[philbur]

Be careful. The program doesn't say but I think the calculated power requirement is at the tool, not the input. How would the program know your spindle drive efficiency.

Regards
Phil

Phil - Thanks! I see! 1W of power is consumed when cutting 1/64" deep at 12.5 IPM

Most of the hobby-type brushless motors seem to be able to produce 100W easily. This cheap 3800 KV motor & ESC looks about right, and the motor case doubles as a heat sink (no carbon fiber shell on this one):

http://cgi.ebay.com/3800KV-Brushless...QQcmdZViewItem

Brief Specs:
Motor RPM/KV: 3800
Motor Max Watts: 250W
Motor Max Continous Current: 8-10A
ESC Minimum Voltage: 4.8V
ESC Max Voltage: 14.4V

So, driving it at 5V (and at 100% "throttle") will give me 19K RPM.

From the numbers above, at 5V the motor could generate a MAX of ~30W of power. So, each 1W consumed at 5V would require 200mA current.

I will only need 1W, so I suspect that that running virtually "unloaded" (the cutter will not be pulling many amps @ 12IPM, and 1/64" deep passes), and even with losses through the coupling system (misalignment, friction, heat, etc.) I would be drawing WELL under 1A @ 5V, with 250mA probably being typical for my application.

How's my math, guys? Did I goof up any where?

---Will

[Greolt]

Will did you see this thead. Probably worth a look.

http://www.cnczone.com/forums/showthread.php?t=23097

An Aussie builder put one of those same spindles (I think) on a machine with the same sort of motor as you are looking at.

Greg

[Stepper Monkey]

The little brushless motors for RC cars do lose bearings pretty quick. They are rebuildable and all, but a couple of hundred watts out of a couple ounce motor and something has to give. They are designed for maximum power out of a very small and light package, not longevity. Many of them require rebuilding every 10 hours of run time or less.
If you want a brushless DC motor, with speed controller built in no less, that will handle high side loadings and long runs, try something a bit larger. Those annoying little electric scooters, and electric bicycles as well, have 250W-400W brushless DC motors that have bearings that can handle a LOT of abuse. A PWM speed control board is integrated into the motor housing on many models. Nice bonus is that they often have a brake circuit on the motor as well. (useful for e-stop!)
You can get them brand new uninstalled >very< cheap off of EBAY as the fad is over for scooters. $20-40 bucks will get you a very nice motor.
They are light, but are still 4"-5" in diameter instead of 1", but no worries about overheating or bearing life....