What makes a misaligned belt drive inefficient?

[hihiip201]

http://constructionasphalt.tpub.com/TM-5-3895-374-24-1/css/TM-5-3895-374-24-1_666.htm

consider the misalignment illustration in the link above.

What makes a misaligned belt drive inefficient? I imagine it is due to increase friction but where does this friction manifest in the system? (which component and how?)

Most sites simply state this as an fact without the physical explanation, I was hoping I can get one here.

 

[Asymptotic]

V belt/pulley power transmission depends upon friction between belt and pulleys. Ideally, both faces of a V belt are in full and equal contact with their corresponding pulley faces, and transmit force equally with belt(s) tightened to the minimum tension required to prevent slippage. When misaligned, 1. forces are coupled unequally and 2. more tension is required to prevent slippage.

Misalignment inefficiencies manifest themselves as vibration, noise, and excessive heating within the v belt, and at pulley/belt interfaces.

On the maintenance side, in a well designed system, belt life is inversely proportional to temperature - the hotter is runs, the quicker it dies. Belt over-tensioning places unnecessary stress on motor and driven equipment bearings, and reduces their life. Misalignment causes excessive and uneven belt wear, and increases pulley wear leading to 'scalloping', less face contact, and an ever increasing need to over-tension the belt.

 

[Merlin3189]

What makes a misaligned belt drive inefficient? I imagine it is due to increase friction but where does this friction manifest in the system? (which component and how?)

I don't know any theory about this, but from simple experience I'd say that misalignment causes contact between the belt and pulley at points where they are not moving in the same direction. If perfectly aligned, the belt ideally meets the pulley at a tangent, when the pulley and tangent are moving in the same direction and speed. Then the belt conforms to the surface of the pulley and again moves at the same velocity round the portion of contact, until it leaves at a tangent.
If misaligned, the sides of the belt meet the pulley when they are moving in different directions. The sliding contact must cause some frictional loss (and wear.)

The tension in the belt and degree of misalignment would affect the normal force between the sliding surfaces, and therefore the frictional force. Since extra friction increases the belt tension, there might be some positive feedback here making friction grow disproportionately with degree of misalignment.

 

[FactChecker]

Friction and the work it takes to bend the belt. I imagine it is somewhat similar to the scrub force of a tire at each end.

 

[hihiip201]

I don't know any theory about this, but from simple experience I'd say that misalignment causes contact between the belt and pulley at points where they are not moving in the same direction. If perfectly aligned, the belt ideally meets the pulley at a tangent, when the pulley and tangent are moving in the same direction and speed. Then the belt conforms to the surface of the pulley and again moves at the same velocity round the portion of contact, until it leaves at a tangent.
If misaligned, the sides of the belt meet the pulley when they are moving in different directions. The sliding contact must cause some frictional loss (and wear.)View attachment 210001 View attachment 210002
The tension in the belt and degree of misalignment would affect the normal force between the sliding surfaces, and therefore the frictional force. Since extra friction increases the belt tension, there might be some positive feedback here making friction grow disproportionately with degree of misalignment.

I agree. The picture in my head is similar to the second picture, with a straight belt driven by a crocked pulley, then the teeth of the pulley will move along the surface of the grooves on the belt which is where they meet.thanks!

 

[hihiip201]

A picture of what I visualize.

looking at the second picture from top view / 3rd picture from rear view of the crocked pulley.

pulley in red, belt in black. the horizontal lines are gears/grooves. and the yellow dot are the contact points, which can also be thought of as one fixed point on a pulley teeth at different time, which we can see slide along the surface of the groove it contacts with.