by **kz2zx** » Sat May 26, 2012 8:46 am

Quick lesson in physics...

Force = mass x acceleration. This is straight-line motion

The equivalent in a rotating system - planet Earth rotates, for example, and so does a motorcycle wheel - is

Torque = Moment of Inertia x Rotational Acceleration

or Τ = I·α

α (alpha) is measured in degrees per second per second (or radians·s^2)

I (inertia moment) is the interesting term here. It's really the static (resting) mass of the object (wheel plus sprocket and the portion of the chain on the sprocket), times the magnitude of the square of the distance from the center of the axle to the center of the distributed mass of the rotating object.

Huh?

The more mass (heavier) the sprocket is, and the bigger the ring of the sprocket, means more mass rotating a distance away from the center of the axle. Thus the same torque from the engine has to work harder to move that mass (think of it having a lever effect working against you, not for you). Two sprockets weighing the same, but one's (thinner and) has more teeth, the larger-diameter one will take more torque to spin up to a speed.

Help or not?

ASMA 47

WERA 147