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Has anyone eliminated the undercarriage step pulleys on a heavy 10L by using a VFD and motor to drive one of the spindle pulleys directly?
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I'm not sure why you would want to do that. ?I run my SB13 on a VFD, and use that for most speed changes, but I do change the belt occasionally. ?You would also have to rig something up to hold the motor in the new position. ?Are you missing the under drive parts?
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Don't do that! ?The speed change pulleys don't just change speed, they maintain constant power so you get more torque at low speeds. ?You wouldn't try to start your car from traffic lights in top gear. ?To function satisfactorily without sped changing pulleys you would need a much larger motor, so that it could a.) provide the necessary torque, and b.) not overheat due to low air flow as the fan slows down. ? Eddie
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------ Original Message ------
From: lrgoodger@...
To: SouthBendLathe@groups.io
Sent: Wednesday, October 9th 2024, 18:54
Subject: [SouthBendLathe] Eliminating the step pulleys
? Has anyone eliminated the undercarriage step pulleys on a heavy 10L by using a VFD and motor to drive one of the spindle pulleys directly?
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Keep the belt and pulleys. The VFD won't give you the same low-speed torque as the belt and pulleys. When you slow down the motor with a VFD, so does the cooling fan. Unless you add some kind of fan, to add airflow, the motor may overheat and reduce its life
expectancy.
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From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of Ron Goodger <lrgoodger@...>
Sent: Wednesday, October 9, 2024 1:54 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: [SouthBendLathe] Eliminating the step pulleys
?
Has anyone eliminated the undercarriage step pulleys on a heavy 10L by using a VFD and motor to drive one of the spindle pulleys directly?
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Why eliminate the step pulleys?? To just simplify the whole shebang.? I know changing the belt to another speed is quick and easy, but why have to do it at all if you can get around it?? You see, I have this 2 hp 3phase motor just lying around doing nothing and I thought I would put it to good use.
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When I bought my Bridgeport Boss CNC, I told the guy I would not buy it until I saw it run.? He hooked it up and it ran, but it sounded like an airplane.? I bought it because he had so much extra stuff that came with it.? When I took it apart to rebuild it, I found out why it was so noisy.? The 2 hp motor had a bad bearing, and it had deteriorated to the point that it did a good bit of damage to the motor shaft.? I searched the internet for something that might replace it and found a brand new, 2 hp Reliance on clearance by a warehouse doing inventory reduction.? I got a $500 motor for $75, so I bought it, knowing I could make an adapter plate so it would fit.? Then I found a shop nearby who did a "wrap weld" on the old motor shaft for cheap and it has been flawless ever since.? So I decided to put the Reliance motor on the lathe with a VFD.
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After 3 years designing robots for the local high school competing in FRC, I have no qualms about building motor mounts.
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I thought about the low speed torque problem, but I figured going to a 2 hp motor would help with that.
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The problem is that the pulleys give you a speed reduction and torque amplification.
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To run your motor that slow and to expect the torque you need you will most likely overheat it. For light stuff it will probably work.
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To get a motor to do what you want you will need to up the size and add some sort of external cooling mechanism to the motor.? Three phase motors designed to run low rpms usually have a fan run by a separate motor to keep it cool. Now you are looking at a larger physical size, so you will still need some sort of drive setup to run the spindle.
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Keep the motor where it is and run a single pulley speed keeping some sort of reduction to up the torque.
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What is the difference if you have a short belt or a long one you will need some sort of drive setup to the spindle.?
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A cog belt setup may be the optimal solution.
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specs on the VFD are telling me this;
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"Yes, a variable frequency drive (VFD) can maintain constant torque at any speed"
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If that is true, doesn't it eliminate the low speed torque concern?
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But you don't want constant torque at all speeds. ?The whole point is, you want MORE torque as you reduce the speed. ?Lower speeds are used for machining or drilling bigger diameters. ?Applying a tool with the same force at a bigger radius means you require more torque. ?Look for a set up that promises constant POWER, then report back here so that we may all go and worship! ? Eddie
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------ Original Message ------
From: lrgoodger@...
