chapter  1
118 Pages

Driveline Systems and Vehicle Performance

The first motorized wheeled carriage capable of moving under its own power was a steamdriven vehicle designed by a French army engineer, N. J. Cugnot (Figure 1.1). This vehicle was constructed in 1769. With all its shortcomings, the steam-driven vehicle-Cugnot’s chariot-had a rational

design. It had the most simple driveline system combined with a most simple steering mechanism. All this stemmed from the fact that the force cylinder was most successfully located above the forward drive and, simultaneously, the steering wheel. The vehicle’s weak spot consisted of its using a ratchet and pawl transmission mechanism that made it impossible for the vehicle to move uniformly. In addition, because of its imperfect steam engine, Cugnot’s chariot stopped every 10 m to allow steam to accumulate in the boiler and to rise to the required level. In 1801, an enterprising English inventor, Richard Trevithick, constructed the first steam-

driven passenger stagecoach and organized, for the first time in history, mass construction of such coaches in the insular part of Great Britain. The rear driving axle of the coach with wheels rigidly fastened to it was driven by a pair of gears from an intermediate transmission shaft. The design of the wheels, taken from horse-driven carriages and their rigid coupling with the driving axle, was the weak link of the first such coaches. The driving wheels, with their smooth and narrow rim, had poor traction with the road and frequently skidded. This was remedied by equipping the driving wheels with an additional device, consisting of a set of pushers and detents-‘‘claws’’. Figure 1.2 presents another vehicle of a similar design of the claws. Performing reciprocating motion were a pair of claws hinged on rods that became alternately coupled with the road surface and assisted in rotating the driving wheels of the carriage without perceptible skidding. Subsequently, in 1813, somebody by the name of Brunton invented pushers and used

them as the principal and sole propulsion device on the primitive locomotive constructed by him (Figure 1.3a). Without exception, all the wheels in Brunton’s locomotive were driven (no torque applied), and functioned as a support structure. It should be noted that at that time few believed in the traction ability of carriage wheels. Even such an experienced mechanic as Trevithick did not fully trust wheels with smooth rims. In particular, he did not trust the wheels of the locomotive that were supposed to roll on smooth rails. For this reason, he placed forged nails on the rims past the flanges of the driving wheels of his two first locomotives constructed in 1803 (Figure 1.3b). The nails

stuck into wooden beams placed along the rails, thus significantly improving the coupling between the wheels and the additional support surface and, hence, improved their traction. One of the nonrail carriages constructed with a drive similar to that of Brunton’s

locomotive was the carriage of D. Gordon. It was constructed in 1824, and consisted of a three-wheeled machine-a steam-driven stagecoach (Figure 1.4). All the wheels in this stagecoach were supporting driven wheels, whereas the propulsion was provided by a ‘‘pusher-leg’’ system with a complicated lever-type drive. In this manner, by placing additional devices in the form of ‘‘pushers’’ and ‘‘claws,’’ the designers of steam-driven carriages gradually and surely approached the invention of a wheel with a tread. It is

of Ground

precisely such a wheel that, in the majority of cases, is capable of ensuring reliable traction between itself and the road surface. In 1805, an American mechanic, Oliver Evans, constructed a suction dredge for cleaning

up the Philadelphia harbor waterfront. According to the inventor, the dredge was supposed to deliver itself to its place of work. For this purpose, Evans equipped it, together with an aft propulsion screw, which served for floating, five wheels (Figure 1.5) that would allow it to move on land. The leading wheel together with the wheels of the front turning axle allowed the dredge to take turns, whereas the wheels of the rear driving axle provided the traction. The rear driving axle of the dredge was driven by a steam engine by means of a belt drive. The Orukter Amphibolas (which was the name of the dredge) was the first motorized amphibious vehicle.