Larger HP Motor on Spindle

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Scra99tch

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I am trying to search for a replacement main motor for the VN12 and am seeing quite a few 3HP motors for sale locally. I am wondering if I should go this route knowing full well the possible gear-train wear I might encounter. Is there much in the way of limiting the HP at the spindle through larger belt deflection (loose between pulleys)? Most of these 3HP motors are a bit higher in RPM so a VFD would take care of that but could I go with different belts that would tend to slip more?

Thanks
 
I don't understand. The higher Hp won't have any effect on your machine unless you use it. You could put a 50Hp motor on, and you're machine would never notice if you stuck to finish type cuts.

?Right?
 
Stock motor from what I read was 1.0 or 1.5Hp @1100 RPM, so probably a 6 pole for 60Hz. A 2Hp or 3Hp 4P motor could be used, when you reduce the speed with a VFD the Hp decreases in a linear fashion so a 3 Hp motor is making around 1.8 Hp at 1100 RPM. The torque would also be reduced based on the difference between a 4P and 6P, so a bit of a wash on that end. You can also reduce the motor overload point with a VFD so you can run it at say 100 or 120%, the default is typically 150%. A standard motor has a higher locked rotor current when running off the line voltage. There can be cooling issues with a TEFC motor when you run them below 15Hz for any continuous duty time under load. If you can find a 6P 2Hp motor than would be a close replacement, but either a 2 or 3Hp 4P, or 6P 1.5 or 2 Hp would work well.
www.ebay.com

Marathon 184TTFB6078 2Hp Premium Globetrotter Electric Motor GT1208 | eBay

Marathon 184TTFB6078 2Hp Premium General Purpose Globetrotter Electric Motor. Catalog #: GT1208. New open box. Works as designed. Assembly : F1 (F2 Modification Available). Drive End Bearing : BALL.
www.ebay.com
www.ebay.com

1.5HP 1200RPM - RELIANCE ELECTRIC P18G4904 NSNB - 1.5 HP ELECTRIC MOTOR 1165 RPM | eBay

Manufacturer's ID: P18G4904. Manufacturer: RELIANCE ELECTRIC. Design: B Catalog RPM: 1200. Condition: New Surplus. Service Factor: 1.15 Insulation Class: F Ambient Temp: 40 C.
www.ebay.com
 
Last edited:
In reply to Shotgun,
I am not entirely sure when they designed the power transmission inside the spindle gear box that they considered large HP motors and the effect on the gears. I just don’t want to stress them out if taking heavy cuts. That’s why I figured a different belt system to err on the side of slipping in the v-notch pulley instead of locking up if I bog it down to much.
 
mksj said:
Stock motor from what I read was 1.0 or 1.5Hp @1100 RPM, so probably a 6 pole for 60Hz. A 2Hp or 3Hp 4P motor could be used, when you reduce the speed with a VFD the Hp decreases in a linear fashion so a 3 Hp motor is making around 1.8 Hp at 1100 RPM. The torque would also be reduced based on the difference between a 4P and 6P, so a bit of a wash on that end. You can also reduce the motor overload point with a VFD so you can run it at say 100 or 120%, the default is typically 150%. A standard motor has a higher locked rotor current when running off the line voltage. There can be cooling issues with a TEFC motor when you run them below 15Hz for any continuous duty time under load. If you can find a 6P 2Hp motor than would be a close replacement, but either a 2 or 3Hp 4P, or 6P 1.5 or 2 Hp would work well.
www.ebay.com

Marathon 184TTFB6078 2Hp Premium Globetrotter Electric Motor GT1208 | eBay

Marathon 184TTFB6078 2Hp Premium General Purpose Globetrotter Electric Motor. Catalog #: GT1208. New open box. Works as designed. Assembly : F1 (F2 Modification Available). Drive End Bearing : BALL.
www.ebay.com
www.ebay.com

1.5HP 1200RPM - RELIANCE ELECTRIC P18G4904 NSNB - 1.5 HP ELECTRIC MOTOR 1165 RPM | eBay

Manufacturer's ID: P18G4904. Manufacturer: RELIANCE ELECTRIC. Design: B Catalog RPM: 1200. Condition: New Surplus. Service Factor: 1.15 Insulation Class: F Ambient Temp: 40 C.
www.ebay.com
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Awesome thanks for the info.

There is a place selling a ton of motors 10miles from me.

I’ll look for a 6pole.
 
Recently, I installed a 2hp 3p 1740 rpm motor with VFD on my Rockwell mill. If you were to install the same on your Van Norman and run it at about 65 %, I would believe that it would be about the same as your original motor. Just have to set the max frequency at 38 cps. From what I remember, running Van Normans similar if not the same as yours, there was a lot of backlash and gear noise when running a 2” facing cutter. Possibly they were in need of adjustmen? My understanding about VFD run motors is that the frequency range should be between 15 to 80 hz. I try to stay at or above 20 on the low end. My .02
 
Keep in mind that the more poles in a motor the larger the frame. A 1 hp 1200 rpm motor is basically equal to a 1.5 hp 1800 rpm motor in size and hp. Check the frame size of the existing motor. For instance, a 3 hp 1200 rpm motor might have a frame size of 215 while a 5 hp 1800 rpm motor has a frame size of 184.

Dave
 
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