Talk:Shaft effect

May 2008

I have also heard (anecdotally) some riders complain about shaft drive when downshifting in a corner that they have gone into at too high a rate of speed. The shaft kicks in INSTANTLY, and often even causes a slight rear end skid (usually to the left). This is quite different than doing the same on a bike with chain drive, as the chain has enough slack, usually, that it takes a moment or so for the speed change to take effect, thereby eliminating the severe change in momentum. I, personally, might add that this effect is not particularly strong unless the rider is WAY too fast for the curve, in which case his bike handling skills and judgement are more of a problem than the engineering. I, personally, prefer shaft drive for the much greater reliability and total freedom from maintenance. All engineering has trade offs, and I consider shaft drive to be worth it. In any case, I have heard this also mentioned as a type of shaft effect, albeit one of secondary priority.Sagemenscircle (talk) 01:55, 5 May 2008 (UTC)

Question

Surely this happens with all motorbikes, regardless of the transmission system? It is how Wheelies are done. Biscuittin (talk) 10:03, 31 October 2009 (UTC)

Currently it is misleading because it doesn't clearly explain that an older style shaft drive will tend to lift the rear wheel, not the front, as when a bike does a wheelie. One source described it as the rear wheel "trying to climb up the bevel gear". I tagged it as needing a rewrite and diagrams.

I think something modeled on the drawings on pages 52-53 of Motorcycle Design and Technology would work best:

• Cocco, Gaetano (2004), Motorcycle Design and Technology, MotorBooks/MBI Publishing Company, pp. 52–53, ISBN 0760319901, 9780760319901 {{citation}}: Check |isbn= value: invalid character (help)
  --Dbratland (talk) 22:27, 31 October 2009 (UTC)

I'm guessing noone is watching as this page hasn't been updated in a while, but I've put up a couple images clarifying the physics involved. Under acceleration Newton's third law says trying to turn the wheel forward exerts a reactionary force against the drive mechanism. In the case of a belt, this makes the top part of the belt tighten and the whole bike "shrug" down just a bit. This is typically obscured because acceleration causes the rear wheel to "Tuck under." A shaft-drive, on the other hand has a rigid connection to the hub so this reactionary force turns the shaft backwards about the rear wheel and the middle of the bike "tightens" and lifts the rider up. Without the Paralever on modern bikes, this effect is like a kick in the pants (or so I've heard). Adam McCormick (talk) 05:10, 18 May 2011 (UTC)

Real world experience says you have mis-interpreted the dynamics of chain drives. Acceleration unloads the suspension (seat goes up) of a chain drive bike. And the torque in the wheel is the same no matter how it is applied or where - close to the hub or far away. The movement of the bike is related to how the swingarm and shock pivots are installed.Tigah Dude (talk) 03:42, 21 June 2016 (UTC)

Shaft Effect in Cars

Dont cars experience Shaft Effect? I might be wrong, but Shaft effect might be the harsh jerkiness of a transmission on a car with a lot of mileage. Anybody agree? Marc S. Dania Fl. 206.192.35.125 (talk) 14:19, 9 July 2012 (UTC)

Cars don't have a swingarm rear suspension. A modified car engine can have enough torque to damage the motor mounts, requiring reinforcement. Or at least rock or twist the car around the yaw axis. But it's related, but really a different thing. --Dennis Bratland (talk) 14:55, 9 July 2012 (UTC)