Belt-in-tube drive base

[Dunngeon]

Originally Posted by pribusin

Thanks Andy,

I looked online but so far came up empty for the thin walled stuff. I'll check Alro - thanks.

What's the motivation for belt over chain?

[pribusin]

1. Weight
2. Chains drives need to be re-tensioned periodically
3. More robust - we've had chains break at the links before
4. Belts run much quieter
5. Try something different

[asid61]

Originally Posted by pribusin

1. Weight
2. Chains drives need to be re-tensioned periodically
3. More robust - we've had chains break at the links before
4. Belts run much quieter
5. Try something different

Against #25 chain, I would say some points are less important than others.
1. The weight of #25 chain for a DT is about 0.7lb, versus maybe 0.2lbs for 5mm pitch 9mm width HTD belts. Adding in the weight of the pulleys (0.1lbs for 24t pulleys times 6 pulleys) versus sprockets (0.03lb for 16t times 6 sprockets) then the total for chain is about 0.9lbs and the total for pulleys is about 0.8lbs. I assumed you would use the same sprockets and pulleys everywhere, so it might be a bit different, but you will probably save little weight.

2. People have run direct C-C chain drives before in tube for whole seasons.

3. We have never had even #25 chain break on us, and there are more stories IMO about belts breaking than chain. OC if you use either the wrong way they will break or throw.
EDIT: Wait, we did have one break once. At Chezy Champs, our intake jammed against a screw head, stalling a BAG on a 25:1 reduction, and the chain actually did break. That was I think the second time we stalled out the intake; the first time it did not break the chain.

4. This is the main reason why I like belts, personally. The lack of noise is so nice and adds to the overall quality. This and minor efficiency gains.

5. Also a great reason. I really like using belts for other applications than DT due to the noise and the look of them, not to mention that you can go exactly C-C with belts, whereas with chains you might need to add a little distance to account for manufacturing tolerances (see this post: http://www.chiefdelphi.com/forums/sh...&postcount=26).

[Captain_Kirch]

If I can throw in my two cents, kickoff is far too close to properly prototype such a system. When it comes to trying something like this you have to give yourself proper time to prototype, fail, iterate, fail again, rinse, and repeat.

Be realistic here, kickoff is in 19 days and you have two major holidays in there (in America at least). This sounds like an off season project to my ear, and the off season is over. It's pre-season, prepare for the build season.

There's time enough to try new ideas when your season isn't on the line.

[End-Game]

I can Speak to a 9mm Belt in Tube Drive, Having just completed a Offseason project with the Team that used exactly that.

We ran a WCP 2 CIM DS Gearbox, Speeds of 16.5 ft/s and 5.5 ft/s, in a 6 wheel drive with a single Belt from the Center to the Front Wheel. We used 24T 9mm HTD Pulleys from VexPro, and they have worked perfectly for our needs. We milled out a bearing hole, and used exact CC plus 5 thousandths to get the right tension.

More Pictures and Information can be found in this thread.
http://www.chiefdelphi.com/forums/sh...d.php?t=139599

I can say without a doubt that this method is highly effective. Thus far, we have run into no problems, other than a few hiccups in assembly. In multiple pushing matches with our 2014 bot (A very pushy robot), we stalled both bots, and did not have any breaking or ratcheting on the belts.

We would make changes if we were to do this in a competition, such as a method to access the belts without disassembling the frame, and maybe a tensioning method, as we have not run the robot for long enough to accurately judge long term wear on the belt.

I am more than happy to answer any other questions that people have.

[Jared Russell]

Originally Posted by End-Game

...and maybe a tensioning method, as we have not run the robot for long enough to accurately judge long term wear on the belt.

HTD and GT2 belts won't stretch by a noticeable amount. Once you have the right C-C spacing, you should never need to touch it again. That said, a tensioning method may make assembly and achieving proper C-C spacing a bit more forgiving.

[Michael Hill]

Originally Posted by Jared Russell

HTD and GT2 belts won't stretch by a noticeable amount. Once you have the right C-C spacing, you should never need to touch it again. That said, a tensioning method may make assembly and achieving proper C-C spacing a bit more forgiving.

I'd echo this as well. The WCP belt C-C calculator works well. However, we made the mistake of not being able to install it with slack and add tension. We just did exact C-C plus a couple thou, so getting the pulley and wheel assemblies on we're a bit of a struggle.

[MrBasse]

Originally Posted by Captain_Kirch

If I can throw in my two cents, kickoff is far too close to properly prototype such a system. When it comes to trying something like this you have to give yourself proper time to prototype, fail, iterate, fail again, rinse, and repeat.

Be realistic here, kickoff is in 19 days and you have two major holidays in there (in America at least). This sounds like an off season project to my ear, and the off season is over. It's pre-season, prepare for the build season.

There's time enough to try new ideas when your season isn't on the line.

Maybe it's just a Muskegon thing, but we are still playing with a prototype drivetrain as well. Both us and 4004 have a pretty good student base to take care of preparation items for the upcoming season. This just feels like a perfect time to keep playing with new ideas. If our season success was determined by the work we do leading up to kickoff rather than after kickoff, I know quite a few teams that would be in trouble every season.