To: SouthBendLathe@groups.io
Sent: Friday, October 11th 2024, 14:08
Subject: Re: [SouthBendLathe] Eliminating the step pulleys
? specs on the VFD are telling me this; ? "Yes, a variable frequency drive (VFD) can maintain constant torque at any speed" ? If that is true, doesn't it eliminate the low speed torque concern?
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Eddie has it exactly right. Power is the product of torque and speed, and cutting engineering says that material removal rate is proportional to power. Anecdote: My 1 HP dc drive is totally inadequate for turning large diameter parts at low speed without the advantage of a belt change and sometimes back gears.
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Gary
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On Fri, Oct 11, 2024 at 06:08 AM, Ron Goodger wrote:
specs on the VFD are telling me this;
?
"Yes, a variable frequency drive (VFD) can maintain constant torque at any speed"
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If that is true, doesn't it eliminate the low speed torque concern?
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The point isn't just torque. Reduced RPM will reduce the air flow
through or around the motor and the motor will overheat unless
you install a separate cooling fan for the motor.? Also, the original
motor, running at its rated speed makes the same torque BUT the
pulley speed reduction increases the torque above the motor's
rated torque.? Roughly speaking, if the pulley ratio reduces the RPM
by 1/2, it increases the torque by 2 times (inverse ratio).
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That is the point.
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Good Luck!
-Blue Chips-
Webb
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So some of this is being overthought.? If you have a good motor don't worry about overheating it.? My 16" has a 3hp motor just like it came with.? It does have an industrial cast iron frame motor (tefc).? I have the belt set at second to fastest pulley setting and leave it there. The VFD must be set to sensorless vector (or VFD brand equivalent) to maintain proper torque at low speed.? Works great and I have never even come close to running out of torque at low speed.? I do overspeed the motor a little to get full rpm out of the spindle.
--
1969 16" x 6' South Bend Lathe
Garage full of old Mopars........
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Well, I have decided against eliminating the step pulleys.? It would be much more complicated than just replacing the motor and installing the VFD.? Then I will have full options available as to power.? With the VFD and three phase motor I will easily be able to overspeed the lathe.? Does anyone know what the physical speed limits of the lathe mechanism is?? At his point, I see no reason to ever do so.? Just wondering.
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On Sun, Oct 13, 2024 at 01:16 PM, Ron Goodger wrote:
Well, I have decided against eliminating the step pulleys.? It would be much more complicated than just replacing the motor and installing the VFD.? Then I will have full options available as to power.? With the VFD and three phase motor I will easily be able to overspeed the lathe.? Does anyone know what the physical speed limits of the lathe mechanism is?? At his point, I see no reason to ever do so.? Just wondering.
?
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My concern is the plain bearings in the headstock. I don't run either my SB9A or my SB13 much above the listed top speed of either lathe.
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??? I think the top speed for my 9A was 1000 RPM . Pretty sure ya
can set limits on the VFD .
animal
On 10/13/24 11:24 AM, Rick wrote:
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On Sun, Oct 13, 2024 at 01:16 PM, Ron Goodger wrote:
Well, I have decided against eliminating the step
pulleys.? It would be much more complicated than just
replacing the motor and installing the VFD.? Then I will
have full options available as to power.? With the VFD
and three phase motor I will easily be able to overspeed
the lathe.? Does anyone know what the physical speed
limits of the lathe mechanism is?? At his point, I see
no reason to ever do so.? Just wondering.
?
?
My concern is the plain bearings in the headstock. I don't
run either my SB9A or my SB13 much above the listed top speed of
either lathe.
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On Sun, Oct 13, 2024 at 02:35 PM, mike allen wrote:
I think the top speed for my 9A was 1000 RPM . Pretty sure ya can set limits on the VFD .
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9A has a listed speed of 1270 rpm.
