Wanted - Low RPM motors

Hi all, I'm a blacksmith in Milwaukee, WI. I have an addiction to older mechanical power hammers. I love to get them fixed up and restored and forging hot steel again.

Many (most) power hammers typically run at slower speeds. In the past to reduce speed I have done a few different solutions.
1) made jack shafts utilizing different pulley diameters to obtain the correct speed.
2) used VFD's to reduce motor speed.
3) used gearboxes to reduce speed.

Those three things usually work, but sometimes circumstances (or space) don't allow for a jackshaft, or an additional gearbox. And sometimes to keep things more "original" a VFD just doesn't play the part well.

So... I'm in the market for some low RPM (induction) motors. 3hp up to 10hp or even a bit bigger. I know they are tough to find, which is why I'm asking around here. I have 3 phase, so no problem there. I have seen them in speeds between 800 and 900 rpm. That general speed is what I'm after.

Thank you for your time,
Aaron

The 900 is synchronous speed, the 865 (or so), like my 1917 10HP Westinghouse is the placarded speed. They are around - always at higher cost than faster ones

They do still make new 900 rpm motors (usually rated between 750 and 850 under load)

I've got a Baldor 900 rpm TEFC 2hp motor that i used to have on one of my power hammers. It's sitting in the corner of my shop now, because I don't have anything that needs a slow motor at the moment, and now my only power hammer is the KA75 that I bought from you, Aaron, a few years back =D

For a 900 rpm (nominal, 60hz) motor it needs 8 poles, which requires 24 windings, instead of 6 on a normal motor. this makes for pretty massive motors.

Here are side by side my 2hp baldor 900rpm and my 2hp 1800 rpm motors, the 900rpm one weighs well over 100 lbs. and is a beast to move about =D
https://cdn.discordapp.com/attachments/436614660997775361/627726051283304479/image0.jpg

Have a poke around the WEG website there is a 6 pole motor 1175 rpm check hp and type of mounting output etc

WEG - Selecao de Motores Eletricos


There is also TECO TECO - Low Voltage Motors

And CMG if your after a chinese one CMG stands for china motor group from memory.

ABB here ABB Motors and Generators
a little poke around abb site gives this for severe duty motors 900rpm Catalog - Baldor.com

I have bought several three phase motors with the 850 and 1150 RPM speed rating, but never more than 2 HP. I consider them ideal for use with a VFD on a machine tool because they will have more power than a 1750 RPM motor of the same rating at speeds below 1750 RPM.

For instance, a motor rated 2 HP at 850 RPM will have 1 HP at 425 RPM (30 HZ) and will still have 2 HP at speeds up to 3400 RPM (120 HZ).

And a motor rated 2 HP at 1750 RPM will have 1 HP at 850 RPM and .5 HP at 425 RPM and will still have 2 HP at speeds above 1750 RPM.

I found my motors on eBay. I recall one (brand new in the box) was bought for $1, but the shipping was a lot more because, as was said, these low speed motors are heavy for their HP rating.

Larry

I have a 16 pole 3 phase motor with a 435 full load rpm but it is only 3/4 HP, it is the size of a modern 10 HP motor though.

I've got this unique motor in the shop atm too https://cdn.discordapp.com/attachments/436614660997775361/628324894039605259/image0.jpg

Century Polyphase induction motor. .75hp 1750rpm, or .5hp 1165 rpm, or .37hp 875 rpm, or .25 hp 575 rpm. The motor is huge, bigger than the 2hp 900 rpm motor i posted above =D Free to a good home if someone wants to pick it up at my shop hehe.

The sort of motors you are seeking were widely used in older elevator hoists. For better or worse, these older hoists are being replaced/updated and going straight to the scrapyard. Find a local elevator service company and see if they will set aside some motors for you before they junk the machine!
There is a yard here in Kansas City that gets a lot of this stuff but their price for outbound motors is .55/lb. Several months ago I fell in love with 10hp 720 RPM Westinghouse from the 20's .....to take it out the gate was going to cost $360!

Some of the woodworking machines like those made by Wadkin had truly massive motors with tiny horsepower specs as they were 8 or 16 pole or something like that. In fact if anyone has connection data for Wadkin 4 speed motors I would love to hear from them.

As a rough rule of thumb for a given physical motor frame: halving the RPM will halve the horsepower. Horsepower is work over time and if you halve the RPM you just halved the rate of work being done for a given motor size. The motor frame of a given size can only support so much magnetic flux in the poles before saturation so there's an upper limit that can only be increased by going to a larger motor frame. Slowing the speed of a motor runs the risk of magnetic saturation so you have to increase the amount of magnetic steel to compensate by going to a larger frame.

AC power transformers have similar design factors: a 100VA rated transformer at 50 hertz will run at 200VA @ 100Hz, 400VA @ 200Hz and so on. That's why aircraft had 400Hz AC: your power transformer could use 1/8th the steel of a 50Hz transformer for the same power rating.

20/10 HP 1705/855 RPM 575 Volt AC 3Ph General Electric Motor | 3 Phase Motors Base Mount | 3 Phase AC Motors | Electric Motors | www.surpluscenter.com

471 pounds two speeds 20/10hp.

Could take it to a motor shop and have them find the midpount of the coils and rewire it for 300 volts. Or 200 volts. But that may not be an option... Or a really expensive way to get around a gearbox.