Torque Distribution through a Two Stage Belt Drive

[billinr]

Hello All

I am trying to work through a belt drive design and I am confused with a simple concept.

I have a two stage system that has a max torque input of 110N. I want to treat this as "worst case", so I assume that all of the torque is used at the final output flywheel.

The first stage has the same ratio as the second stage, but the pulley sizes are different.

I have the belts designed, but my issue is that I need to explain to the customer why I am using a wider belt (poly-v) on the first stage than on the second. The second belt width is 80% of the first. This is what my calculation software tells me is correct.

The drive has been tested, so I know it works - I just do not know why it works.

Could someone explain to me:

When there are multiple stages in a drive, how does the relationship between the ratios affect how much of the torque is consumed in each system? With these two systems having the same ratio, do they each consume 1/2 the torque? (Obviously not, because of the belt width difference??) Is this due to the differences in the pulley sizes?

For a future reference, if the system ratios were different, how does that affect the calculation?

Thanks for any assistance.

 

[Mech_Engineer]

Belt width would be decided by the operating force of the belt. If you have two pulleys subject to the same moment, one twice the radius of the other, then the belt on the larger pulley will only be subject to half the tensile force of the belt on the smaller pulley.