Attempting the impossible

[sdcantrell56]

Originally Posted by ratdude747

from experience, chain tends to have always worked, but belts tend to be way too much trouble.

one of our mentors used to be on a wisconsin team (fondy fire). being from there, he told us something we should have followed: "team 93 once tried to use belts. there is a reason why they never have since."

better yet, i found that someone from there said it here on CD on another thread:



source: http://www.chiefdelphi.com/forums/sh...ad.php?t=68479 post #4


reasons to ban the belt from your drivetrain;

1. belts have a lesser surface of contact. therefore, they skip and slip under less torque

2. related to #1, belts are harder to tension as belts stretch at a faster pace.

3. weight- belt sprockets are HEAVY. unless you have access to a CNC or a very precise mill and operator. if not, you will pay a weight penalty.

4. length- chain can be made shorter and longer, belts cannot.


in the long run, it seems that belts are better in high speed, low torque situations. Chain is for lower speed higher torque situations. unless your wheels are <2" diameter, you can almost always count on high torque. and hence why belts never worked for us.

The amount of misinformation spread in this post is truly alarming. Belt would not be the cause of your drivetrain problems but rather improper use and design of the system. Kevlar/fiberglass timing belts can easily support more horsepower than a 25 chain system.
Yes, alignment is critical and spacing cannot be adjusted without a new belt but this is what design is for. Also in the short time of driving a robot, a properly rated timing belt should not show any noticeable stretch. They definitely stretch exponentially less than 25 chain. I don't think any team should rule out a method of power transfer just because they dont want to put in the effort to properly design and spec the proper components.

This year we had a 6 motor drivetrain geared at 9fps with 8 roughtop wheels. We used gates gt2 5mm pitch belt to connect all the wheels together and never once had a belt fail or even a belt that looked worn after 3 competitions. I will say that our set up wasn't even perfect and the belts still held up to the torque with no problem.

For teams that dont want to take the time to design everything in CAD before hand and design in tensioning devices, sure use 35 chain and take the enormous weight penalty. We will happily be saving 5-10lbs with our timing belt drivetrain