20 Oct 2005 ericzayers   » (Journeyer)

This morning I gave a short presentation to the Belmont Hills "Booming Bears" First Lego League team on the topic of "Design" and showed them some sample drawings and some techniques. They have their playing field all assembled (except for the boat) and have built a motor operated arm for one of the challenges already! I made a poster of Keith Rowell's awesome little Knewt robot to illustrate the evolution of a design. I also dropped off some graph paper, photo paper, 2H pencils for drawing, and a shoebox full of extra legos. They were all studying the Lego ROBOBuilder software for programming their robot.

Last night's AHRC Robot Builder's night out was terriffic. There was a good crowd with enough experienced folks there to help out some of us less experienced folks. Not only that, but the Norcross High Georgia BEST team was working on their project, which was pretty cool (a simulation of repairing the Hubble with a teleoperated robot.) I was blown away by the differnt types of equipment they had (CNC Lathes and milling machines, plastic injection moulding, even a wind tunnel!)

My mission for the night was to work on a drive train for my larger robot. I want to build a standard 2 wheel differrential drive train, and need to some how connect my motor w/ a 5/16" threaded shaft to a wheel with a 1/2" bore - preferably by using some pulleys to create a belt drive that would slip if the wheel stalls. Some folks were more interested in seeing what was going on inside the wiper motor, so we pulled the cover off and peeked inside the coils.

I had 1/4" vacuum cleaner belts and some pulleys I bought at the hardware store. 2x plastic 2" pulleys for clotheslines and a double metal pulley 1 1/2" dia all with 1/4" bore. I had some 1/4" and 1/2" shafts as well. Luckily, Mike Lynch was there and helped out a lot. We used the chop saw to cut some axles from my 1/2" metal rod, and we were able to remove the 1/4" bearing from the metal pulleys by just pressing them out with a vise and some hex sockets, which left us with 1/2" pulleys! We used hex couplers on the 5/16" thread from the motor which also fits the 1/2" bore of the pulleys with the bearings removed.

The pulleys had no hubs, but we drilled and tapped into the middle of the pulley for a 6-32 set screw. I'm advised to use lots of epoxy on the hex coupler to pulley setup, and some lock-tite on the threads of the set screws and the motor threads that connect to the hex coupler.

Don't you hate it when someone asks you what your robot is going to do? In my case, I have no real idea what I want it to do. I will be thrilled if I can get it to move into a straight line and not run into a wall at high speed. I'll have to make a new webpage for my this larger robot and post it on my projects webpage soon. That is, as soon as I can figure out what this robot is going to "do".

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