Speed Calculator

[BrianG]

Griffin: So, it's not just a pure kv factor, it matters how many rotor/stator poles a given motor has as well. Hmm. I was hoping for something like "min rpm for proper ESC operation is motor kv/10", or something along those lines. I really don't feel like adding a couple more specs to each of the motors in my list.

Most of the time, manufacturers don't supply the stator and rotor pole count. Is there a way to get this information manually simply by turning the motor shaft and counting the magnetic "detents" during one full rotation? For example; a Feigao/Wanderer/Nemesis is a two-pole and has two magentic detents per shaft rotation. A Neu is a 4 pole motor, but has 12 magnetic detents per rotation.

macrow: ballooning depends a lot on the tire and the foams used inside. For a tire to balloon out, the sidewalls have to contract and good/harder foams will help limit this. 1" ballooning on a 4.25" tire is a 23.5% increase in tire size! That would make the tires look like pizza cutters and would seriously hamper handling. The calc only show theoretical speed, ot theoretical controllable speed.

[GriffinRU]

Originally Posted by BrianG

Griffin: So, it's not just a pure kv factor, it matters how many rotor/stator poles a given motor has as well. Hmm. I was hoping for something like "min rpm for proper ESC operation is motor kv/10", or something along those lines. I really don't feel like adding a couple more specs to each of the motors in my list.

You should be able to do that by turning the motor shaft by hand and measuring the back EMF. (Eagletree is sufficient to do this...)
And you need to check only one phase.
Count the number of zero crossings per one rotation and than the inverse of that will give you the minimum rpm. (1/# of zero crossings)

[macr0w]

Originally Posted by BrianG

macrow: ballooning depends a lot on the tire and the foams used inside. For a tire to balloon out, the sidewalls have to contract and good/harder foams will help limit this. 1" ballooning on a 4.25" tire is a 23.5% increase in tire size! That would make the tires look like pizza cutters and would seriously hamper handling. The calc only show theoretical speed, ot theoretical controllable speed.

I'm running these in the road. And they do look like pizza cutters at full throttle. And handling goes out the window. From the looks of it 1 inch ballooning was a conservative guess. That would only be a half inch expansion all around.