Amount of coupler purchase required on 1/2'' hex?

[Chris is me]

Originally Posted by Oblarg

That's a cool idea, but it'd be harder to manufacture and I want to be able to swap the gearboxes easily as well as the wheels.

Wouldn't it be exactly the same? Two plates, a tube, some standoffs? You just unscrew the gearbox and lift it up to remove it.

[Joey Milia]

Originally Posted by Chris is me

This is a bit of a tangent, but looking at your specific design, maybe you could build a gearbox that straddles your rectangular tube? Instead of driving a live shaft, have a gear off the gearbox drive another gear bolted to the wheel. I feel like this might achieve what you're trying to do (shifting gearbox with CIMs over drive wheels) a bit better than the coupler solution.

This is a great idea and I think very similar to what 971 did in 2012, and I believe still do. If you go towards this method you might want to have a look at what they did. It's explained here http://www.chiefdelphi.com/forums/sh...ht=971+gearbox

[Oblarg]

Originally Posted by Chris is me

Wouldn't it be exactly the same? Two plates, a tube, some standoffs? You just unscrew the gearbox and lift it up to remove it.

Ah, crud, you're right; removal is actually easier with that design. No idea what I was thinking there.

However, currently the lower half of my shifter is exactly the assembly from the WCP 3-CIM dog shifter; designing it to sit on top of the tube would probably entail changing that, and being a lazy engineer, I want to do as little designing as I can get away with

Moreover, my wheels fit pretty tight right now, so doing that would probably actually lose me overall space, since the tube would have to move in far enough to allow me to put a gear on the other side of the wheel.

[ToddF]

For a coupler, I'd probably take a 1/2" deep well socket (six point) and part it off in the lathe. I'd have no worry that the coupler would fail. As for the shafts, that's what summer testing is for...

[Jared]

I don't think you need to put the hex coupling inside the tube. You could put it in the tube and in the wheel. The sdp si .375 hex sleeves have an id of .625, so you could use it as your drive axle if you want.

If you do something like this, you'll need to make sure that the holes/bearings in the frame as well as the output shaft of the gearbox are concentric, otherwise you'll never get it together.

[Oblarg]

Originally Posted by Jared

If you do something like this, you'll need to make sure that the holes/bearings in the frame as well as the output shaft of the gearbox are concentric, otherwise you'll never get it together.

Yeah, this'll be the biggest issue. Thankfully, our team does know a machinist who can do these things to fine precision, so I'm not too worried about that.

[Chris is me]

Originally Posted by Oblarg

Yeah, this'll be the biggest issue. Thankfully, our team does know a machinist who can do these things to fine precision, so I'm not too worried about that.

The tricky part is lining up the two separate parts perfectly. I would see if you could add some kind of feature to one that aligns it with another.

For example, on our gearboxes this year we counter-bored the hole for our flanged bearing so that part of the bearing would stick out the gearbox. This would snap into the hole in the frame and ensure concentricity.

Many ways to do this, it's just particularly important for this purpose.