the clamps this is equivalent for horizontal effects to a drawbar swinging between hor- izontal guides. For vertical effects it is equivalent to a swinging drawbar having its true point of hitch in the center line of the curved bar itself. ^gp mm — jr^l ' ; " i ^^^HMBM^M^ * V ^ Fig 34a Curved drawbar. This drawbar is the same in effect as that of figure 34, provided the attachment on the curved bar is such as to slide along it readily. If two or more turns of chain are taken around the bar it becomes equivalent to a stationary drawbar. True point of hitch on the implement. — Similarly, the true point of hitch on the implement should be considered. As in the case of the tractor it is a matter of where rigidity in the hitch begins. In a hitch consisting only of a chain or cable it will evidently be the point where the chain or cable is fastened to the implement. In a rigid plow hitch, "A," or "elephant ear" type, as in figure 35, there may be two such true points of hitch, one, the center of the bolt at X governing for horizontal effects; the other, in the center line of the bolts at Y governing for vertical effects. In figure 35a the true point of hitch for horizontal effects is in the part of the clevis which links with the eye at the forward end of the hitch. The true point of hitch for vertical effects is in the center line of the two bolts by which the hitch is hinged to the plow proper. Fig. 35 True point of hitch on the implement. In a rigid plow hitch there may be two such points, one at x governing for horizontal effects, one at y governing for vertical effects. The wooden breakpin at z acts as a safety release. 140 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Fig. 35a True point of hitch on the imple- ment. Here the point governing for horizontal effects is the part of the clevis that links with the eye at the forward end of the hitch, x. The point governing for vertical effects is in the center line of the bolts by which plow and hitch are joined, y. Wooden breakpin at z. Model for studying the effects of offsetting hitch. — A few spring balances and a wooden bar may enable a ready study of the effects produced by offsetting the hitch on the tractor drawbar. The bar as used in figures 36, 37, and 38 represents the drawbar of a tractor in the simple case where the drawbar is at the position of the rear axle, as in figure 23a. The pulls on the upper two spring balances represent the individual pulls of the two drive wheels of the tractor. The pull on the third balance represents the resistance of the load drawn. In Fig. 36 Model for studying effects of off- setting hitch. When hitch is to draw- bar center traction load is divided equally between the two drivers. If there is no sidedraft this holds for all cases where true point of hitch is central, no matter how far for- ward or back. Fig. 37 Model for studying effects of off- setting hitch. When hitch is at a point midway between drawbar center and middle of right driver, the right driver carries three-fourths and the left driver one-fourth of the traction load. Bulletin 349] A STUDY OP SIDEDRAFT AND TRACTOR HITCHES 141 figure 36 where the hitch is to drawbar center, the upper two balances read ten pounds each, the lower balance reads twenty ; that is, the two drivers divide the traction load equally between them. In figure 37, where the hitch is halfway between drawbar center and middle of right driver, the right balance reads fifteen pounds, the left one five pounds, and the lower one twenty pounds ; that is, for the offset shown, the right driver carries three-fourths and the left driver one- fourth of the traction load. In figure 38, where the hitch is squarely behind the right driver, the right balance reads twenty pounds; the left one zero, and the third balance twenty pounds; that is, when the hitch is squarely behind a driver that driver carries the whole traction load. The extra offset drawbar hitch shown in figure 43 is of this kind. Fig. 38 Model for studying effects of offsetting hitch. When hitch is squarely behind a driver, that driver carries the whole traction load. Examples of sidedraft and unequal loading effects. — The following sketches and solutions are given as concrete illustrations of the prin- ciples that have been set forth. Where, as in figure 39, the true point of hitch on the plow is a dis- tance "a" behind the rear axle of the tractor and is offset a distance " b " from the center line of the tractor, the proportions being as shown in this figure : 1. If the true point of hitch on the tractor is at 1, midway between front and rear axles, for each 1000 pounds pull in the hitch member, the sidedraft is 111 pounds, divided equally between front and rear wheels. 2. With the hitch at 2, a distance *4 L forward from the rear axle, the sidedraft is 139 pounds, one-quarter carried by the front wheels and three-quarters by the rear wheels. 3. With the hitch at 3, the middle of the rear axle, the sidedraft is 187 pounds, all carried by the rear wheels. 142 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 4. With the hitch at 4, a distance *4 L hack of the rear axle, the sidedraft is 259 pounds at the drawbar. This is increased by the lever action of the rearwardly extending drawbar to 324 pounds at the rear axle. The same lever action puts a side force of 65 pounds to the left on the front axle. (Offset angle here is 15°.) Fig. 39 How the position of the true point of hitch on the tractor affects sidedraft. Fig. 40 How putting the plow farther back affects sidedraft. Where, as in figure 40, the distance "2a" back from the rear axle is double that of figure 39, the offset distance "b" remaining the same as before : 1. With the true point of hitch on the tractor at 1, for each 1000 pounds pull in the hitch member the sidedraft is 70 pounds, divided equally between front and rear wheels. 