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I have a tach on my SB13. ?If I run the VFD at 60 hz in high gear, it shows within 10-20 rpm of the factory listed speed of 940 rpm. ?I have turn the frequency up and ran it to about 1100 rpm. ?The bearings got a little warm, but not hot. ?I usually don't run it anywhere near that rpm. Mine has a 3 step pulley, most of the time I just leave the belt in the middle and adjust speed with the VFD. I run the motor from 30 to 90 hz.
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Just to throw another thought in the discussion.? I inherited a 1922 15”.? It came converted to top mounted 4 spd truck transmission driven by the original motor.? It has twin v-belts from the motor to the transmission input and twin v-belts to the step pulley, 2nd from the headstock.? Under very heavy loads the belts will walk off the step pulley (working on a collar to stop that) but it also adds a little safety.? I mounted a magnetic pickup on the change gear end of the headstock shaft and connected a digital tach.? Top rpm is 988.? I am attaching the speed chart and photo of setup. Rick Swineford ?
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From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of mike allen
Sent: Sunday, October 13, 2024 2:35 PM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Eliminating the step pulleys? ??? I think the top speed for my 9A was 1000 RPM . Pretty sure ya can set limits on the VFD . animal On 10/13/24 11:24 AM, Rick wrote: On Sun, Oct 13, 2024 at 01:16 PM, Ron Goodger wrote: Well, I have decided against eliminating the step pulleys.? It would be much more complicated than just replacing the motor and installing the VFD.? Then I will have full options available as to power.? With the VFD and three phase motor I will easily be able to overspeed the lathe.? Does anyone know what the physical speed limits of the lathe mechanism is?? At his point, I see no reason to ever do so.? Just wondering. ?
? My concern is the plain bearings in the headstock. I don't run either my SB9A or my SB13 much above the listed top speed of either lathe.
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Thost truck transmission mods were pretty popular back in the day
as the kids say . I always wondered if there was a article in a
old,old Popular Mechanics or like mag showing the mod .
animal
On 10/13/24 3:19 PM, Rick Swineford
wrote:
toggle quoted message
Show quoted text
Just
to throw another thought in the discussion.? I inherited a
1922 15”.? It came converted to top mounted 4 spd truck
transmission driven by the original motor.? It has twin
v-belts from the motor to the transmission input and twin
v-belts to the step pulley, 2nd from the
headstock.? Under very heavy loads the belts will walk off
the step pulley (working on a collar to stop that) but it
also adds a little safety.? I mounted a magnetic pickup on
the change gear end of the headstock shaft and connected a
digital tach.? Top rpm is 988.? I am attaching the speed
chart and photo of setup.
Rick
Swineford
?
?
??? I think the top speed for my 9A was 1000 RPM . Pretty
sure ya can set limits on the VFD .
animal
On 10/13/24 11:24 AM, Rick wrote:
On Sun, Oct 13, 2024 at 01:16 PM, Ron
Goodger wrote:
Well, I have decided against
eliminating the step pulleys.? It would be much
more complicated than just replacing the motor and
installing the VFD.? Then I will have full options
available as to power.? With the VFD and three
phase motor I will easily be able to overspeed the
lathe.? Does anyone know what the physical speed
limits of the lathe mechanism is?? At his point, I
see no reason to ever do so.? Just wondering.
?
?
My concern is the plain bearings in the
headstock. I don't run either my SB9A or my SB13 much
above the listed top speed of either lathe.
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Rick, if you add a flange to stop the belt wandering off, it will chew the edge of the belt, and the belt might even climb onto it. ?Flat belts need a crowned profile on the pulley, and you should check whether yours still has this. ?Compare the step in use with the others. ?If only one of the speed pulleys has been used for an extended period and there has been some slippage, it is possible that the pulley is worn hollow. ?So long as there is some metal left, you can machine the crown back onto it. ?I've never tried it, but a coat of hard epoxy filler might make up any material shortfall. ? All counter intuitive, I know, but that's how they work. ? Eddie
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------ Original Message ------
From: terrapinsystems@...
