Building a Scania V8 R500 - Part 5. Drive

I`m building a Scania R500 - from a 1:24 scale kit produced by ITALERI.

I`ll be looking at aspects of truck construction as I go along, hopefully highlighting some basic truck technology.  It`s easy to think that modern vehicles bear no resemblance to those of the past, but that`s not true.  Suspension and steering; engine, transmission and final drive; and tyres are all there to maximise the laws of physics, and have retained the same configuration since diesel replaced steam.  Cost and natural performance limits have meant that the chassis abandoned long ago in car design is still used in truck manufacture.   Yes, your truck is computer controlled and a modern marvel;  but so is the modern cruise liner - which is still a Titanic underneath.

Building a Scania V8 R500 Part 5 - Driveline

All vehicles use diesel (DERV - diesel engine road vehicle) power.  Modern engines utilize extremely high, common rail fuel systems, where injectors are opened electronically - as opposed to the older, lower pressure systems that used fuel pressure created by the injection pump to open injectors.  Exhaust gas driven turbos, used to increase are mass in the combustion chambers, are common.

All gearboxes are conventional, synchronized, manual types but many have automated clutches.  Manual boxes are often 4-speed with additional input and out put ratios (range-change and splitters).

After the gearbox, the driveline comprises: universal (Hooke`s) joints; splined joints; differential; half-shafts:

Prop-shaft has a universal joint (UJ) at each end.  And a splined joint somewhere along its length

Looking at the UJ at the back of the gearbox.

The centre of the UJ, the centre cross.  The joint is based on this small component.  UJs are needed to allow for change in direction of the prop-shaft.  A UJ is not, however, a constant velocity joint. 

The prop-shaft angle will change as suspension deflects, so its effective length will change in addition to its angle.  A splined joint allows for this extension.

The `diff`is the housing that contains the final drive crown wheel and pinion gear as well as a differential.  Differentials are necessary because the rear, driven wheels will not always run at the same speed (when the vehicle is cornering). Bevel gears rotate in the spider attached to the crown wheel.  Half shafts are splined into the spider.  If one half-shaft slows compared to the other, torque is transferred to the other shaft, via the bevel gears.

Next  Part 6 - wheels and tyres