Variable Speed Mechanism on BP clones

I moved across the country last month to work for a brand new bicycle manufacturing company that is making waves in the carbon fiber segment. They had bought at auction the assets of a Canadian carbon fiber bicycle company that had failed, and in the auction were two BP clones, both 3HP, 575V machines. One was a completely manual machine with an R8 spindle, and the other was originally a CNC knee mill with NMTB40 spindle, but had been de-CNC'ed.

BOTH machines have broken variable speed mechanisms. Obviously, someone had cranked the handles while the spindle was stopped.

What breaks when someone does this? What parts usually need to be replaced or repaired? I assume it's a sprung spring or a broken gear tooth, but this topic is difficult to search in Google.

Secondly, does anyone have any experience with 575V motors? Right now the machines are wired through a 208V-575V step-up transformer the size of a small refrigerator, but it's awkward and I'd like to know if there's a way to wire the motors to work on 208V. I'm assuming the windings are smaller gage wire for low amps/high voltage, but are they really any different inside compared to 208V motors?

If you forward to the 14:10 min mark of the included youtube video you will be able to see the speed adjustment setup. The hand wheel you rotate spins a shaft that is connected to a eccentric. On that eccentric is a "bicycle" type chain that will pull down or allow to raise up a disc to change the speed ( and I will stop there ). There are 5 weak points to the system, the pin that attaches the eccentric to the shaft, the pin that attaches the chain to either the shaft or top plate, the pin that holds the rear of the top plate in position on the adjustment screw, and of course the chain itself. If you try to adjust the speed without the motor spinning you most times will shear a pin, or break a chain. It is NOT a hard fix and anyone that can manage to adjust a derailleur should be able to repair it. If it is just removing the speed assembly from the front of the machine, if you have to open the head to get to the plate that is a whole other story. Then again for a mechanically competent person it should not be too hard.


Bridgeport milling machine Vari Speed Head Assembly - YouTube

Thanks SShep71. As I said, hard to research. I hadn't looked up the term "vari", though I suppose now that would have been a good idea.

There are a couple more series of videos on YouTube on this topic, but all of them, including the one you linked to, show Bridgeport heads, which have a slightly different crank handle configuration than the clones. I wanted to see a clone like mine torn apart before I dove in.

I'm hoping it's something I can access with only the front cover off!

By the time you buy the parts and motor for that, you could put that money down on this drive assy. It's the best money I've ever spent on a machine. Called the AC Pro Drive. There's 5 separate pre-set variable positions. Comes with a 3hp Baldor inverter duty motor. This mill used to sound like a threshing machine.
Eliminates ALL the existing clanky drive components. Not to include the back gears. Quiet as a mouse now!
AC Pro Drive by Ray Behner | Photobucket

Sorry about that, I didn't notice the box "square" head design. Both of my machines are setup like that, I even have a variable speed control that may fit your setup if you need it. I will take a few pictures of the cover off on Wed night, and a fwe more of the control. I have 2 tests on Wed that are going to take priority over going to the shop.