Chapter XVII: Motors

RECONNAISSANCE CAR.

The reconnaissance car as supplied to regiments of 155-mm howitzers, motorized, consists of two units: Reconnaissance body, model 1918; 1-ton truck chassis, White, T E B-0.

Further information concerning these units will be found in Ordnance Handbooks “Reconnaissance Body, Model 1918;” “1-Ton Truck Chassis White, T E B-0” (No. 1972).

Weights and Dimensions.

Rated load capacity (body allowance plus
normal load) 1 ton—1,040 kg.
Body weight allowance 1,500 lb.—862 kg.
Chassis only 3,850 lb.—1,750 kg.
Oil, water and gasoline 190 lb.—86.5 kg.
Chains 69 lb.—31.5 kg.
Tool kit 37 lb.—16.8 kg.
Chassis weight on front tires (without
load) 54%.
Chassis weight on rear tires (without
load) 46%.
Gross weight (capacity load) 7,150 lb.—3,250 kg.
Load weight on front tires 0.78%.
Load weight on rear tires 99.22%.
Gross weight on front tires 27%.
Gross weight on rear tires 73%.
Overall length of chassis (without body) 205 in.—5,220-mm.
Overall width of chassis (at widest part) 61 in.—1,550-mm.
Chassis wheel base 140 in.—3,560-mm.
Permissible loading space back of driver’s
seat 97 in.—2,470-mm.
Width of frame (outside dimension, widest
part) 34 in.—865-mm.
Height of rear end of frame from ground
(empty) 33.75 in.—856-mm.
Diameter of turning circle (right) 60 ft.—18.3 meters
(left) 45 ft.—13.7 meters.
Tread of wheels 56 in.—1,422-mm.
Road clearance under front axle (lowest
point) 10.75 in.—273-mm.
Road clearance under rear axle (lowest
point) 10 in.—254-mm.
Length of reconnaissance body, overall 160 in.—4,072-mm.
Width of body 59.875 in.—1,522-mm.
Height of body, overall (including top) 62.125 in.—1,580-mm.
Weight of body (without equipment) 1,180 lbs.—536 kg.

Brief Description.

The reconnaissance car is provided with a special steel body, mounted on a 1-ton truck chassis, White Model T E B-0. Four seats are built into the body. The two front seats are placed back to back. The two rear seats have a space between them of about 2 feet and are also placed back to back. There is a compartment between the two pairs of seats. The floor boards at the back end are extended to form a foot rest for the rear seat. The car is protected by a canopy top and roll curtains. A full set of tools is carried on the car. Also five chests are provided in which are carried all the special equipment assigned to the car. One chest slides into the body compartment under the rear front seat, one into the compartment between the rear seats, and the other three under the rear seat.

The chassis used is similar to that used with the Staff Observation car on page 95. A complete description and directions for care, operation, and maintenance are contained in the “Handbook of the Reconnaissance Car, Model of 1918.” Ordnance pamphlet No. 1972.

ARTILLERY TRACTOR, 5-TON MODEL OF 1917.

Weights and Dimensions.

Overall length (armored) 133.5 in.—3,400-mm.
Overall width 63 in.—1,605-mm.
Height (armored, to top of muffler) 72.5 in.—1,845-mm.
Length of ground contact 91 in.—2,315-mm.
Ground clearance 11 in.—280-mm.
Weight (complete with full equipment) 9,200 lbs.—4,180 kg.
Ground pressure (9 and 11 inch
treads) 5.6-4.5 per sq. in.
—0.394-0.316 kg. per sqcm.
Weight of each track 545 lbs.—548 kg.
Weight of each track shoe (9-in.) 12 lbs.—5.45 kg.
Width of track shoes 9-11 in.—299-280-mm.
Tread of tracks (center to center of
tracks) 48.875 in.—1,243-mm.
Diameter of turning circle (overall
clearance) 176 in.—4,425-mm.
Engine, number of cylinders 4
Bore 4.75 in.—220.8-mm.
Stroke 6 in.—152.5-mm.
Horsepower at 1,200 revolutions
per-min 56.
Oil reservoir capacity 3.25 U. S. Gal—12.22 liters.
Road speed-gear used (per hour)
Low speed at 1,200 rev. per minute
of engine 1.94 miles—3.12 kilos.
Direct speed at 1,200 rev. per
minute of engine 3.92 miles—6.31 kilos.
High speed at 1,200 rev. per
minute of engine 7.37 miles—11.85 kilos.
Reverse speed at 1,200 rev. per
minute of engine 1.41 miles—2.27 kilos.
Capacity of main gasoline tanks
(two) combined 24 U. S. Gal.—90.5 liters.
Capacity of auxiliary tank under
armor 10 U. S. Gal.—37.85 liters.
Capacity of transmission case 3 U. S. Gal.—11.3 liters.
Capacity of track oiler tank 2.5 U. S. Gal.—9.43 liters.

