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Caterhams have two alternative rear suspension
systems: live axle, and DeDion axle. With a live axle, there are no
universal joints between the wheels, they are connected directly to the
differential. As the suspension moves, the differential moves
also. There is therefore a flexible connection between the
differential and the transmission. With a DeDion axle, the left and
right wheels are still connected by a rigid beam, but the differential is
mounted to the body, with twin universal joints each side. The
DeDion axle is the superior design, and the one I have tried to model.
The axle is located longitudinally by the
ball joint links running forward from the rigid beam. The lateral
location is by the link mounted to the centre of the rigid beam. The
friction peg that joins the rigid beam to this link can rotate, and also
move in a perfect vertical line. The spring units prevent the beam
from twisting. This setup has a very low friction,
probably the best of any Lego suspension I have seen.
The real vehicle uses driveshafts that can
extend/reduce in length as the suspension moves through its motion.
However, as the suspension travel is short, and there is a little extendibility
in the universal joints, it still works well.
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