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Old June 14th 09, 06:24 PM posted to rec.autos.makers.honda
jim beam[_4_]
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Posts: 3,204
Default honda s600 chain final drive? but why?

z wrote:
> turns out the old Honda s600 little sporty cars had a differential and
> half shafts in the rear, but then little sealed chain drives from the
> end of the half shaft to the rear wheel on either side. ???? just to
> reduce unsprung weight?? only reason i can think of.


ok, since nobody else is telling you, i shall.

one of the key components to vehicle performance is weight. lack of it.
drive trains, because of torque requirements, are typically very
heavy. so, if you reduce the torque requirements, you can reduce some
of the weight of the transmission componentry. all you need then is to
have the torque output at the driving wheels, and you're set. [if you
notice, the chain drives are reduction gears, so rpm drops, and torque
increases. it's also worth noting that chains are more mechanically
efficient than gears.]

this approach is not unique. in heavy off-road vehicles for instance,
torque requirements can very high and variable, thus reliability comes
from using relatively low torque componentry through the main drive
line, then [planetary] hub reduction gears for final drive. planetary
hubs are not terribly efficient, but they are very robust. efficiency
is not #1 concern when you're axle deep in mud.

so, going back to the honda, since the vehicle already has a high
revving engine, there is no reason not to take advantage of this and use
a reduction gear at the end of the train, taking advantage of lighter
componentry up to that point. mechanically, it's not a bad system. why
is it not more commonly used? cost, complexity, low revving engines,
limited suspension options. and the highly conservative mind-set of the
typical mechanic.
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