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at A-6 permits of attaching the starting motor securely to the frame side member at a point near the gear box, where it will be out of the way and not interfere with the accessibility of the power plant. When mounted in this manner the drive is by a double universally jointed shaft to a small silent chain sprocket,

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Fig. 360.-Diagram Showing Methods of Transmitting Power of Starting

Motor to Gasoline Engine at A. Simplified Diagram at B Depicts
Means of Interconnecting Starting Switch and Motor Starting Gear.

which connects to a much larger member attached to the engine flywheel or crankshaft.

Q. What is the most popular mechanical pinion shift for starting motors?

A. The complete system shown at Fig. 360-B, is the next most popular of all that have been used. This shows the application of the starting-motor, outlined at A-4. The mechanical interlock between the sliding pinion on the intermediate shaft and the starting switch is clearly shown. Before the pinion engagės the gear on the flywheel rim the switch makes contact, but owing to the resistance interposed in circuit the motor will turn slowly to permit of more ready engagement of the sliding pinion. As soon as the pinion is fully engaged with the large gear the resistance is cut out and the motor draws what current it needs from the storage battery, this being enough to produce the torque necessary to turn over the engine flywheel and the crankshaft to which it is attached at such speed as will produce prompt starting. system of this nature used on the Hupmobile in connection with the Bijur starter is shown at Fig. 361. In this the pinion is shifted by a spring connection as outlined at A instead of a direct rigid coupling. This makes it easier to engage the pinion as the switch can make contact as at D and the spring will draw the pinion in mesh. The spring is also useful under the conditions shown at B where the pinion engages readily but the switch has not yet made contact.

Q. What is an "overrunning" clutch and what is its purpose?

A. The construction of a typical overrunning clutch is clearly shown at Fig. 362. The electric starting motor is secured to a base on the crankcase of the gasoline engine and the motor power is imparted through the medium of the small gear F carried by the armature shaft. This drives géar E, which turns at a lower speed on account of being larger, and that in turn engages with gear D, which is still larger in diameter. The small pinion C, which turns much slower than the motor pinion F, meshes with the large gear B attached to the clutch body. The use of this gearing provides a reduction of 40 to 1, which means that gear F must make 40 revolutions to one of the clutch body.

The ratchet or driven member of the overrunning clutch L is pinned to the engine crankshaft and revolves with it when the motor is operating, rotating inside of the gear B, having a bearing at K and turning in the direction of the arrow. The member L has three flat surfaces, M, cut at an angle to the inside of the

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Fig. 361.-Showing How the Starting Switch and Shifting Pinion are Interconnected in the Bijur-Hup

mobile Starting System.

gear B. On each of these a hardened steel roller, A, is held inside of the gear by a light spring and against the flat surface of the member L. The roller travels with the clutch and runs free against the side of the gear B when the engine is in motion and when the starting gears are idle. As soon as the current is directed to the electric starting motor, the three rollers are bound between the

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Fig. 362.—Diagram Showing Construction of Typical Overrunning !

Clutch.

clutch body and the rachet member carrying them and the crankshaft is driven until such time as the engine speed increases sufficiently to overrun that of the member attached to the crankshaft.

Q. What is the "automatic” pinion shift?

A. This is what is now becoming the most popular method of connecting the starting motor to the engine. A pinion is provided with a spiral thread inside and fits a corresponding thread on the motor shaft. The angle of the thread is such that as the switch

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is depressed and the motor started, the rotation of the armature shaft screws the pinion in and meshes it with the flywheel gear. As soon as the gasoline engine starts, it automatically shifts the pinion out of engagement with the flywheel gear teeth.

Q. Wliat is the Delco starting, lighting and ignition system, and how does it operate?

A. One of the most popular systems is that shown at Fig. 364, which is a complete starting, lighting and ignition system using a single unit to perform the three functions. This is the Delco system and was the first really practical self-starting assembly to receive general application. It is of a single wire or ground type which means that one side of the storage battery is directly connected to the frame of the car, only one wire being carried to the various lamps and other current consuming units. The motor generator is a single unit type and includes the ignition distributor and timer, which is built in the front end of the housing. The operation of the motor generator will be more clearly understood if one views it first merely as an electric motor, suitably connected with the engine to turn the crankshaft and then by an ingenious shifting of the internal mechanism as a generator for charging the storage battery and to furnish current for the lights and ignition, at this time being so arranged that the generator is turned by the engine.

When used as a motor, it operates on the series wound principle and has a spur gear pinion upon the end of the armature shaft nearest the fly-wheel. Interposed between this pinion and the gear teeth cut in the face of the fly-wheel is a pair of gears adapted to slide along and revolve upon an intermediate shaft. This sliding action results in the larger of the gears engaging with the motor pinion, while the smaller one meshes with the gear teeth on the fly-wheel. A one way starting clutch is incorporated inside of this set of gears and is for the purpose of permitting the engine to run ahead of the motor during the short time that the gears are meshed after the engine fires and is running under its own power. The total gear ratio between the armature shaft and the engine shaft is approximately 20 to 1. This means that the

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