2. With hitch at 2, the sidedraft is 80 pounds, borne one-quarter by front and three-quarters by rear wheels. 3. With the hitch at 3, the sidedraft is 95 pounds, all borne by the rear wheels. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 143 4. With the hitch at 4, the sidedraft is 114 pounds at the drawbar, 143 pounds at the rear axle and 29 pounds to the left at the front axle. With the hitch, as in figure 41, at 4 on the tractor and along x to the plow, the offset distance being "&" (making the offset angle 15°), Fig. 41 How the amount of offset distance affects sidedraft. the sidedraft will be 259 pounds at the drawbar (as in case 4 of figure 39) for each 1000 pounds pull in the hitch member. If now the adjust- ment of the hitch on the plow be changed so that the plow leads off to the right, making the hitch member take the position y, offset distance V (offset angle 30°), the sidedraft will be - X 1000, or 500 pounds c for each 1000 pounds pull in the hitch member. For any offset distance "5" and true length of hitch "c" (i.e., the distance between the true points of hitch on plow and on tractor with reference to horizontal effects), the sidedraft at the point of hitch on the tractor will be the fraction - of the pull in the hitch member. c ^ In figure 42, with the values of "a" and "&" as in figures 39 and 41 : 4. With the hitch point at 4 the sidedraft at the drawbar will be 259 pounds for each 1000 pounds in the hitch member. The side force on the front wheels is toward the left. 5. With the hitch point at 5, the side draft at the drawbar will be zero, but the right driver will carry 684 of each 1000 pounds and the left driver 316 pounds. On a heavy pull, this tends to make the right driver slip more and the left one tend to run ahead in a circle with the right driver as a center, thus putting a side force toward the right on the front wheels. 144 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION With the hitch point at 6, halfway between 4 and 5, the side- draft at the drawbar will be 130 pounds for each 1000 pounds pull. The offset of distance y 2 "6" on the drawbar will cause the right driver to carry 592 pounds and the left 408 Fig. 42 "Dividing the sidedraft between tractor and plow." pounds of each 1000 pounds of the forward pull. The forces on the front wheels, that toward the right due to the unequal loading of the drivers and that toward the left due to the oblique direction of the pull, will tend to balance each other. This methocl of hitching is popularly said to "divide the side- draft between tractor and plow." Fig. 43 An extreme offset hitch. This arrangement is sometimes used in orcharding to enable working closer to trees. It is not good practice. If the relations are as in figure 43, all the traction load will be carried by the right driver. This arrangement gives bad stresses in the tractor frame and tends strongly to slide the front wheels toward the right. With this hitch to a medium or large load, it would be almost if not quite impossible to turn to the left. Some tractors are Bulletin 349] A study of sidedraft and tractor hitches 145 designed to do such work well. The frame may be made extra strong. The steering may be made more certain by deep fins on the front wheels and by carrying a large part of the tractor's weight forward. The friction and wear in the bearings due to side forces may in a large measure be relieved by the use of special thrust bearings similar to those used in automobile construction. In the same way proper design in the plow intended for such use may enable it to do good work even when the pull on it is at a considerable angle and the hitch as short as may be necessary for such work. £221 i flHHHl bsyL ^WaT Fig. 43a (Courtesy of Monarch Tractor Co.) Rice binder mounted directly on tractor. Mounting the implement directly on the tractor. — This has been attempted with more or less success by a number of manufacturing companies, but there is still room for work by designers. Some of the advantages that a skilful designer might secure by direct mounting are : 1. Entire avoidance of sidedraft. 2. Equal forces on the drivers. 3. Less power lost in overcoming friction of supporting wheels. • 4. Easy turning in smaller space. 5. Saving of labor cost by making a one-man outfit do work now requiring two or three men. Some of the disadvantages are : 1. The time and labor expense of mounting and dismounting the implement before and after the season's use. 2. The unavailability of the tractor for many other uses while the implement is mounted upon it. 146 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 3. Difficulty in getting through gateways. 