17 Aug 2006 tbenedict   » (Master)

My copy of Dennis Clark's OOPic book finally came in. Yaaay! Only four days later than Amazon thought, but that's one of the prices for living on an island: slow mail. I'm about halfway through it. Good information for anyone using OOPic processors. Lots of info that's not readily available online.

I had to re-arrange the ballast on my mini-ROV. Given the density of stainless, it took a LOT of washers and nuts to make up enough mass for ballast. I swapped it all out for a slab of brass I had lying around, which was drilled to screw into the threaded holes in the motor mount. It wound up being heavier than I needed, so I added more buoyancy. The extra mass makes it a little easier to maneuver, given the overly stiff tether. Still need a better tether...

I'm starting design work on the line follower. Propulsion will be the same, regardless of the rules. So I'm starting with that. I've got several 9kRPM motors lying around I'd like to use. I want to try building an o-ring belt drive system since changing pulley ratios is a simple matter of making a new set of pulleys on the lathe. I'll report on that as it happens.

For the sensor assembly and chassis I've got some 1/2" white nylon sheet (aka $3 cutting board from the local grocery store). It's fairly low friction, so a sensor pad that would double as a "third wheel" on a two-wheel robot makes sense. For that matter, the entire chassis could be cut out of a single piece of nylon. It's not my favorite material to cut (Delrin would be way better) but it's cheap, it's locally available, it's got nice friction characteristics, and it would block ambient light from the line sensors. I'll report on this as it happens, too.

The layout of the line follower sensors will depend heavily on the rules for the competition. Right angle turns would necessitate having sensors forward and outboard that could detect the turn in time for the wheel motors to turn the bot. I won't start on that until the rules have been clarified.

Next Tuesday is the second meeting of our local robot club. In addition to seeing the rules for the competition in Hilo, I'm also excited to see who shows up. School is now in session, so I hope we get a good percentage of the teachers and kids who will be participating in academic competitions this year. Time will tell. This will also be the first time my mini-sumo gets in the ring with another mini-sumo bot. It's funny... I know I'll lose, but I'm excited anyway. At least now I'll have some idea of what I need to do to make it competitive.

Should be fun.

Tom

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