Variable Speed for my Lathe

artycrafty

Hi all, as the title suggests I am looking to add variable speed to my lathe.
I have had the lathe for a number of years now and I am very happy to work on it.
Recently I bought a small variable speed lathe, and it has ruined my turning!
I am not having any problems with it, it's just now when I go back to my large lathe I get frustrated having to change the belt!
Are there any plans out there for making a variable unit?, I think the ones available commercially are a bit too expensive. It would be an interesting project to tackle.
I am afraid to name the brand of lathe that I have, as I am a fairly new member and I don't want to be accused of spamming!
But if the moderator gives a blessing I will name it then!

Alun

As far as I know upgrading to a variable speed system usually involves changing the motor as well as adding the control unit, so making the control unit yourself won't save as much as you might think.

artycrafty

Thanks for the reply Alun, I didn't realise that the motor needs to be changed also.:eek:
I would be murdered if I suggested paying so much for a variable speed system as it would cost as much as the little lathe did.:(
I'm not that well up on the electrical side of the vs.

Alun

Yes, the motor needs to be 3-phase instead of single phase. The only kit I've seen for my lathe (Nova 3000) cost £328 from Haydock Converters in the UK.

artycrafty

That sounds about right for the price of one for my lathe, a Record CL1.
(Is the moderator looking?:D)
Sigh, I may save up and put up with the belt changing for now....
It wouldn't be so bad if the casing wasn't so awkward to manouvre the motor for releasing the belt tension....

slowburner

I think you could probably buy a secondhand electronic variable speed lathe for a bit more money than it would cost (and down time) to modify your CL1.
You can get some cracking deals, if the lathe was a good one to start with. Usually, there will be goodies thrown in because they are specific to the spindle thread etc.. Also this would give you the option of upgrading to beefier 2MT centres. If you haven't got a massive amount of kit specific to the CL1, that's the route I would go.
Arnie

JoeB-

It should be possible to get variable speed on a single phase motor. After all, single phase tools like routers have speed control, so it is possible. It's also far more common for the engineering companies to only supply three phase speed controls, as they'd by more popular.

I've asked a similar question before and not got an answer.

A dimmer switch, for a light, is essentially a speed control, but it's not suitable at all for the lathe. (Perhaps I'm wrong, .. the light dimmers may work by reducing the voltage,.. if so this will cause problems for the motor, and may destroy it if used for too long at low speeds,.. it's technical, but something to do with the motor constantly straining.)


I saw a product recently that might work, but I can't remember where.. similar to the remote control plugs, but this was special, .. I'll post again if it comes to me.


You could try posting the question in the Engineering f.orum... they might know a cheap product that would work on relatively low power single phase motors.

artycrafty

slowburner wrote: »

I think you could probably buy a secondhand electronic variable speed lathe for a bit more money than it would cost (and down time) to modify your CL1.
You can get some cracking deals, if the lathe was a good one to start with. Usually, there will be goodies thrown in because they are specific to the spindle thread etc.. Also this would give you the option of upgrading to beefier 2MT centres. If you haven't got a massive amount of kit specific to the CL1, that's the route I would go.
Arnie

Hi Arnie :D

The CL1 was my first lathe, and to me it's my baby, the thoughts of giving her up for adoption makes me break out in a sweat!
The little variable speed lathe I have is 2mt, so I have accessories for both the 1mt and 2mt, but I might be tempted to look at a second hand lathe if she measures up to my requirements.....hmmmm....I'll think it over.....

artycrafty

JoeBallantine wrote: »

It should be possible to get variable speed on a single phase motor. After all, single phase tools like routers have speed control, so it is possible. It's also far more common for the engineering companies to only supply three phase speed controls, as they'd by more popular.

I've asked a similar question before and not got an answer.

A dimmer switch, for a light, is essentially a speed control, but it's not suitable at all for the lathe. (Perhaps I'm wrong, .. the light dimmers may work by reducing the voltage,.. if so this will cause problems for the motor, and may destroy it if used for too long at low speeds,.. it's technical, but something to do with the motor constantly straining.)


I saw a product recently that might work, but I can't remember where.. similar to the remote control plugs, but this was special, .. I'll post again if it comes to me.


You could try posting the question in the Engineering f.orum... they might know a cheap product that would work on relatively low power single phase motors.

Thanks JB, I'll post over in the engineering forum, as soon as I find it, phew, there is so much to read on here, boards sure is a big place!

Alun

JoeBallantine wrote: »

It should be possible to get variable speed on a single phase motor. After all, single phase tools like routers have speed control, so it is possible. It's also far more common for the engineering companies to only supply three phase speed controls, as they'd by more popular.

I've asked a similar question before and not got an answer.

Routers, drills etc. use so-called "universal" motors which are essentially DC motors (they have brushes but don't have permanent magnets in them) but run on AC, and can be speed controlled quite easily by chopping the waveform in much the same way as light dimmers work.

