VexPro Clamping Gearbox Dead Axle

[Ari423]

I would like to use a VexPro Clamping Gearbox where the non-CIM side is dead axle using a 70t VersaKey gear on a 1/2" round bearing. But I cannot find any documentation from Vex or otherwise about how to put a dead axle there instead of a live axle. Other than using 2 sets of bearings (which seems like a waste of weight and complexity), does anyone have any ideas?

[Chris is me]

Originally Posted by Ari423

I would like to use a VexPro Clamping Gearbox where the non-CIM side is dead axle using a 70t VersaKey gear on a 1/2" round bearing. But I cannot find any documentation from Vex or otherwise about how to put a dead axle there instead of a live axle. Other than using 2 sets of bearings (which seems like a waste of weight and complexity), does anyone have any ideas?

Any particular reason you'd like this to be a dead axle and not a live one?

I think the best COTS solution would be to use a pair of round / keyed VersaHubs in there. You don't really need to bolt the hub down, since all the hub is doing is keeping the 1/2" axle concentric with the 1.125" hole. Just be sure everything's retained and can't slide past each other too easily. Would this mess up the gear spacing (lengthwise, along the shaft)? I dunno.

If you can do any lathework, a 1.125" OD, 1/2" ID spacer wouldn't be too hard to make, or even a single piece shaft with a 1/2" end and a 1.125" end. But I suspect that's not an option for you.

[Ari423]

Originally Posted by Chris is me

Any particular reason you'd like this to be a dead axle and not a live one?

I think the best COTS solution would be to use a pair of round / keyed VersaHubs in there. You don't really need to bolt the hub down, since all the hub is doing is keeping the 1/2" axle concentric with the 1.125" hole. Just be sure everything's retained and can't slide past each other too easily. Would this mess up the gear spacing (lengthwise, along the shaft)? I dunno.

If you can do any lathework, a 1.125" OD, 1/2" ID spacer wouldn't be too hard to make, or even a single piece shaft with a 1/2" end and a 1.125" end. But I suspect that's not an option for you.

I am using the clamping gearbox to drive a sprocket. I thought it would be less complicated to go dead axle since the gears and the sprockets have a bolt circle anyway, but it looks like it may not be.

Adding a hub in there would work, but it would push out the driven gear from full (or almost full) contact with the driving gear to .28" (56%) contact. That may be enough, but it is a little more risky.

While I theoretically could make a custom spacer from cylindrical plastic stock, it seems like too much effort and a source for misalignment.

[asid61]

I think just running it live round axle might be best. As in, use 1/2" round bore or hex bore sprockets/gears, bolt them together normally, and run the bearings in the clamping box.
What's stopping you from just drilling a 1/2" hole in a 2x1?

[Ari423]

Originally Posted by asid61

I think just running it live round axle might be best. As in, use 1/2" round bore or hex bore sprockets/gears, bolt them together normally, and run the bearings in the clamping box.
What's stopping you from just drilling a 1/2" hole in a 2x1?

My plan was to drill a largely oversized hole (1"+) and then use the clamping gearbox's sliding ability to tension the chain on the sprocket. I'm not sure exactly what you are suggesting about running it live axle. Are you saying to just set it up normally as a live axle or something special?

[asid61]

Originally Posted by Ari423

My plan was to drill a largely oversized hole (1"+) and then use the clamping gearbox's sliding ability to tension the chain on the sprocket. I'm not sure exactly what you are suggesting about running it live axle. Are you saying to just set it up normally as a live axle or something special?

I see. I was thinking of either setting it up live axle or machining it dead axle, but if you need to tension it you could look into either tensioning on the other end or running some kind of idler sprocket or other non-shaft tensioner.

[Ari423]

Originally Posted by asid61

I see. I was thinking of either setting it up live axle or machining it dead axle, but if you need to tension it you could look into either tensioning on the other end or running some kind of idler sprocket or other non-shaft tensioner.

I think I'm just going to do it live axle. It doesn't need it, but it seems like a lot less trouble.

[Cothron Theiss]

Originally Posted by Ari423

I think I'm just going to do it live axle. It doesn't need it, but it seems like a lot less trouble.

Much of the VexPro products are based on live-axle motion transfer. Using these products outside of their designed usages certainly isn't against the rules, but it can be more trouble than what it's worth. Figuring out when and how to modify COTS products to your purposes takes some planning and some experience. (Hey, that sounds suspiciously like engineering.)

Also, are you sure the clamping gearbox will hold securely enough to keep the tension in your chain? I know on drivetrains, people have noticed slippage when they used the clamping bearing blocks without the WCP cam. I don't know if you'll run into the same problem.