Belts 9mm or 15mm?

[Knufire]

Originally Posted by Cothron Theiss

While the GT2/GT3 profile is superior to HTD in almost every way, including service life, backlash, vibration, and load-carrying capacity, HTD belts respond slightly better to reversing shock loads. GT2/GT3 are much better suited for most industrial uses, but reversing shock loads are so common in FRC, what's best for industry isn't the same as what's best for us. The people at AndyMark and Vex knew this and made the informed decision to sell HTD pulleys and belts instead of GT2/GT3 after discussing it with people from Gates and other industry vets.





Just to add on to what Eli is saying about Gates' stated torque ratings not always being applicable to FRC purposes, remember that all of those values are rounded averages of many tests.

On the sourcing belt front, you have to remember that the GT2 and GT3 profiles are still patented by Gates, whereas the patent on HTD ran out so there's many, many more suppliers of HTD.

On load ratings on the design manual, those also might be based on fatigue and not instantaneous loading.

[Cothron Theiss]

Originally Posted by Knufire

On the sourcing belt front, you have to remember that the GT2 and GT3 profiles are still patented by Gates, whereas the patent on HTD ran out so there's many, many more suppliers of HTD.

On load ratings on the design manual, those also might be based on fatigue and not instantaneous loading.

Though it's really more the name that's been patented at this point, and not the actual profile, right? Because there are several suppliers, WCP included, that sell a "GT2 compatible" profile. I don't know where the lines are drawn on how close other profiles can get before being in violation of the patents, but I'd say the "GT2 compatible" profiles are pretty close.

And yeah, none of Gates' load ratings are off of instantaneous loading or reversing loads.

[R.C.]

Originally Posted by Knufire

On the sourcing belt front, you have to remember that the GT2 and GT3 profiles are still patented by Gates, whereas the patent on HTD ran out so there's many, many more suppliers of HTD.

I believe patent on gt2 belts are up but gt3 belts are still protected (source: gates rep)

[IndySam]

Originally Posted by Cothron Theiss

Just because I'm curious, why the switch from gear drives? I still remember seeing your 2013 bot at the Smoky Mountains Regional and being in absolute awe. I also remember yours being the best drivetrain at the Regional.

Thanks for the compliment.

We might not. Really going on a simplicity kick and gear drives are not simple. As usual everything depends on the game.

[zuzoom101]

Originally Posted by zuzoom101

We have been using 15mm belts for the last couple of years on the drivetrain, and they have been working great. As long as the alignment is correct, no belts should be broken. We have had to tension them a couple of times through the season, but nothing too worrying.

We tried using 9mm belts on a test drivetrain that we built. It weighed only around 50lbs, and after only 30 minutes of use, we ripped one of the belts. We replaced it and haven't ripped one yet. I would go with the 15mm to be safe, but you have to take the extra width into account when designing the robot.

We used 42T pulleys on 8" wheels both years. The test drivetrain used 42T pulleys with 6" wheels.