Belt vs. Chain

[Ether]

Originally Posted by lemiant

Ok, so I read 234s paper, and it pretty unequivocally states that belts are better. How come everyone still uses chain?

The reasons were right there in the paper:

• Belt requires a more integrated design and precise manufacturing
  
• Wheels and belt must be assembled concurrently, unlike chain
  
• Belt requires more physical space because of the width differences for varying load capacities
  
• Chain drive is a known, proven system for transfer of power from the drive motors / transmissions to the drive wheels and between the wheels

[lemiant]

Originally Posted by Ether

The reasons were right there in the paper:

• Belt requires a more integrated design and precise manufacturing
  
• Wheels and belt must be assembled concurrently, unlike chain
  
• Belt requires more physical space because of the width differences for varying load capacities
  
• Chain drive is a known, proven system for transfer of power from the drive motors / transmissions to the drive wheels and between the wheels

I doubt 1 & 2 would be insurmountable for a team like 1114 (who I happen to know uses #25 chain), or 228. I'm not sure about #3, how much extra space are we talking here. And #4 has never scared a powerhouse out of doing anything.

[Ether]

Originally Posted by lemiant

I doubt 1 & 2 would be insurmountable for a team like 1114 (who I happen to know uses #25 chain)...

You didn't ask if re-engineering their process to use belts would be an insurmountable task for a powerhouse team like 1114.

...And #4 has never scared a powerhouse out of doing anything.

It's not a question of being scared. Experienced successful teams generally allocate their limited resources to tasks that have the greatest benefit/cost ratio.

[Jon Stratis]

The difference in belts versus chains, as others have mentioned here and as our team has experienced, is really one of time. Using belts typically takes more time, as you need to work our more precise distances, figure out precise lengths of belt to order, etc. Chain is quick and easy - you can get a kitbot assembled in a day with a chain drive. For a belt drive, unless you have the exact length of belt on hand, it'll take longer (lead time on ordering new belts).

We've always used chain on our drive system. It's quick, easy, and reliable (we've never had much of a problem with it). We've used belts in some other places as well - most notably in our claw/roller assembly this year and in our shooting turret for Lunacy. In both cases, we had to obtain belts of the appropriate length, and build in tension adjustment (this year, mounting the Banebots motors in slots for adjustment, for Lunacy we mounted CIM motors on rotatable armatures). Both of those tension adjustments were set and forget... but they needed to be planned out ahead of time. Contrast that with our drive system this year, where we through it together and added tensioners after the fact.

As we've told our team countless times... there are a multitude of ways to solve any one problem, and many of those ways are going to provide equivalent results.Chain versus belts is one of those comparisons... they'll both give you the same results, it's really a decision on what you would rather do, and where you want to spend your time.

[lemiant]

Originally Posted by Ether

You didn't ask if re-engineering their process to use belts would be an insurmountable task for a powerhouse team like 1114.

It's not a question of being scared. Experienced successful teams generally allocate their limited resources to tasks that have the greatest benefit/cost ratio.

I would just think that with a 10% performance gain, some of the big teams would have put in the time to work it out.

[Ether]

Originally Posted by lemiant

I would just think that with a 10% performance gain, some of the big teams would have put in the time to work it out.

You have to ask yourself the question, "10% of what?".

When you're talking about teams like 1114, they probably already have a drivetrain that more than meets their needs.

If the day ever comes that they believe they could gain a competitive advantage by allocating resources to re-engineer their drivetrain, I'm sure they will consider doing that.

[AdamHeard]

We've considered belts in out drivetrain, but have always turned them down for a few reasons.

Currently, we almost exclusively use chain; we know chain, we have lots of sprockets, no pre-planning required to chain something up. With belts, we now have an entirely separate set of parts that need to be identified, purchases etc...

The disassembly is a huge disadvantage too. We've never lost a chain on our drive, but if need be we could replace one in under a minute. Switching to belts requires a redesign of our gearboxes, or partial disassembly of a gearbox to install a spare.

[emekablue]

What about belts being used not for the drive, but for the arm. We have had quite the problem with tensioning our arm's chain (other tensioners are too large, and we have about an inch of slack), I think because we are over-torquing the motor. Will putting in belts help solve this problem? Or will a simple change in gear ratio do the trick?

[lemiant]

Originally Posted by emekablue

What about belts being used not for the drive, but for the arm. We have had quite the problem with tensioning our arm's chain (other tensioners are too large, and we have about an inch of slack), I think because we are over-torquing the motor. Will putting in belts help solve this problem? Or will a simple change in gear ratio do the trick?

Correct me if I missed something, but couldn't you just remove the extra links?

[slijin]

You should start by removing the extra links, as lemiant pointed out. Chain tensioners are to be added when you can't remove links any more.

Furthermore, changing between belts and chain does not change the load on the motor. Adding countering forces, such as springs or gas shocks are the kinds of things you want to add to reduce torque on the motor.

[sdcantrell56]

Originally Posted by emekablue

What about belts being used not for the drive, but for the arm. We have had quite the problem with tensioning our arm's chain (other tensioners are too large, and we have about an inch of slack), I think because we are over-torquing the motor. Will putting in belts help solve this problem? Or will a simple change in gear ratio do the trick?

Belts definitely won't help. Shorten the chain and use some counterbalancing to take load off the chain, either surgical tubing or gas strut.

[emekablue]

We did both of that probably during week 6. However we used bungee cords as our counter.

[Karthik]

Originally Posted by Ether

The reasons were right there in the paper:

• Belt requires a more integrated design and precise manufacturing
• Wheels and belt must be assembled concurrently, unlike chain
• Belt requires more physical space because of the width differences for varying load capacities
• Chain drive is a known, proven system for transfer of power from the drive motors / transmissions to the drive wheels and between the wheels

Originally Posted by lemiant

I doubt 1 & 2 would be insurmountable for a team like 1114 (who I happen to know uses #25 chain), or 228. I'm not sure about #3, how much extra space are we talking here.

We've often talked about moving from chain to belts for our drivetrain. Most of our reasons for not making the switch have already been mentioned, but there's one big one missing, which is very specific to FRC. The lead time on the exact belts and sprockets we would want, imported into Canada, is about 2 weeks. We used belts on our elevator and roller claw this year, and acquiring the belts was the largest bottleneck. There's no way we'd sacrifice that much programming, practice and systems integration time on our drivetrain, for the marginal benefit that belts provide. Now, if we could find a way to reduce these lead times, belts would become a very attractive option.

Originally Posted by lemiant

And #4 has never scared a powerhouse out of doing anything.

Hardly. Number four keeps us from doing things all the time. We'll always take a solution that we know works 100% of the time over a solution where we have less confidence. Reliability is one of the keys to a successful FIRST season. We will not give it up for a new solution until we've proven the new solution is just as reliable as the established one.

As our founding mentor Stephen Rourke used to say, "The most effective solution is the simplest one that works".

[Andrew Schreiber]

Originally Posted by lemiant

Ok, so I read 234s paper, and it pretty unequivocally states that belts are better. How come everyone still uses chain?

Use what you know and don't fix what ain't broken.

[Akash Rastogi]

Originally Posted by Andrew Schreiber

Use what you know and don't fix what ain't broken.

OR try some set ups out in the offseason!