Alternatives to Pinion and Spur Gears

[Peter Matteson]

Here is a shot of our prototype from this year that was made from less than $200 total materials including transmissions, polycord belting (fused with a grill lighter), spockets, #25 chain, and Al hex, plate, and round stock.

http://www.chiefdelphi.com/media/photos/37060

We made 5 iterations out of Rought $200 worth of raw materials including the final one shown here:

http://www.chiefdelphi.com/media/photos/37063

The powertrain is banbots RS-545s through banebots planetery transmissions, then a 1:1 driving the rear rollers and the polybelting driving the front rollers.

This is a simple design that looks fancy only because of the machining. We had a wood prototype week 1 of build to test out the dimensions for claw before cutting metal.

[Bob Steele]

#25 chain and sprocket... use aluminum sprockets from AndyMark
Pretty light... easy to service... just watch the RPM's

[thefro526]

I'm not sure if some of the people in here realized you were from Australia and shipping from the US is quite difficult, so some suppliers like AM and McMaster might be out of the question for you.

I was able to find one Australian Company that might be a good supplier for things like chains and belts. http://www.smallparts.com.au/ Seems like they carry a lot of the things suggested in this thread.

[JCharlton]

Polycord is excellent for many purposes. Our grabber from last year used two loops with one being in a figure eight to reverse the direction. It has a significant advantage of slipping rather than putting your motors into stall.

I'm a little worried about the people using open flame to join the ends. I was told by our supplier that the fumes from burning urethane are BAD.

Here's a simple tip: use a hot air gun. Shield all but the ends from the hot air and be patient. When the ends are looking nice and soft mash them together in the corner of an L-angle (to keep the cord aligned) while wearing some gloves (so you don't get burned).

[Spirator]

We have a slight weight issue too because our elbow is being run off a CIM and 27:1 Banebots P80 so we can't output as much torque as we'd like.

We have surgical tubing to counter-act the torque, but we're not sure how well it would work for heavier loads.

Peter, how much does the Bobcat gripper weigh? I'm trying to minimise weight in the design.

[Peter Matteson]

Originally Posted by Spirator

Peter, how much does the Bobcat gripper weigh? I'm trying to minimise weight in the design.

It weighs about 10 lbs including motors and transmissions. We planned for the weight from the begining because we knew the claw needed to berobust enough to take direct hits fromother robots. We could have shaved weight out by making it from 1/8" instead of 3/16 but we had prior experience saying that you can never have enough robustness for a claw.