5 
 
 340 
 
 195 
 
 MINISTRY OF MUNITIONS. 
 
 hnical Department Aircraft 
 Production. 
 
 IMJSC. 
 
 
 KlNGSWAY, W.C.2. 
 
 THE 
 
 9 REMY IGNITION SYSTEM 
 
 ON 
 
 AIRCRAFT ENGINES. 
 
 Instruction Book. 
 
 APRIL, 1918. 
 
 Confidential For the use of Members of the Air Force. 
 
 D.414/177',1. in ,
 
 Magneto Mounting Set (8-cylinder).
 
 TABLE OF CONTENTS. 
 
 Page 
 
 List of Illustrations 2 
 
 Electrical Principles ... ... .-- ... ... 3 
 
 The Remy System ... ... ... ... ... 4 
 
 General Description ... ... ... ... ... 6 
 
 The Battery 7 
 
 The Coil 10 
 
 The Combined Contact Breaker and Distributor.. 12 
 
 6 and 8-Cylinder Contact Breaker ... ... 14 
 
 12-Cylinder Contact Breaker 16 
 
 The Automatic Timing Control ... ... ... 17 
 
 The Condenser ... ... ... ... ... 20 
 
 The High-tension Distributor ... ... ... 21 
 
 Mounting and Driving ... ... ... ... ... 24 
 
 Timing to Engine... ... ... ... ... ... 27 
 
 Control Gear 30 
 
 Wiring System ... ... ... ... ... ... 31 
 
 Maintenance of Battery... ... ... ... ... 35 
 
 Maintenance of Remy Distributor ... ... ... 37 
 
 Sparking Plugs ... ... ... ... ... ... 33 
 
 Possible Troubles... ... ... ... ... ... 39
 
 ILLUSTEATIONS. 
 
 Magneto Mounting Set (8 Cylinder) ... ... Frontispiece. 
 
 Fig. Page. 
 
 1. The Battery Box 8 
 
 2. The Eeversing Switch 9 
 
 3. The Eeversing Switch (interior) ... ... ... 10 
 
 4. The Coil 11 
 
 5. Distributor Unit, 6-Cylinder ... ... ... 13 
 
 6. Distributor Bowl, 6-Cylinder .... 14 
 
 7. Distributor Bowl, 12-Cylinder 16 
 
 8. Automatic Timing Control, 12-Cylinder... ... 18 
 
 9. Alteration to Spindle, 12-Cylinder ... ... 19 
 
 10. Distributor Cap, 6-Cylinder ... ... ... 22 
 
 11. Distributor Cap, 12 Cylinder (interior) ... 23 
 
 12. Distributor Cap, 12-Cylinder (exterior) ... 23 
 
 13. Coupling (B.H.P. Type) 26 
 
 14. Shank Locking Screw 27 
 
 15. Cam-removing Spanner ... ... ... ... 28 
 
 16. Battery Terminal 32 
 
 17. Low-tension Cable Terminal 33 
 
 18. High-tension Cable Connection on 6-Cylinder 
 Distributor 34 
 
 19. Wiring Diagram for Single Set, 6 or 8-Cylinder 40 
 
 20. ,, ,, ,, Double ,, 6 or 8-Cylinder 41 
 
 21. Battery Box, Diagram of Connections 42
 
 ELECTEICAL PBINCIPLES. 
 
 The Kemy Ignition System differs from the usual mag- 
 neto system in that an external source of current supply is 
 essential to its operation. In both systems the fundamental 
 principles involved are identical, but in the Eemy system 
 their application is less direct. 
 
 In the case of a magneto of conventional type, the 
 armature revolves in the field of a permanent magnet, carries 
 primary and secondary windings, and serves as a combined 
 generator and induction coil. Low voltage current is 
 generated in the primary winding; high voltage current is 
 induced in the secondary winding, when the primary circuit 
 is broken by the opening of the contact breaker points. As 
 the secondary winding is in connection with the plugs, via 
 the distributor and leads, a spark passes each plug in order, 
 since the voltage immediately attains a very high value and 
 overcomes the resistance of the gap. The path of the mag- 
 netic flux, which threads the armature windings, changes 
 instantly when the primary circuit is broken, the change 
 of path enhancing the induced voltage in the doubly wound 
 armature. The magnetic field is distorted by the rotation 
 within it of windings carrying current, bait the natural path 
 of the magnetic flux is resumed when the current fails in the 
 primary winding. This change of path causes a very rapid 
 cutting of the multi-turn secondary winding by the lines of 
 force. 
 
 The high voltage induced in the secondary winding of 
 a magneto is due to several factors, including: 
 
 1. The proportional number of primary and secondary 
 turns wound on tha armature core. 
 
 2. The intensity of the magnetic field in which the 
 armature revolves. 
 
 3. The speed at which the armature is revolved. 
 
 4. The angular position of the armature in relation 
 to the magnetic field at the moment when the con- 
 tact breaker points open.
 
 o. The effective suddenness of the break, which is 
 chiefly a matter of the suitability of the condenser 
 to the particular conditions of the moment, as 
 regards speed, etc. 
 
 There is, however, a limit to the maximum voltage in- 
 duced in the secondary winding of a magneto. The voltage 
 rises until the resistance at the sparking plug gap (or safety 
 or testing gap, as the case may be) is overcome. As soon 
 as the pressure in the armature winding has risen sufficiently 
 to overcome this resistance, a discharge takes place over the 
 gap, and no further rise in voltage can occur. 
 
 THE EEMY SYSTEM. 
 
 In the Eemy system, the transformer coil windings are 
 not revolved in a magnetic field. No primary current is 
 generated, and the distorting influence of a winding revolving 
 in a field is not present. The primary current is supplied 
 by a battery, and flows intermittently through the primary 
 winding of a stationary coil; the intermittent flow is 
 governed by a contact breaker, the circuit being completed 
 and broken at regular intervals to suit the timing required 
 at the sparking plugs. The coil is wound with primary and 
 secondary windings over an iron core; when current flows 
 in the primary, the core becomes an electro-magnet, and 
 the windings are within a magnetic field. "When the 
 primary circuit is broken at the contact breaker, the mag- 
 netic field collapses; the lines of force cut the windings, and 
 a high voltage current is generated, exactly as with a mag- 
 neto. However, since the effective rapidity with which the 
 magnetic lines of force cut the windings is less, a greater 
 number of turns of wire are required. The induction coil 
 must be designed for these conditions, and is consequently 
 bulkier and heavier than a magneto armature. 
 
 A piece of iron, such as the core of a coil or armature, 
 can be magnetised by the flow of current in a coil surrounding 
 it. The intensity of the magnet so formed depends upon 
 two factors, viz., the magnetising force applied to it, and the 
 magnetic qualities of the iron itself. In the case of the 
 Eemy coil, or of a magneto armature, the iron used for the 
 cora is specially selected for the work it has to do. Care 
 is taken to use a grade of iron which magnetises very 
 readily, and loses its magnetism very quickly when the 
 magnetising force is removed. The magnetising force arises 
 from the flow of current in the primary winding, and is pro- 
 portionate to the number of ampere turns, i.e., the number 
 of turns of wire, multiplied by the current in amperes.
 
 The coil winding, however, possesses a property known 
 as " self-induction." The effect of this is to delay the 
 attainment of the full value of the current flow, when con- 
 tact is made in the primary circuit; or in other words, to 
 retard the magnetisation of the core. Moreover, the iron 
 core is not capable of instantaneous magnetisation' or demag- 
 netisation. Thus the magnetic condition of the core tends 
 to lag behind the flow of current in the winding. Again, 
 both the core and the winding lag behind the contact breaker 
 with regard to the instant of make and break; magnetisation 
 does not begin instantaneously whan the points close, nor 
 cease the instant they open. Thus the factor of time has to 
 to be considered in the operation of such devices. As the 
 speed of the engine rises, so will the rate of the mean flow 
 of the primary current tend to fall; the faster the engine 
 runs, the less is the time available for each electrical cycle. 
 It is possible to reach a speed at which the delay due to self- 
 induction prevents the current from attaining a sufficiently 
 high value to magnetise the core properly. In magnetos 
 this tendency is compensated by the proportionately in- 
 creased speed of the armature. The faster the armature is 
 rotated, the higher is the voltage generated in the windings; 
 so that the spark intensity of a good magneto is best at 
 high speeds. But with battery systems, like the Remy, 
 the primary voltage does not vary as the engine speed rises, 
 so there is nothing to counterbalance the lag due to self- 
 induction. Consequently all such systems have a limit of 
 speed, beyond which the engine will not run satisfactorily. 
 In practice, however, the limit of speed is not reached. 
 Provided the battery is in good condition, the Remy system 
 will produce a good spark on the fastest running engines in 
 service, and will give the same results at such speeds as a 
 magneto. Where a generator is fitted, there is a rise of 
 voltage with speed up to a point at which the automatic 
 control operates, but the range of variation is less than with 
 a magneto. 
 
