9 mm Wide Belts

[Joe Ross]

Originally Posted by DonRotolo

Go to the belt manufacturer site to get strength ratings.

And when the belt manufacturers site says the belts are way undersized, realize that those ratings are based on working forever (rather then 100 hours) under continual torque loads and at much higher RPMs. Personally, I think the collective experience of the FRC community would be better then the manufacturers site.

[sdcantrell56]

My experience says to never use 9mm wide belts in the drivetrain. Sometimes they will work but sometimes they won't We have run belts the past 4 seasons and have gone back to chain for this season.

[Mr. Van]

Originally Posted by sdcantrell56

My experience says to never use 9mm wide belts in the drivetrain. Sometimes they will work but sometimes they won't We have run belts the past 4 seasons and have gone back to chain for this season.

Uh - this worries me. We're trying belts ourselves for the first time - 9mm. (2 CIM driving 6" AM high-grip wheels via a SuperShifters, WCD.) What were your failure points? Why did you go back to chain?

- Mr. Van
Coach, Robodox

[sdcantrell56]

Originally Posted by Mr. Van

Uh - this worries me. We're trying belts ourselves for the first time - 9mm. (2 CIM driving 6" AM high-grip wheels via a SuperShifters, WCD.) What were your failure points? Why did you go back to chain?

- Mr. Van
Coach, Robodox

What pullies are you running, specifically tooth count? 6" wheels complicates the matter even more, as the load in the belt is higher than with a smaller diameter wheel. Also will you have a means for tensioning or are you setting it up for exact center to center distance?

The failures we experienced were mostly ratcheting, teeth skipping as we changed direction rapidly. This of course accelerates wear and leads to failure quicker than normal. That said, we never had a belt totally fail, although we replaced belts every regional.

Originally Posted by sdcantrell56

What pullies are you running, specifically tooth count? 6" wheels complicates the matter even more, as the load in the belt is higher than with a smaller diameter wheel. Also will you have a means for tensioning or are you setting it up for exact center to center distance?

The failures we experienced were mostly ratcheting, teeth skipping as we changed direction rapidly. This of course accelerates wear and leads to failure quicker than normal. That said, we never had a belt totally fail, although we replaced belts every regional.

Sounds like your belts weren't correctly tensioned. Too much tension on a belt will strip the teeth.

[sdcantrell56]

Originally Posted by Andrew Lawrence

Sounds like your belts weren't correctly tensioned. Too much tension on a belt will strip the teeth.

I didn't say the teeth stripped. I said the teeth ratcheted or skipped teeth during rapid direction changes.

Originally Posted by sdcantrell56

I didn't say the teeth stripped. I said the teeth ratcheted or skipped teeth during rapid direction changes.

Then that could be not enough tension, or too small a pulley size. How many teeth did you use?

[sdcantrell56]

Originally Posted by Andrew Lawrence

Then that could be not enough tension, or too small a pulley size. How many teeth did you use?

Or the belts are outside of their safe working limit. They were 26 teeth, and slightly on the overtight side. In my experience, belts are not very well suited for rapid direction changes with relatively high torque and minimal tooth engagement which is what happens in a west coast drive since pullies are generally kept smaller than 2" diameter.

Originally Posted by sdcantrell56

Or the belts are outside of their safe working limit. They were 26 teeth, and slightly on the overtight side. In my experience, belts are not very well suited for rapid direction changes with relatively high torque and minimal tooth engagement which is what happens in a west coast drive since pullies are generally kept smaller than 2" diameter.

That's very interesting. I've never heard of problems on correctly tensioned belts in a drive. Were you using GT2? HTD is better rated for rapid direction change, though it really shouldn't matter.

[sdcantrell56]

Originally Posted by Andrew Lawrence

That's very interesting. I've never heard of problems on correctly tensioned belts in a drive. Were you using GT2? HTD is better rated for rapid direction change, though it really shouldn't matter.

GT2. I know of plenty of teams experiencing ratcheting with 9mm wide belt. Once you go up to 15mm ratcheting only happens in extreme cases, but then you're much wider than running #25 chain

[AustinSchuh]

Originally Posted by sdcantrell56

GT2. I know of plenty of teams experiencing ratcheting with 9mm wide belt. Once you go up to 15mm ratcheting only happens in extreme cases, but then you're much wider than running #25 chain

We ran 9mm wide GT2 belts last year, and didn't have any ratcheting. We had some wear, but it was what you would expect for a device running outside the rated specifications. 1 set of belts lasted the entire season (2 competitions, 1 offseason, and lots of practice.) Ratcheting occurs when your belts are under-tensioned, which means that your belts were under tensioned. You can look at the failed belt to figure out what was wrong. For comparison, we had a 24 tooth pulley with a 3.5" diameter wheel.

[Mr. Van]

Originally Posted by sdcantrell56

What pullies are you running, specifically tooth count? Also will you have a means for tensioning or are you setting it up for exact center to center distance?

We're using the small 18 tooth pulleys (9 teeth in contact). We will have the means to tension the belts.

I suppose that in the worst case scenario, we'll switch back to 25 chain. Now were are we going to get the weight for that...?

- Mr. Van
Coach, Robodox

[Chris is me]

We experienced ratcheting problems with 9mm belts. Our experience mirrors Sean's. We now use 15mm belts and 24T pulleys for our 6 CIM WCD.

I would be very hesitant to take risks with belt sizing, unless you have a good reason. Looking pretty is not.

[AdamHeard]

Originally Posted by Mr. Van

We're using the small 18 tooth pulleys (9 teeth in contact). We will have the means to tension the belts.

I suppose that in the worst case scenario, we'll switch back to 25 chain. Now were are we going to get the weight for that...?

- Mr. Van
Coach, Robodox

This will likely be an issue.

[Michael Corsetto]

Worth taking a look at this document Adam threw together. Lots of great input from tons of teams on their experience incorporating belts into their custom drivetrains. We referred to this when throwing our off-season WCD belt drive together.

-Mike