Problem! D:

Okay. So, I said I was going to Hydrogel last night. I did. We finished the wheels, the wheel axle adapters, the motor mounts, and made progress on the bearing mounts - both for the central bearing and the bearings on the weapon motor shafts - and the drive motor mounts.

We finished one weapon motor setup completely - and tested it. I was so excited about our wheels cause they were soft and squishy and I thought they would cushion the shell and provide some shock absorption. However, when we put the setup together, and clamped it to the table, and attached the battery, something I never expected happened.

First of all, I'm going to start with listing some statistics on the motors. The Speed 400 motors I picked for the weapon system have a stall torque of 12 oz-in at 7.2V. Which means, with ten, at 12V, it's about 180 oz-in or 11.25 lb-in. Since our little wheels are 2" in diameter, the radius is 1", so the weight to stall them is legitimately 11.25 lbs. We just have to be careful when we drive it to put the motors in neutral when we hit stuff so we don't stall them. And we do need all ten motors. With only 8 the motors would barely be able to handle it.

The RPM of the motor "under load" is 12700 at 7.2V, no load is 19200. It's got kV of 2227, giving an approximate no-load RPM of ~26700 at 12V. Doing a proportion, the load speed at 12V is ~17600 RPM. Which means the edge of the 2" wheels will be spinning at 111000 in / min. If we put the wheels on a 36" circumference circle (diameter - 11.459"), the shell will be spinning at 3071 RPM, and if the outer edge of the teeth is 14", the teeth will be spinning at 11256 ft/min or 127.9 mph. This is good.

So. Now that you know that the wheels are spinning at 111000 in/min or 105.1 mph, what do you think happens to the soft rubber on the wheels?

They explode!

well, sort of. The rubber expands to almost double it's original size and basically shreds itself against anything it touches. Scared the crap out of my dad and I... So we need new wheels. I think these wheels from robotmarketplace will work. They are thicker (7/8" instead of 3/4") and have a 1/2" bore instead of 5/16" so we will need to do a significant amount of work to make them work, but they will work. work. WORK.