 At very low speeds the Remy system is greatly superior 
 to a magneto, because it takes more current from the battery 
 than is generated in a magneto at the corresponding engine 
 speed; in fact, the current taken reaches a maximum when 
 the engine is stationary. As a result, the core of the coil is 
 thoroughly saturated with magnetism at very low engine 
 speeds; and the maximum field is available to cut the 
 windings when the break occurs. Thus, a secondary current 
 of high value is provided, and the low speed spark is intense.
 
 GENERAL DESCRIPTION. 
 
 The Remy system comprises three main units : the 
 battery, the coil, and the contact breaker and distributor, 
 with, of course, the necessary switches and wiring. 
 
 In certain installations some units, such as coils and 
 distributors, are duplicated, as when a pair of 6-cylinder 
 sets are fitted on a 12-cylinder engine; the batteries also 
 may be duplicated to obtain an increased measure of 
 reliability. 
 
 The Remy distributor is made up in a very great number 
 of models, a different series number or letter being allotted 
 for each detail alteration. Hence, the general design of 
 many models is similar, and in many cases the differences 
 are quite slight. The models used on British aircraft engines 
 are as tabulated. 
 
 Model. 
 
 No. of 
 
 Cyl'rs. 
 
 Type of 
 Engine. 
 
 Material of 
 Body. 
 
 Control. 
 
 Spindle End. 
 
 209.0 
 
 6 
 
 Vertical 
 
 Cast Iron 
 
 Manual 
 
 Tongue and Sleeve. 
 
 io8.K\ 
 
 
 
 
 
 ( Parallel ^ in. 
 
 io8.O) 
 
 6 
 
 
 
 
 < diam. by % in. 
 
 io8.R/ 
 
 
 
 
 
 ( long. 
 
 io8.P 
 
 8 
 
 90 Vee 
 
 
 
 
 
 do. 
 
 215.6 
 
 12 
 
 60 
 
 Aluminium 
 
 Automatic 
 
 \ Parallel ^ in. 
 
 215.0 
 
 12 
 
 
 
 Cast Iron 
 
 
 
 1 diam. by -|- in. 
 
 3 6 2 .A 
 
 12 
 
 V 
 
 Aluminium 
 
 Manual 
 
 1 long. (See note 
 
 215.0 
 
 12 
 
 50 
 
 
 
 Automatic 
 
 / below.) 
 
 
 8 
 
 9 
 
 
 
 Manual 
 
 Magneto-mountTng. 
 
 Models 209 and 108 use coil model 171A; some 108P 
 use coil 284B. Models 215 and 362 use coil 179A. Two 
 6-cylinder 108 or 209 distributors may be used on 12-cylinder 
 engines, the arrangement then being equivalent to two 
 6-cylinder verticals. A separate coil must be used for each 
 distributor. 
 
 NOTE: Large numbers of 12-cylinder distributors 
 are being modified before issue by removal of automatic 
 control; increase of manual control range to 18; 
 shortening of shank by \ in. ; and turning down and 
 screwing of spindle end. See sketch, Fig. 9, page 19. 
 
 6
 
 Engine Speed, R.P.M. 
 
 IOOO 
 
 1400 
 
 I 8OO 
 
 2200 
 
 Contact Breaker Gap. 
 
 .020" 
 
 .017" 
 
 .0 1 4" 
 
 .012" 
 
 Type of Remy Set. 
 
 Amps. Hrs. 
 
 Amps. Hrs. 
 
 Amps. Hrs. 
 
 Amps. Hrs. 
 
 I Set 6-Cylinder, I coil 
 2 , 6 2 
 
 I. 9 
 
 3-8 
 
 14 
 
 7 
 
 1.6 
 
 3-2 
 
 ! 7 
 
 I 
 
 1.4 I 9 
 
 2.8 9 
 
 1.2 
 
 2.4 
 
 22 
 I I 
 
 1 8 T 
 
 1 c ' > 
 I ,,12 I 
 
 i-3 
 
 1.8 
 
 21 
 15 
 
 1.2 
 1.9 
 
 22 
 H 
 
 i.i 24 
 1.8 15 
 
 I.O 
 
 1.8 
 
 *7 
 15 
 
 Table showing correct setting of contact breaker gap 
 for various engine speeds; also average current consumption, 
 and hours of running on a standard C.Z.3 6-volt battery. A 
 loss of 10% of nominal battery capacity has been allowed for. 
 
 THE BATTERY. 
 
 Current may be taken from one 6-volt battery of three 
 accumulator cells ; or from a pair of 6-volt batteries ; or from 
 a combination of these. The standard arrangement is to fit 
 one 6-volt Clifton type C.Z.3 battery of 30 ampere-hours 
 capacity on continuous discharge rating, this providing 
 current for the periods of running given in the Table. Obvi- 
 ously the periods stated can only be approximate, as much 
 depends upon the state of battery and the exact conditions 
 of operation. In this connection the imperative necessity 
 of maintaining batteries in the best possible condition must 
 be emphasised, and attention is drawn to the instructions 
 for charging and care of battery given on page 35. 
 
 The dimensions of the battery are 7 inches long, by 4J 
 inches wide, by 7 inches high over lugs for terminals, while 
 the weight with acid is 15^ Ibs. 
 
 The battery is fitted in an outer case of wood, and must 
 be thoroughly secured against movement in any direction 
 and under all conditions of trim of the aircraft. In earlier
 
 FIG. 1. 
 
 The Battery Box : the end is broken away to show fuses. 
 
 One of the external leads goes to coil, via pilot's switch, 
 
 the other to earth. 
 
 installations a simple type of box was fitted; the later type 
 of box has a false end ; a master switch and fuses are mounted 
 upon it ; and the act of fastening the lid secures the battery. 
 Where possible these boxes are to be permanently fixed in 
 position. The special battery box is illustrated in Fig. 1, 
 and measures 9| inches long, by 5 inches wide, by 7f inches 
 high ; the gross weight is 19 Ibs. 
 
 A rotary switch fitted on battery box is connected 
 through a pair of cartridge fuses to the battery terminals, 
 and to the external circuit by way of a pair of screw ter- 
 minals, fixed in the end of the box. This switch reverses 
 the direction of flow of the battery current on each occasion 
 of switching on, thereby avoiding much localised burning of 
 
 8
 
 contact breaker points. Diagonally opposite pairs of ter- 
 minals on the switch are connected to the fuses and to the 
 external circuit respectively; if adjacent pairs are connected 
 
 FIG. 2. 
 The Reversing Switch, with Key. 
 
 by mistake the result will be a short-circuited and probably 
 ruined battery. .The switch, shown in Figs. 2 and 3, has 
 an internal ratchet and pawl spring, so that rotation of the 
 handle or key is limited to the clockwise direction; the key 
 is removable when the switch is open or "off," and should 
 be removed and put in charge of a responsible person when- 
 ever the machine is out of use. 
 
 The cartridge fuses are provided a? protection to the 
 battery in the event of a " short " occuring, and should 
 blow at 15 amperes. In the event of a fuse blowing, a 
 similar one should be fitted, but if no replacement is at 
 hand a piece of 18 gauge tin fuse wire or 30 gauge copper 
 wire may be fitted as an emergency measure. 
 
 FIG. 3. 
 
 The Reversing Switch : Internal view with terminal 
 plate removed.
 
 THE COIL. 
 
 The small static transformer is known as the " coil," 
 that for a 6 or 8-cylinder set being shown in Fig. 4. The 
 coil used for 12-cylinder sets is similar^ but taller and with- 
 out lugs for fixing by the base. The coil, which is of the 
 non-trembler variety, is of simple construction, comprising 
 the usual primary and secondary windings over a soft iron 
 core. The ends of the primary are in connection with two 
 terminals set in a plate of insulating material forming the 
 head of the coil cas/ng, one terminal being marked " BATT" 
 and the other " TIMER," for connection to the battery and 
 contact breaker respectively. One end of the secondary 
 winding is connected to a terminal knob on the side of the 
 coil and thence to the distributor and plugs; the other end 
 is earthed by way of the base. When the coil is installed, 
 not less than one inch clearance should be allowed between 
 the high tension terminal and any part of the engine or 
 machine, so as to avoid all risk of sparks passing to earth. 
 
