One consideration, because of room limits, is for us is to use four 8" pneumatic tires. I think turning via tank drive will be very difficult.
Has anyone tried this?
Would 2 transmissions and four motors be enough to make reasonable turns?
:ahh:
Based on team Indiana’s bot…
Yes. Yes that would work fine.
It depends on whether you are wide or long. Pneumatic wheels also tend to bounce a little bit so you may need to be wider to turn as smoothly.
Note that they were turning on a concrete-like floor.
Turning on 4 wheels, with pneumatic tires on carpet, will be different. Current draw will be a bit higher and you will probably notice some scrubbing.
Edit: Okay, that wasn’t the video I thought it was. Was thinking of the other 4WD RI3D bot that was not on carpet. The video linked used a 6 wheel drive. This video used 4WD
They used six wheels.
It will depend on your track width (distance between parallel wheels) and wheel base (distance between co-linear wheels). The track width should be greater than the wheel base.
If interested this whitepaper goes through the physics of the situation, and provides some general recommendations at the end.
I wouldn’t trust our Ri3D robot on carpet. 6 pneumatic wheels with a drop center is highly preferable to a 4 wheel drive for a number of reasons, scrub being one of them. Another reason for 6 would be that it would have an easier time traversing defenses as shown by many of the Ri3D teams.
The only way to really know is to build some field elements, assemble a drivetrain and test it. That really is the only way anyone will know if they are going to work or not.
Or they can reference the Ri3D teams who did build the field elements, assembled the drivetrains, and tested them 
+1. We are also planning to paint our wooden defenses with some reasonably glossy paint to try to simulate the steel and aluminum and PVC and polycarbonate surfaces on the actual field. Sprockets and chain are coming from Vex tomorrow for a Saturday build and test session of some rather oversize COTS wheels I bought at Lowes for evaluation based on simulations.
If that works, we’ll probably make custom wheels, either in-house using nothing more precise than a drill press, or by CADding and shipping to NASA. Believe it or not, the in-house low-tech solution is my favorite for both technical and aesthetic reasons, not to mention team pride.
To those on the GDC: I LOVE THIS GAME! Non-zero sum (on QP)! Endgame! Weird stuff to do! Flying Boulders! Medieval Language! Real engineering tradeoffs! Even at the end of Saturday, we were still trying to do everything, which was of great “pucker factor” to me and several of our veterans. We’ve now moved two functions to the back burner, and I’m feeling much better about our chances of actually doing those that remain. BOFFO! (And OBTW, I hope we are figuring correctly!)
Thanks that is obvious:) I have looked at the three day builds and have built many chassis in the past but none with pneumatic tires. I was hoping to find a team that may have built a 4 wheeled pneumatic machine and could provide an evaluation. Just trying to gather information.
The GreenHorns did build a 4 wheeled drivetrain with pneumatic wheels. I would caution against using just 4 wheels. 6 pneumatic wheels with a drop center is a much better option. The scrub with 4 wheels is significant on carpet.
In 2012, 2056 had 8 pneumatic wheels which is essentially a 4 wheel drive base with some raised wheels on the end.
Not exactly what you want but similar.