Variable Speed???

[Mike Davis]

I was thinking about adding variable speed to my wood lathe.

Does anyone have experience with that and a rough idea of the cost?


Is it just too much to tackle?

[ptt49er]

That idea has been tossed around in my head as well Mike. Since I just picked up a lathe who's only means of speed change is moving a belt across the pulley. I've wondered what the costs were.

[jimwill48]

If its a jet Mini look at PSI conversaion kit, product #: TCLVSKIT, I believe it about on sale for around $100.00 or so. http://www.pennstateind.com/Merchant2/merchant.mvc?
For a bigger lathe I really have no idea.

James

[Mike Davis]

No, I could line up a few of those lathes on mine.

I need at least a 1 HP if not 2.

[Steve W]

Why not use a Variac? As long as you stay within its current rating, you could slow down a motor considerably with one. Of course, you'd still need to switch pulleys for overall ranges if you want maximum torque but for light-duty stuff, it should work fine.

You can find these at flea markets, electronics surplus places, eBay, among other places for pretty short money.

Steve

[Alan in Little Washington]

Mike, there are generally two ways to go- a variable frequency drive or inverter (VFD) with 3 phase motor or a DC motor and controller.

VFD- VFD's work with 3 phase motors (they will not work with single phase motors) and control the speed by varying the frequency of the normally 60 Hz electrical power (0 Hz to 400 Hz). VFDs usually run on 220V or more . The VFDs for lower hp motors can often run on either single phase or 3 phase input power, though they must be de-rated when run on single phase. Higher hp VFD's (usually above 3 hp) require 3 phase imput. Most VFDs have many programmable options- low/high frequency limits, acceleration/deceleration speed, electronic braking, reverse, etc. The major problem with a VFD is you lose torque at low RPM, and unless you have an inverter duty motor which has better wire, insulation, and cooling, it can overheat if run at low RPM too long. It is a function of the magnetic properties of iron at low frequencies. Because of the torque issues, some VFD lathes (Delta and others) retain their mechanical variable speed, so that you use the VFD within certain RPM bands.

DC motors and controllers are another option, they have a little better low speed torque. Instead of straight direct current, DC controllers vary the voltage and also pulse the power (PWM- pulse width modulation) to control the speed. There are disadvantages to DC motors also.

When you start to get into the higher hp motors, generally above 1.5 hp, both VFDs and comparable DC equipment start to get expensive.

All that being said, I installed VFDs and three phase motors on my lathe and drill press. I increased the hp size of both motors and geared them so the motors run faster at low machine RPM to help reduce the low end torque issue. I got my motors, VFDs, and tachs off Ebay. There are a couple of motor and VFD suppliers that have this kind of stuff like "Drives Wharehouse" and "Automation Direct" but I haven't checked out their prices. When I got my stuff off Ebay a few years ago, it was MUCH cheaper than any of these places, but Ebay has gotten more expensive and can be hit or miss.

In addition to the VFD (and remote speed control knob on my drill press) I added a digital tach to both my lathe and drill press.

The VFD on my 12" Delta lathe. The VFD and a new power switch are mounted to a metal plate which is attached to the headstock housing. Larger (1.5 hp vs 3/4 hp) motor. I removed and replaced both the Reeves drive pulleys, mechanism and speed change lever:



The VFD is putting out 220V at 10 Hz which, with my pulley ratio equates to 337 RPM.




Front panel of my drillpress. Buttons power up the VFD, the little toggle switch is the "run" switch, and the red knob controls RPM.



The VFD is mounted to a metal plate that I attached to the motor mount.

[Mike Davis]

Alan,

I see a lot of DC motors that are made for treadmill exercise machines on Éby. They seem to be relatively inexpensive for 2 HP or so. I know that is an over rated HP, but is that a suitable motor for my lathe?

I am looking for the low end torque to turn large bowls. But, I also need to be able to turn spindles and speed up for finishing. I don't mind moving the belt to a smaller or larger pulley and working within ranges. I'd like to get down to 100 rpm with enough muscle to spin a 200 pound blank and run for hours at a time without overheating the motor.

What is a reasonable expectation as far as cost? Remember I can be patient and look for a good deal.

[NZAPP1]

Mike
I have the set up like Alan has on the drill press I forget what I had paid for it but got the drive and brand new motor off EBay. I am going to up grade my lathe this summer. You can check it out when you pick up you stuff

[FredP]

if you decide to go with the VFD controller I have a 3 PH ?HP unisaw motor from my unisaw that was running fine when I replaced it with a single PH motor. The guy I ought the saw from said it was 3 HP but its a 1948 model and more than likely its 1 - 1 1/2 HP repulsion induction. you can have it if you want to go this route. It is 240 volt. I have offered it for free a few times and no one seems to want it. sned a PM if you are interested.

fred

[mkepke]

Originally Posted by Mike Davis

Alan,

I see a lot of DC motors that are made for treadmill exercise machines on Éby. They seem to be relatively inexpensive for 2 HP or so. I know that is an over rated HP, but is that a suitable motor for my lathe?

I am looking for the low end torque to turn large bowls. But, I also need to be able to turn spindles and speed up for finishing. I don't mind moving the belt to a smaller or larger pulley and working within ranges. I'd like to get down to 100 rpm with enough muscle to spin a 200 pound blank and run for hours at a time without overheating the motor.

What is a reasonable expectation as far as cost? Remember I can be patient and look for a good deal.

Mike - forget the motor for a second. Can your LATHE handle 200# blocks ? You might be trying to 'make a silk purse out of a sow's ear', as they say.

Assuming you've thought of that already, my preference is for a VFD and a 3ph motor. A VFD is much more full-featured than a DC solution: soft-start, braking, remotes, etc. Plus 2 HP 3ph motors are << than 2HP DC motors.

Figure ~$100/HP + ship for the VFD. Check ebay for comps. These guys used to sell motor+VFD combos:

www.dealerselectric.com

Fred's offer is generous..I don't know if a RI motor will handle a VFD at all, or maybe the extra heat will kill it. But it's a free motor.

-Mark

[Alan in Little Washington]

Mike,

Mark has a good point about capacity of your lathe wrt 200# blanks. If I hadn't gotten my lathe, VFD, and 3 PH motor REALLY cheap, that could be said about my lathe.

If you decide to go the VFD route and want a big motor- I have a mint condition, never used (NOS) 3 PH, 3450 RPM, Baldor, TFEC, motor I don't need. I pulled it off of a NOS Shaper I bought a few years ago. Make me an offer.

If anyone else is interested in this motor send me a PM. As I said it is mint, never used and just sitting around collecting dust.

[Mike Davis]

I am sure my lathe can handle it at low RPM, I'm not sure my shop can handle the vibration. The guy that had it before me turned 18 inch bowls at full speed, I'm not that brave. I have the 2 hp reversible motor that he used.

I'm trying to get this sorted so I will have it when I move or if I have to stay here I will pour a pad behind the shop for the lathe and some black smith tools. I'm still looking for parts to build a forge. I'd like to have everything set up by the time I retire.

Alan,

PM me with a price for your motor, I don't have any idea what it's worth.

Than I need to know about the controller, what do they cost and how do I hook it up?