Monarch 10ee drive ideas and solutions

I recently acquired a 1943 10ee round dial. It came with a dc motor that had been upgraded maybe half way through its lifetime. It’s junk. It didn’t come with a back gear box. Now I’m doing a full rebuild and VFD ac motor upgrade. I have a 7.5 hp 1755 rpm 200 volt motor that I’d like to use. My original idea was to ratio the double wide “B” pulleys so that at 120 hertz the spindle would run at 2500 rpm. I set up the motor temporarily with the correct pulleys and a VFD that is too small (because it was one that I have). I’m not convinced that I will have the torque that is needed at lower spindle speeds. I’m toying with the idea of a jack shaft to reduce spindle speed and increase torque. And possibly 240 hertz to get 2500 max spindle speed. Thoughts?

Call Scott at Monarch and see what they use when they repower the lathes they rebuild.

Hal

blainemaxwell said:

I recently acquired a 1943 10ee round dial. It came with a dc motor that had been upgraded maybe half way through its lifetime. It’s junk. It didn’t come with a back gear box. Now I’m doing a full rebuild and VFD ac motor upgrade. I have a 7.5 hp 1755 rpm 200 volt motor that I’d like to use. My original idea was to ratio the double wide “B” pulleys so that at 120 hertz the spindle would run at 2500 rpm. I set up the motor temporarily with the correct pulleys and a VFD that is too small (because it was one that I have). I’m not convinced that I will have the torque that is needed at lower spindle speeds. I’m toying with the idea of a jack shaft to reduce spindle speed and increase torque. And possibly 240 hertz to get 2500 max spindle speed. Thoughts?

Click to expand...

That’s a large margin to overspeed the motor!

Torque drops off as you raise rpm, and the motor balance may not be satisfactory at that speed (maybe bearings too?).

120 or 150 Hz is the very most you can spin a regular 3 phase 1725 motor. And 7.5 hors is not going to have enough torque at low speeds.

Two ways to go - bigger motor - or get a back gear. 10Hp about the min without backgear - 15 better. If you can find a 1200 RPM 15 hp, it would be PERFECT for a 10EE. You could spin that ups to 150 or 180 HZ and still have 1.5 horse at 6 Hz.

Karl

Ok here’s what I’m going to try. I have a variable pitch pulley setup from a snowmobile. I gutted the primary clutch so I can control it with a screw crank. I mounted it to the 7.5 hp motor. The secondary pulley is mounted on a jack shaft on pillow block bearings. It then is connected to the spindle with 2 “B” style v belts. I figure at 50 spindle rpm the motor will turn about 260 rpm which should be about 1 hp at about 9hz. At about 308 spindle rpm the motor would be at full 7.5 hp. As far as high spindle speed, I’m not sure of the ratio on the variable drive. But 2 to 1 overdriven looks like it’s very possible. That would be about 2415 spindle rpm at 60hz. Has anybody tried this? Do you see any problems with this idea? Thanks

So the snowmobile you are attaching to the 10ee - you'll have it on blocks? Will you be disconnecting it to ride it in the winter? I wonder if the gas motor will cause excessive vibration? I suppose you'll need to route the exhaust gas outside the shop.

A simple drive solution perhaps:
I own a Harrison 1330 CNC lathe.
Nice little machine. It was made with a high and low speed range.
To accomplish this the drive motor (no gear box) is mounted using a flange on the motor that mates to a foundation plate. (sort of like an angle plate)
The main mounting bolts pass through the plate and are actually lever style handles that allow hand loosening/tightening of the bolts.
Those bolts pass through the plate in slotted holes.
The entire motor is set on an over center lever that has a length adjustment screw as part of the assembly....

The spindle end is fitted with duplex pulleys...large and small with a multi groove.
On the motor there is a matching set of duplex pulleys, opposite to the spindle.

To change the range, you loosen the two clamp handles, lift the lever (that takes the tension off the belt. Then you jump to the opposite pulley set and lower the motor, set the clamps and your
up and running.....No idler, same belt works on both speed ranges. Height adjustment on the lift lever takes care of belt tension when its in the locked (down) position.
Change over takes about 15 seconds...Clean, simple and quiet....AC vector drive spindle motor (10hp Fanuc) gives spindle speeds from 20-4000 with this pulley setup.

Could provide photos if anyone is interested.....

Cheers Ross

If the motor is Inverter rated spinning up is not much an issue, except noise. A 5hp Black Max 1750 motor is rated to 5100rpm. That 1:6 BG is handy for so many things, I would never give it up. Monarch upgrades are 7.5 hp with BG and 10 HP with no BG. My EE was built with 5hp and 4000rpm. When converted to 5hp Inverter drive torque in lower rpm ranges was not acceptable, due to "Cogging Effect". The small spindle pulley was replace by a pulley from a 2500rpm machine, and low rpm use in direct is fine. And the BG is still regularly used.

I do not recall the exact ratio of motor to spindle speed. But 2000 motor rpm is about 1800 spindle rpm direct drive.

It has been awhile, but others have purchased used motors with back gear unit attached from Monarch, for what seemed reasonable prices, I remember a photo posted of several used motors and back gears.
The current back gear box used on their new AC drive is different looking.

Karl_T said:

120 or 150 Hz is the very most you can spin a regular 3 phase 1725 motor. And 7.5 hors is not going to have enough torque at low speeds....
Karl

Click to expand...

Karl, this has NOT been my experience.

My '42 EE used to have the Ward-Leonard DC drive and backgear.

I've replaced it with an Allis-Chalmers 1800rpm 480v 3ph 7.5hp motor, driving a Gates Polychain toothed belt at a 3:1 reduction ratio to the spindle.

The motor has been stripped of it's TEFC cooling fan, and a fixed-speed 240vac ball-bearing fan is mounted in it's place. The motor has been fitted with fresh bearings, same type as original when it was built in the mid '50's.

The motor is driven by a first-generation Allen-Bradley 1336 10hp drive programmed to run 3hz to 216hz, yielding a motor speed of basically zero to 6480rpm, and spindle speed of 2160.

The power source for the 1336 is a 10kva single-phase 120/240 - 480 dry transformer wired backwards, so that the primary powers L1 and L3 of the VFD, while my 240v panel powers the input. I've tapped my connections across one leg of the 120/240 side to provide 120v power for my lathe's lights, coolant pump, and accessories, so the whole works is powered by a no-neutral 240v/50A range plug.

I have it set up for dynamic braking with DC injection for about 2.5 seconds, and coast-to-stop on power loss.

The torque available at ANY speed above just slightly started, is ghastly dangerous. Contrary to my initial concerns, the toothed-belt drive is plenty smooth. It may not be as 'silky' as the flat-belt drive was, but it does NOT want for power under any circumstance.

If the motor is a good quality industrial unit, balance will never be an issue. I would recommend that any USED motor be opened up, cleaned out good, fitted with new bearings, and a fixed-speed fan. I've found circumstances (particularly with 'smarter' drives) where some motor designs don't 'like' a given frequency... a result of the inductive reactance of the windings, etc., cause it to have a bit of non-linearity, or sometimes the reactive voltages are high, and the result is an 'overvoltage' fault or something similar pops up. While 'tuning' up the drive, find those points, and adjust the motor parameters a bit, and that clears up.