24,000 RPM Spindle Motor on 2 x 72 Sander

BelnapCustomKnives

BelnapCustomKnives

Joined
Oct 30, 2015
Messages
139
Last year I started working on a new sander frame and while I was at it decided to look around for a different motor option. Anyone that has seen my grinding style knows that I like to grind fast and hard. My previous motor was a 5 HP 3450 RPM. It was a hoss. But it was also very heavy and large and no VFD. Bought a 3 HP, 3 PH, 400 Hz, 220 V, water cooled, 24,000 RPM spindle motor and VFD for $242.00 delivered. Took me a while to design a suitable drive to allow the motor to operate in its full power range. I designed a tiny 1.125" diameter drive wheel. This would provide 7200 SFPM belt speed when motor is at 24,000 RPM. That was my target belt speed. It is great for doing fast initial removal with my bevel guide. The bevel guide puts heavy even pressure on the entire face of the belt and requires a good motor to be able to pull the belt under those heavy loads. Turns out that ceramic belts such as Cubitron really like these grind conditions.
I began initial testing this week. The VFD has an auto torque compensation setting and I adjusted it up. So far I am very impressed with the motor in all RPM ranges with ability to pull the belt under load. It is an absolute angry beast when running at high RPM and shreds the metal off without trouble.
The drive wheel failed due to design issues that can be overcome in future with better materials. So far the whole thing has cost $500.00 to have a 3 HP VFD motor that is far less than half the weight and about 1/4 the size of the standard 3 HP motor currently being used in many 2 x 72 machines.
See some development videos and bevel grinding.

 
Wow ! Thats smoking fast motor.
I am surprised that small drivewheel and its low contact area gives enough traction on a belt.
 
Haha! Jeezus, I was sure the whole kit and kaboodle would take off! :D

I like the lateral thinking, good job. :thumbsup:
 
I’m guessing it’s a cheep Chinese huan yang spindle motor. This company makes all kinds of things for crazy cheep. The same company made my 10hp VFD for my press. Thy swore up and down it would handle my motor. Well guess what item has been gathering dust while I have been going back and forth with emails trying to get a replacement. So I learned my leasson, it was hard. buy once cry once, buy cheep buy again next week.
 
Those motors have a HP rating calculated on the speed. It is usually called "developed HP", and not comparable to actual HP. You see the same thing in a hand held 3HP router that only draws 6 amps, or a 5HP shop vac that draws 7 amps..
 
Those spindle motors actually do develop the rated hp - or at least the watts. Take a check on the amps used at 220 vac and you'll see the watts are right up there with rated hp. Those are normally used as CNC spindle motors and work really good.

That's a neat looking grinding jig you've got - like to see more detail on that.

Ken H>
 
I’ve tinkered with the idea of doing something similar with a 1/8 rc motor those go to 8hp and 10,000 rpms.

Something you may have overlooked, those bearings at the drive that’s a really good idea, bearings on your tracking and platen wheel are gonna wear soooo much quicker. Look into some ceramic bearings.
 
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