The Angular Velocity in Belt Drives

AI Thread Summary
In belt drives, the relationship between the angular velocities of the driven pulley (w1) and the following pulley (w2) is defined by the equation w1/w2 = d2/d1, assuming no slip occurs. The discussion highlights a misunderstanding regarding the torque on the following pulley, which arises from the tensions in the belt's tight and loose sides. It is clarified that if the system is frictionless, both sides of the belt will have equal tension, leading to no net torque. However, if friction is present, it creates a torque that can affect the pulley’s rotation. Ultimately, the balance of torques, including those from the belt and any external forces, determines the pulley’s ability to maintain a constant angular velocity.
daigiaga1994
Messages
6
Reaction score
0
Consider the belt drives, the driven pulley: diameter d1, angular velocity w1 and the follow pulley: diameter d2, angular velocity w2.

Assuming that the driven pulley rotate with a constant angular velocity and the belt does not slip on the pulleys, we have w1/w2=d2/d1, so w2 is constant( because w1 is constant).
But I think that the follow pulley will have a torque which is caused by the tensions in the tight and loose sides of the belt. Because of this torque, the follow pulley can't rotate with a constant angular velocity. This is opposite to the above statement ( w2 is constant).
Please explain this misunderstanding for me, thank you.
 
Engineering news on Phys.org
You have torque (and a tight and loose side) only if the following pulley has friction, and this torque will exactly cancel the frictional torque.
 
mfb said:
You have torque (and a tight and loose side) only if the following pulley has friction, and this torque will exactly cancel the frictional torque.
But I think, the effect of the belt on the following pulley are the friction forces ( tangent to the pulley) and the press forces ( normal to the pulley). So only friction forces can create the torque on the pulley. That is my thought.
 
How is that in conflict with my previous post?
If the whole setup is frictionless, both sides will have the same tension. If there is friction, making the pulley slower than the belt or "trying" to slow down the pulley, then you get an accelerating torque from the belt and a braking torque from friction (probably close to the axle).
 
mfb said:
How is that in conflict with my previous post?
If the whole setup is frictionless, both sides will have the same tension. If there is friction, making the pulley slower than the belt or "trying" to slow down the pulley, then you get an accelerating torque from the belt and a braking torque from friction (probably close to the axle).
yeah, but I wonder that Why the following pulley can rotate with a constant velocity with a torque( due to friction exerted by the belt) ? ( In this case, assuming that the friction between shaft and pulley is negligible ).
Thank you.
 
daigiaga1994 said:
( In this case, assuming that the friction between shaft and pulley is negligible ).
If that is true, friction from the belt is negligible as well.
 
Hi.Daigiaga, sorry but you are forgotten the exterior torques over the two pullies which equals the torques of the belt
 

Similar threads

Equivalence of torque & angular velocity transfer function
Replies
11
Views
3K
Torque calculations: Rotating vertical shaft
Replies
5
Views
5K
Angular Velocity: Pulley and belt system
Replies
11
Views
3K
Application of angular impulse to a problem
Replies
7
Views
2K
Acme leadscrew vs timing belt getting really high numbers
Replies
3
Views
5K
Brownian Ratchet (exercise framed by Feynman's Lectures, l. 46)
Replies
32
Views
2K
Change in Angular Velocity While Orbiting With No Torque
Replies
30
Views
3K
I Is There a Better Model for the Relationship Between Friction and Velocity?
2
Replies
63
Views
4K
Conservation of angular momentum
Replies
22
Views
3K
Effect of Load Torque on Belt Tension and Power Transmission
Replies
12
Views
7K

Hot Threads

Recent Insights

Back
Top