1953 16x30 Pratt Whitney Lathe

TylerBajsa · Apr 13, 2020

First post! I hope this is the right thread. I just got a 1953 16x30 Pratt Whitney Lathe last month. It has a 7.5 hp motor which was originally 3 phase but the previous owner rewired it to run directly to a (single phase) 220v breaker. I had a 220v outlet installed specifically for this. But to my dismay, when the electrician came to get it running, he needed to know what the amperage/amps of the motor was. I've looked far and wide for both answers online and a plate on the motor itself with the specifications with no success.

I thought I would turn here next to see if anyone could offer some insight. I can't say for certain that this is the original motor but I wouldn't be surprised if it was.

If all went well, I've attached some pictures with what I know bad angles.

-Tyler

Mebfab · Apr 13, 2020

Those pictures give no info about the motor. And it cant be original.Several reasons, but one is original motor would almsot certainly be heavy cast with fins. Also you cant run a 3 phase motor directly from single phase (needs converter)

johnoder · Apr 13, 2020

Manuals can be emailed if you would like to PRIVATE MESSAGE me that email address

DO PLEASE put something in the subject line so I will have a clue of what is wanted

TylerBajsa · Apr 13, 2020

Mebfab said:
Those pictures give no info about the motor. And it cant be original.Several reasons, but one is original motor would almsot certainly be heavy cast with fins. Also you cant run a 3 phase motor directly from single phase (needs converter)

Now that you metion it, I see this motor has been welded on to a differnet base plate so it's most certainly not the original. However, the electrician seemed pretty confident that if he knew the amperage, it could be done. If worse comes to worst, what's the most...practical converter out there?

rwilliams · Apr 13, 2020

Also, I doubt they used bar codes and plastic, type material, labels in '53.

Bob

thermite · Apr 13, 2020

TylerBajsa said:
Now that you metion it, I see this motor has been welded on to a differnet base plate so it's most certainly not the original. However, the electrician seemed pretty confident that if he knew the amperage, it could be done. If worse comes to worst, what's the most...practical converter out there?

Simple, dumb "RPC". Full stop.

So-called "static" converters don't. "Convert". They just trick the notor into running crippled. Not a good scene for a variable loading creature as lathes be, least of all in this size range.

VFD is a complexity you don't really need, and shorter life as well.

As you aren't REALLY even certain as to the present motor HP - until "maybe" you fish a camera on a "selfie" stick around the other side of it and find the "real" data plate, I'd go with a 15 HP idler as "don't care" if it is a fractional HP load through as much as 10 HP.

At 7 - 7.5 HP load-motor, a mere 10 HP idler MIGHT (or might not..) struggled to get a clean start, even if it ran the lathe just fine even under fairly serious loading. Starting larger motors can be a right bitch.

My case, for 7 HP motors, (2 of those) I use a 10 HP idler than can add a 7.5 HP or a 5 HP, run any one, or any combination - 5 HP to 22 1/2 HP "nominal" as total idler resource.

OTOH, one of my machine tools has four motors on it, the others at least two, so I gain usable flexibility from that modest extra investment where others might never.

2CW

cyanidekid · Apr 13, 2020

welcome to the site Tyler.

first off, just so you know, some regulars on here are prone to long winded, strangely written, sometimes insightful but most often tangential in the extreme posts.

its obviously a modern motor, and if the previous owner said he had changed it to 220-240 single phase, don't waste your time thinking about phase converters just yet. find the actual motor plate. did the electrician look for one? it may be hidden on the underside of it, especially if it is a cobbled up mount, if you are not familiar with them, they are usually (often) a stamped aluminum plate riveted to the housing. find that first.

thermite · Apr 13, 2020

cyanidekid said:
welcome to the site Tyler.

first off, just so you know, some regulars on here are prone to long winded, strangely written, sometimes insightful but most often tangential in the extreme posts.

No fear. We forgive yah for it. "In advance, even" -so long as useful content is conveyed.

its obviously a modern motor, and if the previous owner said he had changed it to 220-240 single phase, don't waste your time thinking about phase converters just yet. find the actual motor plate. did the electrician look for one? it may be hidden on the underside of it, especially if it is a cobbled up mount, if you are not familiar with them, they are usually (often) a stamped aluminum plate riveted to the housing. find that first.

Good advice, but...

In 7 HP? A(ny) motor-savvy electrician wudda looked for one if not two "humps" for cap start/cap run as are characteristic of the single-phase breed, and/or at least evidence of starting centrifugals and the winding.

Could was the PO simply had either a static or rotary converter not conveyed with the lathe, didn't clarify that was what he meant as to "converted to run..".

IF it HAS been converted to single-phase motoring in much over 3 HP?

Likely a majority of Machinists might side with converting it BACK ... even if that wants a converter.

PITA to "pull" a motor and put back if yah can avoid that, but sometimes, newly acquired machine not without the odd "mystery", it ends up the cheaper and wiser move if made sooner, rather than later.

cyanidekid · Apr 13, 2020

who says it currently has a "7.5 HP motor"? was the op just looking that up on the inter-web perhaps? find the plate.

who says the electrician was knowledgeable and competent to wire up a machine? "YEA I can bend a stub up like a champ, pull wire like a maniac!! service factor, cap start, WWHHATT??

thermite · Apr 13, 2020

cyanidekid said:
who says it currently has a "7.5 HP motor"? was the op just looking that up on the inter-web perhaps? find the plate.

who says the electrician was knowledgeable and competent to wire up a machine? "YEA I can bend a stub up like a champ, pull wire like a maniac!! service factor, cap start, WWHHATT??