4. Increased difficulty of getting out if mired down or stalled in sand. Implements drawn by two-wheel tractors. — A near approach to a directly mounted tractor plow is found in several front-wheel-drive tractors now marketed in which the rear of the tractor is borne by the plow itself. Sometimes another implement takes the place of the plow behind one of these tractors. Cultivators, disk harrows, mowers, and seeders have been used in this way. Rotary tillers. — One or more American manufacturing companies are experimenting on a directly mounted rotary tillage machine which gives considerable promise of efficiency and effectiveness. A small number of such machines have recently been used in Wisconsin, Texas, Fig. 44 Implement attached to two-wheel tractor. to direct mounting of the implement. A near approach and California. A similar machine has been in use for a number of years in Europe. It consists of what is in effect a set of spring-tooth- harrow teeth mounted on a rapidly revolving drum. This machine, by its chopping action, in one operation reduces the soil to uniformly fine pulverization as deep as required. Thus it replaces plow, disk harrow and spike tooth harrow. A soil free from large stones and other obstructions is best adapted for its successful use. At least one European type, it is claimed, climbs out of the ground without injury to itself when it reaches a large rock. Some of the advantages claimed for these machines are : 1. More thorough and uniform pulverization. 2. More efficient use of the power of the motor. 3. No compacting of the subsoil. 4. Rendering unnecessary the use of disk harrow, drag, and clod crusher following the plow. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 147 One disadvantage is that trash such as cornstalks is not well turned under. Direct mounting of binders has met with some success in this country. Figure 43a shows a rice binder mounted on a Monarch tractor by W. J. Shepard of Marysville, California. A number of these were used during the last three seasons in the rice fields of the upper Sacramento Valley. The Avery Company of Peoria, Illinois, manufactures a special header for mounting on the front end of an Avery 12-25 tractor. The Caswell Tractor Grader, figure 44a, manufactured by Caswell Manufacturing Company, Cherokee, Iowa, is a direct mounted grader Fig. 44a (Courtesy of Caswell Manufacturing Co., Cherokee, Iowa) A direct mounted grader. which loosens the soil, elevates it to a box holding two cubic yards, hauls to the desired place, and dumps or spreads as desired. Special tractor hitches. — Chain hitches are very convenient and satisfactory for many purposes. They are easy to apply and remove. Their length can readly be adjusted. They show definitely the direc- tion of the forces upon them by lining up with those forces. Their flexibility is desirable in certain cases. They have, however, certain disadvantages. They cannot hold a wheeled implement on a down grade. With them one cannot back a plow to clear out accumulated trash unless a pole is supplied in addition. They are not so stable as a rigid hitch would be when the plow strikes a hard spot. The common crossed chain hitch is often used and has the valuable property of preventing the implement from "cutting the corners" when the tractor turns. The pulls in the two chains are usually not equal and may vary from moment to moment through a wide range. This is true when it is used for plowing, especially when turning a 148 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION corner. It keeps the plow in the ground on the turns better than a rigid, hitch and enables the plowing of a straighter furrow when there are slight irregularities in the steering of the tractor. It does not eliminate sidedraft and unequal loading of drivers when the center lines of tractor and plow are offset. A hitch of this type is shown in use in figure 45 and its adjustment is explained in figure 46. There is on the market a patented chain hitch said to eliminate sidedraft. It consists of a chain passing over four sheaves which are attached two to a bar fastened to the tractor, and two to a similar bar carried by the implement, as shown in figure 47. Its characteristics are much the same as those of the common crossed chain hitch. A hitch, model of which is shown in figure 47, was tested in 1919 by L. J. Fletcher and the writer in the presence of the patentee and his engineer. The hitch was used be- tween a Cletrac tractor and a John Deere three-bottom tractor moldboard Fig. 45 Common crossed chain hitch. Prevents wagon or other implement from cutting corners. Enables plows to stay in full depth around turns and to go straight ahead in spite of slightly irregular steering. plow for the purposes of the test. The plows stayed in the soil very well on the turns. That sidedraft was present was shown by the fact that the tractor oper- ator had to hold the steering wheel to- ward the unplowed land in order to go straight ahead. Fig. 46 Model of common crossed chain hitch. Chains should have a ring at one end and a grab link or a grab hook at the other for convenient attachment and adjustment. To cause implement to move over to right, lengthen chain at x or shorten at y. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 149 The line of direction of the combined pull of all the chains may be found readily if we assume the pulls in the chains all equal. This assumption is very nearly correct if the four sheaves have little friction on their shafts and are not pinned to prevent their turning. In figure 48 draw the bisectors of the angles made by the two portions of chain running from each sheave. These bisectors will meet in two points, A and B. The line AB through these two meeting points shows the true direction of the tractor's pull upon the plow when this hitch is used. It will be noted also that the points A and B are at equal dis- tances from the points at which the sheaves are fastened on the two attachment bars. Only in the case where the line AB is parallel to the direction of motion of the tractor will