Myford 3 phase motor upgrade

Hello all.

I am thinking of replacing the motor on my super 7 for one of these fancy 3 phase jobs.

When I run the machine in the higher range of speeds I get a great deal of vibration, the machine is really not happy,

I have checked everything else is as it should be and to the best of my knowledge all seems ok except for a slight runout on the motor pully.

as these units all seem very expensive, does anyone have any experience which could help my decision?

Thanks in advance

Brian

Edited By Brian Abbott on 01/10/2014 22:30:29

no experience of three phase but i also had severe vibration when using the highest speeds on my S7.
i changed my V type drive belts to the link type and the vibration all but totally dissapeared.
£50 is a hell of a lot cheaper than paying 100s of pounds for 3 phase simply to get rid of vibration

z

Edited By Ziggar on 01/10/2014 23:18:14

Hello.

the machine had a link type belt between the counter shaft and the spindle when I first bought it,

problem I found was the belt was to big to get onto the highest speed pully so changes it to a standard belt.

Did you change both belts and can you remember the make?

thanks in advance

Edited By Brian Abbott on 01/10/2014 23:50:09

Hi Brian, are you thinking of the complete kit or a DIY set up? The DIY route is not difficult and can be cheaper. Whichever you go they are worth the effort, it will quite transform your lathe.

Re vibration possibly due to belts, are you using "cogged" belts and do you release the tension when not in use to reduce the risk of putting a set in them.

chriStephens

i bought my belts from here one at a time [not rich enough to do both at the same time]

i got the Fenner easy fit type

and ive had no problems at all since changing them

Z

Edited By Ziggar on 02/10/2014 01:06:10

I have found that if the belts are left under tension when the lathe is not in use they take up a "set" which causes vibration until the machine settles down again. I always relax the belts after use to avoid this problem and so far it works.

I too have a S7 which I fitted with a 3ph 1HP motor. The change is a huge step in performance in the speed control, power and smooth running. I very rarely change the belt position because with the power and speed control, even thread cutting can be undertaken without back gear but at low speeds, the motor temperature has to be watched

The torque produced by a single phase motor varies with its rotation while that from a three phase motor is (theoretically) constant. Thus a three phase motor gives less vibration and a better finish. Changing to three phase and inverter setup transformed my lathe.

Go for it!

Russell.

Before buying an expensive package, consider buying separate items. Motors are readily available, but check that it is the type with six terminals, other wise is can be a bit tricky to locate the star point which requires a motor to be dismantled( motor rewind people will fix it at a price, easy if you know how). Inverters are available on the net from the Far East and ebay at a good price and there appears to be lots of helpers around if you get stuck with the set up. Should you need a remote control package, they are easy to make up and the bits area available from Maplins.Three phase motors are inherently smoother in operation 12 pulses a rev as apposed to 4. Also 3 phase motors are simpler than single phase, no switch, capacitor or start winding to go wrong. Regarding the belts have a trip to your local bearing factors, they will have a range of belts suitable for Myford lathes and I have found half the price of the lathe dealers.Ted

Thanks all for your advice, not sure which way to go..

Trying the new belts seems like it may sort out the vibration, but then the flexibility of a 3 phase setup sounds

good.

If i where to try the DIY option, can anyone suggest where to buy the motor ?

Guess i would just look for a 240volt 3 phase 1hp motor..?

On another note. Just paid a visit to Rotagrip for some tool steel, only down the road to me.

Fantastic place..well worth supporting.

thanks all

Brian

I suggest you talk to Transwave whose ad should be just to the right and up a bit from here--->

If you mean Rotagrip near Hockley flyover in Brum, Transwave are pretty nearby in Tyseley.

Neil

Edited By Neil Wyatt on 02/10/2014 13:50:50

I've found these people to be good. Their Marelli motors are designed specially for inverter drive, ie., They have improved cooling for low speed running. I would think that a 0.55 kW (3/4 hp) motor and inverter would be about right for your Myford.

Russell.

