2-Speed Motor Speeds

[twhite]

It is a low speed lathe, the older Clausing-Colchester Lathe Brochure would indicate that the original motor was 900 and 1800 RPM (brochure indicates dual speed was 2.5/5Hp, single speed indicates 3Hp) on the 15"lathes which would be most likely to match the speed range of the lathe. It may be when the person told you it was wired for low speed they meant the single speed motor is connected to the low speed switch setting on the lathe. I would also question if the overload fusing/heaters were changed. If you do not need the high Hp/torque, you probably would be better off with a three phase 5Hp motor and running it off of a RPC or VFD. A VFD with a 5Hp motor would give you the most flexibility if you need the speed range. Not a big fan of static converters on lathes or surface grinders.

Thanks for the brochure.


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[walterwoj]

Boy, I feel dumb... I have the same book from vintage machinery and I swear I looked for that in it... Thank you for your responses. Now that I know it's 1600/900 rpm I can either match it on the vfd when I get it or pulley swap the motor to get the right speeds. I will double check the wiring too but I'll be redoing most of it for the vfd so I can get it running the way I want.

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[Beckerkumm]

Do you have three phase available or is the vfd necessary to convert from single phase using the converter? If you need to convert, I'd run it with the static and see if everything works, how the finish quality is, and how precisely you can get it to turn. If there is little wear and you can get the machine to turn with less than .001 variation, the machine is well worth spending the money for a new motor and vfd. A vfd will run a 10 hp put will be pretty expensive at the size needed for single phase input. Dave

 

[walterwoj]

I'm going to start with the static to get a feel for it. I checked the data plate for the 10hp motor and it says 1760rpm, so it should technically be going faster than hi speed, I don't think the guy I got it from knew what he was talking about. I just got it off the trailer last night so now I'm going to work on getting it in the garage tonight.

Once it's hooked up I'll put the tach on it and find out for sure.

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[Beckerkumm]

The original motor was likely a single winding 8 pole motor with a Dahlander connection. When switched to high, 4 poles dropped out. It may be that a single speed motor needs to be wired to low speed on the drum switch so the guy may actually be correct. If the switch and wiring were changed, the owner would delete the high-low designation. If the original drum switch is still intact, the low speed probably makes sense as little wiring was modified. There are two speed motors with separate windings but they are very large frame and more expensive so I doubt that is what was spec'd originally. Dave

 

[mksj]

The other concern would be if the original motor was 2.5/5.0Hp, then the wiring and switch gear would not be rated for a 10Hp motor even on a static converter. You might check the current with a clamp meter. It should run the same as the high speed setting as the original motor unless he changed the pulley size.

 

[woodchucker]

It is very likely a single speed motor; you said you were told it is wired for low speed, that is all it can be, that is the speed that it was manufactured for, that is why I suggested looking at the nameplate for the speed.

I wonder if its a 230- 408 volt motor and it's wired for 408v which would give you low speed. My surface grinder was wired for 408 and it was slow, we wired it for 230v to make sure it was good before I bought it, and it sped up.

 

[walterwoj]

So I got the motor running today to check the speeds and there is something funky going on...

The motor runs at 1700rpm - correct for the nameplate but it's got the wrong pulley, this one is a 2-groove and the machine takes 3 belts (only has 2 right now).

I set the gears for the highest speed (1200) but the chuck only spins at 593rpm. I strongly suspect that the motor pulley is also the wrong diameter.

Does anybody know the right pulley size for this?

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[walterwoj]

For reference this is my shifter setup.

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[mksj]

The motor pulley appears to be about the same diameter as the headstock pulley from the manual, and yes it is a 3 belt pulley. Levers appear correct for high speed, but I wonder per Woodchucker comment that the motor may be wired differently giving a lower motor speed. You might get an inexpensive non-contact tach to check the motor speed and spindle speed. I would check thr motor wiring. A 10Hp motor on that size lathe is a bit wonky, even with a static phase converter, the wiring is most likely not rated for that size motor.