Back here again a year and a half later for some updates.
I ended up using a Turnigy 6374 motor with 149kv for the main turning spindle, and a 45mm 510KV motor for the milling spindle. Neither one is sensored. I used two 12v server power supplies in series to give them up to 24 volts and up to 60 amps.
The electric stuff worked decently, but the mechanical connections were bad. I tried to transmit torque with a set screw since the motor shafts are so small. I should have gone with the APS motor since it has a 10mm keyed shaft.
Now I'm building a second version of the machine, and it must be a lot more powerful and reliable. So I'm going to buy the 63mm alien motors for both the turning and the milling spindles. I just wanted to run a few numbers by some of the experts here.
First of all....
How much torque can a keyed 10mm shaft transmit in foot-pounds? I don't know how hard the steel is on RC motor shafts, I'm guessing around 50 Rockwell C.
The 6374 alien motors are advertised as having a bit over 3 kilowatts. They don't specify if that's peak power, at what RPM, or how long they can maintain that, or if it's input or output. I'm skeptical that they can hit that power at all. Someone enlighten me please!
But assuming they can do that just a second, it means we can approximate their torque. A 6374 90kv sensored outrunner that can do a full 3200 watts would reach it's max power at about half of it's max RPM. So 90kv * 48 volts = 4320 RPM maximum, half of that (rounded down) is about 2100 RPM. Doing a quick power-torque-rpm conversion, I'm getting a torque output at that RPM of just over 15 newton-meters, or 11 foot-pounds. Since the max power is at half the max RPM, and the torque decreases linearly with rpm, that means the maximum possible torque this motor can output at 0 RPM would be approximately 22 foot-pounds.
Is my estimate process correct? Can someone please give me guidelines for how much power and torque these motors are capable of, and how long that can be maintained? I know some of you on this forum have these very motors on your longboards.
My new machine will have chevron-toothed timing pulleys at a 1:1 ratio. I'll probably be using the VESC as the main motor controllers, possibly the new ODrive to test outrunners as servos. Encoders on motor shafts as well. a stack of 4 hot-swap server PSUs to supply 48 volts at 60 amps or so; the power supply can be tapped for voltage at 12v increments.