Transmission losses

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Most are aware that horsepower measured at the crankshaft will be greater than that measured at the rear wheel, but no one seems to have any idea exactly what the loss is, and whether the loss is greater with a primary chain than it is with a belt drive? To properly evaluate this, either a water brake, or an eddy current dynamometer is required, the loss cannot be calculated/guestimated from a rolling road test. I am particularly intrigued by this because most rear wheel horsepower would seem to be highly optimistic. Phil Irving was once asked this question obout the Vincent, and said that he had never measured it, but would estimate it to be in the region of 10%.
Of course the outcome could depend on what gearbox was used, some boxes being more efficient than others, and in the case of the Japanese multi cylinder machines, the all enclosed gear primary drive has to be taken into account, although these machines hardly lend them selves to having their power measured at the crank.

Has anyone ever taken the trouble to find out?
 
A decent rule of thumb for chain and gear losses would be about two percent for each pair of shafts transmitting power--two percent in the primary, two percent in the gearbox for the indirect gears, and two percent in the final drive chain.



Tim Kraakevik
kraakevik@voyager.net
'72 Combat, '74 RH10 850
 
Tim references imply you are in the right ball parks as regards the % of each drive line components drag but, that % is a sliding scale depending on the power fed it. 50 hp crank will lose more % of its crank power than a 100 hp engine, as the total drive drag is essentially a constant per rpm, so it'd be mo better to ask how much actual hp does the drive train drain no mater what is driving it, electro, hydro or Commando. Here's pretty recent pages and pages of this can of worms to catch up on before repeated beating of dead horse. Best estimates vary from 8 hp to almost 15. I guesstimate to split the difference as skewed toward 10-ish total hp drain expected.

crank-shaft-t14241-15.html
 
I did an oring chain conversion. I put the oring chain on right out of the box and lost AT LEAST 25% power. I then soaked and cleaned all the white crap off that it was shipped with and regained most oif the loss.
I have since reverted to the "standard" 530.
 
Thin oiled plain chain is about as friction free chain as it gets. Next is the X-ring chains which get almost as free as plain chain pretty quick. O-ring chain to me stands for Obsolete stiff as can be no matter what till about worn out. If ya dig deep into chain dynamics and lube function you find the lube is mainly to flush out inside generated grit and keep outside grit outside more than lowering friction or cooling function. Steve Maney states his 920 enginge peak at 7200/100.4 hp on his crank dyno and show 90-ish on rolling drum rwhp dyno.
 
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