Variable Speed for old Lathe - where do I start

[Gazob]

I have been turning bowls on my Durden Top Turn 400 now for a few months.

The biggest limitation seems to be the lack of Variable Speed and Reverse.

Where do I start the Planning for adding a 3 Phase Motor and VFD, what do I need to take into consideration when selecting and who do I buy from.
Is there a prewired plug and play option that doesn't cost the earth, is there any value over buying the components separately.

Garry

[BobL]

Go to the Electronics sub-forum (https://www.woodworkforums.com/f271) and read the the two top stickies in that forum.

As you will see it's not always as easy as it sounds although sometimes folks get lucky. :D

[powderpost]

Some time during the 90's, I bought a complete variable kit from Woodfast. Since then a lot has happened to Woodfast. Might be good to contact Jim Carrol at "Carroll's Woodcraft Supplies", to see if those kits, or something similar, is still available. Might save you a lot of heart ache?

Jim

[hughie]

Well much depends on your budget.
But you have to work out where and how your gonna put the three phase motor and if your going to change the pulley set up.Presuming you have already worked out what size you want Its often a good idea to have or keep a stepped pulley set up to make up for any loss of torque. Also you want to look at ebay or FB market place for a motor, it will be cheaper.
Then sort out your VFD, you can get them on ebay as low as $90 to drive a 2.2kw motor. The manuals can be a challenge with strange english etc. Dont forget to get a pot I would recommend 10 turn this will give fine motor control and also if you bump it , it wont change the speed too much. With one turn this can be very hectic, also available on Ebay very cheap. Also you will need a electrical box of suitable dimensions to allow the VFD to dissipate the heat, you can if you wish mount the whole thing on the wall. But if likely to move the lathe it might be better to mount it all on the lathe. Depending the VFD you may need a contactor with a 240 volt coil. But above all else if your not a sparky, go find one preferably a mate.

Alternately you buy DVR type set up which is expensive or a EU/Japan/USA etc made VFD etc which aint cheap. My first one was Lenz made in Germany original price was 1400.

[BobL]

.
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Dont forget to get a pot I would recommend 10 turn this will give fine motor control and also if you bump it , it wont change the speed too much. With one turn this can be very hectic, also available on Ebay very cheap. .
.


I've tried using a 10 turn pots but found they were too slow.
If VFD remote pots are well positioned they should not get bumped.
I've got 9 VFDs in my shed and have had them for up to 11 years and not once do I recall bumping one.

An alternative to a 10 turn pot for fine speed control is to use two pots (one for coarse control and one for fine) and a couple of resistors.
There are several wiring arrangements that can be used and I describe one (H-Pattern wiring, easily found on the internet) in this post where I installed this on my MW lathe.
https://www.woodworkforums.com/f271/vfd-install-summaries-213878/10#post2079349

I also installed two pot control on my MW mill, but on my DP I just used a bigger knob and find that to be fine .
This one is from a clothes dryer timer.
498435

[Colin62]

An alternative to a 10 turn pot for fine speed control is to use two pots (one for coarse control and one for fine) and a couple of resistors.
I can’t imagine needing that level of control on a woodworking lathe. I suppose if you’ve got OCD* and need it to be running at a round number but I don’t find any practical difference between 700 rpm and 723 rpm.


* I started off trying to fiddle with it for round figures, because that’s neater, but gave up quite soon. I often don’t know what speed I’m using, just a general feel where it is and of how safe it is for what I’m busy doing.

[BobL]

I can’t imagine needing that level of control on a woodworking lathe. I suppose if you’ve got OCD* and need it to be running at a round number but I don’t find any practical difference between 700 rpm and 723 rpm.

I agree, a bigger knob is probably good enough for a WW lathe. I even have a Tacho but I put that on mainly because I had a spare one and so a young bloke I was teaching could adjust the speed to what I recommended without me being there all the time. I don't really use it myself except sometimes when I make the BMHs - if it's too slow it can overheat and even stall the motor - if it's too fast it self cools the heated PVC and makes it harder to form the bell mouth..

[LanceC]

Garry, I wrote about my experience at post #21 of this thread: https://www.woodworkforums.com/f8/restoring-80-woodfast-lathe-234911-post2235613?#post2235613

[hughie]

I use 10 turn on all my lathes. The pot knobs I use allow me to turn using one finger, so its never been an issue for me.

[BobL]

I like the variable speed pots used on the 9000 series VFDs.

The knob is not really attached to a pot (knob turns endlessly) but a pulse generator(?).
Regular slow turning changes frequency to the 0.1Hz level but the faster you turn it the MUCH faster the frequency changes. They take a bit to skill to master but once you get the hang of them they are very good. They are definitely overkill for WW lathes but useful for other machines.

