belt drive VS chain drive

[VPpanther]

Hi
we are building a robot for a special project. the importance here is durability, we are hoping to build this for it to have minimal maintenance (we will be handing it over to people who don't know their way around robots). It will be a full fledged FRC robot. Our main questions, emphasizing durability:

1. chain or belt drive?
2. Colson high performance wheels or just the regular wheels
3. is there a specific type of drive train we should go for?

[piersklein]

Belt drive: belts don't stretch and I've only ever seen one break
Colsons: Much, much, much grippier and more durable than standard KOP wheels
6 wheel drop center: reliable drive system you shouldn't have much trouble with

[EricH]

Originally Posted by piersklein

6 wheel drop center: reliable drive system you shouldn't have much trouble with

Before going that route...

Is there any particular application for this robot? Terrain you expect it to encounter?


And I will note that I've seen teams have a lot of trouble with 6WD drop center. Not in the 6WD drop center part, mind you, in the execution of said 6WD drop center.

You can make anything work well if you put enough work into it. If your team has the means, I would suggest trying everything you can. See for yourself what works well for your team and what doesn't. Try and make a modular design that will allow you to swap out parts to see what will work better for you. For the most part, there really isn't a universal "better" design choice for teams.* You can be successful with anything if you try hard enough.

*While there is no "end all be all" best solution, there are some that are generally more effective than others given the circumstances of FRC and the style of competition. Of course, those are all case dependent.

[VPpanther]

thank you for the quick responses

my first guess would have been that chain would be more durable because its metal, could you enlighten me on that?
and I'm not sure if we could do a drop center chassis because the rocking back and forth would severely impact what we're trying to do. The robot would probably only have to face level surfaces most of the time with the odd bump now and again (its actually for a sponsor to take to tradeshows and events to advertise). Would it be bad to just have all 6 colson wheels touching the floor at ounce? (i was leaning toward what 610 did last year but on a larger scale: http://prntscr.com/67dvyj )

We have a very tight budget so we sadly don't have the opportunity to test solutions before implementing them

[EricH]

Originally Posted by VPpanther

and I'm not sure if we could do a drop center chassis because the rocking back and forth would severely impact what we're trying to do. Would it be bad to just have all 6 colson wheels touching the floor at ounce?

What ARE you trying to do, in general terms?
What is the expected floor?
What sort of upper elements do you anticipate having--precision or "meh, whatever, it's close enough" in terms of motion?

Without knowing those, it's not going to be very easy at all to give anything like a "correct" answer, not that one exists. Knowing those, we can steer you around the pitfalls and away from any "incorrect" answers. This is especially important if you've only got one shot.


I would probably go with you don't want 6 colsons on the floor simultaneously, but that would also depend on wheelbase vs trackwidth--the higher the trackwidth/wheelbase ratio, the more "stick" you can get away with in your wheels.

[Tom Line]

Originally Posted by piersklein

Belt drive: belts don't stretch and I've only ever seen one break
Colsons: Much, much, much grippier and more durable than standard KOP wheels
6 wheel drop center: reliable drive system you shouldn't have much trouble with

Do you have data showing a colson wheel has a higher coefficient of friction than a traction wheel?

[VPpanther]

Originally Posted by EricH

What ARE you trying to do, in general terms?
What is the expected floor?
What sort of upper elements do you anticipate having--precision or "meh, whatever, it's close enough" in terms of motion?

Well the robot is for a sponsor, they will take it to tradeshows and events to advertise their products. so the robot will most likely be facing clean level surfaces with the odd bump every now and again. upper elements wise it will have a humoniod type of structure with a head,shoulders, and arms so leaning toward precision. right now our dimensions are looking to be 34'' by 40'' and about 7-9 feet tall (the upper portion will be very light consisting of mostly sheet metal, so it will be very bottom heavy)

[EricH]

That's a bit better. 6WD colsons will probably work (and if it doesn't, you might be able to find some Lunacy wheels on AndyMark and use those--they're slick enough). That wide/long of a robot, you can probably get away with "flat" configuration, though I'd actually suggest using "mixed wheels", with at least one end being smoother/less "sticky" than the rest.

A couple of other items to bear in mind: I'd go single-speed transmissions, geared for a "reasonable" speed (say about 10 ft/second or less), but with two motors on each (in case of one failing). We're dealing with foot traffic here, so precision driving could be important. Also, some form of safety system should be on there, say a drivebase lockout (again because we're dealing with lots of people).

I'd agree on the superstucture being more "precision" than not; after all you don't want it rocking onto some potential customer's head while under the control of your sponsor.

[VPpanther]

oh okay, thanks for all the insight. I'll relay your suggestions to the team. much appreciated!

[brentyi]

Originally Posted by VPpanther

my first guess would have been that chain would be more durable because its metal, could you enlighten me on that?

Belts generally have steel or fiber glass tension members, which are pretty strong and keep them from stretching.

Quieter and lighter than chains, too.

[dradel]

I'd go with belt drive. It doesn't sound like there is going to be a whole lot of abuse going on. Maybe look into going with an andymark am14u. Easy to build and seems more than stout enough for what you guys are doing. That and no worry about needing hub adapters or anything.

[GeeTwo]

Originally Posted by VPpanther

Well the robot is for a sponsor, they will take it to tradeshows and events to advertise their products. so the robot will most likely be facing clean level surfaces with the odd bump every now and again.

I know this may sound rather strange, but kiwi may actually be the best answer for this set of requirements, and will bring a bit of cool factor as well.

upper elements wise it will have a humoniod type of structure with a head,shoulders, and arms so leaning toward precision. right now our dimensions are looking to be 34'' by 40'' and about 7-9 feet tall (the upper portion will be very light consisting of mostly sheet metal, so it will be very bottom heavy)

Honestly, i'd shoot for plastic rather than sheet metal if you man manage it. Not only is it lighter, but it's friendlier/less intimidating. For all the negative things that Douglas Adams had to say about Sirius Cybernetics, I have to admit that "Your plastic pal who's fun to play with" sounds a whole lot better than "Your sheet metal pal who's fun to play with".

[GeeTwo]

Originally Posted by piersklein

Belt drive: belts don't stretch and I've only ever seen one break

For the record, chains don't stretch unless exposed to many times their rated load. The holes in the large links do expand a bit, which tends to increase effective chain pitch, and produces an effect which looks like stretch.
Also for the record, timing belts do break. This is why most recent automotive maintenance schedules recommend replacement after about 90,000 miles. Given that autos are normally driven at something close to 60 miles per hour, this corresponds to approximately 1,500 hours of operation.
The big point that will probably decide what is best for your current application: belts are much quieter!

[Scott Kozutsky]

It's all about implementation. We had belts on our versachassis WCD last year and we switched to chain because the belts were breaking (they were waaay out of spec. load so that makes sense). The equivalent pitch diameter and width of 25 chain was much stronger and performed fine (24t 9mm belt vs 18t 25 chain).

My experience with chain and belt:

Belt is lighter, do not stretch, are quieter, and more efficient than chain.

Chains requires less precision, are much smaller for the same strength, are much easier to source (especially up here in Canada), can be easily modified to different lengths, have many more available sprocket sizes, you can easily make any sprocket you can't source if you have a CNC mill, and chains can be easily bolted to for a function.

We like the compactness and general ease of use of chain so we decided to use it over belt this year.