This evenings session on the Scania 143 was centered on building the rear suspension. The truck is what is termed as a 6 x 2 that is there are 6 wheels of which 2 are powered. In this particular case the last pair of wheels at the rear of the truck are unpowered and are located on what is termed as an air lift axle. By law trucks are limited in the maximum weight that they can be but there are also limits on the weight that individual axles can carry. Therefore most UK trucks which can weigh up to 44 tonnes gross have 6 axles spread over the tractor unit and trailer in order to be legal. However once partly or fully unloaded they don't need as many axles to legally carry the weight they have left. With 4 tyres on an axle costing in the region of £1000, if you can save wear on them you save money. Therefore over the years truck manufactures have developed what are termed as Air Lift Axles. These usually are usually air operated but can be manual and pistons lift the axle and tyres up off the road. The tyres don't wear saving money, there is reduced rolling resistance saving fuel and with fewer axles the truck is more maneuverable when making tight turns in restricted areas. All in all a win, win situation.
In building the model form of this set up you have to try to make sure everything lines up so that once the chassis is on its wheels they all sit level on the ground. Not as easy as it sounds but I have managed to assemble the suspension unit and attach that to the chassis and the powered rear axel is also now glued in place. The rear air lift axel is only partly glued in and I am hoping that will give me enough wiggle room should I need to move anything to get the wheels all sitting on the ground - it is literally held in suspension!
The next job is to get the front axle constructed and in place so that I can temporarily get the wheels on and see just how skillful I have been or more probably just how much bodging and brute force I will need to get the chassis level!
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