"...prone to long winded, strangely written, sometimes insightful but most often tangential in the extreme posts."

Welll.... Tyler is getting an edumacation. One way or the other?

Bet he is sore grateful he asked about motors, not hemorrhoids, too!

FWIW-prolly-good-enough for branch circuit and idler sizing, 21 Full Load Amps @ 230 VAC 3-Phase, a 7.5 HP Reliance "Dutymaster" here as serves as one of the RPC idlers.

Paolo_MD · Apr 14, 2020

Especially if the electrician was competent/familiar with electric motors, one reason he wanted to know the true amperage is related to motor overload protection.

This time Bill (thermite) might have a good point suspecting that the previous owner has rigged together a static phase converter as the way to run the lathe on single phase. This is independent from the motor being original or not.

Paolo

Richard King · Apr 14, 2020

I mentioned Stephen Thomas who is the moderator of PM woodworking forum. He as a nice planer and is in NY.

thermite · Apr 14, 2020

Paolo_MD said:
Especially if the electrician was competent/familiar with electric motors, one reason he wanted to know the true amperage is related to motor overload protection.

This time Bill (thermite) might have a good point suspecting that the previous owner has rigged together a static phase converter as the way to run the lathe on single phase. This is independent from the motor being original or not.

Paolo

Store-bought max 10 HP, (ISTR it was a Phase-a-Matic?) was wot had hung for many years on the backside of the 7 HP motored Cazeneuve HBX-360-BC I bought from Milacron.

BAD DEAL for the motor! I cannot condemn that sort of travesty strongly enough!

TylerBajsa · Apr 14, 2020

cyanidekid said:
welcome to the site Tyler.

first off, just so you know, some regulars on here are prone to long winded, strangely written, sometimes insightful but most often tangential in the extreme posts.

its obviously a modern motor, and if the previous owner said he had changed it to 220-240 single phase, don't waste your time thinking about phase converters just yet. find the actual motor plate. did the electrician look for one? it may be hidden on the underside of it, especially if it is a cobbled up mount, if you are not familiar with them, they are usually (often) a stamped aluminum plate riveted to the housing. find that first.

I do have a few other motors from other machines and most of them do have riveted plates. So yeah I'm familiar. I've checked every angle at least 3 times and still no plate has showed up.

and thanks for the invite.

TylerBajsa · Apr 14, 2020

Paolo_MD said:
Especially if the electrician was competent/familiar with electric motors, one reason he wanted to know the true amperage is related to motor overload protection.

This time Bill (thermite) might have a good point suspecting that the previous owner has rigged together a static phase converter as the way to run the lathe on single phase. This is independent from the motor being original or not.

Paolo

Yes he was concerned about overloading the motor and killing it.

thermite · Apr 14, 2020

TylerBajsa said:
I do have a few other motors from other machines and most of them do have riveted plates. So yeah I'm familiar. I've checked every angle at least 3 times and still no plate has showed up.

That plastic-label bizness does reek of single-phase. HVAC, pump motors and sech went that way ages ago to shave the last penny of costs.

It's a damned good lathe for its era.

Might just start plotting and scheming for another motor for it? Decent 3-Phase + an RPC, you won't ever have to do either of 'em twice.

TylerBajsa · Apr 14, 2020

thermite said:
That plastic-label bizness does reek of single-phase. HVAC, pump motors and sech went that way ages ago to shave the last penny of costs.

It's a damned good lathe for its era.

Might just start plotting and scheming for another motor for it? Decent 3-Phase + an RPC, you won't ever have to do either of 'em twice.

Maybe. This lathe has a lot of work that still needs to be done so what's one more thing? I'll have to sell a few more cutting boards before I can make another big purchase for my workshop. XD

cyanidekid · Apr 14, 2020

TylerBajsa said:
I do have a few other motors from other machines and most of them do have riveted plates. So yeah I'm familiar. I've checked every angle at least 3 times and still no plate has showed up.

and thanks for the invite.

I do have a couple of motors with the stick-on plastic labels, so yours may have had that, and it's come off. (usually cheaper ones, obviously).

you can readily determine the nature of the beast just by looking at the wiring, how many poles feed in to it?

as to its HP, the frame size and mounting configuration, shaft diameter, overall dimensions will let you narrow down the horsepower to a significant extent. look up the NEMA frames, and the motors available in each. Graingers catalog or the web will have enough info to let you narrow it down.

since the motor is already mounted, (and probably works) don't ditch it until you have at least figured out what you likely have. Cheers, and good luck!

Froneck · Apr 19, 2020

3 phase motors can't be rewound/rewired to run single phase. The fact you have a bar code means it's not original. Motor in my 16" P&W is 7.5HP and looks original, is 3 phase. As I see it was mentioned in another post check the wiring at the motor, they will be good indication if it's single phase. Motor shaft diameter will not since 10HP and 7.5 HP have a 1-3/8" shaft. 5HP is 1-1/8" Check the motor pulley diameter, it may have been changed to use a faster 3600RPM motor which is usually lower in cost. Usually single phase motors are much larger than 3 phase of equal HP. There is not much room for a larger frame motor in my P&W base and I seriously doubt if a 10HP single phase motor will fit even thought the less expensive newer motors have sheet metal frames.

1953 16x30 Pratt Whitney Lathe

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