I'd rather fight than switch! (changing speeds on belt driven lathe)

Is there a way to adapt a belt driven lathe with three pulleys into something a bit less primitive to change speeds?
Please think mechanically. No, I am NOT hauling it out of the basement for another lathe...
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A couple of ideas. I have a Taiwan lathe that has a flat area over the headstock. It collects things so it is a pain to lift up to change belt speeds. My solution is to make a shallow tray that sits there and all the things collect on top of the tray. Much easier to lift the tray to get to the belt change than to lift ten different things.
The other thing is to install a three phase motor and a vfd. I did this and find I don't change the belt nearly as often. Cheap used three phase motors can be found. Cheap vfds are harder to find.
Dan
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Dan sez:
". . . .Cheap used three phase motors can be found. Cheap vfds are harder to find."
Check with Iggy. He seems to be the repository of all things "cheap".
Bob Swinney
wrote:

A couple of ideas. I have a Taiwan lathe that has a flat area over the headstock. It collects things so it is a pain to lift up to change belt speeds. My solution is to make a shallow tray that sits there and all the things collect on top of the tray. Much easier to lift the tray to get to the belt change than to lift ten different things.
The other thing is to install a three phase motor and a vfd. I did this and find I don't change the belt nearly as often. Dan
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Right now I am looking for a 1 HP, 56 frame with foot mount, electric motor, with at least 2" shaft (K56 frame or bigger shaft would work also), rated for belt driving. I am having hard times finding one.

I am finding the opposite, cheap VFDs abound on ebay, if you look into the drives category closely.
i
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Ignoramus4185 wrote:

> I don't wonder, that's a big shaft for a 1 hp motor, 5/8" - 3/4" is more the norm.

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I meant 2" long shaft. :)
Most 56 frame motors have 5/8" shaft, though I recently gave one Rec.Crafts.Metalworking member a 56 frame motor with a 3/4" frame, 56-75 was the frame number, IIRC.
i
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Ignoramus4185 wrote:

I would not have thought that a 2" shaft size would be very common in such a small horsepower motor.
???
Dead easy to sleeve a 2" pulley to fit a 1" or 7/8" shaft, though.
Cheers Trevor Jones
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Sometimes "Primitive" as you put it is best. perhaps a bit more slack on the belt will make changes easier for you and possibly limit damage if something BAD happens like a chuck collision
Speed to the input motor can be changed using a VFD but that can also reduce the available torque while reducing speed. By using the belts the same or very close to the same overall power is delivered since the lower belt speed will raise the torque.
This MIGHT be a non issue for you but it is something to note. the VFD will change the frequency of the incoming AC which then changes the rotation speed of the motor thereby changing the rotation speed of the lathe spindle once its been fed through the gearing of the lathe.
if you know the rpm speed of the spindle at a given belt speed halving the input AC frequency will halve the speed of rotation without changing belts.
But this is USUALLY done on 3 phase motors and it may not be applicable
I'm looking to use a VFD on my mill coupled WITH the belts with the primary purpose of the VFD to create the three phase that my mill wants if i have some fine speed adjustments as well then so much the better but i will take into account the range i could adjust it without significantly changing the torque. but if i am making gross speed adjustments my machine was made with the belt drive for a reason
Hope this helps to give you ideas
Brent Ottawa Canada
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Louis Ohland wrote:

Three phase motor and a VFD.
Dial-a-speed after that!
Cheers Trevor Jones
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It isn't mechanical other than bolting in a 3 phase motor and using a VFD. I'm always amazed by guys with lathes and bridgeports in the basement. I had enough trouble getting said machines to the ground level garage and unloading.
Actually three pulleys with back gear (assuming) is pretty sweet. With a VFD you can stay in good part the torque curve. That is why I'm fixing the varidrive on my Clausing 6903 instead of gutting it and going the VFD way.
Wes
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If it's a small lathe you can install a variable speed motor from a treadmill fairl cheap & easy ;) Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
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That's what I did. Glommed onto a brand-new 2.5 hp DC motor on Ebay for about $50, but *continuous* duty rather than intermittent (intermittent would probably do except that it's right at 95 degrees in the shop today). Found a controller for $25, good to 2.5 hp but it needed a bigass heat sink. Found the heatsink in a pile of junk at the university, "sure, go ahead, sure you don't need another?"
I had to turn a new drive pulley for the motor and make an adapter plate, but the whole thing works a treat on my 13 x 40 South Bend. To change speeds, I turn a little knob.
Best -- Terry
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Nick Hull wrote:

