Help to Rejuvenate a Powermatic Model 90

[Jeff Alley]

I am relatively new to turning. Have an old delta that I have turned spindles on for roughly a year and joined an AAW club recently. Am interested in bowl turning and more spindle work and acquired a Model 90 from a school. It is 3 phase, 1 HP and probably made in late 70's. At the very least I have to get a static converter to run 220 single phase in, 3 phase out. I understand I will lose about a third of the HP. I am wondering if I would be better to go with a VFD (single phase in, 3phase out) and use my the stock motor (if it will be compatible) or should I get a drive rated motor and VFD. Would you advise staying with the 1 HP if I go down the new motor route or a larger HP rating. Should I pull out the reeves pulley system. I believe this lathe has a jackshaft between the headstock and motor. Are there any links or threads I can read regarding some of these changes. Thanks for your comments.
Jeff

 

[Dale Miner]

There may be some disagreement with the following, but here is my two cents worth.

Get the static converter, or, depending on cost, a single phase replacement.

The model you have with the jack shaft goes down to about 250 rpms, and that speed is low enough that bowl blanks if given a little prep should not cause any undue balance issues. The reeves drive system in the model 90 is built like a tank, and would be tough to do away with even if you wanted to. Give it some preventative maintainence before putting it into service.

The 1 hp motor is enough if you stay with the reeves drives system, because, as you slow the spindle down, you are gaining torque, like shifting in to a lower gear in a transmission. I doubt that the motor will stall under a heavy cut when you are in the slower speeds, even with the loss of power from the static converter. More likely to slip the belt than stall the motor. If you have the headstock apart, replace the belt(s) if anything less than pristine.

The power issue becomes a factor when doing heavy cuts with the spindle running at faster rpm values, but typically, the upper end of your range is reserved for finishing cuts or spindle work. Even the lathes with VFD's have multiple belt pulleys to gain torque at slow speeds. The reeves drive is like having a continously changing set of pulleys available.

A downside to a static converter, other that a reduced power output, is that typically, the motor will have a more pronounced hum when running.

When weighing the cost of the converter/single phase replacement, consider resale value of the machine should you ever decide to upgrade.

Turned out to be about 3 cents worth,
Dale M

 

[Jeff Alley]

Thanks for the reply Dale. The club I joined has a lathe guru and he does not seem to think much of the reeves drives, "they were good in their days but the vfd is the way to go". I see various converters from $80 to $150 from ebay to Mcmaster Carr and it seems to be a quick fix. Not sure what frame the motor has so a little difficult to spec a single phase motor and that seems like the most logical fix. I'll see how many others weigh in.

 

[James Engle]

I have a Powermatic 90 with a static converter and 3 phase Baldor 1 hp motor and it does not lack for power. It runs well and so far it is trouble free and easy to use. It is gold in color and I believe it is a 1990 production showing little wear so far. Initially I thought I would need a variable frequency drive but so far I dont. I have not used the outboard turning option but if I did then the slower rpm may be of value but I am not sure I will need to go slower than it already does..

 

[MichaelMouse]

If you leave the Reeves, which will outlast ANY electronic controller with just minimum maintenance (consider the abuse it's endured as a school lathe!), you can keep your motor at nearly full rpm and power output at low rpm. Thus the 1hp will act like two or three.

 

[Joe Greiner]

If you leave the Reeves, which will outlast ANY electronic controller with just minimum maintenance (consider the abuse it's endured as a school lathe!), you can keep your motor at nearly full rpm and power output at low rpm. Thus the 1hp will act like two or three.

Amen.

MOST IMPORTANT: Lubricate the motor and spindle shafts where the pulley sheaves slide. If necessary, devise a removable hatch for access.