Brief Description.

The 5-ton artillery tractor, Model 1917, is a self-propelled road vehicle of the “Track laying” type; that is, the power is transmitted to the ground through a flexible endless chain which acts as a track and is composed of steel links and shoes cast integral and connected by hardened steelpins. The advantage of this type of tractor as compared with the usual type of wheel tractor or truck, is its ability, due to very low unit ground pressure, to negotiate very soft and uneven surfaces, impassable to the usual type of self-propelled vehicle except under the most extreme difficulties.

The general design and construction of the 5-ton tractor does not differ materially from that of the modern truck except in the method of transmitting the power from the transmission unit to the ground. It is used solely as a power vehicle for hauling howitzers carriages and caissons. Each carriage and carriage limber are drawn by one tractor and each pair of caissons are drawn by one tractor.

A complete description and instructions for care, maintenance, and operation are contained in the “Handbook of 5-Ton Artillery Tractor, Model of 1917.” (No. 1996).

Outline Specifications.

=Engine.=—Four cylinder, four cycle, valve-in-the-head type. Bore 4.74”. Stroke, 6”. Cylinder case in pairs. Horsepower 56 at 1,200 revolutions per minute.

=Radiator.=—Honey-comb tubular type. Eight separate headers.

=Ignition.=—Eisemann, Model G-4, high tension magneto with automatic impulse starter.

=Carburetor.=—Model A Schebler carburetor with Stewart vacuum feed system; 1.5”.

=Governor.=—Centrifugal flyball type mounted on special shaft and driven off camshaft gear.

=Master Clutch.=—Dry plate multiple disk type.

=Transmission.=—Selective sliding gear type. Three speeds forward, one reverse. Direct drive on second. Stepped up on high.

=Drive.=—From transmission through bevel gears to steering clutch shaft through steering clutches to spur pinions, which mesh with intermediate spur gears, thence through outside gears, encased, to sprocket drive sleeve and drive sprockets.

=Steering Clutches.=—Two used of dry plate multiple disk type.

=Steering.=—By means of steering clutches operated from hand steering device and brake bands operated by foot pedals, which act on outside of steering clutch drums.

=Control.=—Steering gear located on the right hand side. Change gear, master clutch operating lever, and brake lever, left of steering gear, left to right respectively. Spark and throttle levers operate on sector clamped to steering column. Steering clutch pedals right and left at bottom of, and in front of steering column.

=Brakes.=—One set. External contracting type. Raybestos, or equal, lined. Operate on steering clutch housings.

=Gasoline Tank.=—Terneplate tanks. Two independent duplicate tanks each of 12 gallon capacity. Auxiliary terneplate tank under armor, 10-gallon capacity.

=Main Frame.=—Cast in one piece-open hearth steel.

=Roller Frames.=—Four frames steel channel, joined by oscillating shaft. Two frames right and left front. Two frames right and left rear.

=Truck Rollers.=—Six on each side of tractor, fitted with roller bearings, turned on steel gudgeons, flanked to follow track rail.

=Track.=—Made up of malleable iron track shoes with track links. Integral, fitted with space blocks, and 1.25” pins.

