I have a large gear having a moment of inertia about it's axis of
0.5Kgm2. If I wanted to accelerate it from static to a rotational speed of 16 RPM in say, 2 seconds, what torque do I need to apply to a driving pinion meshed with the gear? The gear ratio is 18:1. Assume gear mesh efficiency at 100% for this argument.
Example problem....A force of 5 N is applied to the rim of a bicycle wheel 0.50 m in diameter. The mass of the wheel is 1.5 kg. What is the angular acceleration of the wheel?
For straight line things, Force = mass times acceleration, and for rotating things, torque equals moment of inertia (mass analog) times angular acceleration (acceleration analog)
Here, the moment of inertia is
I = mr2 = 1.5 kg x (0.25 m)2 = 0.0938 kg.m2
and the torque about the center of the wheel is
t = Fr = (5 N) x (0.25 m) = 1.25 N.m
so the angular acceleration call it a(ang), of the wheel is
That example is not too hard to work through, I don't think. So next, let's try YOUR problem.
Given, that.... moment of inertia I = 0.5 kg.m2 and.... angular accel a(ang) = 2 x pi x 16 / ( 2 x 60) = 0.838 rad/s2 ...expressed as radians per second per second
So you can say pretty quickly, that the torque you need on the gear's axis to spin it up is t = I times a(ang) and that comes to t = 0.5 kg.m2 times 0.838 rads/sec2 = 0.419 N.m
The meshing pinion needs to apply eighteen times less torque if we neglect ITS moment of inertia, and that would be 0.023 N.m
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.