there be no sidedraft. If the attachment bar is not symmetri- cally placed on the tractor, or rather if the sheaves are not sym- Fkf. 47 A patented chain hitch. The chain passes around four sheaves, two of which (those on the tractor) may be pinned to prevent their turning. This hitch does not prevent sidedraft. metrically placed with re- spect to the center line of the tractor, so that the line AB does not pass through the midpoint of the rear axle of the tractor, there Fig. 48 Diagram of the hitch of fig- ure 47. The line AB shows the true direction of the pull. There is sidedraft if the line AB is not parallel to the direction of motion, and unequal loading of the drivers unless the line BA produced passes through the midpoint of the rear axle of the tractor, 150 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION will be unequal loading of the drivers. Evidently it is possible with this hitch to "divide the sidedraft between tractor and plow," as with other hitches previously explained. Hitches to adapt horse gang plows for tractor operation. — When the tractor makes its first appearance on a ranch, there are usually on hand a good many implements in fair condition designed for horse operation. Often at a small expense of time, labor, and materials these may be adapted for tractor operation and do fairly satisfactory work. It would be foolish, however, to assume that these adapted implements could generally be made to work as well as implements especially designed for tractor operation. Since plowing requires more power than any other farming opera- tion, it is usually the particular job for which the first tractor is purchased. Several gang plows designed for horses may be hooked up together and drawn by rods or chains from one heavy crossbar, as in figures 49 or 50. Fig. 49 Common crossbar plow hitch used for adapting horse gangs for tractor operation. Each gang after the first has its right wheel removed and the axle hung by chains or clevises and rings from the nearest beam of the gang next ahead, as shown in figures 51 and 52. This arrangement enables much closer placing of the gangs ; at the same time the amount of freedom given the axle enables the plows to make the turns without "piling up." Figure 53 shows a similar arrangement designed by the Oliver Chilled Plow Company for their Bonanza gang. The cast iron spool can slide lengthwise of the axle and roll backward and forward in the guide. The John Deere Plow Company manufactures the device shown in figure 54 for use with their New Deal gang plows. When the several gangs are hitched to an ordinary crossbar, the chains or cables drawing the rear gangs are necessarily longer than those for the front gangs. The longer hitch to the rear gangs tends to make them plow deeper. To equalize depth of plowing the hitch may be made lower on the rear gangs. Sometimes, as in figure 55, a piece of pipe or a wooden bar carried by a wheel is used as a "lift" to equalize the depth of plowing and also to prevent fouling of the chains- and gangs at the turns. Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 151 Fig. 50 Common crossbar plow hitch. Detail showing connection to drawbar swinging between horizontal guides. Fig. 51 Adapting horse gangs for tractor operation. Supporting the right axle of one gang by ring and chain from a beam of the next forward gang. This home-made device gives the necessary freedom between gangs on the turns. Fig. 52 Adapting horse gangs for tractor operation. King and clevis support for the axle of a rearward gang. Removing the wheel brings the gangs closer to the tractor and makes oper- ation easier. Fig. 53 Special axle support designed by the Oliver Chilled Plow Company for their Bonanza gang plow. 152 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 54 (Courtesy of the John Deere Plow Co.) Special axle support designed by the John Deere Plow Co. for their New Deal gang plows. Fig. 55 "Lift" for the longer chains when several gangs are attached to a common crossbar. The wheel and pipe prevent the rear gangs from plowing too deeply. They also help prevent chains and gangs fouling at the turns. The Wilson oblique hitch, figure 56, pulls evenly on all the gangs with little or no chance of fouling on the turns. A larger number of gangs can be used than with the common crossbar, because the gangs are closer to the tractor. Also a narrower headland is required. Fig- ure 57 shows this hitch in use, Bulletin 349] A study of sidedraft and tractor hitches 153 \ 1 1 o y o 0) s o r I II Fig. 56 Wilson oblique plow hitch. Facilitates turning by hitching gangs closer to tractor. All gangs are same distance from oblique beam. Little chance for fouling on the turns. Depth of plowing is about the same for all gangs. Design covered by U. S. patent issued to S. Wilson, Davis. Fig. 57 Wilson oblique plow hitch in use. The hitch shown here has also been used for several disk plows drawn by the same tractor. Pierce harrow cart. — In dry-farming operations throughout the interior valleys of this state it is sometimes necessary to use harrows capable of covering a width of as much as seventy feet. When land is free from large gullies a harrow cart, if well designed and built, is a very satisfactory means of carrying the drawbars needed for the numerous sections. In 1915 a harrow cart was designed and built by 154 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 58 The original Pierce harrow cart built in 1915 by George W. Pierce, of Davis, is still in use. Has been copied by grain raisers throughout the interior valleys of California. Fig. 59 The original Pierce harrow cart. Close-up view showing some details of construction. The small size wheels cut into the soil, increasing draft, and are hard to lubricate. Fig. 60 Cart made by J. C. Luft of Davis. The original Pierce design is followed closely. Slightly larger wheels are used to reduce draft and wear. