Just noticed something, is it going to be okay for those middle sprockets to only contact the track on the bottom?
It shouldn’t be a problem, however you should put more brushings on the top of the tracks so they smoothly mesh with the sprockets that do come in contact at the top.
For some reason I always figured that the narrow chassis would turn better but I was wrong! 
Yeah there does need to be more support at the top. It flops a little. And I have to move the bushings on the bottom. When I drew it up on paper everything worked out, but the bushings are about 1/8" away from touching the tracks. I just don’t know how long the plexi will last. A side piece fell off my workbench and shattered. Thank god I had an extra made up.
A quick picture with my phone. This chassis along with the motors, are going to need a ton of bracing!
http://i172.photobucket.com/albums/w6/jbflix/0106082034.jpg
Yeah, brace it, its deffinately gonna need some support!
That rover is gonna be awesome when you’re done. Very unique looking.
Unless you’re really hooked on having see-through sides, I would strongly recommend you ditch the plexi and get some decent plastic, like Delrin. Its more expensive, but it will never shatter, and its about 100 times easier to work with…
You can drill it, machine it, tap it, cut it, file it, whatever. I tend to cut larger sheets to size on my table saw.
http://www.huv.com/MicroRaptor-Chassis-small.jpg
huv.com/MicroRaptor-Chassis.jpg
(click for a big version)
That’s a picture of the chassis for MicroRaptor that I just machined over the weekend. Its cut (on a CNC mill) from 1/4" Delrin.
- Jon
True that.
yeah, that’s true, I’ve workes with plexi-class a couple of times and it shatered all the time, gets frustating 
And the cutting tools to score and break the glass are very innaffective unless you have the patience to score it 50 million times so the cut is deep enough to break. Even so, it can only be done for cutting out small pieces of straight edge acrylic. 
For now the plexi will do, but I’d definately like to be able to change the material. What would be the cheapest place to pick up some derlin?
McMaster charges ~$45 for a 24"x24" sheet of 1/8" black derlin.
I wasted too much plexi, just trying to get a general shape cut out. My jig saw kept cracking everything, up until I got the finest tooth blade I could find. Definately not worth the effort, but it will work for now.
I have never had plexi crack on me with my table saw non-ferrous metals blade, it really works!
depends on the thickness though. Is he using 1/8" or 1/4"?
Working with plexiglass is an art. I used to build sumps and overflows for salt water tanks and still use a 3 foot long acrylic sump that uses 1/2", 1/4" and 1/8" acrylic. I cut allt he pieces by snapping them. A couple scores was all it took. It broke alot of pieces when I stated working with it though.
It takes patience and practice to get good at it. I don’t think it’s a great building material for robots unless they are small or the plexi is very thick.
What kind of tank do you run? I have a 54 gallon planted discus tank with a fluval canister filter. It’s my “happy place”.
I have a 120 gallon reef tank, 40 gallon sump, 2 seaclone 150 protein skimmers, assorted soft corals and leathers with a Maroon Clown, Bubbletip anemones and some gobbies.
I also have a 75 gallon reef, 33 gallon sump, Euroreef skimmer, assorted corals and some puffers.
Sorry this is horribly off topic. 
Sweet setups. I’d like to eventually do a larger tank, but I’m content with my 54 corner for now. I don’t think I’ll ever do a reef - too much equipment. I think a massive planted freshwater community tank would be a lot of fun to watch, and it would be very low maintenance.
Sorry for the mini-hijack. 
no worries 8)
That’s where I got all my delrin. The price seems reasonable to me… but I’m not exactly looking for pennies in the sofa cushions. 8)