 As the resistance of the primary winding of the coil is 
 quite low (under one ohm.), in the event of the battery being 
 switched on with the engine standing and contact breaker 
 points closed, the current consumption and consequent 
 heating up of coil would be excessive and possibly dangerous 
 to the structure of the coil. Therefore, to keep the current 
 within reasonable limits under such conditions, a small 
 ballast resistance is fitted on the coil in series with the 
 
 FIG. 4. 
 The Coil : 6 and 8-cylinder type. 
 
 primary circuit. The resistance takes the form of a helix 
 of resistance wire carried on a grooved porcelain disc and 
 protected by a pressed steeel cap, the wire being selected 
 for its property of rapidly increasing in resistance as its 
 
 10
 
 temperature rises. In a 12-cylinder set, with circuit closed 
 and engine standing, the current is no less than 6 amperes 
 at the moment of switching on when coil is cold. In 10 
 seconds the current falls to 4 amperes, and in 20 seconds 
 to 3i amperes, with a further and gradual fall to 3 amperes 
 in about 5 minutes. As there is nothing beyond the heat- 
 ing of the coil to indicate the fact that current is flowing, 
 there is some risk of the battery being discharged if any 
 carelessness is displayed in connection with switching off. 
 It is highly necessary, therefore, to see that the ignition is 
 switched off when the engine is stopped for any cause, and 
 that the key of the special switch is removed to prevent the 
 current being switched on again by meddlesome persons. 
 
 As the core of the coil becomes an electro-magnet when 
 current flows in the windings, and the external field varies 
 with conditions of speed, contact breaker setting, etc., there 
 may be a certain amount of interference with the compass 
 if latter is too near the coil. In ordinary installations, how- 
 ever, there is not likely to be any appreciable compass error 
 if wiring be carried out in accordance with instructions. 
 
 Coils for 6 or 8-cylinder sets are to be fixed by suitable 
 bolts, studs, or screws through the lugs on the base, and 
 the base must be in good electrical connection with engine. 
 For choice, the coil should be fixed to the engine itself, but 
 where this is inconvenient it must be placed as near as pos- 
 sible to the distributor, and the base earthed by seating it 
 upon a strip of aluminium, copper, or brass, of which an 
 end is secured to the engine by a good bolt or other fastening. 
 This earthing strip should be permanently fixed in place, 
 so that there will be no risk of re-fitting the coil with its 
 base unearthed, should it be disconnected at any time. 
 Coils for 12-cylinder sets should be fixed by saddle clamps, 
 kept well clear of the high tension terminal, and the bases 
 earthed to the engine by a cable connection or bare metal 
 strip connected to the terminal provided. 
 COMBINED CONTACT BREAKER AND DIS- 
 TRIBUTOR. 
 
 The combined contact breaker and distributor unit 
 (Fig. 5), commonly spoken of as the " distributor," con- 
 sists of an iron or aluminium bowl-shaped casting containing 
 the contact breaker mechanism; with a cap, moulded in an 
 insulating material known as Bakelite, fitting the bowl as a 
 cover, and forming the distributor proper. The distributor 
 cap is secured by a pair of spring clips, and must be removed 
 to inspect or adjust the contact breaker, a dowel pin being 
 provided to ensure the cap being replaced in the correct 
 position. 
 
 11
 
 The distributor bowl, or body casting, has a shank 
 turned to | inch diameter for fitting into a suitable housing 
 on the engine camshaft casing or on the drive-gear box, and 
 is to be secured against turning by a setscrew, which must 
 at all times be w r ell fitted and locked. This shank is bored 
 (and, if of aluminium, lined with bronze bushes) for a steel 
 spindle carrying the driving pinion or coupling at its outer 
 end, and the cam or cams at its inner end. The spindle is 
 lubricated by grease, a screw-down grease cup being pro- 
 vided. Where the distributor is fitted to the end of the 
 camshaft housing, or in any other position where plenty of 
 oil is likely to work along the spindle, no grease need be 
 used ; it may even be necessary to drill a drain hole to pre- 
 vent excess of oil working along the spindle into distributor. 
 
 Fio. 5. 
 Distributor Unit. Six Cylinder Model. 
 
 12
 
 In the detail arrangement of the contact breaker and 
 cams, the 6 and 8-cylinder models differ from the 12-cylinder, 
 inasmuch as the former have one-piece spindles and single 
 cams; while the latter have two cams set upon a separate 
 piece of shaft which is mounted on the main spindle, and 
 may be driven through the medium of an automatic device 
 for controlling the timing. The arrangement of contact 
 breaker lever springs differs also, while the condenser is 
 mounted within the bowl of the 12-cylinder distributor only. 
 
 6 and 8-CYLINDER CONTACT BREAKERS. 
 
 In the case of the 6 and 8-cylinder contact breakers 
 (Fig. 6), the 6 or 8-faced cam is held upon the tapered 
 spindle end by a lock nut, no key being fitted, as fric- 
 tional grip upon the taper is sufficient for the very light drive. 
 Above the nut, the spindle is turned down to carry the dis- 
 tributor rotor, which is driven by a dowel pin set in the outer 
 face of cam, and by a spring clip registered by the same 
 dowel and clamped down under the lock nut. 
 
 FIG. 6. 
 
 The Distributor Bowl : 6-cylinder, showing Contact 
 Breaker. The Distributor Rotor is seen removed. 
 
 Within the distributor bowl is a circular base plate 
 carrying the contact breaker lever and contact points, and 
 capable of being rotated for timing through about 20 by a 
 control lever fixed thereto by a pair of studs and nuts. The 
 lever is, of course, outside the bowl, and two slots are formed 
 
 13
 
 in the back of the bowl to clear the lever studs, a stud on 
 opposite side, and a terminal for lead from coil to fixed con- 
 tact. The base plate carries an insulated bracket in which 
 the adjustable contact screw is fitted; a pivot on which the 
 contact breaker lever works; and a stud serving to carry a 
 spring, which retains the lever in position on its pivot. The 
 lever is a light steel pressing, with a fibre striker pad at 
 mid-length and a contact rivetted into the end remote from 
 the pivot; this contact, of course, meets the stationary 
 contact already mentioned. The contacts are of tung- 
 sten or, in certain models, platinum alloy. The 
 lever spring is of th'e helical variety, with one end anchored 
 to the base plate and the other pulled round 1 turns and 
 hooked to the lever : its function is to bring the contact 
 points together when the flats on the cam clear the striker 
 pad, thereby completing the battery circuit and permitting 
 current to flow through the primary winding of coil. The 
 noses of the cam lift the lever, and so break contact, at 
 regular intervals of 60 or 45 as the case may be; but the 
 angle of " make," during which the contacts are closed, is 
 greater than the angle of " break," and the Remy is known 
 as a " closed circuit system " for this reason. 
 
 As in the case of an ordinary magneto, the gap to which 
 the contacts are adjusted affects the timing somewhat; in 
 the Eemy system the gap, further, has considerable influ- 
 ence on current consumption. It will readily be seen that 
 reducing the gap increases the angle through which the 
 points are closed, and so allows current to flow for a longer 
 period (at any given engine speed), or vice versa. As the 
 current flow is intermittent, its average value, as read upon 
 an ammeter, depends largely upon time of " make," hence 
 a longer " make " increases the current reading. 
 
 It has been seen already (page 5) that there is a limit 
 of speed for efficient performance, and here it may be noted 
 that the limiting speed may be raised by reducing the con- 
 tact breaker gap ; a reduced gap is also good for high speeds, 
 because the "fling" of the lever is reduced and the striker 
 pad and contacts suffer less. For low-speed engines a gap 
 of '020 inch is satisfactory, but for higher speeds it is advis- 
 able to reduce this to '015 inch, or even to -010 inch in- 
 extreme cases and with 8-cylinders 
 
 12-CYLINDER CONTACT BREAKER. 
 
