10EE drive VFD no backgear

I recently purchased my second 10EE...

Machines Used | Monarch 10EE Toolroom Lathe with Taper Attachment and Chucks


20 years ago I went VFD with backgear and 5 hp three phase motor. Biggest job in last 20 years is adding way oil. That is why I only considered another 10EE for my second home. Allows shipping all chucks and tooling between sites as needed.

Machine work to fit the backgear is quite a large job, but doable.

I am considering purchase of a 900 RPM 10hp 3 phase motor and driving it with a VFD with no back gear. A gearing of 3:2 will give spindle speed range of 40 to 2400 with motor speeds of 60 to 3600. With today's VFDs will have 2/3 hp at bottom speed - plenty for threading. Top motor speed of 3600 is plenty safe.

My google foo is poor - surely this has been done before. Comments please.

I am NOT interested in saving the antique DC drive. Any purists here have a chance to buy this at a fair value.

Karl

I used a 7.5 hp 3 phase motor (Century/Gould) mounted inside the striped out Reliance case. Chopped the reliance motor shaft off as its the input for the gearbox and mounted a lovejoy coupling to connect them. Allows the entire gearbox to be pulled out without removing the motor. Ensured proper/quick alignment of pulleys and belts, kept everything looking stock and was dead easy without a lot of extra hardware and machining. I run it through a VFD off simple spilt phase (1 phase) 250 so I don't need 3 phase wired. Like you said, add way oil and run. No fuss no muss. Can't seem to upload pics, but if you want a few and better description, just email me. Don

Do you feel you will need a vector duty motor to handle the 240 hz needed ? Another option would be a two speed motor. You would want a two winding motor rather than a Dahlander type but many vfds can be programmed so you could run both speeds. The motor would need less hp- maybe 5 at the 1800 winding but the frame would need to be large to handle both windings. Dahlander motors are more common but the need to bridge the low leads when running high can complicate the vfd set up. Others probably know how to accomplish that though. Dave

Thank you for the info. I had thought a few Monarchs were done this way back in the day. And yep the key here is newer technology VFDs and 8 pole motors. Not available several years ago. I've priced all the parts at around $2K - not bad.

FWIW, my first 10EE is refitted just like Don's in post 2 with a three phase motor sitting inside the DC motor carcass. I seem to remember it as a putsy time consuming process.


PS. What is the price of a single phase DC drive if the motor is rebuildable? IF (big if) I can find a shop to rebuild about what will that cost?

I am aging and want the machine re built so it will never need to be touched while I am on this side of the grass. Just tweaking on the existing electrical to get it going again is not good enough.

This was an ingenious way of using what’s there to do the conversion! Pretty cool!

You might be tight on space, I would use a 7.5 or 10 hp 1200 rpm and size the drive pulley to your liking...Phil

Karl_T said:

I recently purchased my second 10EE...

Machines Used | Monarch 10EE Toolroom Lathe with Taper Attachment and Chucks

I am considering purchase of a 900 RPM 10hp 3 phase motor and driving it with a VFD with no back gear. A gearing of 3:2 will give spindle speed range of 40 to 2400 with motor speeds of 60 to 3600. With today's VFDs will have 2/3 hp at bottom speed - plenty for threading. Top motor speed of 3600 is plenty safe.
Karl

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From an operational perspective, there's no reason why you cannot... just space, of course.

I know this with absolute certainty, as my '43 round-dial runs with an 1800rpm Allis-Chalmers 7.5hp with a 3:1 reduction to the spindle, and a VFD running overspeed (210hz) and it works just dandy... good finish quality, and rip-my-arm-off torque, with no backgear.

My drive


That's either a Carlisle RPP or Gates Polychain... I don't remember exactly.

Nothing special about the motor, other than 1800rpm 230/480 of late '50's vintage, nix'd the internal cooling fan for a constant speed fan in the shroud.

VFD is an OLD Allen-Bradley 1336 10hp (first gen) 480v drive, fed by a 7.5kva single phase transformer, 240v in, 480 out, into L1 and L3 of the 1336.

There is nothing to be gained by using a Dahlander motor with q VFD. I recently tangled with a cold saw set up that way. Except that the speed control pot is a little easier to set when the motor is switched to half speed since the lower half of the speed range is spread over the full pot. The hp at half speed is the same. The switch is a mess, many jumpers and a nightmare to hook up. Talking to the manufacturer, is was clear that some benighted engineer had originally designed it that way and over the years they had gradually changed their saws to a simple single speed motor and VFD. I did the same thing on this one, leaving the motor on high speed permanently. I don't know how a two winding motor would work.

The DC motor with a smooth power supply, filtered, not rectified single phase, is far smoother at low speeds. If you don't want the MG, use at least a three phase Variac with a full wave rectifier feeding one of the old 3 hp DC motors with the gearbox. They are big and ugly, but they are as smooth as a servo motor. A single phase supply, unless it has some large chokes and capacitors, will drive in 120 jerks per second.

The main problem with these conversions is losing all the fine points like field loss shut down, braking on reversing and avoiding plugging, shutting off the field current after a delay to allow braking to avoid heat buildup, etc. Getting the spindle to turn is easy but retaining all the details isn't.

Bill

I'm curious, Where do you find the pulleys for your setup? I'm thinking about doing the same thing.

Heychris_1 said:

I'm curious, Where do you find the pulleys for your setup? I'm thinking about doing the same thing.

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Just order yesterday. could not find it on Mcmaster Carr, my go to source. found a 2.35 OD double pulley with QD bushing online Zoro

PS getting tired of all the BS on this site so only posting the build thread over here
Monarch 10EE rebuild 10Hp VFD no backgear | The Hobby-Machinist

Yep, you should be proud of yourself for chasing another person away. AND never giving any decent help to anyone - just spewing BS.

Termite why do you not start your own thread it would make it easier to ignore. As others have said you are not a machinist, have never made anything in living memory, don't have a running lathe and just repeat what others have said or done. If you want to post your bs do it in your own new thread instead of constantly polluting other peoples.
Bob