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 155 George W. Pierce, of Davis. The original is still in use, and shown in figures 58 and 59. It has been copied by many ranchers throughout the Sacramento and San Joaquin valleys and is being manufactured commercially by J. C. Luft of Davis, and Milton Carpenter of Dixon. Fig. 61 Luft cart in use on Sidney Watkins ranch. Note how, even with a light load, the small wheels cut into the soil. Fig. 62 Castor wheel made by M. Carpenter, Dixon. The swivel wheels permit hitching tractor to an end of a boom and pulling the cart and all over if it runs foul of a fence. Because of their small size the wheels cut in badly, making draft heavy and wear rapid. The Luft make, figures 60 and 61, follows closely the original Pierce design except that the wheels used are relatively larger making for lighter draft. Several sizes may be had to order. Those built by Carpenter, figure 62, have castor wheels smaller relatively than those of the original Pierce. The swivel mounting of the wheels enables attachment of the tractor to the end of a boom to pull the cart clear if it should run foul of a fence or other obstruction. If this is attempted with a cart having fixed axles, breakage is almost sure to result. 156 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Figure 63 shows the "A arrangement ' ' of sections used with a homemade cart built by the Haussler Brothers, east of Davis. It has the two main sets of harrow sections drawn separately and at a con- siderable angle. The land between the two wings is harrowed by a section attached by a small cable to the top of the mast. This arrange- ment gives little trouble on the turns and in the gullies. The cart shown in figures 64 and 65 embodies two desirable features not found in the other carts shown, namely large, broad-tired wheels, and the frame hung underneath the axle. The large wheels do not cut Fig. 63 Home-made cart of Haussler Brothers. The "A" arrangement of the sections prevents piling up at the turns. The middle section is drawn by a small cable attached to the top of the mast. Two sections of spring tooth harrow attached directly under the cart, loosen up the tractor tracks. Pig. 64 An improved harrow cart. The large wheels decrease draft and bearing wear. The underhung frame puts the boom near the ground, enabling a more nearly level pull. This means better work, less draft, and less trouble at the gullies. The sections may be attached to the boom in any manner desired. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 157 so deeply into the soil, hence require less draft. Lubrication and bearing-wear troubles also are greatly reduced because of the slower turning. The low boom gives less trouble when one end is over a gully and permits a more direct pull. In all these carts the intention is to transport from field to field by uncoupling the booms which butt together under the mast and placing them on the cart, then piling the harrow sections on top. In some cases this is quite a job. A quick and easy means of overcoming the gate bugbear is to pull the cart onto a low sled, release the open Fig. 64a Side view of the cart of figure 64. Two sections of spring tooth harrow dig up the tractor tracks. Wheels from an old combined harvester are good shape and size. Fig. 65 An underhung frame, large wheel harrow cart in field near Dixon. The attachment of the long booms to the cart frame is less convenient than the form shown in figures 64 and 64a. 158 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION hooks by which the sections are held, pile the sections on the cart, attach a cable* or chain to the sled, and slide the cart lengthwise of the booms through the gateway. Multiple implement hitches are often desirable. Usually such hitch- ing presents little difficulty. Figure 66 shows a spike-tooth harrow attached by a chain behind a disk plow. Pulverization is very much better and moisture is conserved if the dragging is done at once after plowing. The hitch shown is not the best possible, as it puts all the drag load on the right-hand end of the plow, thus increasing the wear on the plow wheel bearings. A better arrangement would be the use of a narrower drag hitched more centrally on the plow. Fig. 66 Harrowing while the clods are soft. Much better pulverization is secured, especially in dryAveather, if the drag follows the plow immediately. One man's time is saved by using a tandem hitch. Figure 67 shows a tandem hitch including a double disk harrow, a smoothing harrow, and a grain drill. This makes a one-man outfit out of implements which, if used separately, would require three men. One difficulty is that some of the implements may get less attention than they require. For drawing two or more grain binders by the same tractor, several hitches are on the market. Figures 68 and 69 are representative types. (See list of manufacturers of tractor hitches, page 163.) In all of these binder hitches some sidedraft is certain to be pro- duced by the oblique pulls. For this reason it is well to make sure that the bearings of all carrying wheels are in good condition, clean, well adjusted, and constantly