# Speed question

How fast would a high speed holonomic drive on 2.75" wheels be in comparison with a high speed 4" tank drive.

Math.
Let’s set high speed 4" tank as 1.
The wheels will be smaller, so it will be slower. The circumference will change speed, so 2.75" wheels will be 2.75/4 times as fast.
X-drives are √2 times faster (right here for the explanation by Oliver from AURA), so overall, the drive will be 2.75 / 4 * √2 ≈ 0.9722718241315028, which means the holonomic will be basically the same as the tank, just a bit slower.

You could use mecanum wheels on a high speed (160 RPM) drive if you think the theoretical 3% speed loss is too much.
Or you could use turbo on the X-drive (240 RPM) instead of high speed (160 RPM).

And this is all in theory, so in real life, it may be a bit different (but it should be close enough).

Thank you @Vex 9185.
New question.
Would a robot with torque motors, a 1.8 : 1 drive ratio on 4" wheels be able to drive without stalling for an entire match?

Easily, assuming your robot isn’t extremely heavy.

Would an average skyrise robot’s weight have been too much for it?

I believe it should be able to take up to around 16 pounds, but don’t hold me to that number.

MATH the other way is to go:

4" wheel has a circumference of 12.56" (4*3.14) so every revolution it will move forward 12.56".
Unloaded motor rotation is 100 RPM, or 1.67 revolutions per second.
So a 4" wheel will move 21" (20.97 to be exact) every second.

2.75" wheel has a circumference of 12.56" (2.75*3.14) so every revolution it will move forward 8.64".
But there is a speed “bonus” on holo drives of 1.41, so every revolution it will move forward 12.18"
Unloaded motor rotation is 100 RPM, or 1.67 revolutions per second.
So 2.75 wheels in holo drive will move 20.3" every second.

Difference is 5/8" per second. On a race across the field (~6 seconds) the holo drive will be ~4" behind.