Sprocket with hub or without?
 

I was just looking at different sprockets to put on the Toughbox output to change our ratio while still using the Toughbox and KOP wheels/wheel sprockets. I was wondering what kind of difference an FRC team would see between a sprocket with a hub and one without. The ones provided in the KOP have hubs but what advantage do they convey, the force of the key spread over greater area?

Basically my question is, are we going to see a difference between something like McMaster part 2299K314 and 6793K133 in this application?
If you can't tell I'm heading into EE not ME ;)

Re: Sprocket with hub or without?
 

Generally, hubless sprockets are better for dead axle applications, as they transfer the torque from the sprocket to the wheel by bolts, with the assumption that there are bearings in the wheels for the axle. Since they are "dead-axle", the axles do not spin.




Sprockets with hubs are better for live axle applications, as they use the broached (either keyed or hex) shaft of the axle to transfer the torque. With live axles, the bearings must be in the robot chassis, as the entire axle spins.

Re: Sprocket with hub or without?
 

[Edit: I got beat to it. The above post is totally more informative.]

You're going to have more shaft support on the sprocket with a hub, but at the price of a LOT of weight. We usually machine the hub down till it's gone, and mount the keyed sprocket between two shaft collars. Much lighter, and plenty strong enough for a correctly designed chain system.

Re: Sprocket with hub or without?
 

Isn't machining away the hub of a sprocket with a hub the same as just adding a key to a sprocket without a hub?

Re: Sprocket with hub or without?
 

Yes, but where we get our sprockets only sells them with hubs. Takes a bit of time, but is well worth the cost savings for us.

Re: Sprocket with hub or without?
 

the difference is in how thick the two sprockets are. The hubless sprocket is designed to be attatched to something flat, not just put on a shaft. The hub sprocket is designed to mount to a shaft.

Usually the hub type sprockets are very heavy and the hub portion of it is much larger outside diameter than it needs to be.