and sufficiently lubricated. Bulletin 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 159 Fig. 67 (Courtesy of the Emerson-Brantingham Implement Co., Rockford, 111.) Tandem hitch for double disk harrow, smoothing harrow, and grain drill. This arrangement saves man labor, but the drill may get less attention than it needs. Fig. 68 (Courtesy of the Emerson-Brantingham Implement Co., Rockford, 111.) Binders in tandem. Prompt harvesting often means getting the grain before the wind threshes it out for the crows and the sparrows. An operator is required for each binder. Fig. 69 (Courtesy of the Meadows Manufacturing Co., Bloomington, 111.) Binder hitch. This hitch is usable between binder and tractor or between first and second binders. It prevents the binder from "cutting the corners. ,J 160 UNIVERSITY OF CALIFORNIA — -EXPERIMENT STATION SUMMARY Sidedraft is no mysterious bugaboo. It is subject to all the laws of mechanics that apply to forces in general. Sidedraft is a force acting sidewise on a tractor or on any imple- ment. It is always present if the resisting force of the implement pulls to one side instead of parallel to the direction of motion. No hitch, patented or otherwise, can prevent sidedraft when the center lines of pull of the tractor and of resistance of the implement are offset and the hitch is to the center of a symmetrically placed draw- bar. Test for sidedraft. — A clevis or any other free link in a hitch will set itself in the direction of the force it is transmitting. If that direc- tion is not parallel (in the horizontal plane) to the direction of motion, sidedraft is present. Effects of sidedraft. — Causes poor work, makes steering hard, in- creases wear, repairs, and breakdowns, and makes for inefficiency in general. Sidedraft reduced. — It may be reduced by making the total pull required and the offset angle as small as possible. Its effects may be lessened by a method known as ' ' dividing the sidedraft between tractor and plow." It is possible to remove all sidedraft from tractor and implement by offsetting the hitch on the tractor drawbar so that the pull will be straight forward from the implement; out when this is done the tractor drivers are loaded unequally, which may produce effects even worse than sidedraft. Sidedraft is sometimes unavoidable and sometimes inexcusable. Down draft on an implement due to poor adjustment may cause nearly as much trouble as sidedraft. How a plow works. — Side forces and vertical forces are always and necessarily present when a plow is in use. Plow adjustments. — Read, ponder, follow the directions given in the handbook furnished with the machine. Drawbars of some types reduce sidedraft effects; others increase them. The true points of hitch on tractor and implement determine in a large measure how the combination will act when in use. Direct mounting of tillage and harvesting machines upon the trac- tor has large possibilities, in that sidedraft may be eliminated and high efficiency secured. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 161 Homemade hitches. — Many good hitches for special purposes have been devised by farmers and others. Descriptions and photographs of some of these are given in this bulletin. A review of trade publications having tractor hitch or plowing information gives names of available works, their contents, and where and how obtainable. A list of manufacturers of tractor hitches is given on page 163. BIBLIOGRAPHY The Tractor Field Boole, 1921. Pub. by Farm Implement News, Masonic Temple, Chicago, 111. Equalisers and Hitches (1918), by E. A. White. Pub. in " Transactions, ' ' Am. Soc. Agr. Engrs., vol. XII, p. 124. Plow Bottom Design (1918), by C. A. Bacon. ''Transactions," Am. Soc. Agr. Engrs., vol. XII, p. 26. A Study of the Plow Bottom and its Action on the Furrow Slice (1918), by E. A. White. ' ' Transactions, ' ' Am. Soc. Agr. Engrs., vol. XII, p. 42. The Botary Tiller or Soil Milling Machine (1914), by Max Patitz. * 'Trans- actions," Am. Soc. Agr. Engrs., vol. VIII, p. 57. Tractor Hitch Merits Serious Consideration (1918), by J. E. Schipper. "Auto- motive Industries," June 27, 1918, p. 1257. Tractor Drawbar Implements and their Hitches, by F. N. G. Kranich. "Trans- actions," Soc. Aut. Engrs., 1919, Part I, p. 777. List of Principal French, German, Italian, and Russian Works on the Plow. "Transactions," Am. Soc. Agr. Engrs., vol. XII, p. 237. Coordinating Theory and Practice in Tractor Plow Design and Operation, Includ- ing the Plow Hitch, by A. C. Lindgren and O. B. Zimmerman of the Experi- mental Department, International Harvester Co. "Agricultural Engineering," Jan., 1922, Am. Soc. Agr. Engrs., St. Joseph, Mich. TRADE PUBLICATIONS HAVING PLOWING OR TRACTOR HITCHING INFORMATION In general, hitches designed for use with a wheel-type tractor of one make may be used readily with tractors of the same type but of other makes. Likewise, equipment designed for one make of track-type tractor will work on tractors of the same type but of different makes. But, usually, equipment designed for track- type does not work well with wheel-type, and vice versa. Advance Rumely Thresher Co., 17 Main St., San Francisco. "Instructions for Operating the 12-20" [or other size], 72 pages. Laying out fields for plowing. Tractor plowing hitch. Free, in limited num- bers, to owners of ' ' Oil Pull ' ' tractors. 