=Track Drive Sprockets.=—Two. Teeth mesh with opening in tracks.

=Blank Sprockets.=—Two. Fitted with roller bearings which turn on steel gudgeons. Used to adjust track tension.

=Track Supporting Rollers.=—Four on each side of tractor, two mounted on brackets attached to front roller frame channel, and two in the rear mounted on spring bracket which is bolted to main frame.

=Springs.=—Four double coil springs at rear, two on each side between rear roller frame and bracket on main frame and four—two on each side of equalizing bar at front.

=Equalizing Bar.=—Spring supported on front roller frame sections.

AMMUNITION TRUCK.

The ammunition truck supplied to regiments of 155-mm howitzers, model of 1918, motorized, consists of two units: Ammunition truck body, model of 1918; 2-ton truck chassis, Nash model 4017-A and 4017-L.

Further information concerning those units will be found in the Ordnance Handbooks. “Ammunition truck body, model of 1918” (No. 2002); “2-ton truck chassis, Nash model 4017-A and 4017-L.”

Weights and Dimensions.

Weight of body 1,200 pounds.
Overall length of body 120 inches.
Overall width of body 56 inches.
Overall height of body 54 inches.
Width of floor (inside) 43 inches.
Length of floor (inside) 114 inches.
Height of sides (inside) 36 inches.

Brief Description of Ammunition Truck Body.

The ammunition truck body, model of 1918, consists of a box-type steel body opening only at its rear end. The body is designed to accommodate original packing cases of any type of ammunition. When this vehicle is used near the front lines all four sides and its floor are lined with detachable heavy cocoa matting to prevent undue noise. A tarpaulin cover attaches to the body, and so protects its contents.

In addition to the designation of “ammunition truck,” as explained the ammunition body with various loads is designated when mounted on chassis models as follows: “Wireless,” “Telephone,” “Tanks,” “Personnel,” “Baggage,” and “Ration.”

The chassis and bodies for the above are identical for all purposes. The differences in chassis and body equipment and the load carried when the truck is used for different purposes are noted under tables of equipment on page 161. All of the above bodies are mounted on a 2-ton Nash truck chassis.

Outline Specifications of all 2-Ton Chassis, Nash Models

Rated load capacity 4,000 lb.—1,820 kg.
Body weight allowance 1,200 lb.—546 kg.
Weight of chassis only 6,700 lb.—3,030 kg.
Maximum gross weight (including
chassis, body and load) 11,900 lb.—5,420 kg.
Percentage of chassis weight on front tires
(without load) 66.66%
Percentage of chassis weight on rear tires
(without load) 33.33%
Percentage of load weight on front tires 30.00%
Percentage of load weight on rear tires 70.00%
Percentage of gross weight on front tires 45.00%
Percentage of gross weight on rear tires 55.00%
Overall length of chassis (without
body) 202.50 inches—5,100-mm.
Overall width of chassis (at widest
part) 78.50 inches—1,950-mm.
Chassis wheelbase 124.00 inches—3,155-mm.
Length of frame back of drivers seat 117.13 inches—2,980-mm.
Width of frame (outside dimensions) 38.13 inches—968-mm.
Height of rear end of frame from
ground loaded 35.50 inches—890-mm.
Height of rear end of frame from
ground unloaded 38.50 inches—980-mm.
Diameter of turning circle 50.00 feet—15.25 meters.
Tread of front wheels 60.50 inches—1,540-mm.
Tread of rear wheels 60.50 inches—1,540-mm.
Road clearance under front axle
(lowest point) 14.75 inches—374-mm.
Road clearance under rear axle
(lowest point) 14.75 inches—374-mm.

Brief Description, Models 4017-A, 4017-L, and 4017-F.

