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View Full Version : Frankenlathe lives! Electronic variable speed conversion on a MC1100



Zeeber
29th February 2016, 04:17 PM
I recently bought a Carbatec MC1100 lathe second hand, the motor was shot and shorted out the electricity. It was the ideal donor for the Frankenlathe project – converting it to electronic variable speed. After cleaning and oiling the bed, taking off the banjo and tailstock and putting the lathe on wheels (it has the cast iron legs, which is very heavy – I take the wheels off office chairs whenever I see them on the pavement, and make little skateboards for moving the lathes), I took the motor off and removed the cover on the headstock. The motor mount is part of the motor, so not really user friendly, and I removed it. I found a new 3-phase motor that is 1.5kW (2hp) on a bargain basement sale price of $80. It’s a 4-pole motor with a RPM of 1450, shaft size of 24mm and a flange mount. Next I sourced a VFD for the same specs from eBay and paid $129, two aluminium pulleys for $22 (single v-belt, 24mm to fit the motor shaft, and keyed). The pulleys are 120mm and 100mm diameter (at 1450rpm on the motor, that will turn my spindle at 1740rpm when I put the big pulley on the motor and the smaller one on the spindle shaft).
I removed the Reeves pulley mechanism – that’s the one where the two pulleys mesh together, adjustable with the handle in the front, that left just the shaft inside the headstock. Removed the handle, the electrical on/off switch, all the electrical wiring. I drilled and tapped 4 holes on the front, and drilled two bigger holes for the two cables passing through the headstock into the VFD. The VFD screws on to the front of the lathe, if you position it nicely, it covers all the old holes.
I made a bracket the looks like a capital letter F lying on its side. The bottom leg of the F screwed into the headstock using the three holes where the previous mount was removed, I drilled and tapped two more 8mm holes just to have it nice and steady. The motor was then mounted on the bracket with a bolt through the flange – this enables it to pivot to move the motor to replace belts. The back of the motor rests on a T-piece that swivels as well. It would have worked better if it was a foot mount, but this worked out ok. I took an old alternator bracket and braced the flange to the bracket – this is the adjustable part. Both the pulleys were drilled and tapped to put a grub screw in there, then mounted and aligned. I cut the original cover to use it again – the current motor is slightly larger and mounted more forward (shorter shaft).
That part finished, I wired the motor through the headstock to the VFD, using the electrical grommets where it passes through. The 3-phase motor has 3 wires and an earth, apparently wired in a star or delta pattern (?) – mine was bridged across all three which makes it a star configuration. The three wires (U, V and W) goes to the output on the VFD where it is labelled U, V and W (easy). The green goes to the ground terminal on both the motor and the VFD. The power from the wall (220V) comes in with a L and N, and a green earth wire. The earth goes to the same terminal as the earth from the motor, while the L and N goes to R and T on the VFD.
So far so good – throw the switch on the wall, and the VFD starts up, the fan fanning and the lights lighting. There are 35 parameters to set – I looked on the internet and all of them are different numbers but basically the same information. Min and max inputs, etc, so I checked the plate on the motor first, then set it to max 50Hz (as specified on the motor). There are 7 programmable speeds, so I set them to 7, 14, 21, 28, 35, 42 and 50Hz – will experiment and see if I can relate that to spindle speed somehow. You can also set the speed with the up and down buttons, the digital readout shows you the Hz (at this time). On the VFD are other inputs as well, so you can use other devices (?) to plug in there and adjust things, I’m assuming they are meant to be from sensors, etc but I won’t use them. So the parameters were set to use the keypad for input.
I let it run for a while, adjusting the speeds up and down, monitoring for any issues, heat or any other form of things that shouldn’t be there (smoke, sparks, etc). So far nothing untoward has happened, and the next step is to turn a few things – a mate of mine wants some bobbins for his girlfriend’s spinning wheel, so that will be a good test.
I’ll try and get the photos on here soon.

Paul39
2nd March 2016, 02:43 AM
Zeeber,

Keep an eye on the motor temperature when running at slow speed for long periods. The motor fan may not provide enough flow to keep it cool. You could provide another fan running at full speed to add cooling.

Nice conversion. Some photos would be good.

BobL
2nd March 2016, 09:43 AM
There are 7 programmable speeds, so I set them to 7, 14, 21, 28, 35, 42 and 50Hz – will experiment and see if I can relate that to spindle speed somehow. You can also set the speed with the up and down buttons, the digital readout shows you the Hz (at this time). .

I agree with Paul, 7 and 14Hz may be to slow for the fan to adequately cool the motor AND the motor power output at those speeds will also be low.

