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Originally Posted by Sidtech
Isn't is possible to put the casters on springs to always keep the wheels even?
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Yes, it is.
In practice, you're better off with some delrin type skids or small wheels. The ones that 885 used this year were litterly made out of some plastic I found in the shop and done by eye in about an hour. They ended up workin surpringly well, so they stayed on instead of getting replaced by more professional examples.
Lets see about pictures...
This link shows one side of 885's drive train for 04. Extreamly simple. The only real problem we had with it was one that was ultimatly tracked down to a 40 amp breaker that was opening far to soon. At 8fps the speed diffrence in the drill motors became annoying. It wasn't unmanigable, but enough of a problem that our driver wanted a solution. A PID loop was installed to compensate, using encoders and some simple programming. After that, she drove wonderfully. You can also see the skids, on the inside edge of the frame. They appear as light brown blocks, much like the plywood frame. They are acutally made out of 'stallpoly' (the stuff used to make bathroom stall deviders). A bolt is acutally threaded through them and holding them on (I love this plastic!). One was ripped off late in the season and replaced with a Delrin copy. As far as I can tell, they were quite sasifactory for a quick hack job.
This shows the location of the wheels. The center of the wheels is where those gray dots (encoders) are. The balence came out surpringly well, favored to the front (ideal, for our needs). We didn't really try for that, it just work it's self out that way. As long as you can rock the bot back and forth with out much effort, your fine.
This
shot shows 95's bot from 2002. You can see the wheels near dead center of the bot, acutally a little rear of center. The skids on this bot are also very flashy (as was the bot period). Instead of just plain skids, delrin 'wheels' were made, and mounted on plain shafts. Their shape allowed them to 'bite' into the carpet when going forward and helped keep the robot tracking straight. When turning, they provided enough friction to keep the bot from over rotating. This is by far the easiest to handle 'bot I've ever driven.
Here's 95's 2000 bot. The drive wheels are hidden, but you can pretty much figure out whats going on. I can't recall what the skids used were, but they don't stand out much, so probably just small wheels or some delrin.
Also, 95 used 2 wheels this year. They havn't uploaded any pictures from this year yet, but it is just a refined version of 02's drive.
Obviously, there is a little bit of family in all these bots.
I have loads more pictures of 95's 2 wheelers and 885s latest. Just let me know if you want to see them.
-Andy A.
And I just can't resist...
Link