Belt pull on v-belt mower deck

[grandnat_6]

Hi,

I'm trying to find the belt pull on a mower deck. The deck consist of 3 spindles and a spring loaded back idler with one v-belt.

The engine driving the spindles is a 20 HP twin cylinder engine operating at 3600RPM. Main drive spindle is 3600 rpm (1:1 ratio) Engine manual says max torque is 32.5 ft lbs @2500 rpm.

What I did was use a small hanging scale fixed to the deck with the other end of the scale fixed to the belt.

I then used a torque wrench on the main drive spindle until either the belt slipped or until I reached 33 ft-lbs. Which ever came first. I reached the 33 ft-lbs before the belt slipped. The scale showed there was 165 lbf on the belt.

Would this be a correct method to determine belt pull? Would RPM's, weight of the spindle, mower blades need to be considered? If so how?

Reason I'm trying to find the belt pull; so I can design the spindle shaft and find the bearing loads to size bearings.

I did use gates design IQ for this. It was great but says I need more than one belt and I think the tension it says the belts should have is much greater than is actually there.

Thank you for the help!

 

[Navin A S]

Yes, your method for calculating the belt pull is correct. You need to take into consideration the RPMs, weight of the spindle, and mower blades when determining the size of the bearings that you will use. The higher the RPMs and weight, the larger the bearings that you will need. The size of the mower blades will also have an effect on the size of the bearings. If the blades are large, then the bearings need to be able to handle the extra load. Additionally, you should factor in the amount of tension that the belts should have in order to ensure that they do not slip.