Belt Driven Drive Trains

[GeeTwo]

Originally Posted by jkelleyrtp

Stemming from this, is there a maximum length before it is necessary to drive to another pulley and belt system. I could imagine that longer stretches of belts would be more likely to hop teeth and shorten the lifespan, but I see a few teams running belts through their tubing for all 3 wheels.

The length of the belt in this case would be less of a concern than the shallow engagement of the belt with the middle wheel. If you're going to transfer torque, you want to keep the belt firmly against the sheave and spread that torque load out among as many teeth as possible, which usually means 150 to 180 degrees of belt/sheave contact. With three essentially co-linear sheaves on one belt, very few teeth will engage the middle wheel, and the tension in the belt will not do very much to keep those teeth engaged. A snug-fit tube would help a bit on forcing engagement, but would still limit the torque transfer to just a few teeth, greatly increasing the rate of wear. This effect would be even worse if you're driving the middle axle West-Coast style.

[Travis Schuh]

Originally Posted by jkelleyrtp

Stemming from this, is there a maximum length before it is necessary to drive to another pulley and belt system. I could imagine that longer stretches of belts would be more likely to hop teeth and shorten the lifespan, but I see a few teams running belts through their tubing for all 3 wheels.

Gates actually recommends that you down rate the maximum torque of a belt system when the center to center distance is short, however this is assuming a properly tensioned system. They have more details in their design doc that is linked to above, each torque table has a length correction factor.

For example, with a short 5mm HTD belts (less than 87 teeth), the maximum torque for a sprocket size is down-rated to 80%. A belt longer than 219 teeth has a correction factor of 120%.