They're limited in the continuous output power they can deliver though, so lathes and other higher powered machines tend to use AC induction motors which run synchronously, i.e. at the line frequency so any speed control can only be achieved by changing frequency and in some cases phase too.

I think that in principle you could design a single-phase variable speed system, but seeing as the principal market for such devices is in the industrial 3-phase world, they just aren't available commercially. I also understand that 3-phase motors also offer some advantages in terms of ease of starting and use in short duty cycle environments.

artycrafty

Alun wrote: »

Routers, drills etc. use so-called "universal" motors which are essentially DC motors (they have brushes but don't have permanent magnets in them) but run on AC, and can be speed controlled quite easily by chopping the waveform in much the same way as light dimmers work.

They're limited in the continuous output power they can deliver though, so lathes and other higher powered machines tend to use AC induction motors which run synchronously, i.e. at the line frequency so any speed control can only be achieved by changing frequency and in some cases phase too.

I think that in principle you could design a single-phase variable speed system, but seeing as the principal market for such devices is in the industrial 3-phase world, they just aren't available commercially. I also understand that 3-phase motors also offer some advantages in terms of ease of starting and use in short duty cycle environments.

You lost me after the word "drills".... :eek:

JoeB-

Ha ha, and me!

I've asked this though.. what happens if you put a diode on the live wire. This will only pass current in one direction, so half the waveform has been chopped, hence half the power.

People say that there's excessive start up current, but the motor will be turning so this isn't an issue.

No help for a variable speed lathe, but would it work to allow me to use large router bits on a 1970's overhead router machine, which normally spinds at 24,000 say. What effect would cutting half the AC current have, by inserting a diode which only allows current to pass in one direction??

Thanks Alun for the info on universal motors, and induction motors etc. I know all about the brushes, just had to replace them on two routers,.. the makita one for the second time, (third set). I must use them a lot.

slowburner

Alun wrote: »

Routers, drills etc. use so-called "universal" motors which are essentially DC motors (they have brushes but don't have permanent magnets in them) but run on AC, and can be speed controlled quite easily by chopping the waveform in much the same way as light dimmers work.

They're limited in the continuous output power they can deliver though, so lathes and other higher powered machines tend to use AC induction motors which run synchronously, i.e. at the line frequency so any speed control can only be achieved by changing frequency and in some cases phase too.

I think that in principle you could design a single-phase variable speed system, but seeing as the principal market for such devices is in the industrial 3-phase world, they just aren't available commercially. I also understand that 3-phase motors also offer some advantages in terms of ease of starting and use in short duty cycle environments.

Thanks Alun, even though most of went over my head too.
I've heard that replacing 3-phase motors with single phase (even induction motors) can result in vibration, especially in lathes and bandsaws.

slowburner

JoeBallantine wrote: »

.....but would it work to allow me to use large router bits on a 1970's overhead router machine, which normally spinds at 24,000 say.

Could you use pulleys to reduce the speed?

1chippy

how about adapting the covers to make them easier to change.i know very little about lathes so just a suggestion

artycrafty

1chippy wrote: »

how about adapting the covers to make them easier to change.i know very little about lathes so just a suggestion

The belt and drive need to be covered as the shavings go everywhere!

slowburner

Did you try contacting the manufacturer of the CL1 - just a thought.

Carlow52

have a look here
http://www.inverterdrive.com/group/AC-Inverter-Drives-230V/default.aspx
these are AC Inverter Drive Speed Controllers but are only cost effective at small horsepowers

Also look here

http://www.torsiondynamics.com/contact.php

Must go before Alun chops off my waveform:D

Just kidding: great post

Alun

Carlow52 wrote: »

Must go before Alun chops off my waveform:D

It's all quite simples really (especially if you have degree in Electronics ) ...

Here's a chopped waveform for you ...

http://www.sprags.com/

artycrafty

slowburner wrote: »

Did you try contacting the manufacturer of the CL1 - just a thought.

Hi Arnie, That is a task that I've carried out several times but they are not ones to return emails or calls unfortunately, kinda like grab the money and run...

artycrafty

Carlow52 wrote: »

have a look here
http://www.inverterdrive.com/group/AC-Inverter-Drives-230V/default.aspx
these are AC Inverter Drive Speed Controllers but are only cost effective at small horsepowers

Also look here

http://www.torsiondynamics.com/contact.php

Must go before Alun chops off my waveform:D

Just kidding: great post

Thanks for the links, but I am crosseyed looking at the varieties available, do you have experience with any of these and could point me in the right direction please?

slowburner

artycrafty wrote: »

Hi Arnie, That is a task that I've carried out several times but they are not ones to return emails or calls unfortunately, kinda like grab the money and run...

Surprised by that. Last time I was on to them they were fine. I think you have to register and go through a laborious process to get any decent response.

Alun

slowburner wrote: »

Surprised by that. Last time I was on to them they were fine. I think you have to register and go through a laborious process to get any decent response.