With a non-vector drive VFD (I assume yours is for the price paid) for speeds below those generated by 50Hz the motor power output is proportional to the frequency.
Between 50 and 120 Hz the power is approximately the same and above 120 Hz it starts to drop off.

At 7Hz the motor will only output 7/50 x 2 ~ 1/4 HP and 14Hz will generate 1/2 HP.

The most powerful speed range is thus about 20 to 120 Hz so it would have been better to choose pulley sizes to enable these frequencies to be used.
A 1450 RPM motor is only doing 2900 RPM at 100 Hz which will be well within bearing specs and the fan will be easily able to cooling the motor.

Small motor manufacturers don't usually use bearings specifically for 1450 or 2800 rpm motors and bear in mind that some countries use 60Hz where a 2 pole motor has a theoretical speed of 3600 rpm so the motors have to be able to cope will all these variations.

Zeeber
2nd March 2016, 10:30 AM
So, what you are saying is that although the motor is rated at 50Hz, I can safely go up to 120Hz in my settings? Ie, run the motor at 120Hz? Not that I would want anything more than 2000rpm (just under 70Hz on the current pulleys). If you can confirm this, I will change the pulleys to give me a range of 300rpm to 2000rpm at 20 - 120Hz.
I'll also get one of those temperature indicator strips to stick on the motor, which will give me a visual clue as to the motor speed.
Thanks for the advice.

Paul39
2nd March 2016, 11:04 AM
Zeeber,

If you are going to do bowls or any large diameter stuff, you may consider getting a pair of two step pulleys so that you could have a variable speed high and low range.

That way the motor speed will be high enough to give you some torque when you are gouging out the inside of a bowl.

Zeeber
2nd March 2016, 11:10 AM
Thanks Paul, the reason I'm doing this is so I don't have to change belts manually, so I don't think two-step pulleys will work.

Ok, just done the maths, and in my limited abilities, it looks as follows:
If the motor gives me 1450rpm at 50Hz, and I want to work in a range upwards of 20Hz, I should use the following:
At 20Hz, the motor is running at 580rpm, so to get 300rpm (well, 348) I should use a 120mm pulley on the motor and a 200mm pulley on the spindle shaft (or 80 and 120mm – trying to save money by using the 120mm pulley I already have).
That means that at 120Hz, the motor will be at 3480rpm, giving me 2088 rpm on the spindle shaft – that is just enough (or with the 80 and 120mm pulleys, it will be 387 – 2320rpm – sounds a little better).
Anyone want to confirm my calculations? If they are right, I think I’ll go with the 80/120mm combo, it might just fit better in the headstock.

Woodturnerjosh
2nd March 2016, 01:07 PM
I have the original cast iron 6 speed pulley's from my old VL200 gathering dust somewhere. I'm not sure if they'll fit but if you want them they're yours (if I can find them ;) )

Cliff Rogers
2nd March 2016, 01:53 PM
If you get one of these, you can check what it is actually running at.
HOT Sell Digital Laser Photo Tachometer RPM Tach Meter Motor Speed Gauge SN | eBay (http://www.ebay.com.au/itm/Hot-Sell-Digital-Laser-Photo-Tachometer-RPM-Tach-Meter-Motor-Speed-Gauge-SN-/151770410824?hash=item235638af48:g:aUIAAOSwLVZVwxUZ)

Zeeber
2nd March 2016, 02:41 PM
I have the original cast iron 6 speed pulley's from my old VL200 gathering dust somewhere. I'm not sure if they'll fit but if you want them they're yours (if I can find them ;) )
Thanks Josh, I'll stick with the single pulleys for now - found a guy that sells aluminium pulleys for about $12 ea or 2 for 20, so hard to pass that up.

That laser tacho looks good, thanks Cliff - might check it out, but at the moment still in the testing phase, hoping nothing will blow up...

Will try to get the pictures on here soon.

artful bodger
2nd March 2016, 07:42 PM
Well I am going to be the party pooper. The stick in the mud. The naysayer and general conversation downer if you will.
Unless you are turning an astonishing variety of large and small stuff and going from hither to tither at the drop of a hat it is my opinion you are wasting your time with the variable speed whateveryoucallits.
So there! Cop that.
Looking forward to the ensuing conversation.

Woodturnerjosh
2nd March 2016, 08:11 PM
I couldn't disagree more but I guess it depends on the sort of work you want to do. When I fitted a VFD to my first lathe it made a huge difference to my turning. I wouldn't be without again.

BobL
2nd March 2016, 09:03 PM
So, what you are saying is that although the motor is rated at 50Hz, I can safely go up to 120Hz in my settings? Ie, run the motor at 120Hz? Not that I would want anything more than 2000rpm (just under 70Hz on the current pulleys). If you can confirm this, I will change the pulleys to give me a range of 300rpm to 2000rpm at 20 - 120Hz..

