DC to AC motorswap

The parts from the WIAD are slowly moving out the door. Its pleasing to help other keep their machines working.
The installation of a 5hp AC and VFD is moving along. I had read several of the posts regarding fitting the Backgear unit to the new motor. A common issue was the input gear having splines, while older models had keyways. One guy splined his motor shaft, another made a gear from scratch, another bought a old style gear with a keyway and each was successful. I figured that I'd just find someone to EDM the gear to remove the splines and cut a keyway. This was done because I did something uncommon for me,I "assumed" that the gear was to hard to machine a keyway in. Well the EDM guys wanted CAD drawings, so I called my son and after several discussions had a set of drawings. This morning I was about to send out the CAD drawings, with the gear in my hand, wondered how hard is this gear really. While a file slide off the gear teeth as expected, the bore shed silver with the file. Darn this could have been done last week, instead of making drawings, making chips. Chucked it up in the old 16, thinking that carbide would not like those spline teeth, I set the cutter to take all the spline and alittle more on the first cut. 50rpm .0035 feed, lots of lube. Not wanting to chip a handfull of TPMG inserts was why so slow. It walked through without a single squeal. Sped her up and finished the bore job. Now the keyway, setup the broach and thought that if it won't cut 1/4 width, I'll do a 1/8 first then 1/4. Started with 1/4 and pushed right through. Quite a bit more tonnage to push the broach, but not worrisome at all.

So if you are concerned about the input gear splines, don't be, cut them out and move on.

my wheels don't slow me down

"The parts from the WIAD are slowly moving out the door. Its pleasing to help other keep their machines working."

Received yesterday afternoon. Many thanks!


"So if you are concerned about the input gear splines, don't be, cut them out and move on."

Aren't most 1725 rpm, 5 HP ac motors 1-1/8" shaft, while the keyed Monarch dc motor's shaft is 1-1/4"?

Did you bore the splined gear to 1-1/8" and then broach for a key, in order to match a 1-1/8" shaft?

Did you incorporate a seal into the back gear adapter plate?

Yes, the major dia of the splines is about .95 so its not a big step to 1.125, then run the broach through and its done. I checked our old parts inventory and found a Kawasaki crankcase seal that fit the shaft perfect, then bored the adapter plate 1.600 and we're in. Tomorrow I'll bore the back of the plate to fit the c-face of the motor and put it together. The adapter was bolted to a large faceplate on the SB16, and just cleared the ways, which had been notched sometime in the past. The motor shaft needs to be extended .800 so I'll bore a hole in the end of the motor shaft, thread it, then screw in a .800 extension that I'll then cut a keyway through and be done.

my wheels don't slow me down

If this is the same lathe that you're looking to slow down with a 2500 rpm pulley you don't really need to make the back gear work *and* slow it down. 5HP VFD and backgear is going to give you a heck of a lot of low end already, if you use sensorless vector you'll be able to beat my 3HP DC drive. I can't imagine what you might be cutting where you'd need more power than that.

Threading is much better at the slower speeds. That's the only time I kick her down in low range. My 3hp VFD has adequate power for clock making.

Jeff Major

"The motor shaft needs to be extended .800 so I'll bore a hole in the end of the motor shaft, thread it, then screw in a .800 extension that I'll then cut a keyway through and be done."

What is the thickness of the adapter plate? Steel or cast iron? Surface ground?

J-type motors often have longer shafts.

The plate is 6061, 1 inch thick, the plate is bored .200 to pilot onto the face of the motor. The GE motor shaft lenght is 2.75, as is the Marathon I'm using, but the spacer shortens the shaft by.800. adding on the end seems the best way to achieve this. I did consider making a new bell for the motor, That would be the best way, but would require a piece 9 X 12 X 3. 32 Lbs AL or 75 steel and alot of cutting. It could be built up in pieces, but I want to use the 10EE this year. So the gearbox adapter is now done, and I started the stub to add to the motor. Looking closer to chips now.

my wheels don't slow me down

Did you take the motor apart to do the machining on the end of its shaft?

Yes, 4 bolts and a deadblow hammer. About the easiest thing to do on the project. Hard to believe its been 9 years since I did that, The Monarch looks the same, I do not.

Toms Wheels said:

Yes, 4 bolts and a deadblow hammer. About the easiest thing to do on the project. Hard to believe its been 9 years since I did that, The Monarch looks the same, I do not.

Click to expand...

Yes, time flies. My Monarch and I share the same birth year - 1956 - and we're both in need of some serious attention!

So once you got the motor apart, what kind of a setup did you come up with for the machining?

Thanks, Bill (Hoppy)

I left the rotor bearings on the rotor, and supported the bearing in a steady. Bored, threaded a hole in the end of the shaft, then inserted a piece to extend the shaft. After turning to size I cut the keyway, and drilled a piece of keystock for small shcs to keep the key in place, secured with Loctite.

The adapter plate is the toughest thing. each of the gearbox groups is slightly different. There was interference between one of the gearbox bolts and the motor bolt holes, I had to turn the motor a bit so they did not overlap. I made a sleeve to slide onto the motor shaft and fitted a oil lip type seal into the adapter, used silicone around the motor face to seal oil.

Thanks very much! I appreciate your help.

I realize this is a very old thread, but if Tom or Hoppy are still reading on here, I'd like to connect with you as my 52 10EE with its original 3hp DC motor is failing and I want to convert to a 5hp 3-phase/VFD setup maintaining the backgear arrangement. Bill

Bill,

Unless the "Magic Smoke" has gotten out of the DC motor, it's probably going to be a lot easier to replace the DC controller than to go with a AC motor swap, especially since you want to keep the backgear.

I see from this postthat it has a custom DC controller. Have you considered going with an off the shelf DC drive?

Cal

I briefly thought about getting a new DC controller as that would be the easiest solution since I already have everything else in place. And my trusty old 60 yr old 3HP Reliance motor still works fine and has enough power for everything I use it for. Can you recommend a relatively inexpensive DC controller? Bill

I'm not sure about the "inexpensive" portion. . .

But this thread is a real good read for modern parts that can be found:
Parker/Eurotherm 514C/507 4Q SSD DC Retrofit into 1961 10EE Modular

Also, you said something in your system is failing. I don't know what that is. But there is a chance you need to do some maintenance to the motor itself, which could solve some problems.

I'm no expert in it, you'd need others to comment. I've just been reading up a bit, and mentally preparing to go through a system sometime in the future.