[hughie]

I like the variable speed pots used on the 9000 series VFDs.

The knob is not really attached to a pot (knob turns endlessly) but a pulse generator(?).
Regular slow turning changes frequency to the 0.1Hz level but the faster you turn it the MUCH faster the frequency changes. They take a bit to skill to master but once you get the hang of them they are very good. They are definitely overkill for WW lathes but useful for other machines.

Toys Bob :) we all love our toys

[hughie]

I can’t imagine needing that level of control on a woodworking lathe. I suppose if you’ve got OCD* and need it to be running at a round number but I don’t find any practical difference between 700 rpm and 723 rpm.


* I started off trying to fiddle with it for round figures, because that’s neater, but gave up quite soon. I often don’t know what speed I’m using, just a general feel where it is and of how safe it is for what I’m busy doing.

For me, its fairly simple change speed to suit what I am doing or till run smoothly. A rev counter would be something else to look at. But in Bobs case the young pupil wouldnt have an eye for rev/speed so it would be useful

[NeilS]

For me, its fairly simple change speed to suit what I am doing or till run smoothly. A rev counter would be something else to look at. But in Bobs case the young pupil wouldnt have an eye for rev/speed so it would be useful

Me too...

I've never had a rpm readout on any of my lathes. I start slow and gradually wind up to the max speed before I see/hear any vibration, then increase the speed as the blank comes into balance. Occasionally I accelerate through the harmonics to get to vibration free running at a higher speed, but that takes some judgement as to whether that can be achieved before doing it... get that wrong and even a heavy lathe will want to walk out the door by itself!

Like Bob, I've found the rpm readout on the lathe at the local men's shed to be useful when giving advice to inexperienced turners. One of the few good things about that lathe is that it resets the speed to zero every time it is stopped. It would drive me mad but it's ideal for that setting.

[NeilS]

Garry, I wrote about my experience at post #21 of this thread: https://www.woodworkforums.com/f8/restoring-80-woodfast-lathe-234911-post2235613?#post2235613

Lance

Your reported experience after implementing your VFD precisely summarises my experience.

[Gazob]

Thanks for all the Input.

Looking at ebay I see a 2hp motor VFD combo for sale for around the $600 mark. Single Phase variable frequency drive with 1.5kw Electric motor for belt sander | eBay (https://www.ebay.com.au/itm/174740656804)
any input on this Motor VFD Seller combo appreciated.

Current Motor Pulley has a 19.05 bore and 2 grubscrews, motor listed has a 20mm shaft with a key, Current motor is pretty big, don't think I would have Issues mounting the one in the link in place of the existing motor, but havent measured anything yet, will open it up at some point and try to get either a Manufacturer + part number or actual dimensions.

The lathe has a removeable front panel which currently houses the on/off switch, mounting the VFD here would probably be sufficient, haven't looked deep enough to see whether the linked VFD has a remote option, or whether I even care that much, The VFD linked above has what I assume is a speed control knob on its faceplate.

Is there any advantage in going to 3hp, cost wise it would be $100, of what will probably end up being a $1000 upgrade.


Garry

[NeilS]

Is there any advantage in going to 3hp, cost wise it would be $100, of what will probably end up being a $1000 upgrade.




The only time I wish I had a bit more neddy than my VS 1.5HP is when I'm coring larger diameter blanks. Coring is one of the most HP demanding tasks on the lathe. My 1.5HP struggles with that when cores get up around 18" diameter.


498550


A 2HP unit would be more than adequate for my purposes if I was not coring up to that size. Even with just 1.5HP I can manage to do regular turning up to 21" diameter outboard.


498551

[BobL]

Is there any advantage in going to 3hp, cost wise it would be $100, of what will probably end up being a $1000 upgrade.


It depends how often you expect to be operating at lower motor speeds.

A 3 Phase motor that runs at 1440 rpm using a VFD will have full power only from about 50 to 100Hz or 1440 t0 2880 rpm.
Above this speed the power drops off and running at really high speeds is not safe so a max of about 125Hz is recommended.
Below 50Hz power drops off proportional to Frequency.
A standard VFD (known as a V/F VFD) only has half power at 25Hz.

There are two ways that help this.
The easiest is to get a more powerful motor.
Doubling the motor power will produce the original motor power at 25Hz.

The next is to get a "Vector Drive" VFD. This produces more power at lower frequencies.
This is not an automatic gain and some fiddling with the VFD parameters and running an auto tune is required.
The actual power gain varies but a well tuned VFD will nominally produce the same power at ~12.5Hz that a V/F produces at 25Hz.
Real wins occur at very low frequencies (eg 5Hz) where a Vector drive will be producing even more power than what a V/F VFD powered motor would output..