162 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Avery Co. of the Pacific Coast, 1401 Front St., Sacramento, Calif. "Avery Tractor Hitch Book," 48 pages. Laying out fields for plowing, harrowing, and drilling. General for hitching moldboard plows. General for hitching disk plows. Hitches for 2- or 3 -disk plows. Homemade hitches for two 8-foot or 10-foot disk harrows or drills (dimension sketches). Homemade hitch for three 8-foot disk harrows or drills (dimension sketches). Hitch for Push Header and Header Barge. Free on request. C. L. Best Gas Traction Co., San Leandro, Calif. Blueprints (dimension drawings). S. K. 5, "Hitch for three No. 31 Oliver Plows." (This is about the hitch shown in fig. 49.) S. K. 6, { ' Hitch for four Gang Plows of four 10-inch bases each. ' ' S. K. 7, " Hitch for five Oliver Bonanza Gang Plows to a C. L. Best ' Track- layer. ' " S. K. 78, "Hitch for three 10-foot double disks or drills." S. K. 79, < ' Hitch for 70 feet of harrows. ' ' S. K. 80, "Hitch for 20 feet of Harrows and two 10-foot drills." Sent to farmers on request. J. I. Case Threshing Machine Co., Eacine, Wis. ' ' Plow Manual, ' ' 42 pages. Plow hitches; plow adjustments; laying out fields for plowing. 50 cents postpaid. Emerson-Brantingham Implement Co., Eockford, 111. "E-B Tractor School Text Book, ' ' 40 pages. Hitches for: one or more drills, one or more moldboard plows, one or more disk ploAvs, one or more mowers, one manure spreader, combination hitch for disk and spike tooth harrows. Free on request ' ' while they last. ' ' Holt Mfg. Co., Stockton, Calif. ' ' Instruction Book for Caterpillar Disk Plow, ' ' 20* pages. Hitch for two or three disk plows. Free to farmers on request. International Harvester Co., 201 Potrero Ave., San Francisco. "Internal Com- bustion Engines and Tractors," 175 pages. Plow adjustments, care, and operation. Free on request. Oliver Chilled Plow Works, San Francisco. ' ' The Oliver Plow Book, ' ' 200 pages. A general work on soils, plows, plowing, adjustments, hitching. $1.00 post- paid. Twin City Company, Minneapolis, Minn. "Instruction Book for Twin City 12-20 Tractor," 80 pages. General work on tractor management. Hitch for : combination of plows and peg or disk harrows, two or more disk harrows, two or more mowers, two hay loaders, two or more grain drills. Plan of a general utility drawbar. Free on request. (Give size of tractor if not 12-20.) Vulcan Plow Co., Evansville, Indiana. "Service Book, Vulcan Tractor Plows, No. 41 Series," 44 pages. Field notes on plowing (4 pages). Free on request. Yuba Products Company, 433 California St., San Francisco. "Instructions for Operating and Adjusting Yuba Plows," 24 pages. Hitches, etc., for one or two Yuba Disk Plows. Free on request. BULLETIN 349] A STUDY OF SIDEDRAFT AND TRACTOR HITCHES 163 MANUFACTUEERS OF TEACTOE HITCHES The Avery Co., Peoria, 111. 1401 Front St., Sacramento, Calif. Combination safety release and automatic coupler. Buller Coupler Co., Hillsboro, Kansas. Automatic coupler for tractors, wagons, and automobiles. Safety release hitches. Milton Carpenter, Dixon, Calif. Pierce Harrow Carts. Caswell Manufacturing Co., Cherokee, Iowa. Wm, L. Hughson Co., Agents, San Francisco. Hitches for all makes of tractors and implements, corn binders, one or more grain binders, one or more dis\ harrows or grain drills; multiple hitch for various implements; adjustable offset plow hitch. John Deere Plow Co., Moline, 111. San Francisco. Hitches for grain drills, disk harrows, and New Deere Gang Plow. Dultmeier Manufacturing Co., Manning, Iowa. Stub poles and other simple tractor hitches. Emerson-Brantingham Implement Co., Eockford, 111. Hitches for two or more Osborne binders, any size. Grand Detour Plow Co., Dixon, 111. Lever adjusting plow hitch for sidehill work. Safety release hitch. Hansmann Manufacturing Co., Long Prairie, Minn. Hitches for all makes of tractors and implements. Hitch for one or more binders. Automatic binder hitch truck. Tractor guide (for plowing). Steer- ing poles for separators. Steering poles for graders. Hitches for two to five grain drills. International Harvester Co. Hitches for one or more binders, one or more mowers, corn binder, corn picker, Deering or McCormick push harvesting machine, manure spreaders (stub tongue), disk harrows (stub tongue), wagons, grain drills. La Crosse Plow Co., La Crosse, Wis. Lever hitch for adjusting plowcut in side hill work. J. C. Luft, Davis, Calif. Pierce Harrow Carts. Meadows Manufacturing Co., Bloomington, 111. Hitches for tractors and binders of any make. For one or more binders. South Bend Chilled Plow Co., South Bend, Indiana. Safety release hitch. Towers & Sullivan Manufacturing Co., Eome, Ga. Safety release hitch. Tractor Appliance Co., New Holstein, Wis. Outch releasing safety hitches. Vulcan Plow Co., Evansville, Indiana. Safety release hitch. Lever adjusting plow hitch for side hill work. Walter A. Wood Mowing and Eeaping Machine Co., Hoosick Falls, N. Y. Simple tractor hitches for various implements. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION No. 253. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. 261. Melaxuma of the Walnut, "Juglans regia." 262. Citrus Diseases of Florida and Cuba Compared with those of California. 263. Size Grades for Ripe Olives. 268. Growing and Grafting Olive Seedlings. 270. A Comparison of Annual Cropping, Bi- ennial Cropping, and Green Manures on the Yield of Wheat. 273. Preliminary Report on Kearney Vine- yard Experimental Drain. 275. The Cultivation of Belladonna in Cali- fornia. 276. The Pomegranate. 278. Grain Sorghums. 279. Irrigation of Rice in California. 280. Irrigation of Alfalfa in the Sacramento Valley. 283. The Olive Insects of California. 