hey guys… ive been wondering this for a long time ever since i was a little kid… but i never knew who to ask. since there are approximately 2 billion people on this website i figured maybe someone would know…
so… when you were little and you saw on mr. wizard the bicycle tire demonstration when it was spun to a high rate of speed and then of course its hard to turn it…
so, assuming a RWD automatic car… you have that effect which is probably VERY pronounced, as everything spins at a high rate of speed and is usually very heavy:
four wheels and the brake assemblies, and the two axles in the rear
the crankshaft of the engine and the torque converter
the driveshaft
say youre crusing along at 70mph, 2500rpm, with a 4 speed transmission with the overdrive ratio being .67, with the converter locked up.
the crank and the torque converter are spinning 2500rpm
the transmission and the driveshaft is spinning 1675rpm
if the rear end gears are 3.42:1, then the axles, the front and back wheels, and the brakes are all spinning nearly 490rpm, right?
take into account all the weights and it seems like anything other than going in a straight line would be a gyroscopic nightmare… can anyone tell me how handling is affected? im sure in CART and IRL these effects are even more of a factor with over 10,000rpm engine speeds etc etc…
anyone have any clue?
Car engineers pretty much have a handle on these effects.
For one, assuming no road crown and no traction, an axle spinning its wheel(s) will “pull” laterally (always in the same direction). Google right hand rule.
Other forces you mention (e.g., motors list in one direction due to rotation), are responsible for a lot of the asymmetry in automotive design. Here, the underhood engineers developed motor mounts that are asymmetrical, are flexible and designed to handle these forces.
Hijack: What if you are on perfectly flat ice with a perfect central weight distribution (theoretically) and start a forward peel going 'til the speedo says 200? Will you begin to turn/swivel/rotate in a certain direction or just stay pointing in the orginal direction? My guess is the former… but which way? My guess is clockwise…
As a matter of fact, to the extent that gyroscopic effects will do anything to the car, they’ll tend to keep it going straight. But they won’t be very large to begin with. When you have something rotating, angular momentum (the property responsible for gyroscopic effect) has more to do with the distance mass is from the axis than it does with the rotational speed. The axle of a car will have very little angular momentum, since all of the mass of the axle is very close to the axis. Even on the wheels, the most massive part is only about six inches or so in radius: The tires aren’t all that heavy. Then you’ve got to consider that the rest of the vehicle is pretty massive, so gyroscopic effects will have less relative significance.