Roller Claw
 

For the 2011 season our team used a simple pneumatic claw and we wanted to attempt a roller claw during the off season. We plan on using two P60 gearboxes with Banebots RS-395 motors but what we can't figure out is how to drive the wheels/conveyor belt to pick to tube up. Can someone please explain how to drive the wheels while still keeping it as simple as possible?

Re: Roller Claw
 

We did this on our roller claw.

Inside the square tubing, we drilled holes for 1/2" ID bronze bushings. (We used bronze bushings to ensure we had adequate material left on the tubing; ball bearings would've been too big to fit, and we had more than adequate power to make the lower efficiency a non-issue.) From there, we used #25 chain and 1:1 sprockets to go from the gearbox to powering the hex shaft. In a perfect world, you could add a keyway to the part of the shaft to add a key to match the sprocket, but we got away with grinding a flat spot down on the sprocket part of the shaft and using the sprockets' set screws to drive the rollers. (Mind you, we didn't use the claw as much as some teams. I can only encourage you to test on your own and draw your own conclusions on longevity.)

We used 1/2" hex stock, turned down on a lathe to fit inside the bushings, then made up some plastic inserts to fit inside PVC pipe and broached it to match the hex shaft. (Since we were riveting it all together, we did NOT want to go fishing for a lost key. Besides, we had a broach.) I want to say we added E-clips to these, but I can't confirm it from the photos. Even without them, the riveted claw structure should do a lot to constrain the roller on the shaft.

Our claw had its fair share of issues, but this aspect of it was fine.

Hope this helps!

Re: Roller Claw
 

we mounted our bane bots to the back of our claw and used belt-drive one wood dowel that had grooves cut into it. we had large o-rings rest in the grooves and had an identically cut dowel on the front edge of the claw. there was enough slip in it (not on the tube) to keep it from killing it self. it worked great. here's a pic.

Re: Roller Claw
 

If this is for the offseason,

I'd highly recommend using the RS-550 or 775, not the 395.... The first two are a much better choice.

-RC

Re: Roller Claw
 

we used the CAN buss to detect current on the roller. once the current draw for the motor on the roller exceeded 14 amps, it automatically shut off, we tested around a bit and i think that this method was much more reliable than any other sensor at telling when there was a tube in the gripper. a limit switch can be bent, and many other sensors are easily broken.

Re: Roller Claw
 

We used two plates of lexan that sandwiched two 550's with 104:1 gearboxes in the base of the claw, and four rollers in the "fingers" of the claw. The gearbox output shaft extended from inside the claw. The four rollers had shafts that also extended out of the claw. Each 550 powered the nearest roller with a 1:2 chain reduction, and then each roller powered the one in front of it with some polycord loops.

It actually looked a lot like 1730's, but with chain instead of belt, both chains on the same side, and the chain outside of the frame. We also used smaller rollers and polycord.

Re: Roller Claw
 

Our roller claw used Delrin pulleys that we turned on a lathe and rubber O-rings on both the drive pulleys and for the the main contact surface of the gripper. We keyed the delrin pulleys mounted on the motor shafts, used 3/8" hex-shafts and 3/8" bearings and broached the rollers that were on the driven end of the gripper, and used simple round shafts on the front end of our gripper. If I had a picture of the whole assembly, I would attach it. It worked fairly well for the most part; however, eventually the O-rings began to wear and had to be replaced.

Re: Roller Claw
 

Banebot wheels are awesome for roller claws. Make sure to get Shore 30A ones for maximum grip. Also use Banebots 550 geared somewhere in the range of 26:1 depending on wheel diameter.

http://banebots.com/c/WHB-WS

Here is a video of our bot using them, along with a 360 view of our claw.

http://www.youtube.com/watch?v=SZ7jTKJNLzg

Re: Roller Claw
 

Team 48 has a really nice looking/purposeful roller claw, if they wouldn't mind us basing ours around it of course. :P