The problem with the treadmill motors is their speed: 6000 - 7000 rpm. Throttling them down loses hp. E.g., a 2.5hp 6000 rpm motor run at 600 rpm only produces 1/4 hp. Same thing happens with 3 phase + VFD, but you can start with a 1725 rpm 3 phase.
Bob
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Louis Ohland wrote:

> If you want a mechanical solution and don't want to fit a car box. In the 30s n 40s there were quite a few makers of conversions for flat belt drive machine tools: Berkeley Power Drive, Cullman Drives Drive-All, Given Vari-Speed and Schulzte's by Westlof Tool etc all offered either variable speed or gear speed selection and they still seem to be around.
However, nowadays the VFD is the simplest way to go.
Tom
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For a mechanical solution, you may be limited to a gearbox of some type, and a considerable amount of fabrication of parts. To add a gearbox, it would most likely involve moving the motor, but constructed so the motor and gearbox maintain a rigid mechanical connection to the lathe bed or headstock.
There is a planetary-type pulley that Smithy offers (don't know about Grizzley/others), as an expensive optional part, that has a reduced speed output. I've contemplated how a HSM might build a similar contraption, and suppose that it could possibly be constructed from some automotive automatic transmission gear assembly parts, because I don't know of any other commonly available planetary gear sets. The concept of building one of these might include a lock for hi and lo ranges, built into a 3-step pulley.
If you were to obtain or build a zero-to-any-speed variable speed drive, you will suddenly discover how beneficial they are. It's just so great. When I adapted a DC motor to one of my machines, which was a 2-belt machine, the difference was almost unbelieveable. http://www.kwagmire.com/shop/lathe/Cface_motor_mount.html
WB ......... metalworking projects www.kwagmire.com/metal_proj.html

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The mount stuff is nice, but what of the controller?
From my surfing, I'm looking for a 90vdc PWM motor. The stock AC motor is 1HP/1750RPM/13.5A - 115V. I don't expect to ever get much above 1,000RPM with the current AC motor. BUT I hate the slowest speed that it has right now - 150RPM. I like to thread well below 100RPM, otherwise, just like in Mr. Roger's Neighborhood, can you spell "crash" with me?
Wild_Bill wrote:

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What? No back gear?
LLoyd
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I know how to backtrack, is that good enough?
I do know the lathe in question lists speeds down to 150RPM. How does a "back gear" work?
Lloyd E. Sponenburgh wrote:

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On Wed, 8 Aug 2007 08:31:48 -0400, "Lloyd E. Sponenburgh"

150 rpm is "back gear" on an HF 9x20 and others (actually 130 rpm on mine). Motor couples to a jack shaft that couples via toothed belt to the head.
You have to get creative to go slower, like changing out the motor for a variable speed one.
A lot of people just turn the head by hand for threading, leaving the motor decoupled. Lots and lots of mods via google showing different ways to turn the head by hand...
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Leon Fisk
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The C-face motor for the machine project on my webpage was actually a gearhead motor (worm drive), but I removed the box to try out the motor with the machine. The motor is an industrial, sealed, 1.5HP Permanent Magnet (PM) Indiana General with ball bearings. I picked it up used for $10.. the seller though it was 3-phase, although I could see what it was.
I had a new old stock GE controller that I wouldn't have bought if I would've had to have paid the full price for, but I got it for about $18 plus shipping. I still haven't gotten around to finishing the other webpages related to my metalworking machines.
There are a lot of choices for DC variable speed drive components. I wasn't comfortable with the treadmill motor option, because they aren't adequately cooled and the cases are usually open. The ones I've seen are cheaply made consumer low-grade designs.
The actual motor controllers/drives can be fairly simple, or somewhat complex, such as the setup I chose. I wanted the drive to be wall-mounted, or attached to the machine stand, but out of the way, since it's in a fairly large enclosure. That required a remote box for the controls near the machine within convenient reach.
A 90VDC PM motor is a good choice for a home shop. When the motor HP goes beyond 1 or 1-1/2 HP, the drive will probably require 240VAC input, instead of 120VAC input for up to about a 1HP DC motor.
KB Electronics produces some very versatile DC drives, as well as numerous other manufacturers. The drive's protection features could be the most important features. Protection for the drive circuitry, and for the motor, should be considered.
WB ......... metalworking projects www.kwagmire.com/metal_proj.html

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