The chassis of all these models is of 124-inch wheel base and is fitted with a Buda model H-U four-cylinder engine, dry disk clutch, four speed transmission, and a drive to all four wheels through shafts and internal gearing. Although the greater number of units in all three chassis are alike, there are certain structural differences which exist, mainly in the model 4017-F chassis as against the other two. The 4017-F is a two wheel steer chassis, while the others have four wheel steering. All of them use four wheel drive and braking. The models 4017-A and 4017-L are fundamentally the same, differing only in certain details of equipment. Model 4017-L has an acetylene generator and searchlight, and oil side and tail lamps, both speedometer and odometer and an impulse starter on the magneto shaft, while the 4017-A has no impulse starter, uses a Bijur electric generator, storage battery and electric lamps, and is fitted with an odometer only. Aside from the two wheel steering and the necessary changes brought about by it, models 4017-F and 4017-L are practically the same, though a few slight differences exist in the dash, the brake cross shaft and rods and the wheel universals as described in detail in the Ordnance Handbook No. 1999.

The engine is a standard design L-head, Buda model H-U using force-feed lubrication, pump cooling, and fitted with a Stromberg carburetor feeding through cored passages in the cylinder block, and Eisemann magneto, and on the model 4017-A only, with a Bijur generator.

The clutch is of the dry plate type and the drive from it is through an open two-joint propeller shaft to a four speed sliding jaw-clutch type transmission. From the latter extend two-joint propeller shafts, one forward and one rearward, to internal gear-drive axles. The live member has exposed axle shafts extending from it, and the ends of these shafts are fitted with a universal joint and a spur pinion, the latter meshing with an internal gear bolted to a disk steel wheel. All the wheels are interchangeable and are all driving and steering wheels in models 4017-A and 4017-L, while in the model 4017-F only the front wheels steer.

A complete description of the 2-ton truck chassis, models 4017-A, 4017-L, and 4017-F, with instructions for care, maintenance, and operation, is given in the “Handbook of the 2-ton Chassis Nash Models 4017-A, 4017-L and 4017-F,” Ordnance Pamphlet No. 1999.

HOW TO DRIVE.

Before starting an engine the driver should see that the gear shift lever is in neutral position and that the emergency brakes are set. The spark lever should be set at the proper position. If battery ignition is used it is best to have the lever in full retard position, as the spark will occur no matter how slow the engine is cranked. If magneto ignition is used the lever should be advanced slightly as a hotter spark is obtained in the advanced position than in the retarded. There is less probability of a kick back when starting on magneto since it is necessary to turn the engine at a fairly high rate of speed, approximately 100 R. P. M. to generate sufficient current to produce a spark.

The position of the throttle hand control should be set so that the throttle will be slightly open. In case the carburetor is equipped with an air-choking device this should be closed to cause a rich mixture for starting.

The ignition switch should be turned on and the engine cranked by pulling up quickly on the crank handle a quarter turn at a time. If an electric cranking motor is provided depress the starting button and advance the spark. If magneto ignition is used it is best to spin the engine. Crank the engine with the left hand if possible and stand in such a position that if the engine should kick back the crank will not cause injury.

After the engine has started release the choke on the carburetor advance the spark and close the throttle to a position which will prevent racing. If a special dash adjustment is provided for regulating the mixture allow this to remain in a position to cause a rich mixture until the engine warms up.

To Start the Car.

Allow the engine to warm up sufficiently to overcome missing and to run smoothly. When satisfied that the engine is running properly release the emergency brake. In case the car is on a grade apply the foot brake to prevent the car from moving. Press the clutch pedal all the way down and move the gear shift lever to first speed position. The clutch should be allowed to engage gradually and at the same time the throttle should be opened sufficiently to prevent stalling, but not cause racing of the engine. If the foot brake has been employed it should be released as the clutch is engaged. After the clutch has been fully engaged the throttle should be opened sufficiently to accelerate the car to change to the next higher speed. The throttle should be controlled by the foot accelerator pedal. Once the car is in motion the driver must at all times keep his eyes on the road in the direction in which the car is moving or about to move when changing direction.

To Shift Gears (Increasing Speed).