Yes, you do. I've used it to query a replacement part for my bandsaw and it went OK. They used to have an online forum at one time but that seems to have vanished.

brightspark

Try asking these guys, no idea of cost though

http://www.acpd.co.uk/optidrive-e1-inverters.html

Write down all the details from the motor before you contact them, it will help them determine the right product for you.

Alun

brightspark wrote: »

Try asking these guys, no idea of cost though

http://www.acpd.co.uk/optidrive-e1-inverters.html

Write down all the details from the motor before you contact them, it will help them determine the right product for you.

I've seen these single phase inverters before, there are some on one of the sites Carlow52 mentioned too. It's the number of parameters that you need to program into them, presumably to match the characteristics of the motor being used, that puts me off, one on the other website even boasts of being able to be programmed by Smartphone!

It sounds to me like it uses a lot of electronic trickery to make the whole thing work properly with a wide range of motors, and TBH I think I'd prefer a 3 phase matched inverter and motor sold as a kit to be honest.

I'd also be interested in whether the torque characteristics would be the same especially at low speed, something that's quite important for a lathe, and if I remember correctly low end torque was one of the advantages of 3-ph motors.

But if someone else wants to try it and see, I'd be interested to hear the results.

slowburner

Alun wrote: »

I've seen these single phase inverters before, there are some on one of the sites Carlow52 mentioned too. It's the number of parameters that you need to program into them, presumably to match the characteristics of the motor being used, that puts me off, one on the other website even boasts of being able to be programmed by Smartphone!

It sounds to me like it uses a lot of electronic trickery to make the whole thing work properly with a wide range of motors, and TBH I think I'd prefer a 3 phase matched inverter and motor sold as a kit to be honest.

I'd also be interested in whether the torque characteristics would be the same especially at low speed, something that's quite important for a lathe, and if I remember correctly low end torque was one of the advantages of 3-ph motors.

But if someone else wants to try it and see, I'd be interested to hear the results.

+ the capacity to run in reverse?

Alun

slowburner wrote: »

+ the capacity to run in reverse?

Also true IIRC.

slowburner

Alun wrote: »

Yes, you do. I've used it to query a replacement part for my bandsaw and it went OK. They used to have an online forum at one time but that seems to have vanished.

Alun, it looks as if you might be the man to answer this. I've a bandsaw from the same manufacturer (nothing but trouble btw). I have to yank the blade by hand to get the wheels running :eek:. The company reckoned this is probably a faulty capacitor. Can I pick one of these up in an electrical store and are they specific wattages?
Apologies to all concerned if I'm going off topic here.

galwaydude18

If you get the numbers off the capacitor and go to an electronics shop they should be able to sort you out with a new one. It will probably be White in colour and big enough. I had to replace the capacitor in my planer thicknesser last year as I burnt it by using a lead that wasnt strong enough for the current that the motor was pulling on start up. I am now using a 2.5square leaf now for it

Alun

Exactly, you need to get the capacity (in uF) and voltage rating, also the type of lead on it as there are two main kinds, spade terminal and flying lead versions. Maybe just take the old one off and take it along with you might be the best bet.

On my Record bandsaw it's located underneath the big black plastic box on top of the motor.

Incidentally there are two kinds of capacitor used in AC motors, start capacitors and run capacitors. You can find motors that use one or the other and sometimes both depending on the motor. A faulty start capacitor will result in a buzzing noise and the motor not starting unless you give it a push, a faulty run capacitor will result in lumpy, rough running.

On my BS300 bandsaw it looks like I have a run capacitor only .. you can usually tell by the fact that run capacitors are rated at 450V, but start capacitors at 250V and run capacitors are usually lower capacity than run capacitors. The run capacitor on my saw is a rated at 25uF 450V AC 50Hz On my lathe however, I have both, one rated at 160uF / 250V and the other at 10uF / 450V.

Here's an eBay seller that sells a good variety of them in case you luck out finding one in a bricks and mortar shop ...

http://stores.ebay.ie/Rare-Electrical-Supply/Capacitors-/_i.html?_fsub=18071047&_sid=207916280&_trksid=p4634.c0.m322

slowburner

Thanks to you Galwaydude and Alan.

Hopefully, I won't have to change the wiring in the capacitor box but I'd better have a look at some of the leads I've been using. I certainly have 2.5 square on the table saw - but not on the bandsaw - better address that. Not something I would have thought about.

It's a BS350 (you have to admire their imaginative model names ) so it's more than likely the start capacitor as you say. I'm pretty sure there's just the one.
Even though I don't have a clue what I'm doing half the time, I really enjoy taking machines apart and re-using the motors. I have a real penchant for lovely quiet induction motors.
Anyway, I dismantled an old hand drier to get at the motor - but I didn't continue when I saw 415v on the capacitor - I figured it was 3ph. But then the wiring didn't look like 3ph and my head began to hurt. So now I understand that a 1ph motor will/might have a 415v run capacitor.
My enlightenment continues.