285. The Milk Goat in California. 286. Commercial Fertilizers. 287. Vineerar from Waste Fruits. 294. Bean Culture in California. 297. The Almond in California. 298. Seedless Raisin Grapes. 299. The Use of Lumber on California Farms. 304. A study on the Effects of Freezes on Citrus in California. 308. I. Fumigation with Liquid Hydrocyanic Acid. II. Physical and Chemical Prop- erties of Liquid Hydrocyanic Acid. 310. Plum Pollination. 312. Mariout Barley. 313. Pruning Young Deciduous Fruit Trees. 316. The Kaki or Oriental Persimmon. 317. Selections of Stocks in Citrus Propa- gation. 319. Caprifigs and Caprification. BULLETINS No. 321. 324. 325. 328. 330. 331. 332. 334. 335. 336. 337. 339. 340. 341. 342. 343. 344. 345. 346. 347. 348. 349. 350. 352. 353. 354. 355. Commercial Production of Grape Syrup. Storage of Perishable Fruit at Freezing Temperatures. Rice Irrigation Measurements and Ex- periments in Sacramento Valley, 1914-1919. Prune Growing in California. Dehydration of Fruits. Phylloxera-Resistant Stocks. Walnut Culture in California. Preliminary Volume Tables for Second- Growth Redwoods. Cocoanut Meal as a Feed for Dairy Cows and Other Livestock. The Preparation of Nicotine Dust as an Insecticide. Some Factors of Dehydrater Efficiency. The Relative Cost of Making Logs from Small and Large Timber. Control of the Pocket Gopher in Cali- fornia. Studies on Irrigation of Citrus Groves. Hog Feeding Experiments. Cheese Pests and Their Control. Cold Storage as an Aid to the Market- ing of Plums. Fertilizer Experiments with Citrus Trees. Almond Pollination. The Control of Red Spiders in Decidu- ous Orchards. Pruning Young Olive Trees. A Study of Sidedraft and Tractor Hitches. Agriculture in Cut-over Redwood Lands. Further Experiments in Plum Pollina- tion. Bovine Infectious Abortion. Results of Rice Experiments in 1922. The Peach Twig Borer. CIRCULARS No. No. 70. Observations on the Status of Corn 172. Growing in California. 173. 82. The Common Ground Squirrel of Cali- • fornia. 174. 87. Alfalfa. 175. 110. Green Manuring in California. 111. The Use of Lime and Gypsum on Cali- 178. fornia Soils. 179. 113. Correspondence Courses in Agriculture. 126. Spraying for the Grape Leaf Hopper. 181. 127. House Fumigation. 136. Melilotus indica as a Green-Manure 182. Crop for California. 144. Oidium or Powdery Mildew of the Vine. 183. 148. "Lungworms." 184. 151. Feeding and Management of Hogs. 188. 152. Some Observations on the Bulk Hand- 189. ling of Grain in California. 190. 155. Bovine Tuberculosis. 193. 157. Control of the Pear Scab. 198. 159. Agriculture in the Imperial Valley. 199. 160. Lettuce Growing in California. 201. 161. Potatoes in California. 202. 164. Small Fruit Culture in California. 165. Fundamentals of Sugar Beet Culture 203. under California Conditions. 205. 166. The County Farm Bureau. 206. 167. Feeding Stuffs of Minor Importance. 208. 169. The 1918 Grain Crop. 170. Fertilizing California Soils for the 1918 209. Crop. 210. Wheat Culture. The Construction of the Wood-Hoop Silo. Farm Drainage Methods. Progress Report on the Marketing and Distribution of Milk. The Packing of Apples in California. Factors of Importance in Producing Milk of Low Bacterial Count. Control of the California Ground Squirrel. Extending the Area of Irrigated Wheat in California for 1918. Infectious Abortion in Cows. A Flock of Sheep on the Farm. Lambing Sheds. Winter Forage Crops. Agriculture Clubs in California. A Study of Farm Labor in California. Syrup from Sweet Sorghum. Onion Growing in California. Helpful Hints to Hog Raisers. County Organizations for Rural Fire Control. Peat as a Manure Substitute. Blackleg. Jack Cheese. Summary of the Annual Reports of the Farm Advisors of California. The Function of the Farm Bureau. Suggestions to the Settler in California. CIRCULARS — Continued No. 212. 214. 215. 217. 218. 219. 224. 225. 228. 230. 232. 233. 234. 235. 236. 237. No. Salvaging Rain-Damaged Prunes. 238. Seed Treatment for the Prevention of 239. Cereal Smuts. Feeding Dairy Cows in California. 240. Methods for Marketing Vegetables in California. 241. Advanced Registry Testing of Dairy Cows. 242. The Present Status of Alkali. 244. Control of the Brown Apricot Scale 245. and the Italian Pear Scale on Decid- 246. uous Fruit Trees. Propagation of Vines. 247. Vineyard Irrigation in Arid Climates. 248. Testing Milk, Cream, and Skim Milk for Butterfat. 249. Harvesting and Handling California 250. Cherries for Eastern Shipment. Artificial Incubation. 251. Winter Injury to Young Walnut Trees during 1921-22. Soil Analysis and Soil and Plant Inter- 252. relations. 253. The Common Hawks and Owls of Cali- 254. fornia from the Standpoint of the Rancher. 255. Directions for the Tanning and Dress- ing of Furs. 256. The Apricot in California. Harvesting and Handling Apricots and Plums for Eastern Shipment. Harvesting and Handling Pears for Eastern Shipment. Harvesting and Handling Peaches for Eastern Shipment. Poultry Feeding. Central Wire Bracing for Fruit Trees. Vine Pruning Systems. Desirable Qualities of California Bar- ley for Export. Colonization and Rural Development. Some Common Errors in Vine Pruning and Their Remedies. Replacing Missing Vines. Measurement of Irrigation Water on the Farm. Recommendations Concerning the Com- mon Diseases and Parasites of Poultry in California. Supports for Vines. Vineyard Plans. The Use of Artificial Light to Increase Winter Egg Production. Leguminous Plants as Organic Fertil- izer in California Agriculture. The Control of Wild Morning Glory.