Before starting a driver should practice moving the gear shift lever to the different positions and getting his feet and hands accustomed to the location of the foot pedals and hand levers. Then it will not be necessary to look away from the road in order to shift gears or in any other way to control the operation of the car. To change gears the clutch pedal should be depressed (it may not be necessary to push it all the way down against the floor boards) and the foot removed from the accelerator pedal at the same time. Move the gear shift lever from first to neutral position, pausing if necessary and then move to second speed position. Engage the clutch immediately and open the throttle with either hand or foot control as soon as the clutch is engaged. The process of changing from second to third or third to fourth is identical. Bear in mind that before each change is made the speed of the car should be accelerated. Care should be taken when changing from lower to a higher speed that the car is moving at a sufficient rate of speed so that an undue strain will not be put on the engine. Practice alone in driving the particular apparatus will acquaint the driver with the necessary speed required to change from one gear ratio to another.

To Shift Gears (Decreasing Speed).

When it is desired to change from a higher to a lower gear ratio release the clutch and allow the hand or foot throttle control to remain open far enough so that the engine will speed up. Move the gear shift lever to the neutral position and again engage the clutch for an instant. Release the clutch immediately and quickly move the gear shift lever from neutral to the next lower speed position and engage the clutch immediately, opening the throttle by hand or foot control.

Another method of shifting to a lower gear ratio is to leave the throttle open and release the clutch just enough to allow it to slip and the engine to speed up. The gear shift lever should then be moved through neutral directly to the next lower speed position and the clutch engaged. This method does not require as much practice but is objectionable since it wears or burns the clutch facing.

To Stop the Car.

To stop the car, the throttle should be closed, the clutch released, and the brakes applied, all being performed at the same time. The amount of pressure applied at the brake pedal depends upon the distance in which the driver desires to stop the car. Before allowing the clutch to engage after the car has stopped, move the gear shift lever to the neutral position. If the car is to stand apply the emergency brakes. If the engine is to be stopped speed it up by opening the throttle just before turning the ignition switch to the position “off.” If the weather is cold use the choke when stopping the engine or set dash adjustment to give a rich mixture. This will make starting easier if the engine is started in a reasonable length of time.

Driving Suggestions.

In operating a car it is always best to alternate the service and emergency brakes rather than to use one continuously, to equalize the wear on them. When approaching a very steep down grade it is safest to move the gear shift lever to a lower speed position, closing the throttle and permitting the car to drive the engine. When the grade is not excessively steep the engine can be used as a brake with the position of the gear shift lever remaining unchanged. This will save the brakes and tend to cool the engine. The brakes should never be applied suddenly enough to slide the driving wheels except in cases of emergency. When a stop is to be made apply the brakes soon enough so that the motion of the car will be gradually diminished and brought to a stop at the point desired.

To avoid accidents on the road all rules and regulations governing the driving of motor vehicles on the road should be observed. When turning corners or approaching cross-roads warning should be given to avoid collision with other vehicles which may be hidden from the view of the driver. Before backing the machine the driver should be sure that the road is clear. In manipulating the car the front wheels should never be turned by moving the steering wheel when the car is not in motion. This puts undue strain on the steering apparatus and will cause lost motion in the steering gear. If it becomes necessary to move the front wheels of a car while it is standing still, they should be moved by applying force not only to the steering wheel but also by pulling the front wheels around.

When a car skids, the tendency is for an inexperienced driver to apply the brakes and turn the front wheels in the opposite direction to that in which he is skidding. This should not be done as it only accentuates the skidding and the car may be ditched or skid into another vehicle or the curbing. When the machine starts to skid turn the steering wheel in the direction in which the car is skidding and partially close the throttle but not entirely, or it will have the same effect as applying the brakes. When the car straightens out the power may again be applied gradually, and the machine brought back to the center of the road. When skidding on narrow roads it is best to apply the power and steer to the center of the road. This will aggravate the skid for a moment but brings the machine around at an angle with the front wheels in the center of the road. The momentum of the car will cause the rear wheels to climb back onto the road again.

ENGINE TROUBLES.

