pic: 1671 Swerve Module



The module of 1671’s swerve drive.

Slick! Care to answer some questions about your design? More specifically, why cantilever the belts, rather than put them inside the module? Also, I love the use of belts. When routed correctly, they outperform chain in both lifetime and torque transmission.

Also, a tip on top support crab modules: For FRC level contact, you might find yourself wanting more support on that top pivot. Even a single degree of deflection of the module makes you lose 90% of your contact patch on the ground…

Thanks
I was actually thinking about putting the belt sprockets on the inside of the module. But I then thought that having them on the outside will allow easier access to the belts. We have never used belts before does it matter how easy they are to access?

We used belts exclusively this year, and even though we had some slippage during shoving matches and bump crossings, we never had to replace a belt, and no visible wear occurred. So no, I don’t think you need access.

Okay, thank you guys.
I will modify the cad today it is a pretty quick fix.

As long as it’s properly tensioned, the system should be fine. However, properly tensioning and aligning belts can a bit of a dynamic situation when in FIRST. Constantly flexing frames can lead to sudden losses or gains in tension, unless you can design a quite rigid chassis.

I really dig the direction you’re heading in, so keep it up! A Belt drive crab isn’t common, and if you can pull it off it ought to yield some nice weight advantages.

Yeah I have wanted to use belts for quite some time now. But we were nervous about starting it without testing so we waited for the offseason to come around.

Yeah a weight advantage is always good to have.

Looks nice! Is it based on the 118 swerve modules (or 221’s “Revolution Modules”)?

If you’re going to run a swerve with belts, you should look into 1717’s 2010 machine:

They might be able to give you some advice on it.

You said this is for an off-season project? Can’t wait to see the final version(s)! Remember to post pictures, and good luck with it.

Edit: One more thing. For an off-season project, this probably won’t matter, but for a competition robot, if you have the machining capabilities, time, and budget, you should probably replace those shaft collars with snaprings. Those setscrews have a nasty habit of coming loose at the worst possible times, and snaprings take up a heck of a lot less space and weight, too.

Yeah I looked at the revolution first but wanted to change some things, mainly the use of chain.

1717 does have an awesome swerve I was talking to them about it at the la regional. Our overall base however is using 3 wd in place of the usual 4. So this cuts the weight of a whole module.

I will definitely look into that thanks for the tip. :slight_smile:

And yes we will post more pics as time goes on.

Nice. Keep up the good work.

One more thing I just remembered. I can’t tell from the picture, but do you have thrust bearings/bushings in place to distribute the thrust loads from those miter gears? Since the gears are working at an angle, there will be a significant thrust load along their axes. If you don’t have a bearing/bushing in place to handle this, you can end up damaging parts very quickly. We found this out the hard way in our worm drive kicker gearbox this year. If you go to the 221 website and take a look at the close-ups of the Revolution (or download the CAD file), I believe you can see the thrust bushings implemented correctly.

Yeah it is hard to tell from the picture, but yes there is bearings in place for that purpose. The angle makes it difficult to tell.

Any thoughts on replacing the timing belt on the outside with gears, perhaps even with a slight reduction? I imagine that would be a little easier to maintain.

Yeah I had looked into that too. I went and looked at 148’s swerve system from 2008 (tumbleweed) they used gears on the outside too. But in the end I realized that it really wasn’t the direction I wanted to head (light weight module). So I talked with my mentors and they brought up timing belts and showed me a great site for belt parts. But the module frame remained the same.

Okay
I finished the changes on the module tonight and uploaded the new picture. It should be up soon. Thank you guys for all your help.

During 118’s Crab Module Lecture in 2009, they suggested making the reduction after the miter gears as large as possible in order to reduce the amount of torque transferred through the miter gears. This prevented them from slipping under heavy load due to the slightest misalignment. It may also make the gearbox lighter since you might only need a single reduction coming out of it.