英语翻译32.7 Springs serving also as torque and thrust membersTh

英语翻译32.7 Springs serving also as torque and thrust membersThis system,Fig.32.3,known as the Hotchkiss drive,is the most widely used.The springs A are rigidly bolted to the axle casing B.Their front ends are pivoted in brackets on the frame or vehicle structure,and their rear ends connected to the structure by means of either swinging links,or shackles C.or simply sliding in brackets as in Figs 35.7 and 37.18.Obviously torque reaction causes the springs to flex,or wind up,as shown exaggeratedly in Fig.32.4.Brake torque of course would flex them in the opposite direction.Since the front ends of the springs are anchored to the pins on the structure,they will transmit drive thrust and brake drag.The freedom of their rear ends to move fore and aft of course allows for variations in the curvature,or camber,of the spring with vertical deflection.Wind-up of the springs under brake or drive torque causes the axle to rotate through a small angle,causing its nose either to lift,as in Fig.32.4,or to drop.In the illustration,the spring wind-up has shifted the alignment ofthe final drive bevel pinion shaft from its normal attitude LO to LN,in which circumstances the propeller shaft would be subjected to severe bending loads were it not for the universal joints at O and M.When the axle moves upwards relative to the carriage unit,it must move in the arc of a circle whose centre is approximately the axis of the pivot pin at the front end of the spring.The propeller shaft,on the other hand,must move on the arc of a circle centred on its front universal joint.Because these two centres are not coincident,the distance between the front universal joint and the forward end of the bevel pinion shaft will vary as the propeller shaft swings up and down.This variation is accommodated by the incorporation of a sliding joint somewhere in the drive line between the gearbox output shaft and bevel pinion in the axle.Usually a sliding splined coupling is formed on a fork of one of the universal joints,but sometimes a universal joint of the pot type,as for example in Fig.26.12,is used.The example illustrated is the Birfleld Rzeppa constant-velocity joint,another would be the very neat and simple universal joint used on the inner ends of the swinging halfshafts of the 1955 Fiat 600 rear-engine car.In the latter instance a rubber joint at the outboard end of each shaft accommodated the cyclic variations in velocity.Rotation of the axle about a longitudinal axis,for example if one wheel only rises,is accommodated mainly by flexure of the springs,in a torsional sense,of rubber bushes,and by deflections of the shackles or within clearances in sliding end fittings.For cross-country vehicles,however,special forms of connection of the spring ends to the frame are sometimes used to isolate the springs from such twisting effects.Figs 37.13 to 37.15.