Edited By Russell Eberhardt on 03/10/2014 07:59:20

Hi Brian,

The cheepest 1HP 1400 rpm 3 phase motor I could find was item number 110912538780 on eBay It was £82.00 I have just looked and there are 4 left It works fine with Teco inverter also bought on eBay for £55.00

Les

( Sent from my Nexus7 sitting on a beach in Rhodes Greeece))

Edited By Les Jones 1 on 03/10/2014 09:31:59

I put an ad on the homeworkshop site and picked up 2 3 phase motors that someone had replaced with single phase on ex industrial machines for 20 quid. Someone on here has posted that ordinary 3 phase motors are quite happy with inverter drive. I'm in the process of fitting one to my VMB mill, if that's successful the other will go in the S7.

On the belts, depending on which S7 version you have, the link belts can be a problem. I started out with a black one from RDG sold as suitable for Myford, but the pulley vee in the later big bore lathe is too narrow for it. Ended up with a more expensive red proper Gates belt from RS, but even that is a bit wide and I get slipping if the cut is too aggressive. The lathe is better but still I don't like using the top range of speeds, there is a lot of vibration even though the first stage reduction uses poly-vees. Maybe a 3 phase motor will be better. I must say I hadn't considered the possibility of set in the belt, I'll give a try to releasing the belt tension when I leave the lathe.

Thanks all..

Really showing my ignorance here but..if i buy a foot mounted motor ( i.e a Marelli motor ) will i need to change the current motor mounting plate ?

The idea of a made to measure system does really appeal, but at £400 odd quid they ain't cheep.

maybe look at getting the old motor off this weekend and have a proper look,

thanks

As I understand it Myfords use imperial size motors as standard, which come with a hefty premium as the vast majority of motors available today are metric size frames.

If you replace with a metric size motor you will have to make some changes.

Neil

.

True, Neil ... but thankfully the mounting plate arrangement is very simple.

Most significant points will probably be (a) the shaft diameter and (b) the fact that the original Myford fit motors are vibration isolated [this I doubt will be any problem if changing to 3-Phase & Inverter, which is much smoother]

MichaelG.

Just goes to show that Fleabay is not always the best choice. The same motor from the link I posted earlier is £50 + VAT.

Russell.

Not going to be as expensive as i first thought now i have a better understanding..

Will get the parts on order and see how it goes..

Thanks All for your advice,

I've just finished replacing the 0.75KW 1ph Imperial motor on my pillar drill with a metric 3ph +VFD. The old motor had a 5/8" shaft with 4.7/8" x 3" mounting holes in the foot, the new one has a 19mm shaft with mounting holes 125mm x 100mm. I had to bore the pulley to 19mm, cut a new internal keyway, and make new mounting feet to fit the drill's mounting plate. A new Imperial frame 56 motor was around £150, the new frame 80 one was £50, both +VAT of course. It was a lot of work to save £100, but worth it in the end. If you do it, don't forget to check the position of the pulley relative to the mounting holes - don't ask me how I know.

I have a Super seven and a fobco drill both purchased new over 40 years ago,both have the original motors and drive belts,neither of them vibrate and both have had a lot of use earning me a living,I have never required or desired to make changes to the Myford, On the other hand 1/2 inch capacity bench drills usually have a bottom speed of 450 to 500 rpm which can be a pain when reaming or straining the drill with over capacity drills, I had a need for larger capacity drilling so bought a used1 inch capacity Meddings ,with low sped of 100rpm which gave reamers an easier life and allowed the use of a tapping attachment. A while back out of curiosity after reading lots about electronic speed control on this forum I looked up the cost of a speed control on the fobco,it was a lot more money than what I paid for the Meddings.

Is the vibration being experienced due to modern motors being imported and not being so good as the old uk built motors,as there were never any moans about single phase motors in the dim and distant past,a solution could be find a good used uk built motor. My father bought a brook gryphon motor in 1950 to drive saw bench and has been used since to power lathes (wood and Metal) and now drives my power hacksaw daily,a very good motor.