If the machine will not start the trouble, can only be located by a systematic search. It is always best to look over the ignition system first, then see if there is any gasoline in the carburetor. It will often take some time to find the trouble. However, if the engine once starts there is little difficulty in locating the trouble as there will always be an indication which should point to the source of trouble. The great difficulty with inexperienced drivers is that they do not reason out the matter carefully before attempting to remedy it. Also an inexperienced man usually looks for trouble in the same place no matter what the indication may be. Nearly all difficulties arise from one of three sources, ignition, carburetion, or engine. These are outlined in the following table. The trouble is located by the trouble it gives the driver.

=I. Engine misses=:

A. Ignition.

1. Plugs.

a. Short circuit. b. Broken porcelain. c. Too large a gap.

2. Cable.

a. Broken. b. Grounded.

3. Instrument.

a. Dirty carburetor. b. Interrupter points on magneto.

B. Carburetor.

1. Water in carburetor. 2. Dirt in the line. 3. No pressure or no
gas.

4. Too lean a mixture.

C. Engine.

1. Cold.

2. Valves sticking.

=II. Back Fires Through Carburetor:=

A. Ignition

1. Wired wrong.

2. Timed wrong.

B. Carburetor.

1. Water in carburetor.

2. Dirt in line.

3. No pressure or no gas.

4. Too lean a mixture.

C. Engine.

1. Valve sticking (Inlet).

=III. Engine Knocks:=

A. Ignition.

1. Retarded spark. Spark too far advanced.

B. Engine.

1. Carbonized cylinders (pre-ignition).

2. Overheated engine.

3. Loose bearings.

4. Loose pistons.

=IV. Engine Lacks Power:=

A. Ignition.

1. Retarded spark.

B. Carburetor.

1. Too rich a mixture.

C. Engine.

1. Exhaust valve not seating.

2. Carbon in cylinder.

3. Overheated engine.

4. Lack of lubrication.

5. Governor connections sticking.

D. Brakes.

1. Dragging.

E. Clutch.

1. Slipping.

=V. Engine Overheats.=

A. Ignition.

1. Retarded spark.

B. Carburetor.

1. Rich mixture.

C. Engine.

1. Cooling system.

a. Fan belt off.

b. No water.

c. No circulation.

d. Anti-freezing mixture.

2. Carbonized cylinder.

3. Lack of lubrication.

=VI. Engine Stops:=

A. Engine and car stop gradually.

1. Trouble with fuel.

B. Engine and car stop suddenly.

1. Mechanical trouble.

C. Engine stops suddenly, car gradually.

1. Trouble with ignition.

=VII. Engine Won’t Stop:=

A. Ignition.

1. Cable.

2. Switch.

B. Pre-ignition.

1. Carbon in cylinders.

2. Overheated engine.

Consider how each of these indications may differ so that it is possible to locate the exact source of trouble without first investigating. If the car has been on the road for some time and the engine misses it will either miss regularly in one or more cylinders or irregularly in all cylinders. If the former, the miss is due to ignition. The cylinder in which the miss is occurring can be easily determined by short circuiting each plug with a screw driver. This is done by allowing the screw driver to touch the central electrode of the plug and also the engine. When a plug is short circuited and it does not affect the operation of the engine, it shows there was no spark jumping across the electrodes of the plug. If the cable to this plug is disconnected and held a short distance from the electrode of the plug from which it was removed, a spark will or will not jump this gap. If it does jump the gap it shows that the plug is short circuited. Then the plug is either carbonized or the insulator is broken. If a spark does not occur place the cable near the engine and if a spark occurs it shows that the gap was too large at the electrodes of the plug. If no spark occurs it shows that the trouble is not in the plug but at some point ahead of this. If the engine is firing on all but one cylinder the trouble must be some place between the distributor rotor and the plug. First see if the distributor is dirty and then check up the cable to see if it is broken or grounded. One point to be remembered is that the parts of the magneto or the battery ignition system incorporated in the instruments will affect the operation on all the cylinders and there is no need of looking for the trouble there if only one cylinder misses. If every other cylinder to fire misses and magneto ignition is used, it is often due to the time lever housing being jammed over to one side so that the interrupter points are opened only by one cam. In no case is it necessary to file the interrupter points to overcome a miss, for the interrupter affects the operation on every cylinder and not on one.