Correct


I'll also get one of those temperature indicator strips to stick on the motor, which will give me a visual clue as to the motor speed.
Thanks for the advice.

Temp and speed are not well related.
Temp depends on current and that depends on how much load you are imposing on the motor.
You can over heat the motor even at 50Hz if you impose too high a load on it.

You can get an idea of the speed of the motor by using the VFD display as this should be able to be set for Motor RPM

Cliff Rogers
2nd March 2016, 09:03 PM
I love my VFD, I also love having the reverse that comes with it.

BobL
2nd March 2016, 09:08 PM
Once you have one VFD you'll want to fit these to most machines in your shed with one.

Sometimes you don't want to FANG things at speed right from the beginning but see how a machine behaves at a slow speed and build things up from there.
On my 1m long belt sander when I change belts I like to set the tracking at low speed so that the belt does fly off or destroy itself by ramming into the roller mounts.

One of the really neat things you can do with a VFD is when a machine has a bit of vibe at one speed you an often just change the speed of the motor just slightly and this dramatically reduces the vibe.

Stopping can also faster using a VFD.

Zeeber
3rd March 2016, 08:27 AM
Well, everyone is welcome to their own opinion and I respect that. But my philosophy has always been to not knock something until you have tried it. I had a DVR before, and it is great to have EVS. When you start an uneven bowl, you can adjust it to where you feel comfortable and lose the wobble, then wind it up higher as you go. I like to finish with a finishing cut at high speed, then immediately slow it down to do the sanding and not overheat the piece of work with it spinning too fast. As most of you have mentioned, the EVS does change your turning for the better – you tend to not change speeds as you should if you have to do it manually. And we can all agree that not everything gets done at the same speed, or should I say not everything should be done at the same speed. You could, of course, but you will not get the same results. In my old club (I won’t mention names), there were some fellas who would not adopt any new technologies, they are the same guys that kept using cheap sandpaper until it was shiny, instead of changing to new technologies like diamond dot or similar. The results were obvious when you looked at their heat-cracked work. Guys like Terry Scott and Robbie Graham from NZ or Brendan Stemp from over in the Grampians are masters of their art because of their attention to detail. And I’m smart enough to know I don’t know better than them, so I gratefully accept their advice and learn from their years of experience. Long story short, if you think that EVS is from the devil, I humbly disagree.
Photos of the conversion added here – I hope to be able to take one soon with the cover on, and of the bracket, but my photo technology is playing up at the moment.373158373159

Zeeber
3rd March 2016, 08:29 AM
Sorry, BobL - I meant give me a visual clue as to the temp (not speed).

Correct



Temp and speed are not well related.
Temp depends on current and that depends on how much load you are imposing on the motor.
You can over heat the motor even at 50Hz if you impose too high a load on it.

You can get an idea of the speed of the motor by using the VFD display as this should be able to be set for Motor RPM

BobL
3rd March 2016, 09:34 AM
The photos of your location for the VFD suggest it is not the best, its too close to the main source of dust where its internal fan will suck in a lot of dust and lead to problems.
To me it also looks like it's in the way.

Even with serious dust extraction I would look at moving it away from the lathe itself

Ideally VFDs (especially cheap ones) should be in a vented enclosure in a position where it is expose to minimum dust and a remote (on/off/speed.etc) controls brought forward.

Possibly the worst place is under the bench since a WW lathe throws most dust forward where it then eventually falls to the floor. When operational the underneath of a wood lathe is usually the dustiest place in a workshop.

A better location that is still within arms reach is behind or above the lathe where there is less dust.
However this is not a natural position for turning a machine off so remote control is advisable

Some folks place their VFDs on a wall behind their machines but because I sometimes move my machines around I still attach the VFD to the machine.
It looks like it is immediately above the lathe but it is actually set back and attached via a SHS post to the back edge of the lathe bench with the power in. out and control cables running down the middle of the SHS.
Note the small galv cover/ top shield , this protects it from things dropping onto it and reduces the amount of dust settling out on it that inevitably falls out in a workshop.
The remote control is the white box just above the chuck on the lathe stand
http://www.woodworkforums.com/attachment.php?attachmentid=362025&d=1445639336

The disadvantage with this position is that (although my dust collection is very good) a small amount of fine dust does escape and being fine it rides upwards on warm air currents.
A light dusting with clean compressed air every now and then helps.
I also have an emergency switch at hip height on the edge of the bench just to the right of the pic.
It's not a true E-switch which applies a braking current to the motor, it just cuts the power to the VFD.
This stops the motor and spindle within a second so it does not coast to a stop.