 The larger set (Fig. 7) is generally similar to that 
 already described; the essential difference is in the adoption 
 of double-decker cams and contact breaker levers, the latter 
 
 14
 
 and their springs being mounted on two common pivots. 
 The two adjustable and stationary contacts are carried on a 
 single insulated bracket fixed to the rotatable base plate as 
 
 FIG. 7. 
 
 The Distributor Bowl : 12-cylinder. Part of bowl has been 
 
 broken away to show the contact-breaker, and the distributor 
 
 rotor is shown lifted clear of spindle. 
 
 visual, the lower screw being distinctly awkward to adjust 
 without special cranked spanners. There is a second 
 insulated bracket fixed to the base plate that carries the 
 pivot on which the contact breaker levers are mounted, with 
 an upturned lug to which the lever springs are anchored. 
 The double springs are of the flat leaf type, but the outer 
 leaf of the two is cranked slightly so that it rubs on the inner 
 one only at the tip ; the free end of the inner leaf presses the 
 back of the fibre striker pad. As these springs do not carry 
 current, special bronze spring " brushes " are provided to 
 make contact between the bosses of the levers and the 
 bracket, but these do not affect the operation of the levers 
 in a mechanical sense. The levers are made of light steel 
 pressings, with metal bosses forming pivot bearings; the 
 fibre striker pads are fixed by two rivets. No means of 
 lubrication of the pivots is provided, as the trace of grease 
 put on during assembly is relied upon, and serves for some 
 time. The lever bosses are separated on the pivot by a thin 
 steel washer, a similar washer being fitted under the lower 
 lever; they are retained in place by a light flat spring leaf 
 mounted on the end of the bracket to which the main lever 
 and brush springs are fixed. A low tension lead is con- 
 
 15
 
 nected to each of the two insulated brackets, one lead being 
 in electrical connection with the other when either pair of 
 contacts are closed. 
 
 On the back or underside of the base plate there is a 
 pressed steel ball race housing fixed by three screws through 
 its flange, the cage of balls also being retained in position 
 by the same housing. The flange is turned on its edge to fit 
 within a shallow recess bored in the bottom of the distri- 
 butor bowl casting, thereby centralising the bearing with 
 the main spindle. The steel spindle, which runs in the 
 bearing formed by the shank of the bowl or the bushes 
 therein, is extended some distance above its bearing, and 
 carries a device of the "centrifugal governor" type for con- 
 trolling the timing, while above this again is a plain parallel 
 portion on which the "camshaft" fits. The camshaft is a 
 short steel sleeve having the inner ball race (corresponding 
 to the outer race which is fitted to the contact breaker base 
 plate) mounted at its lower end, with a pair of 6-nosed 
 cams, held down on a taper by a lock nut, above the ball 
 race, and a projecting upper end to carry the distributor 
 rotor. As the ball race should run true with the base plate 
 and contact breaker, and the sleeve fits the spindle end, it 
 follows that the upper end of the spindle will be effectually 
 steadied, and so the whole assembly runs true. This 
 arrangement should be run in the vertical position to obviate 
 irregularities in contact breaker action, with consequent 
 unevon firing; in fact the vertical position is to be recom- 
 mended for all types of Kemy distributor, for several reasons. 
 
 THE AUTOMATIC TIMING CONTROL. 
 
 Standard 12-cylinder Kemy distributors are fitted with 
 the automatic timing device, but some late models are being 
 supplied without this. The arrangement (shown in Fig. 8) 
 comprises a pair of composite steel and lead crescent-shaped 
 governor weights, with a system of links and damping 
 springs. On the upper side of the governor is a steel plate 
 with two lugs, and a central hole fitting the spindle. One 
 end of each of a pair of links is pinned to one of the lugs; 
 the other ends are under control of the governor weights. 
 Thus, as the weights move outwards, the plate is turned 
 about the spindle, and the relative angular positions of the 
 plate and the driving spindle are changed. The camshaft is 
 driven off this plate by a dowel peg at the lower end of the 
 camshaft, fitting into a notch in the plate : therefore any 
 change in the setting of the governor is reflected on the cams 
 
 16
 
 FIG. 8. 
 
 The Automatic Timing Control : 12-cylinder. 
 
 The end of camshaft, with ball race, is seen about to be 
 
 slipped on spindle end. 
 
 and distributor rotor, the effect being to advance the firing 
 point with increase of speed. The full advance so obtained 
 is 30 at 2,000 r.p.m. of crankshaft. 
 
 It has been found that the automatic control gear is of 
 no value on an aircraft engine : it is, therefore, in all cases 
 to be rendered permanently inoperative. The governor gear 
 is to be removed entirely, and the collar at upper end of 
 flat-sided sleeve turned down to just clean up the diameter 
 inside the two long crescent-shaped slots. A hole to clear a 
 ^ inch pin is to be drilled in face of sleeve, and a pin of good 
 inch steel wire (such as silver steel or spring wire) is to be 
 fitted in lower end of camshaft in place of the original small 
 driving peg. The details of this alteration are shown in Fig. 
 9, which also shows a modification to the driving end of 
 spindle, and the distributor shank, as arranged for use on the 
 Napier " Lion " engine. It will be seen that the distribu- 
 tor shank (by which the whole is mounted) is shortened by 
 inch while the A inch spindle is turned down to f inch 
 diameter and fitted with a No. 3 Woodruff key to take the 
 drive of the pinion. The hole in the end of the 
 sleeve need not be in any particular angular relation to the 
 spindle even if the driving pinion be already fixed to the 
 latter as the timing can be reset by moving the cams on 
 their seating. 
 
 As the range of manual control is limited to 10 when 
 an automatic advance is provided, it becomes necessary, on 
 doing away with the latter, to increase the range of manual 
 control by lengthening the slots in back of distributor bowl 
 
 17
 
 1 
 
 ' 
 
 8 
 
 S 
 
 18
 
 to allow extra travel to the lever. The slots need judicious 
 treatment, for it is essential that the lengthening process be 
 not carried to such excess that the distributor rotor blade 
 will be clear of the electrode pins at the moment of "break," 
 either at full advance or full retard position of control; 
 having regard also to the always present possibility of a pin 
 or two being bent. 
 
 The maximum range of manual control to be obtained 
 is 18, equal to 36 on the crankshaft, and in opening out 
 the slots, metal must be removed from both ends in such 
 proportions that the leading tip of rotor blade has just 
 reached the electrode pin at fully advanced firing position. 
 The trailing edge of the blade will then be just about to 
 leave the pin at fully retarded position, while there will be a 
 safe air gap at all times from the blade to those pins to 
 which it is not desired the spark shall pass. A certain 
 amount of extra retard may be given in extreme cases, up 
 to a total of 20 range; but 18 is to be looked upon as 
 standard, and will be found sufficient for practically all 
 engines. On no account is the length of, or the angle sub- 
 tended by, the rotor blade to be changed, and any range of 
 control beyond the standard 18 is to be given only upon the 
 authority of a responsible officer. 
 
 THE CONDENSER. 
 
 It has already been noted that the condenser has in- 
 fluence upon the voltage in the secondary winding of the 
 coil, and therefore upon the actual spark at the plug points; 
 but its primary function is to reduce the local burning of 
 contact breaker points, which would otherwise very quickly 
 render the whole system useless. The condenser in any 
 magneto or battery-coil system acts by way of an electrical 
 "shock absorber," or "buffer," on the opening of the con- 
 tact breaker points and consequent breaking of the primary 
 circuit, with the effect of preventing the formation of the arc 
 which tends to draw out between the contacts as they 
 separate. The current flowing in the primary circuit, in- 
 stead of persisting at the contacts in the form of a miniature 
 arc while the contacts are opening, spreads over the large 
 surfaces of the condenser in the form of a " charge " upon 
 the dielectric material between the plates of foil, the 
 condenser being connected in parallel with the contact 
 breaker points. 
 
 The condenser of the 12-cylinder set is exceptionally 
 bulky, and is enclosed by a sealed metal cass fixed to the 
 contact breaker baseplate within the distributor bowl. Two 
 
 10
 
 metal strips are soldered to insulated terminals in the side 
 of the casing, and are connected to the two brackets carrying 
 the contact breaker levers and stationary contacts. The 
 two terminals are, of course, in connection with the two sides 
 of the condenser within the casing. In the case of the 6 
 and 8-cylinder distributors, which have small bowls (as fewer 
 H.T. electrodes and terminals have to be arranged around 
 the cap) there is no room for the condenser, so it is made up 
 in a different form and enclosed in the coil casing. In 
 neither case can anything be seen of or done to the actual 
 condenser, and the only point to remember in connection 
 with it is that faulty joints in the connecting strips of the 
 12 cylinder set, or incomplete earthing of the coil base of 
 the 6 or 8 cylinder sets, may ba the cause of otherwise in- 
 explicable burning of contact points, and misfiring or total 
 stoppage of engine. 
 