To: SouthBendLathe@groups.io
Sent: Sunday, October 13th 2024, 23:19
Subject: Re: [SouthBendLathe] Eliminating the step pulleys
? Just to throw another thought in the discussion.? I inherited a 1922 15”.? It came converted to top mounted 4 spd truck transmission driven by the original motor.? It has twin v-belts from the motor to the transmission input and twin v-belts to the step pulley, 2nd from the headstock.? Under very heavy loads the belts will walk off the step pulley (working on a collar to stop that) but it also adds a little safety.? I mounted a magnetic pickup on the change gear end of the headstock shaft and connected a digital tach.? Top rpm is 988.? I am attaching the speed chart and photo of setup. Rick Swineford ? From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of mike allen
Sent: Sunday, October 13, 2024 2:35 PM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Eliminating the step pulleys ? ??? I think the top speed for my 9A was 1000 RPM . Pretty sure ya can set limits on the VFD . animal On 10/13/24 11:24 AM, Rick wrote: On Sun, Oct 13, 2024 at 01:16 PM, Ron Goodger wrote: Well, I have decided against eliminating the step pulleys.? It would be much more complicated than just replacing the motor and installing the VFD.? Then I will have full options available as to power.? With the VFD and three phase motor I will easily be able to overspeed the lathe.? Does anyone know what the physical speed limits of the lathe mechanism is?? At his point, I see no reason to ever do so.? Just wondering. ?
? My concern is the plain bearings in the headstock. I don't run either my SB9A or my SB13 much above the listed top speed of either lathe.
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They are dual v-belts.? The crown is still there. They tend to stay in the middle until heavy load is applied.? The flange will hit the top of the v and yes will occasionally wear the outer belt edge, but the bottom is doing the driving. ?It doesn’t get a lot of use right now. Rick ?
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From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of eddie.draper@... via groups.io
Sent: Monday, October 14, 2024 6:48 AM
To: Rick Swineford <terrapinsystems@...>; SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Eliminating the step pulleys? Rick, if you add a flange to stop the belt wandering off, it will chew the edge of the belt, and the belt might even climb onto it. ?Flat belts need a crowned profile on the pulley, and you should check whether yours still has this. ?Compare the step in use with the others. ?If only one of the speed pulleys has been used for an extended period and there has been some slippage, it is possible that the pulley is worn hollow. ?So long as there is some metal left, you can machine the crown back onto it. ?I've never tried it, but a coat of hard epoxy filler might make up any material shortfall. ? All counter intuitive, I know, but that's how they work. ? Eddie
? ------ Original Message ------
From: terrapinsystems@...
To: SouthBendLathe@groups.io
Sent: Sunday, October 13th 2024, 23:19
Subject: Re: [SouthBendLathe] Eliminating the step pulleys
? Just to throw another thought in the discussion.? I inherited a 1922 15”.? It came converted to top mounted 4 spd truck transmission driven by the original motor.? It has twin v-belts from the motor to the transmission input and twin v-belts to the step pulley, 2nd from the headstock.? Under very heavy loads the belts will walk off the step pulley (working on a collar to stop that) but it also adds a little safety.? I mounted a magnetic pickup on the change gear end of the headstock shaft and connected a digital tach.? Top rpm is 988.? I am attaching the speed chart and photo of setup. Rick Swineford ? ? ??? I think the top speed for my 9A was 1000 RPM . Pretty sure ya can set limits on the VFD . animal On 10/13/24 11:24 AM, Rick wrote: On Sun, Oct 13, 2024 at 01:16 PM, Ron Goodger wrote: Well, I have decided against eliminating the step pulleys.? It would be much more complicated than just replacing the motor and installing the VFD? Then I will have full options available as to power.? With the VFD and three phase motor I will easily be able to overspeed the lathe.? Does anyone know what the physical speed limits of the lathe mechanism is?? At his point, I see no reason to ever do so.? Just wondering ?
? My concern is the plain bearings in the headstock. I don't run either my SB9A or my SB13 much above the listed top speed of either lathe.
|
Ron Goodger
eddie.draper@btinternet.com
Mark Z
Rick Swineford