Zeeber
3rd March 2016, 11:02 AM
I'm with you, BobL - the position and the dust is a major concern for me. BUT - the overriding factor was the ability to turn the headstock to outboard, so the VFD had to be mounted on it. My intention when putting the cover back on is to make a canopy (?) for the VFD to prevent direct intrusion from particles (leaving enough air to cool). The secondary airborne particles needs to be taken care of by the dust extraction hood, and while it will not be 100% efficient, it will have to do. I have thought of different ways to mount this, but couldn't see any other way than this (maybe a pedestal type arrangement on top of the headstock?). There seems to be enough space available in the headstock to push it back about half the depth of the VFD, maybe that will help, but worried that I might compromise the structural integrity of the cast iron headstock when I make a hole that big...
I have monitored my own turning on the other lathe to see whether the position of the VFD would impede when turning, and while it will get in the way every now and again, one can usually make another plan - for me, I work mostly on the other side (bowls) and on the spindle side (pepper grinders).
As for the remote switch, my DVR had only the same controls as the VFD, so I"m not considering putting any other switches in at the moment.
All valid points though, and worth considering. This is a first for me, and I hope to take the lessons learnt from here to do the conversion on my Nova 3000 next.

Christos
3rd March 2016, 05:56 PM
...... BUT - the overriding factor was the ability to turn the headstock to outboard, so the VFD had to be mounted on it. .....

I think this is mounted in the wrong position. I am only going by how I turn and sometimes after turning the piece around I might want to touch up the bottom. As I am right handed, it puts your body right up against the head stock or as have done in the past, change to a left handed position and that puts the tool right up against the head stock. Where this is located it does not give you a good angle with the tool to make a push cut.

Can this not be mounted or attached in a different location and still be able to turn the head stock?

BobL
3rd March 2016, 08:58 PM
I think this is mounted in the wrong position. I am only going by how I turn and sometimes after turning the piece around I might want to touch up the bottom. As I am right handed, it puts your body right up against the head stock or as have done in the past, change to a left handed position and that puts the tool right up against the head stock. Where this is located it does not give you a good angle with the tool to make a push cut?
Yep - that was exactly my concern.


Can this not be mounted or attached in a different location and still be able to turn the head stock?

Of course it can, the VFD does not need to be anywhere near headstock - The VFD is ideally mounted a couple of metres away from a lathe and all that runs between the VFD and the lathe is a 3P power cable for the motor and a remote cable (I use Cat5 Cable) which can be mounted on the headstock or below the headstock on the lathe base.

artme
4th March 2016, 09:24 AM
Well I am going to be the party pooper. The stick in the mud. The naysayer and general conversation downer if you will.
Unless you are turning an astonishing variety of large and small stuff and going from hither to tither at the drop of a hat it is my opinion you are wasting your time with the variable speed whateveryoucallits.
So there! Cop that.
Looking forward to the ensuing conversation.

I agree!! Maybe because I simply can't afford to convert to VFD!!!:D:D:D

NeilS
4th March 2016, 04:03 PM
Well I am going to be the party pooper. The stick in the mud. The naysayer and general conversation downer if you will.
Unless you are turning an astonishing variety of large and small stuff and going from hither to tither at the drop of a hat it is my opinion you are wasting your time with the variable speed whateveryoucallits.
So there! Cop that.
Looking forward to the ensuing conversation.

Added a variable speed control to my old Woodfast about twenty years ago and I wouldn't have a lathe without one since then.

I find many good reasons for them, but the most valuable for me is being able to quickly find the rpm just below the point at which an out of balance blank (just about all of mine begin that way) starts to vibrate the lathe. As the blank comes into balance I just nudge up the speed knob. That saves me a lot of time (never "wasting" it) and I just find it makes turning more enjoyable.

NCArcher
5th March 2016, 10:25 AM
Is the motor still connected in Star? Can you show a pic of the terminal box and the motor nameplate?
You should be connected in Delta for 220V 3 phase.

I'm not much of a turner but I wouldn't want to turn on a non EVS lathe. I converted an ex school Woodfast and the variable speed is brilliant. Especially for a noob like myself where I really have no idea what speed I should be turning at. Very simple to nudge the speed till it feels right.

BobL
5th March 2016, 12:30 PM
Is the motor still connected in Star? Can you show a pic of the terminal box and the motor nameplate?
You should be connected in Delta for 220V 3 phase..
It's not essential to connect it in ∆, however it will only develop half power. This is what I did with my Woodfast. It had a 1/2 Hp motor and I added a 1HP Y motor and it developes pretty of power for what I do (mainly spindle work) which uses 50 to 120Hz anyway.

Sometime I will convert that motor but then again I also said that 2 years ago :-)