 THE HIGH TENSION DISTRIBUTOR. 
 
 Except for the arrangements of cable connections, the 
 distributors for all types are similar, consisting of a cap 
 moulded in " Bakelite," or " Condensite," and carrying 
 a number of nickel alloy electrode pins set parallel to the 
 spindle and arranged symmetrically about its axis. These 
 pins are set into brass inserts moulded into the cap, and are 
 non-adjustable in the sense that they can be set only by 
 bending by hand. Therefore, when they are once prop3rly 
 set great care must be exercised to avoid bending them ; they 
 can be trued up only with some tro.uble, and the whole body 
 may have to be removed from engine for the purpose. The 
 high tension leads of the 6 and 8-cylinder sets are attached by 
 knurled brass ferrules (fig. 10); those of the 12-cylinder 
 
 FIG. 10. 
 
 Distributor Cap : 6-cylinder. 
 A cable terminal ferrule is seen in action. 
 
 20
 
 set are inserted through holes in the cap, and connected up 
 inside by small screws (figs. 11 and 12). In each case, the 
 lead from secondary winding of coil is connected to a carbon 
 contact, fitted in the centre of the cap, against which runs 
 a steel button on a spring blade fixed to the rotor. The 
 rotor (shown lifted clear of its normal position in figs. 6 and 
 7) is a small block of " Bakelite " having a nickel alloy 
 blade and the pick-up spring on its upper or outer face, and 
 a brass tongued strip in its lower face. The blade is fixed 
 by a single screw, and may be turned over when reversing 
 the direction of rotation of the distributor to suit various 
 drives, no further alteration being required beyond re-timing 
 of the cam or cams. (The automatic timing control can be 
 reversed only in the workshop; but, as already stated, this 
 is not used on aircraft engines). An arrow is stamped on the 
 
 FIG. 11. FIG. 12. 
 
 The Distributor Cap : 12- Distributor Cap : 12-cylinder. 
 cylinder. Showing Electrode The single lead is that from 
 Pins and Screws securing Terminal Stud on side of Coil, 
 Cables. and conducts the secondary 
 
 current to Rotor Arm. 
 
 outer and of rotor blade to show direction in which it is 
 intended to run; the other end of the blade projects beyond 
 the rotor block and forms one electrode of the safety spark 
 gap. The gap, set to about f inch (say 9 to 10 mm.), is 
 between the projecting tips of the rotor blade and the brass 
 strip on back of rotor; it serves as a " vent " for the current 
 should any abnormally high resistance be inserted in leads 
 from distributor to earth, as in the case of a lead dropping 
 from a plug and hanging in the air. It does not, however, 
 protect the coil in the event of a failure between the coil 
 
 21
 
 and distributor, or while the distributor rotor or cap itself is 
 out of place ; so the battery should not be switched on unless 
 the distributor is closed up, or a temporary f inch safety gap 
 rigged between coil-to-distributor lead or coil-terminal and 
 earth. 
 
 As the light rotor-driving pin is prone to break off on 
 some engines where vibration is considerable, all 6-cylinder 
 rotors are now being provided with a spring steel clip in 
 addition to the pin. The clip is registered by the pin, but 
 the real drive is taken by the frictional grip of the cam- 
 securing nut which is screwed down upon the clip. 
 
 MOUNTING AND DRIVING. 
 
 The actual driving spindle of the Remy contact breaker 
 and distributor runs at half the speed of the crankshaft on 
 all engines of the usual 4-stroke cycle type; so that, in 
 effect, the drive is at camshaft speed. The simplest scheme 
 is to mount the Remy unit upon some part of the camshaft 
 casing and arrange a plain form of dog coupling to the end 
 of the camshaft or the vertical drive shaft, if the latter runs 
 at half engine speed. Where such a simple drive cannot be 
 arranged, intermediate gearing must be used; such as a 
 bevel pinion or skew gear on the Remy spindle driven by a 
 corresponding gear of proper ratio, mounted on the engine 
 camshaft-drive-spindle, pump-shaft, or the like. 
 
 An alternative to the direct drive, lending itself ad- 
 mirably to the replacement of a magneto by a Ramy set, is 
 the " magneto mounting geared base " illustrated complete 
 in the frontispiece. This consists of an aluminium base 
 casting, carrying a pair of ball bearings in which runs a steel 
 spindle with the same taper as a standard magneto spindle. 
 This carries a small spiral gear meshing with a gear on the 
 spindle of the vertically mounted distributor. The distri- 
 butor is mounted by its turned $ inch diameter shank as 
 usual, and the coil is fixed by its base to a bracket provided 
 for the purpose. As the distributor spindle must run at 
 half crankshaft speed, the gear ratio must be selected 
 according to the type of magneto being replaced. The stan- 
 dard ratios are 2 to 1 for 8-cylinder sets replacing 8-cylinder 
 magnetos of the four sparks per revolution type; and 3 to 1, 
 for 6-cylinder sets replacing 6-cylinder magnetos of the two 
 sparks per revolution type. The base is arranged with four 
 holes (tapped f inch U.S. thread, 16 per inch, which may 
 need just clearing with a f inch Whitworth tap to take 
 British screws nicely) pitched 50 mm. The holes are in 
 
 22
 
 the same relation to the spindle, and the latter is the same 
 height from the base, as in a standard magneto mounting. 
 With this arrangement there is, of course, the very sound 
 objection that weight and extra gears are added; while the 
 fact that the drive is first geared up and then down again is 
 against it. The practical advantages, however, will out- 
 w.'i^h the disadvantages in most cases, and the fact remains 
 that the scheme is a very convenient one and needs abso- 
 lutely no alterations to the engine itself. 
 
 The best all-round position for mounting a Bemy distri- 
 butor is with the spindle vertical, and 12-cylinder sets, at 
 least, must be so mounted to avoid difficulties due to the 
 overhung length and weight of the body and rotating por- 
 tions. In most cases ths upright position renders the con- 
 tact breaker, etc., much more accessible than the horizontal; 
 but it may be found that an inclined position, say 30 from 
 the vertical, has great advantages on some engines and 
 machines. The mounting must be reasonably stiff, and in 
 this connection the effects of vibration must be kept in 
 mind, as excessiye vibration is apt to upset the regular 
 operation of the contact breaker and so cause misfiring at 
 certain speeds. Where the style of running of the engine is 
 known before fitting the Eemy system, an important point 
 to remember is that the contact breaker lever should lie 
 along the line of maximum vibration, and not move across 
 it. When fitting up an engine of which the vibration effects 
 are unknown, it is wise to be prepared for a slight modifica- 
 tion if necessary, should the running prove unsatisfactory 
 at first. In the case of a certain 6-cylinder engine, the Eemy 
 distributor unit is mounted horizontally upon the rear end 
 cover of camshaft casing, the centre line of the driving 
 spindle coinciding with the camshaft centre. As originally 
 fitted, the contact breaker lever hung vertically, and con- 
 sequently its movement was athwartships, in which position 
 the engine vibrations caused irregular firing at high speeds. 
 Turning the distributor body through 90 brought the lever 
 horizontal -and above the cam, so that the line of engina 
 vibration lay along the lever, instead of across it in the path 
 of its motion as originally; this slight change effectually 
 cured the misfiring trouble. 
 
 Owing to the small inertia of the rotating parts and the 
 absence of the magnetic pull present in a magneto, the drive 
 is smooth and easy, and couplings need not be so heavy as 
 for a magneto. For a direct drive a very satisfactory arrange- 
 ment is to form a plain tongue A inch by $ inch by A inch 
 
 23
 
 FIG. 13. 
 Coupling B.H.P. type. 
 
 long, on the end of the spindle, engaging a corresponding 
 slot in the- end of the driving shaft or coupling. The tongue 
 should be offset ^ inch from centre, so that it cannot be 
 replaced wrongly and so upset the timing by half a turn. 
 The detail of this type of coupling as applied to the B.H.P. 
 engine is shown in Fig. 13. 
 
