pic: Sprocket legality?

[MattC9]

loading photo ...

[Akash Rastogi]

Floating tension sprockets are perfectly legal. Might want to support the end of that shaft by the way.

[Chris is me]

What could be illegal about that sprocket?

[thefro526]

Originally Posted by Akash Rastogi

Floating tension sprockets are perfectly legal. Might want to support the end of that shaft by the way.

Looks like they've got the holes to mount the bearing block...

And teams have used floating idlers for years, they work great.

[sanddrag]

For anyone who is interested in getting sprocket center distances just right, I've had fair luck using the numbers from this calculator http://www.team-moon.com/index.php/calculators/chain/, at least for #35.

[dtengineering]

The sprocket might be fine, but in this particular photo I would have some very real safety concerns about things (such as human hands) getting caught in the chain.

I'm sure that a guard for the chain and/or a robot exterior that inhibits access have been removed for clarity, but just a friendly reminder that just because a part is legal, the application of that part will not neccesarily pass tech if it is deemed to be unsafe.

Jason

[Lil' Lavery]

I'd be more worried about that P60's internals.

[Richard Wallace]

Originally Posted by Lil' Lavery

I'd be more worried about that P60's internals.

I would, too.

From the Banebots site: "We recommend maximum torque not exceed 35 ft-lb for all P60 Series Gearboxes. It is possible to mount motors that will exceed this in higher gear reductions. Higher reduction gearboxes should be utilized primarily for speed reduction. Designs utilizing a P60 gearbox / motor combination that will exceed 35 ft-lb should include a method of limiting torque to prevent damage to the gearbox."

I can't see the whole arm in this picture. If it swings past the top, shock load through a tight chain just might cause the hole in the P60's output carrier plate to deform from its nice double D shape into an ugly bow tie.

[CrazyCarl461]

Originally Posted by Akash Rastogi

Might want to support the end of that shaft by the way.

You should be able to run these gearboxes like this ok, just scoot the gearbox over and run that sprocket right next to the face. That way, almost all of the load is torsional with a little bit of shear and hardly any bending. Four more holes and you're running like a champ!

[MattC9]

Thanks for all the replys, they have all been great. I took this picture right after we put the sprocket in and now it does have a 2nd point of contact. Our arm is a 4 bar linkage with a 30in "finger" on the end of it and it weighs about 35lb, so I think our gear box should be fine. Our main mentor loved the idea of putting a guard on the chain, that will come out sometime tomorrow.

[Hawiian Cadder]

a 35 lbs arm that is longer than a foot to its center of mass will be a problem for that bane bots. i would recommend some more reduction. ex, our wrist is similar, but weighs 15 lbs and the torque of the the gear setup powering it is well over 130 ft lbs.

[Creator Mat]

Originally Posted by MattC9

Thanks for all the replys, they have all been great. I took this picture right after we put the sprocket in and now it does have a 2nd point of contact. Our arm is a 4 bar linkage with a 30in "finger" on the end of it and it weighs about 35lb, so I think our gear box should be fine. Our main mentor loved the idea of putting a guard on the chain, that will come out sometime tomorrow.

I would be careful on relying on the p60 gear box for that application. You said your arm is 35 pounds, well if that is true any time the center mass of the arm is greater than 1 foot away from your pivot point. The gear box is at a significant risk of stripping its inner gears.

Torque= Force X Distance
35 ft-lb=35lb X 1ft

[MattC9]

Ok, quick update we kept the whole arm as our 30lbs with holding allowance, and it only weighed 22lbs!! Including the supports. So the p-60's were only lifting about 20lbs.

[Gdeaver]

I wonder if the banebot people monitor this forum or is it too much for them to endure.

[DonRotolo]

Please let us know here how that gearbox held up in competition, we're interested.