If the miss is irregular it is due to carburetor or to fuel trouble. To locate the trouble open the pet cock at the bottom of the carburetor and if there is any water in the carburetor it will run out. This operation also shows whether or not the gas runs freely. If it does not there may be dirt in the line or no gasoline supply. After everything else has been tried to overcome the trouble, adjust the carburetor to compensate for too lean a mixture.

When an engine is first started it will often miss. This is due to the engine being cold. Under no circumstances should time be wasted to overcome missing until the engine is warm. If an exhaust valve sticks it will cause the engine to miss as the gases will be forced out on the compression stroke. This is difficult to locate as it is a regular miss but usually results from an overheated engine.

If an engine backfires when first started and does so continuously it is best to check up on the wiring and timing of the ignition system. If the engine is running smoothly and suddenly starts to backfire through the carburetor it is possible that the magneto coupling has slipped.

If there is water in the carburetor it may suddenly shut off the supply of gasoline and cause so lean a mixture that backfiring results. Dirt in the line or running out of gasoline would have the same effect. If backfiring in the carburetor is experienced in addition to the missing of the engine it is probably due to too lean a mixture. Backfiring also results from the inlet valve sticking or not seating properly.

If the engine suddenly develops a knock while in operation it may be due to the ignition being too far advanced for the condition for which the car is operating and the spark lever should be retarded. This will be noticed mostly when the car is under a hard pull such as on hard hills or going through sandy roads. If the engine develops a knock, after having been run for a short while, which can not be overcome by retarding the spark it may be due to carbon in the cylinders or an overheated engine, both of which would cause pre-ignition of the charge. By pre-ignition is meant that the incoming charge when under compression is ignited due to the heat in the cylinder regardless of when the ignition spark takes place. Loose bearings and loose pistons will knock but these should be easily distinguished from ignition knocks as they are present at all times.

If the engine shows a lack of power it may be that the ignition system is too far retarded due to the coupling driving of the magneto having slipped. If too rich a mixture is used it will cause a loss of power but can easily be distinguished by the black smoke which is given off at the exhaust pipe. Every precaution should be taken to locate the trouble when an engine shows a lack of power as it may be caused from the valve not seating properly, carbon in the cylinders, overheated engine, lack of lubrication, or the governor connection sticking. If lack of lubrication is causing the trouble it will soon lead to mechanical trouble such as scoring the cylinder walls or burning out the bearings. An engine will often give an apparent indication of a lack of power due to the brakes dragging or the clutch slipping.

If an engine overheats it is best to check up and see whether or not the car is being operated on a retarded spark or if the mixture is too rich. The usual trouble of the engine overheating are troubles experienced with the cooling system. Fan belts often break or slip, the water may have leaked out somewhere in the cooling system, or the circulation may be stopped up in some way. If anti-freezing mixtures are allowed to remain in the cooling system in warm weather they will cause overheating of the engine due to their low conductivity of heat. Carbon in the cylinder causes the cylinder to overheat and is detrimental to its operation. If the engine is not lubricated properly it will overheat due to the additional friction of the parts.

If after the car is in operation the car and engine slow down gradually the trouble is without doubt due to lack of fuel or some trouble with the fuel system or the carburetor. When the car stops under these conditions the engine usually backfires into the carburetor just before the car stops.

If the car and the engine stop suddenly it is an indication of some mechanical trouble such as a frozen bearing, broken connecting rod, or some other part which suddenly puts a brake on the movement of the car.

If the engine suddenly stops operating and the car continues to coast the trouble can be traced to the ignition system. A disconnected or a broken wire usually causes the trouble.

If the engine will not stop when the ignition switch is thrown to the “off” position it is possible with magneto ignition that the cable between the switch and the magneto is broken or disconnected. That is, the switch does not connect the primary of the magneto to the ground. If the engine is overheated, due to lack of proper cooling or carbon in the cylinders, the engine will continue to operate due to the pre-ignition.