Sounds Good eh, BUT
Running at low speeds can lead to over heating as the motors fan may not turning fast enough to cool the motor.
A bigger motor helps simply because it has a greater thermal inertia but only for a while.
This can be more effectively dealt with by adding an independently powered fan like a large computer fan.

There is a temptation to get extra large motors but this can lead to unsafe situations like damage to the lathe if something gets stuck.

[Gazob]

So 2hp in place of 1hp is probably okay, unless I had plans to increase my swing with a riser.

Using the current drive pulley, lowest speed of 350, I will still have 1hp down to 175rppm

At this point 600mm platter and 400mmm bowl is probably all ill be doing.

Is that ebay linked combo what I should be looking for.

Garry

[NCArcher]

That is not a terrible price for a motor VFD combo. You could get it cheaper if you shopped around a bit but Conon are pretty good to deal with.
The motor by itself is around $250. Getting decent VFDs is becoming more expensive and that is not a vector control VFD. They recommend that combo for a belt grinder, which you pretty much run flat out most of the time anyway so it would be fine for that but I would look at a vector control VFD as Bob suggested.

[BobL]

So 2hp in place of 1hp is probably okay, unless I had plans to increase my swing with a riser.

Using the current drive pulley, lowest speed of 350, I will still have 1hp down to 175rppm


And if you got a Vector Drive VFD you could 1HP down to <100 rpm.

[hughie]

Sounds Good eh, BUT
Running at low speeds can lead to over heating as the motors fan may not turning fast enough to cool the motor.
A bigger motor helps simply because it has a greater thermal inertia but only for a while.
This can be more effectively dealt with by adding an independently powered fan like a large computer fan.

Did this often when working the packaging industry, 120mm cabinet fan fitted the end of the motor solved most of the heat issues

[NeilS]

And if you got a Vector Drive VFD you could 1HP down to <100 rpm.

Like Jim (Powderpost), I also retrofitted a VFD unit (I presume that was what it was) to a Woodfast back in the 1990s. It wasn't cheap at the time but it was a quality European unit and of interest to this discussion is that it ran down to just 10rpm on the lowest pulley setting, which was very nice for particular tasks like sanding warped pieces.

That lathe had quite a big left hand outboard swing and I don't remember its 1HP ever flinching at anything I put on it for regular turning.

My current Woodfast (C1000X) only goes down to 20rpm, which is slow enough for most purposes, although I did find a noticeable difference between 10 and 20rpm, which I wasn't expecting.

Vicmarc still have lathes that go down to 10rpm.

[dogcatcher]

I converted a wood lathe using a sewing machine servo motor. Sort of like this Lathe Motor upgrade - adding a 550w 3/4hp brushless servo sewing machine motor - YouTube (https://youtu.be/4htyv7Bg3rY)

Motor cost me a little over a $100 USD. Nothing else needed to control it, but I did add a sperate pot to control it at the front of the lathe.

[NeilS]

I converted a wood lathe using a sewing machine servo motor. Sort of like this Lathe Motor upgrade - adding a 550w 3/4hp brushless servo sewing machine motor - YouTube (https://youtu.be/4htyv7Bg3rY)

Motor cost me a little over a $100 USD. Nothing else needed to control it, but I did add a separate pot to control it at the front of the lathe.

I could see that this is an economical solution for some small diameter work, like a dedicated pen turning lathe. But, I would miss the auto soft start for larger diameter work that is built into my VFD. With a pot you could probably manually wind up the speed gradually to replicate that and that may be ok if you are not frequently stopping and starting all the time. But that might be a minor inconvenience if you are wanting to save some dollars.

However, I don't know just how economical this style of servo motor unit would be for larger diameter wood lathe work. Here are two offerings as a retrofits in the 1.5 to 3hp range...

Amazon.com (https://www.amazon.com/Servo-Motor-Incremental-Encoder-1-5kW/dp/B08GFJCYTK?currency=AUD&language=en_US&th=1)

https://www.ebay.com.au/p/2181125437

Most lathe manufacturers go with a VFDs and 3ph induction motor for VS control, but I can see that Harvey is using the servo motors on theirs TURBO T-60S 24"X48" Wood Lathe With Servo Motor – Harvey Woodworking (https://www.harveywoodworking.com/products/t-60s)

Some discussion in the following on the use of servo motors on wood lathes...

Servo motors vs the other motors | American Association of Woodturners (https://www.aawforum.org/community/threads/servo-motors-vs-the-other-motors.17420/)