pic: New gearbox CAD

I saw the Pink gearbox from this season, and was really inspired. This is the result. 5.6 lbs with motors. Each gearbox plate is .133 lbs.

Gears are steel 20dp gears from Martin, .375 face. Questions and comments welcome.

That is quite beautiful. However, I have one question…how are you mounting the cims to the plate. It doesn’t look like you have any corresponding holes for it.

CIM’s have 4 holes, two filled with bolts that hold the housing together. That’s what you’re seeing. The other two are used to hold the gearbox together and to the frame of the bot.

I still don’t understand though. Are you running extra long bolts through the transmission and into the CIM? If so aren’t they really small bolts?

Pretty sweet. I love elaborate cutouts. (IN CAD)

Well if you get it cut on a waterjet or laser its not too bad in real life either:D

They’re #10-32 bolts. Four of them will be more than strong enough to support the gearbox. If my stress tests indicate otherwise, I may add another set of standoffs. We shall see.

So the holes on a cim are threaded for 10-32? That certainly changes things for the better.

Yep. I remember one year we accidentally used #10-24 on our gearboxes… And I kept wondering why it stripped out all the time.

HAHA thats never good. Maybe I’ll have to integrate that into one of my transmissions.

Whats the estimated output speed of the output shaft?

Under load, it’s calculated to be around 550rpm. When put to a 4 inch wheel, top speed is calculated at 9.67. I’m assuming 2 inch wide roughtop wheels for this system, but this gearbox could be mated to quite a few different systems.

By the way, if anyone wants the CAD for this, feel free to PM me. It wasn’t too difficult to make, so I’d have no problems handing the CAD out.

I’d bet you could get another pound out of it in those gears if you wanted to, but overall, nice work.

What is the advantage over the toughbox?

I like the CIM mounts. That’s a very compact way to do it.

I guess It would be the weight savings.

I’m not really a fan of the same 4 bolts holding the gearbox together, the motors on and the gearbox to whatever structure it is mounted to. No matter what, that is going to make assembly and mounting a much bigger pain that it needs to be. I’ll agree it cuts down on parts and weight, but I don’t think it’s worth it.

No, actually. The gears are heavily “dished” out on the other side, in order to keep those components to a single lathe process. There’s practically no weight I can save by removing materials, only adding material.

The advantage it has over the toughbox is custom ratio, massively lighter, more stylish, more precise, and better bragging rights.

It would be a bit of a pain to assemble. However, depending on what kind of drive system that it would mate to, two of the mounting bolts may be countersunk. That would aid a bit in assembly.

A straight-forward single-speed gearbox–simple in its mechanical design, but the weight savings and sideplate design make it very elegant…something defintely to brag about if this is on your robot!

And yes, “elegant” can be used to describe a gearbox…ask the Germans!!

I like it.
mike d

It does look like much more of a hassle to mount, but thinking of the end product with those gearboxes mounted nicely would make it worth it. Pain for Beauty. :stuck_out_tongue:

Countersinking would aid in assembly but it still would be more complicated to assemble than needed. Very interesting design though, kudos.

The weight savings and more custom ratios.

A big difference is one is made for mass production and one is made to build a few of. The cost to mass produce something like this would be quite a bit greater then the price of the Toughbox (e.g. more machining).