 Where it is necessary to drive by a gear pinion, the end 
 of spindle is to be turned down to form a shoulder and allow 
 the boss of the pinion to act as a thrust collar, a fibre or 
 bronze washer being inserted between the shank of the distri- 
 butor and the pinion to take up excessive end play. The end 
 of the spindle is to be screwed & inch British Standard Fine 
 Thread, and provided with a nut and split pin to secure the 
 pinion, a feather key being fitted to take the drive. This 
 arrangement is shown in fig. 9 and should be adhered to 
 where possible. 
 
 The screw for locking the shank of the distributor in the 
 housing socket should have a cylindrical point as indicated 
 in fig. 14. The point is to enter a hole drilled in the shank 
 to receive it, care being taken that the screw is of such 
 length that the head will be well down on a spring washer 
 before the end bottoms in its hole, or the threaded part 
 reaches the distributor shank. The hole in the shank can 
 best be drilled, or at least started, in position, using a A" 
 drill guided in the tapped hole; it should be very slightly 
 countersunk to prevent burrs being raised, and not drilled in 
 so far as to touch the spindle. ' Should it be necessary at any 
 time to change the angular position of distributor, the old 
 locating hole should be plugged neatly, as by a screw, or white 
 metal, filed off flush. 
 
 FIG. 14, 
 
 Detail of Tip of Screw for locking Distributor Shank 
 in Housing. 
 
 24
 
 TIMING TO ENGINE. 
 
 It does not follow that both ignition systems on a given 
 engine should be set to give exactly synchronised firing, as 
 somewhat depends upon plug positions in relation to inlet 
 and exhaust valves; it is a common practice to allow two or 
 three degrees extra advance on the system firing the plugs 
 on the exhaust valve side of an engine. Determination of 
 the timing is, however, not a matter that need concern us 
 here, as this is usually settled by the engine builder and 
 indicated upon the " timing plate " on the crankcase or 
 elsewhere. It is, however, important that every cylinder 
 should be fired at the same advance on each system respec- 
 tively; where two 6-cylinder Eemy sets are fitted to a 12- 
 cylinder engine special attention must be given to this point. 
 An exact method of securing this is described later, as also 
 a method whereby the relative settings of the Remy and 
 magneto systems may be checked. 
 
 The timing of all types of Eemy contact breakers is 
 effected in a very simple manner by shifting the cam upon 
 the spindle; to facilitate loosening of the cams, the tool 
 shown in fig. 15 will be found useful. The cams in 6 and 8- 
 cylinder sets may be loosened with the spindle in place by 
 slacking the locknut a turn, and using the special tool to 
 prise up the cam off its seat. To shift 12-cylinder cams the 
 short cam-shaft must be removed, when the hexagonal end 
 below the ballrace can be held in a vice or with a spanner, 
 while the upper locknut is slackened. The cams (which are 
 in one 'piece) may then be wedged away from ths ball race; 
 or if not jammed too tightly they may be started off by 
 "thumping " the spindle end down on a block of lead or end- 
 grain wood, the cams, of course, being gripped in the fingers 
 meanwhile. In an engine works it would probably pay 
 to make a simple stirrup screw-extractor tool for this pur- 
 pose. 
 
 AW 
 
 rzs 
 
 FIG. 15. 
 Cam-removing Spanner. 
 
 25
 
 Tha cam having been loosened, the engine must be 
 turned in the forward or running direction until the piston 
 of No. 1 cylinder is in the full advance firing position as 
 indicated by makers' instructions or markings. (It is im- 
 portant to turn engine forward in bringing it to firing point, 
 as the backlash in the driving gears between the crankshaft 
 and Remy distributor may amount to several degrees, and 
 would introduce serious error were the shaft turned back- 
 ward). To ensure the piston being on compression stroke, 
 note that both valves are closed; if the axhaust valve be 
 open, the shaft must be moved through a complete revolu- 
 tion to come to firing point. It is necessary, of course, to 
 see that the contact breaker points are set to the desired 
 gap before the cam is loosened ; it is desirable to set the gap 
 to the opening indicated in table on page 7. The control 
 lever being set to full advance (that is, to the limit of its 
 travel in a direction contrary to that of the cam) the cam is 
 to be turned with the fingers in the running direction until 
 the contact points are just opening, with the rotor arm 
 pointing to the dowel peg in turned register edge of bowl. 
 As the rotor is driven by a pih in the earn, it follows that 
 the rotor and cam are always in same angular relation ; hence 
 there is no real need to trouble about timing tha rotor; the 
 only reason for setting it in this position is that it is con- 
 venient to know at a glance which is the terminal for the 
 cable to No. 1 plug. The cam may now be pressad home 
 on its taper spindle ; after removing the rotor gently to avoid 
 disturbing the cam, the locknut may be tightened up to 
 secure the drive. 
 
 The timing may now be checked electrically by the 
 aid of a small battery and lamp or bell, connected as 
 follows: One terminal of battery to lamp or bell; lamp or 
 bell to lead on Remy contact breaker baseplate; other ter- 
 minal of battery to earth on body of distributor or on engine. 
 Move engine a quarter turn or so backwards from firing 
 position, then turn slowly forward; the lamp will light up 
 or bell will ring until the exact point at which firing would 
 take place, whan the lamp will go out or bell stop on the 
 opening of the contact breaker. Should the setting be a 
 degree or so earlier than required, adjust the contact breaker 
 points very slightly closer and try again; should timing be 
 late, set the gap wider. But in no case should the setting 
 be more than a couple of thousandths ('002") different from 
 that given in the tabla. One thousandth of an inch adjust- 
 ment of the contact points corresponds to about of crank- 
 shaft movement. Twelve-cylinder sets should be checked- 
 in the same way. 
 
 26
 
 \Vhere two 6-cylinder Re my sets are used on one 
 12-cylinder engine, they should be timed independently 
 as above (working from the appropriate piston and 
 crank in each case) and then checked as a complete 
 tn. To effect this, connect the two contact breakers 
 in series by wiring up from battery to lamp, lamp to 
 contact breaker X<>. 1, and contact breaker No. 2 to 
 other pole of battery. Then, as the engine is turned 
 round, the lamp will alternately burn and go out, each 
 firing point through the series of 12 cylinders being 
 indicated by an extinction of the lamp. 
 
 Similarly, the timing of the Remy system may be 
 checked against the magneto by wiring up from battery to 
 lamp, lamp to Remy contact breaker, and earthing terminal 
 on magneto contact breaker cover to other pole of battery 
 Then, as the engine- is turned, the lamp will go out if Remy 
 is firing before or exactly with magneto; or will burn less 
 brightly for a few degrees during the angle through which 
 the magneto is in advance of the Remy system. If a bell 
 be used instead of lamp, there will be a change of note when 
 the lamp would go dim, due to the extra resistance of the 
 primary winding of the magneto being put into circuit when 
 the contact breaker opens. 
 
 Xote. In checking magneto timing electrically as 
 described above, a low voltage battery should be selected 
 (not more than two dry cells giving about 2| volts, or 
 one accumulator cell giving 2 volts) ; otherwise the 
 resistance of the magneto primary may not be sufficient 
 to effect a very noticeable change in the brightness of 
 lamp. A carbon filament lamp is better for this purpose 
 than the more efficient metallic filament type. 
 
 CONTROL GEAR. 
 
 As already stated, the range of timing control provided 
 is 20 for 6 and 8-cylinder Remy contact breakers, and 18 
 (increased from 10) for 12-cylinders. As the speed is 
 half that of the engine, the angular range on the crank- 
 shaft is twice these amounts, or 40 and 36 respectively. 
 No magneto provides such a wide range on the crankshaft, 
 a very usual range being about 20 some types of magneto? 
 afford much less. It is highly desirable that the timing of 
 both Remy and magneto systems be arranged to synchronise 
 (subject to any desired extra advance on one system as 
 mentioned on page 27) throughout the full range of magneto, 
 though this is not always easy to provide for. Where both 
 
 27
 
 are variable the two systems are to be coupled up to fhe one 
 control, lever in cockpit, as it is not advisable to fit indepen- 
 dent controls. 
 
