pic: GBX-116, Drill press swerve drive

Presenting GBX-116, an easy-to-create swerve drive for teams without mills or lathes.
Total weight is 6.97lbs as shown, but it needs a few 8-32 button head screws from Vex. A chassis with this as shown weighs approximately 34lbs.
Geared for 16.5fps. One cim per module, but can easily be upped to two.

The only “machined” parts on this are the top bar, which is made from 2x1, and the caster box, which is made from a piece of 3x5 or 3x6. It can be made from bent sheet metal as well. To make these pieces, you need a good eye and a ruler graduated in 0.01" increments, or just a drill press and x-y table. Of course this can be made with a mill if you want.

There are two 3/8" shafts which need to be cut within 1/16" or so, and a vex hollow shaft to act as a dead axle which is about the same. Everything else is COTS.

The CAD is missing screws, tensioners, and encoders currently, but there are many places to mount encoders and tensioners. Once those are all added, I’ll release the CAD and toleranced drawings for this.

I would make a shifting version of this, but those designs require tolerances good enough for gear mating, and I want to avoid gears as much as possible. There is already a pair of gears in this module due to the lack of commercially available 3/8" hex bore sprockets. Hopefully Vex or Anymark will stock those eventually.

Input is more than welcome, as always. Experience with drill press/ x-y tables is also much appreciated, as I’m not sure what kind of tolerances you can get with those.

This looks really, really impressive. I’ve wanted to make an easy-to machine swerve for a while now.

I’m not sure if I would use sheet metal for the caster box. It’s weak across the joints, so I’d be worried about my box doing a parallelogram. Cutting it from extrusion would be much stronger.

17 fps seems fast for a 4-cim. It’ll accelerate okay, but I’d be worried about blowing breakers if you hit something.

12-14 theoretical might be more reasonable.

Pleeeeaaaaaase release the CAD for this. I really want to check it out!

It is very easy to change the speeds via the large top sprocket.
I will release the CAD soon, once I think it’s complete. Perhaps later today.
Thank you!

You’re really going to have an awfully hard time getting good enough tolerances for gear meshing with just “a good eye and a ruler.”

Yeah, I’d imagine this would have to be milled. Or at least the caster box.

You feel my pain.
This is why MOE went away from Vex bevel gears on our final version. This, with This (375 hex hub) is the best we were able to find, its awkward but it might work better for you. I dont feel comfortable doing gear meshing on a drill press.

Also, what’s that random gear on top for?

I considered those, but the width held me away. Looks like I’ll have to switch over.

The random gear on top is because of the lack of 3/8" hex 1.875" bolt circle hubs, but AM has them os I’ll switch over. I was hoping to be able to buy everything from just Vex, but it’s fine.

Very nice.

I thought the random gear on top could be used for the encoder.

It could, maybe. But I would rather put an encoder on the CIM for simplicity.

Does anybody know if banebots gearboxes come with the long screws to put them together, or do you have to buy those seperately?

They come with the screws. However, If you use some 6-32 hex stand offs and 6-32 screws, you can face mount it. Also this allows the motor to be replaced without total removal of the trans.

you have a picture of this method? Do you mean putting standoffs on the face of the gearbox?

Only picture I could find showing them.