ANN: Canopus Treaded Tank Now Ready

Over the last month or so, Earl, Phil, and a few others here asked about the inverting tank base I have been working on -- originally called
Carina, now named Canopus. It is now ready for public consumption, and is available here:
http://www.budgetrobotics.com/shop/index.php?shop=1&cat9
Please note that Canopus is not a hacked toy. Its motors are Hitec HS-700 ball bearing servos, premodified for continuous rotation (these alone retail for about $30 each at many hobby stores). I don't have anything against hacked tank toys, just that I designed Canopus to be something more.
Thanks to all those who inquired. I hope Canopus can be of use to some of you.
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
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On Sun, Dec 07, 2003 at 10:17:19PM -0800, Gordon McComb wrote:

Looks like an excellent new addition to your robot line-up, Gordon. Oddly enough, I had just ordered a couple of Scooterbots from you to build with my kids over Christmas. I specifically looked to see if Canopus was available, but alas, I was apparently a day or two early with my order. Perhaps I'll pick one up next time around ... I'm thinking a MAVRIC-II would look very nice on a Canopus :-)
One question about the tracks - looks like each "tread" has a pair of holes. Do those holes go all the way through? If so, perhaps one could mount a phototransister / illuminator pair on either side of the track - the track itself could serve as the encoder. Just thinking outloud ...
Cheers, -Brian -- Brian Dean, snipped-for-privacy@bdmicro.com BDMICRO - Maker of the MAVRIC ATmega128 Dev Board http://www.bdmicro.com/
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Brian Dean wrote:

I figured they were for Christmas -- one green, one red. Christmas is always a fun time to machine colored plastic. Everything looks so festive!

The holes don't go through. However, the edges have a small bit of serrated "flange" and with the right slotted switch could be used for odometry. Might work, but a better approach may be this: The inside of the tread is cogged, and an IR detector/receiver could be used to detect when each cog goes by. The cogs are larger than the little flanges on the edges of the tread.
The cogs protrude down about a quarter of an inch, and are approximately 1/4" wide by 1/8" thick (the 1/8" side faces the edges of the tread).
Measuring movement of the tread might be better than putting an encoder on the drive wheel, which can also be done -- there's a good quarter-inch flat rim on the outside of the wheel that you could readily attach a paper disc to. However, with this setup, the drive is meant to "clutch" if the tread gets stuck (the tread has to pretty much jam completely for this). The idea here is to save the gears in the servos. The odometer would read that the drive wheel was turning.
(Hmmm...come to think of it, one detector on the the drive wheel and one on the tread could detect movement *and* stalled conditions.)
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
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