 If synchronous timing be too difficult to provide for, 
 the control should carry both systems through their respec- 
 tive full ranges, but they will not then be in unison at any 
 but the full advance firing point, while the Eemy will have 
 something like double the retard of the magneto referred 
 to crankshaft angle, of course. As aeroplane engines are 
 practically always run at full advance, this is not a serious 
 defect, and the arrangement works well in practice; it may 
 not be quite so satisfactory on airship engines which may be 
 required to run for long periods at much below full speed and 
 power. In some cases, it is possible to lock the magneto 
 to full advance, fitting control gear to the Eemy system 
 alone, the job being greatly simplified thereby and much 
 work saved. As the engine may be started up on the Eemy 
 system very easily, there is no need to provide timing control 
 on the magneto with any reference to starting; and even 
 if a hand starter magneto be used on the main magneto, 
 the timing of the starting spark is independent of any con- 
 trol on the magneto, so that the retard on the latter is not 
 really needed. 
 
 Whatever scheme is adopted for the control, the 
 actual fittings must be carefully designed, and well made 
 and fitted; otherwise slackness and backlash will develop 
 quickly, upset the synchronisation of the timing, and cause 
 uneven running. Ball-and-socket joints should be used 
 where necessary to provide for possible want of alignment 
 as on the final link from parts carried by machine to parts 
 carried on engine, or to distributor itself. Screw adjustment 
 is required to allow of the two systems being brought to- 
 gether at full advance; and strong stops should be fitted to 
 limit the travel of hand lever, so that no undue stress can 
 be placed upon the connections or the control lever of the 
 distributor by a muscular pilot. 
 
 WISING SYSTEM. 
 
 The plan of wiring to be followed will vary somewhat 
 with the type of distributor and the engine to which it is 
 fitted ; but in any case certain precautions must be observed 
 if trouble is to be avoided. The most important point to note 
 is that all go and return leads must be run in pairs, close 
 together, so that the magnetic field due to current flowing in 
 the one will be neutralised by the field due to opposed flow 
 in the other. If this rule is not followed, there may be 
 serious interference with the compass, particularly if any 
 
 28
 
 leads run near it. On the other hand, a properly wired up 
 system will have no observable effect upon the compass, 
 although in the same machine there might be an error of two 
 points or more with an improper wiring plan. 
 
 As pilots have accustomed themselves to the use of 
 switches of the tumbler variety, it has been decided that the 
 " driving " switch must be of this type. Therefore, the 
 special Eemy reversing switch is used only as a master con- 
 trol, mounted on the battery box, though it may be arranged 
 for the use of the observer in dual control machines, the box 
 being so placed in such cases that the observer can reach the 
 switch readily. The tumbler switch is mounted adjacent 
 to the magneto switch, so that both can be operated to- 
 gether by a " wipe " of the hand; and, if desired, indepen- 
 dent switches may be used for each of the circuits in twin 
 set engines. 
 
 The cable used is the same as for the magneto system, 
 namely, rubber covered 7 to 7^ mm. diameter for high 
 tension, and 4| to 5 mm. for low tension leads. The 
 " pigtail " fitted to the contact breaker is a special material, 
 and if not long enough to reach the coil terminal marked 
 ' TIMEE " may be joined up to the 5 mm. by a soldered 
 and taped joint. Or the pigtail may be removed altogether 
 and a new and longer one fitted. All cable ends for battery, 
 coil, and earth connections must have soldered terminal 
 eyes or thimbles fitted. The connections to distributors are 
 made in a special manner, while the plug ends of H.T leads 
 are to be fitted with standard terminals as for the magneto 
 system. 
 
 Low Tension Cable 
 
 Solder. 
 
 FIG. 16 
 
 Battery Terminal in Section. Above, cable shown stripped 
 for fitting. 
 
 29
 
 The battery connections are made by lead coated brass 
 bolts, which pull into taper holes in the lugs on plates of end 
 cells, each bolt being drilled with a hole of two diameters 
 one to clear the insulation and one to clear the conductor 
 only. The insulation must be stripped back for about f to 
 inch, the wires cleaned and coated with Fluxite or other 
 non-corrosive soldering compound, and the small end of the 
 hole in the bolt similarly treated. The end of the cable is 
 pushed into the hole of the bolt until the conductor appears ; 
 the latter is then pulled through tightly by the pliers to 
 squeeze the rubber up into the larger portion of the hole ; the 
 wire, still firmly held, is soldered to the bolt, and finally any 
 excess length is cut off and the end trimmed up. Fig. 16 
 shows a terminal in section, with the cable in place and the 
 bolt pulled up into the lug. 
 
 Other low tension cable connections are bo be made with 
 terminals such as that shown in Fig. 17, the wire in every 
 case being well soldered to the thimble in addition to the 
 pinching of the metal. A special terminal thimble, having a 
 larger eye than standard, may be required for the earth con- 
 nection to the engine, for return of battery circuit, or for the 
 base of the 12-cylinder coil. 
 
 Soldfi 
 
 FIG. 17. 
 Low Tension Cable Terminal 
 
 The high tension connections are variously made. That 
 on the coil requires a rather objectional form of hook or fork 
 terminal, and is invariably to be secured in place by a binding 
 of small wire say about 22 gauge, or such as is used for 
 locking wire on cable strainers about the machine. The 
 12-cylinder Remy distributor is delivered with a set of leads 
 attached, and these should be carefully examined for possible 
 deterioration while in store : the rubber may show signs of 
 cracking if sharply bent. Should the leads need renewal 
 the method is obvious, but care must be taken that each 
 lead goes to its proper terminal screw within the distributor 
 cap. The lead from the coil goes to the side, and is secured 
 by a screw of which the head may be seen outside the cap. 
 
 30
 
 The leads are attached to the smaller distributors by 
 simple brass ferrules, which screw down on taper-ended 
 terminal studs and grip the end of conductor between the 
 stud and ferrule. A terminal is shown sectioned in the 
 sketch of the distributor cap (Fig. 10), and a made-up con- 
 nection in Fig. 18. To make these connections with abso- 
 lute security, bare the conductor of the cable for between 
 -& and J inch, remove the ferrule and insert the cable; see 
 that the conductor is through into the threaded hole, and 
 open out the strands with the tip of a small prick punch or 
 similar tool. Then, keeping the cable carefully pushed 
 home into the ferrule, screw the latter hard down on the stud 
 and pull it tight with pliers. 
 
 The group of H.T. leads should be taped together close 
 to distributor, and steadied by a saddle clip, so that their 
 weight does not hang on distributor. The brass ferrules 
 may be taped over to cable to prevent unscrewing and stiffen 
 the connection against vibration. 
 
 Distributor 
 
 Terminal 
 
 Cable. 
 
 FlG. 18. 
 
 High Tension Cable Connection on 6-cylinder Distributor. 
 Above, Cable stripped for fitting. 
 
 The ends of high tension cables attached to plugs are 
 to be fitted with any usual form of terminal thimble, and 
 the cables are to be supported and otherwise treated in the 
 same way as magneto cables. The usual numbered brass or 
 ebonite ferrules for marking leads are required, and must be 
 slipped on the cables before the end thimbles are fitted. 
 Should there be any doubt as to the number of a lead when 
 drawn through a conduit or otherwise hidden, the lamp and 
 battery may be used to test it. 
 
 31
 
 MAINTENANCE OF BATTEEY. 
 
 Two batteries are to be available for each engine 
 fitted with Remy ignition one for "ready-use" and 
 one on charge. No battery is to be used for more 
 than 10 hours' running on one charge, and in any case 
 a recharged battery is to be fitted for each day's flying. 
 Only by strict adherence to these rules, and by paying 
 particular attention to battery charging and main- 
 tenance, can reliability in flight be ensured. 
 
 NOTE. Where a dynamo-generator is fitted for 
 battery charging, and the installation is thereby ren- 
 dered self-contained, the order as to changing the bat- 
 tery daily does not apply. 
 
 Instructions for care of batteries are given on the label 
 attached to each, and these directions must be followed if 
 the best results are to be obtained and the battery kept in 
 good condition. New cells, which are received uncharged, 
 require special treatment, and upon this the future behaviour 
 of the battery greatly depends. 
 
