6 Wheel Drive vs. 8 Wheel Drive

[JVN]

Originally Posted by GRT808

We went with a 8WD 8" Blue Nitrile Tread 0.125" drop because we were worried about the barrier and how well our robot would cross it. We knew the configuration we chose would cross without a problem but after seeing some of the teams at CMP, I think we wish we looked a bit closer at 6WD because of its superior maneuverability (for us anyways). We had a lot of traction and pushing power with the 8WD though, which was useful for the balancing.

Hi Grant,
You said a lot there, but also not a lot.

You described what configuration you chose, and what challenges you hoped it would overcome. Can you explain what specifically about your chosen configuration you thought would lend itself to overcoming those challenges? Do you have anymore insight into your process which lead to this decision? Was there prototyping involved - CAD or otherwise?

Can you explain why you think 6WD has superior maneuverability?

What characteristics of your drive do you think lended themselves to high traction and high pushing power (which are related)?

-John

[Aren Siekmeier]

2175 went 10 wheel with 4" plaction this year for a few reasons: As mentioned, you can hang more of your robot off with wheels closer together (specifically, with our CG just behind the wheels, you could get as far as half the robot hanging off, though we never did). Also, we need to not bottom out on the bump, but also have as low a cg as possible, so many small wheels did this for us. We dropped the center 3 on each side (6 total), so it behaved much like an uneven 8 wheel in terms of stability, which was nice for shooting, balancing, and just for stability in general. Not really many problems turning (contact rectangle 9" long by 28" wide), though it did stall out when attempting minor adjustments (the driver got good at it). I imagine a 6 wheel would do better there, since it can lift it's end wheels off the ground in the turn. Also lots of contact surface, so some could argue more traction (though I haven't seen or even sought data to support this).

We definitely did our share of CADing the wheel layout, checking for clearance, cutting cardboard profiles, making wooden wheels, etc.

Unfortunately, some other poor design (little review, not enough manpower, not enough time, etc.) meant we didn't actually get our CG low enough to get over the bump (or do a lot of other things).