Re: Drop Axle Guni project shelved


feel the light wrote:
Moves power through a pair of sprockets and chain at a friction loss of
x. The power loss alternates from pedal to pedal, as each takes it's
turn as the driven set. So power loss in the drive train would be x,
plus the friction of the sprocket set on the other side that is
coasting, y. x will be much greater then y, as it is a percentage of
the power needed to drive the whole vehicle, y is a percentage of the
power needed to rotate the pedal and unloaded chainset, a much smaller
value.
With the jackshaft design, the power on each stroke goes up to the
shaft with a power loss of x, and back down to the wheel through a
second driven set, at another loss of x. The coasting side pedal does
the same. So the friction loss of the jackshaft design will be 2x plus
2y.
We can ignore the minor friction loss of the jackshaft bearings, as
it should be the same as the loss from the pedal stub shaft bearings in
the other design.
With motorcycle roller chain, x would equal at least 6 % of the drive
power. Bike chains I don't know. Probably more like 2-3 %.
As far as what is the fastest design ?, that may come down to what
pedal placement is better for the rider. If having the pedal axis
below the wheel axle is OK, then that design has a slight power edge.
If it impairs the ride ability at all, that may suck.
Wouldn't it be great if the lower pedal setup improved stability !
Best case scenario , improved rider power and reduced drive line loss
.
Who knows ? One thing I remember from that bike chain friction
article, was that a tight chain had lower power loss. That is
fortunate, as the setup with the solidest feel is also the most
efficient.



Regarding your comparative analysis: 2 short chains on each design =
the exact same friction parameter. It matters not which side the
chains are located.

As far as tight chains go, however, that is the ONLY real-world issue
which you can discern while riding. There is a delicate balance in
chain tension necessary to eliminate crank slop, while not inducing
chain friction. Ask any giraffe mechanic.


--
unisk8r
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