Team 3495 Drivetrain teaser

Sorry for my poor chief Delphi use, I couldn’t get the image in correctly.

E.T.? Is that you?

Nice idea. I’m guessing four modules? Will they be actuated or passive? Are both of those wheels belted together? Why choose this over a larger single wheel?

Belts? No chain? Wow, ok. Not sure if your are aware of this but belts slip under a lot of pressure, chain is much more reliable.

Source? Proof?


You’re really going to need to post more information than that, about your experience. How your belts were used, were they tensioned, how, what drivetrain configuration, etc.

Belts should not “slip” in normal operation when properly configured, and hundreds of teams have run successful belt drivetrains at this point. If you’re going to make sweeping generalizations, at least back them up with a post longer than a single word.


keep in mind that when the front wheel goes up the back wheel goes down effectively RAISING your bumper relative to the bottom of your robot.
Mind your bumper zone

@Bruceb We did keep that in mind, the bumpers will never be below 4 inches when actuating.

And how was this experience?

In 2010, my rookie season, we used belts for our drive system. For some reason, our current Engineering Director opted for the worst possible choices for a belt driven drive system. From what I remember, the belts we had were no more than 3/8" wide and felt more “plasticy” than rubbery. We also used plastic timing pulleys. Our tensioning system consisted of delrin pegs that could be tightened down onto the belts.

This system was so awful and gave us so many headaches that we converted it to chain. We also stripped a few belts. THAT was an awful experience.

In 2011 I was elected Engineering Director and vehemently was against using belt for the drive system, because of my “experience.”

In 2012, a student that I referred to join the year before took my place as Engineering Director, and he didn’t use belts either. The big difference in that drive system that year is that it was a drop center WCD sliding bearing block tensioned system. This allowed us to tension chain without plastic pegs.

Because of this, we decided to give belt another chance after the season. We switched out the chain for belt. This time around, we used aluminum timing pulleys and belt that was around 1" wide and much thicker than the pathetic belts we used in 2010.

In 2013, We were so satisfied with our results using belt and tensioning that we started of the season using a belt driven system. We went on to win our first two winner banners ever, and as the drive coach of that year, I can testify to the aggresive defense we played at Colorado in order to win. Not once did our pit crew have to fix or replace anything on our drive system. They were actually bored since the rest of the robot barely broke either, and our disc shooter was belt driven as well.

“Experience” is only valuable if it results from continuous trial and error. I can’t assume that your experience is limited to only a few unfavorable attempts, but when it comes to belt, I have a feeling that your experience was with a system that could have been built better.

Testify brother. Since my team was on receiving end of your belt drive defense in the match you linked, I can also testify. It was strong enough to break our gearbox in that match. Neither belt nor chain is superior; it depends on the application, and on how well you build it.

Is that a tank bogie?

Basically, without the treads though. this may or may not work, we’ll see by the end of today though.

Not to stoke the fire or anything, but JPBlacksmiths’ prediction was correct. We encountered a lot of slipping when trying to go over the obstacles. We just weren’t getting enough contact from the belt to the sprocket, only about a fifth of the sprocket was being used.

We have since switched to using chain (for the first time ever) for our four modules. We still have belts going from the gearbox to the modules, as it has much better contact and does not slip whatsoever.

Thanks for everyones opinion on the matter, they were taken into consideration and our robot is much more effective because of it.

The general rule of thumb is 120 deg engagement for belts/pulleys and sprocket/chain. This can be mitigated through the use of static rollers or properly designing the system to accommodate belt lengths. ALWAYS use a belt length tool like WCP to determine lengths. Never design your modules and then try to fit a belt on.

IMO belts run smoother, weigh less, and require less maintenance than chain. Properly tensioned belts will give you less headache than chain that is “cut to fit” because you are slave to the number of links in the chain. Also, behavior of #25 chain is different than #35 and might introduce slip into the system.

Yeah, we usually don’t mess this up but this robot required a lot more power than we originally thought. We had to re-gear our drivetrain but it’s looking really good after all the stuff we did.

I agree with you on belts though, they are a lot cleaner than chain.