 The acid used in accumulators is to be " brimstone " 
 sulphuric acid of best quality, and will be of approximately 
 1.84 specific gravity as received in carboy or jar. It must 
 be diluted with water to a specific gravity of 1.250, which 
 will be got by mixing about four parts of water to one of 
 acid. The density or specific gravity is taken by a hydro- 
 meter graduated for the purpose, and this is most conveni- 
 ently handled when used in a glass container having a rubber 
 suction bulb, so that a small quantity of liquid may be 
 withdrawn from any cell for test. When mixing acid and 
 water, an open mouthed stoneware jar should be used, and 
 the acid must always be poured into the water never vice 
 versa. On the mixing of acid and water considerable heat 
 is liberated, so that if water be poured into raw acid the 
 sudden generation of steam may splash the acid about most 
 dangerously. Water may be added to dilute acid, but not 
 to raw or strong acid. The specific gravity must be taken 
 finally when mixture has cooled down, and should be 1.250. 
 The acid is not to be put into cells until arrangements have 
 been made for them to be put on charge, and the first charge 
 should be continuous if possible, or for not less than 20 
 hours' non-stop. In any case, the first charge must be 
 continued for about 40 hours at 2 amperes until all plates 
 are gassing freely and the acid is milky with small gas 
 
 32
 
 bubbles, when the voltage should be about 7.8 while the 
 charging current is still on, dropping to about 6.2 volts in a 
 short time after charging is completed and the current 
 switched off. The vent plugs must be removed during 
 charging, and replaced tightly afterwards; the cells should 
 be wiped down dry and clean all over on coming off charge. 
 The screwed portions of the terminal bolts and the nuts may 
 be smeared with vaseline or lubricating grease to prevent 
 corrosion, but there is no object in greasing the lead lugs 
 and connections. 
 
 Before fitting a battery in a machine, even if it has just 
 come off charge, the voltage of each cell should be checked 
 by a small voltmeter reading to, say, 3 volts, in order that 
 any cell showing a low reading may be detected and taken 
 in hand at once. Should a cell show a low voltage, test the 
 acid, when the density may be found low. If correct, the 
 individual cell may need further charging, which can be 
 given by connecting the leads to the lead lugs between cells 
 instead of to the end lugs only. Should any cells show 
 signs of dirty white patches of "sulphate," special attention 
 must be given to the acid which they contain, and they 
 should undergo prolonged charging at half or less* than half 
 normal rate. 
 
 About once in two or three months of use the acid 
 should be emptied out and cells well washed out with clean 
 water, the battery having first been charged. They must be 
 drained well before being filled up with fresh acid, or the 
 latter will be further diluted and its gravity unduly reduced. 
 They they should be immediately put on charge and well 
 "topped up" again. Batteries not required for service for 
 a time should be given a freshening charge every two or 
 three weeks until gassing freely ; or if to be put out of service 
 for some considerable time, they may be charged, emptied, 
 washed out and drained before putting away for storage in 
 a dry and not too cold store. 
 
 As it is not possible to keep very accurate records of the 
 amount of current taken from these small batteries, the only 
 way to ensure their being kept in good condition is to charge 
 them frequently until they gas freely and are well up in 
 voltage. Then, if a freshly charged battery is fitted for eacn 
 day's flying, there should be no trouble through batteries 
 giving out prematurely. 
 
 MAINTENANCE OF EEMY DISTKIBUTOK. 
 
 This requires very little attention, but periodic thorough 
 inspection should be made and logged. 
 
 33
 
 Screw down the grease cup on the spindle bearing a 
 turn before each flight, but only if grease be necessary, as 
 on some engines plenty of oil works along from camshaft 
 casing. 
 
 See that all cable terminals are tight, and that the 
 cables are not chafing or perished, particularly at the plug 
 ends and on the battery. 
 
 Keep contact breaker points clean, absolutely free from 
 oil, trimmed up, and to correct gap (see Table on page 7). 
 If not too badly pitted they may be trimmed by drawing 
 between them a strip of fine emery cloth, a little extra 
 pressure being applied by the finger meanwhile. The cloth, 
 of course, must be reversed in order that both points may 
 be cleaned. If badly pitted, a dead smooth file may be 
 used, care being taken to get the surfaces flat, so that they 
 come together fairly. On no account should any contact 
 points be dressed up with a hammer, or they may be 
 loosened and drop off while running. 
 
 About once a week remove the contact breaker lever, 
 well clean the pivot bearing, fibre pad, etc., and apply a 
 couple of drops of oil to the pivot. . Wipe the cam clean, 
 and then apply the merest trace of greaseiness by a rag 
 smeared with vaseline or bearing grease. Occasionally wash 
 out behind the contact breaker base plate and give a drop 
 or two of oil to ease control. 
 
 Keep inside of the distributor clean, but do not attempt 
 to get the nickel electrode pins or rotor blade actually bright. 
 Avoid bending the pins, and maintain clearance from rotor 
 blade at | mm., or barely 1/32 inch. 
 
 SPARKING PLUGS. 
 
 It does not follow that the type of plugs found best for 
 use on the magneto ignition system of a given engine will be 
 the best for the Eemy system; and, in all cases, only com- 
 parative trials can determine which plug will be best. 
 Whenever possible the same type of plug should be adopted 
 for both ignitions, so as to minimise the number of spares 
 required. 
 
 Moreover, the plugs need not of necessity be set to the 
 same gaps for the Eemy as for the magneto system. The 
 Eemy system will fire over a wider gap than most magnetos. 
 The maximum gap to which plugs should be set depends 
 largely upon the type of engine as regards its compression 
 ratio, and the altitude to which the aircraft is likely to go. 
 
 34
 
 High compression engines in machines flying very high 
 require the smallest gaps, say .015 inch. For engines of 
 moderate compression in low flying machines the gap may 
 be increased to as much as .025 inch, but it is better not to 
 exceed .020 inch as a general thing, as the gap is liable to 
 increase when the plug heats up. Bad misfiring at high 
 altitudes will almost certainly be due to the use of too wide 
 a gap to the plugs. 
 
 Plugs should receive the same attention in the way of 
 cleaning and adjustment as those used for the magneto. It 
 may be noticed that the electrodes burn less rapidly, but this 
 need not give rise to any doubts in regard to the effectiveness 
 of the Eemy spark. 
 
 POSSIBLE TEOUBLES. 
 
 No Sparks. 
 
 Look for disconnected or broken lead; switches not oa 
 (all must be on together); possibly battery not in place at 
 all; contact breaker lever stuck with points open; points 
 very dirty; fuse blown; switch defective and not making 
 proper contact; coil resistance burnt out; coil base not 
 earthed. 
 
 No Spark on Certain Plugs. 
 
 Faulty high tension leads from distributor to plugs in 
 question ; electrode pins in distributor badly bent ; plugs 
 
 faulty. 
 
 Intermittent Firing. 
 
 Loose primary connections; battery running down; 
 dirty or sticky contact breaker; bad plugs; bad carburation; 
 leaky or sticky valves ; excessive amount of oil on plugs ; 
 chafed or partly broken lead. 
 
 Occasional Misfiring. 
 
 Usually due to dirty plugs; frequently bad carburation 
 or valves. Eun on both ignition systems and see if any 
 difference. If alike, trouble more probably due to mixture 
 or valves than to plugs. Battery running down. 
 
 Loss of Power. 
 
 May be due to several causes, but if no irregularity of 
 running observed merely loss of revolutions probably 
 through control gear being in need of attention and not 
 
 35
 
 giving proper full angle of advance. Cam may have slipped 
 on taper of spindle through lock nut slacking off, but this 
 most unusual. Key or fixing of driving gear may have 
 sheared or allowed slip to take place. When properly timed 
 at full advance the revolutions and power running on Bemy 
 ignition should be equal to results on magneto; but when 
 retarded, revolutions on Eemy may be lower, if not 
 synchronised with magneto throughout full range of control. 
 
 Sparking at Contact Breaker. 
 
 Oil on points; or points very uneven and not meeting 
 squarely, possibly due to wear on pivot bearing or defective 
 springs. If very bad and persistent, possibly through 
 defective condenser; loose condenser connection (12-cylinder 
 only); or base of coil not well earthed (6 and 8-cylinder 
 only). 
 
 36
 
 PILOTS 
 SWITCH 
 
 SWITCH 
 
 BATTERY 
 
 FIG. 19. 
 Wiring Diagram for Single Set, 6 or 8-cylinder. 
 
 The 12-cylinder wiring is similar, but the lead from battery 
 
 to " earth " goes to the second terminal on back of contact 
 
 breaker instead of direct to engine 
 
 37
 
 FIG. 20. 
 Wiring Diagram for Double Set, 6 or 8-cylinder. 
 
 38
 
 To Carlh 
 (picjine) 
 
 sversinq Su/itch 
 
 To Pilofe Su>ifch 
 and Coil 
 
 FIG. 21. 
 
 Diagrammatic view of interior of Battery Box, showing 
 arrangement of cable connections. 
 
 89