DIY Brushless spindle

Hi there,

I've been fiddling about with my Clarke CL300 lathe and I've managed to get it reasonably solid. So much so I've been cutting 8mm linear rails, like those used on CNC Machined, the case hardened stuff.

I bought a cheap PVC cnc machine a while back from china, Zen Toolworks look-a-like. Turns out the machine was missing loads of parts and the spindle was a piece of crap. I pulled the ER11 chuck off the end of the spindle and binned it and made up all of the missing parts on my LynxCNC machine with the intention of using this little machine to route PCB's.

I had a couple of 8mm linear rails laying about and the ER11 chuck is also 8mm. Coupled with a few 628 bearings and aluminium tube press fitted together and you've got a spindle.

Chucked up a 1/8 carbide engraving tool into the chuck and with my metric DTI measured 0.01mm of runout 12mm away from the nut face. Pretty sweet for something knocked together out of scrap parts!

Trouble is, I turned the end of the 8mm rail down to 3mm to fit a brushless motor directly onto the spindle. It turned nicely but it wasn't until I tested it and the body of it got extremely hot to the touch that I realised something wasn't quite right.

It was then I looked up the motor thinking that the speed may have been a little too high. The motor is what I bought from the link at the bottom of the page.

4500KV :disillusionment::disillusionment:

That combined with a 12V PSU Bumped to 15V give a nice 65,000 RPM, no wonder the poor little spindle got hot! The bearings are only rated to 37,000 RPM

My question is, is there an EASY way of quelling this enormous amount of heat?

I could get another small brushless motor to fit, BUT, I only machined little more than necessary to fit the entire motor onto the shaft so anything longer is out of the question.

I could drop the voltage down to about 9V (I think) but that'd still give ~40,000RPM.

A little stuck really. A potentially awesome spindle for milling PCB's but to bloody quick!

RC Helicopter Brushless Motor 2623 4500KV for EP200 EP100-in Parts & Accessories from Toys & Hobbies on Aliexpress.com

Ok, tried turning the PSU down as low as possible. Unfortunately, 10.5V was the lowest and the ESC didn't seem to like it a great deal so it would appear 12V is the nominal. That's still 54,000 RPM. Though, I do think it's considerably less than that because 4500RPM/V is the no load speed and it's only a small motor so I would imagine that under load, even just spinning the spindle it's probably 5-10K less.

Anyone know of any brushless motors that can be had cheap that have a 3mm shaft with a reasonable KV, say 2000KV?

If you have space could use a lower speed, higher torque motor with a belt & pulleys?
I made an engraving spindle mounting for my milling machine which takes belt drive from the spindle with a 4.8:1 drive ratio giving me a 28 800rpm engraving spindle from the 6000rpm mill spindle.
You can buy round section Poly Belt in a range of sizes and it's fairly easy to cut & weld to size and pulleys are easy to make up if you have a lathe. My first belt has done 12 hours run time at full speed without problems,
Regards,
Nick