Myford Motor Options

[Allen Smithee]

The motor in my Super 7 is starting to show its age. One of the bearings is starting to rumble, the centrifugal switch can be slow to operate and I get the impression it's not as powerful as it once was. I could overhaul the motor, but it would still be a high-mileage lump with vintage outlook and period features, so on balance I think the better solution would be just to replace it.

So the next choice is whether to simply replace it with another single-phase motor (perhaps slightly bigger), or whether to treat myself to a  3-phase one with a VFD. The 3-phase one would be 4-5 times the cost, but the general view seems to be that the torque and smoothness coupled to the speed control functions is worth the investment.

So the questions:

1. Is 3-phase worth the effort on a Myford Super7B?

2. If no, which single-phase motor is recommended (would it be worth uprating to 1hp rather than sticking to the current 3/4hp)?

3. If yes, which packages are recommended? I see the Newton-Tesla one comes up a lot, and seems to be a well thought-out package for easy installation, but are there alternatives worth considering?

4. What are the pros and cons?

TIA,

AS

[Spinky]

IMHO
1) Definitely
2) You can have my old single phase motor if you want to come and pick it up as it's never going back on the lathe!
3) I fitted a Newton Tesla package - straightforward installation and, if it costs a little more than putting the bits together yourself, well worth the extra few quid to avoid the hassle. High quality VFD and it just works.
4) Hardly ever have to change the speed on the belts - just use back gear for low speeds No cons as far as I'm concerned!

[Jo]

The VFD's providing variable speed is a major plus point, many people upgrade just for that facility.

You need to think out were the new switch gear will go. Anything will be safer than the original barrel switch thingy designed so you can knock it as you walk by 

Jo

[nj111]

A 3 phase motor offers far more torque, if that's what the Newton Tesla package offers I'd go for that without question.

[AVTUR]

Ten years ago I traded in my old second hand Super 7 for a new top of the range Big Bore Myford fitted with a VFD.

I agree completely with Spinky but the other thing I like is the soft start of the motor (the gentle run-up to speed).

I would not like to go back to the old capacity start single phase motor.

AVTUR

[Alyn Foundry]

You're in safe hands with Newton Tesla.

I've been running with VFD's for over 30 years now. My first Mitsubishi 2.2 KW unit supplied by George only just recently packed up due to a motor insulation breakdown. The motor was nearly 80 years old!!

I only have one machine still on single phase because its motor requirements are greater than the 2.2 KW units currently available.

Cheers Graham.

[Allen Smithee]

So people feel its a marginal call then...

I had heard that some people have been running Myfords up to 3,000rpm using the newton-tesla package. Has anyone tried it? Obviously that's not something you'd want to do often, or for long, and only after making sure all the spindle lubrication is topped up, but I could see that being potentially useful for fine cuts with carbide insert tools.

AS

[Mike Bondarczuk]

Hi,

Just another very positive response related to VFD and I have a Newton Tesla system on my Myford 7 Tri-Leva and it just makes things so so so simple to use, even screw cutting without having to go to back gear.

Certainly extremely simple to install and programme, if you want to change the base parameters, and lovely and smooth drive as a result.

Mike

[Trevorc]

Newton Tesla gets my vote. Excellent.
Trevorc

[Daggers]

The newton setup is first class, examined the setup at a show, it is well thought out and looks good.
I’ve been in the market for a motor upgrade for my S7 for some time. The motor on my machine is not the original and is 0.5hp and open framed, a disaster waiting to happen.
My budget would not extend to the Newton, my first choice, therefore i had to look for a cheaper diy setup.
Thought the details, good and bad might be of interest.
The parts i end up purchasing :-
Motor 0.75Kw 1hp three phase 4 pole 1400rpm TEFC B3 £100
VFD from banggod  .75kw £70
3 off 22mm push momentary n.o switches £9.50 (on/off/jog)
Emergency red button switch £9
1k 2w single turn pot with switch £9 (rpm)
On/off/on lever switch (forward/reverse) £6
Box for VFD £10
Box for pendant controls £8
Heavy wire 3&7 core £10
Total Approx with hardware £234($314)
Current Newton price approx £500($655)

As you can imagine there are some problems, but not insurmountable.
Lathe motor carry frame needs to be altered to fit the b3 motor mount.
Original two speed motor pulley needs boring out to 19mm from 5/8”(16mm)
Vfd needs programming to the motor and wired to suit the purchased switches.
Boxes need building, etc.

Given the budget i would go for the Newton, lot less work.

One piece of advice i was given is not to overpower your S7, it is not required and could cause more problems than it fixed.

Hopes this is of interest, good luck.

[pgp001]

I converted mine to 3 phase a couple of years ago, best mod I ever did. My S7 was purchased new by my late father and I inherited it in 2003.
It has the better quality industrial stand with a proper electrical control panel on it, so I removed that and made my own bespoke version for the Allen Bradley inverter that I got for nowt.

The panel lettering was engraved using my David Dowling pantograph.

I very rarely need to change the belt onto a different pulley, very occasionally I use back gear.
Normal use sees it on top speed of the headstock pulleys and low speed on the primary drive, and that seems to do everything I need with no noticeable loss of power or torque.
I always run the primary belt a bit on the slack side, so if I ever get a jam up on a parting tool etc, it will slip and not overload or break anything.

Phil

[Charles Lamont]

I have had a VFD on my Super 7 for several years now, but have been controlling it directly on the panel. I see from dates on photos that I cut the holes in a remote control box over six years ago. Last month I finally got my tuit and made brackets and did the painting (which was the main reason for avoiding the job).

The wiring was complicated by my wish for a jog button that only moves the motor (at a slow preset speed) while the button is held down. On the VFD, jog also requires enable and either forward or reverse signals. The VFD can be programmed for either switched or momentary inputs. Set for momentary inputs it latches forward or reverse for itself. This would not work with my 'inching' jog requirement. So I had to use switched mode on the VFD and put latching relays in the button box for forward and reverse . Even so, it required two NO switches on the forward button to separate the latch and run circuits so that jog did not make the forward relay latch. (My arrangement does not bother with an inching jog in reverse.)

The control buttons are the Telemecanique 'Harmony' range; green: forwards, blue: reverse, yellow: jog. White and black are for the coolant pump, whenever I get that organised.

One word of advice: I forgot to add a couple of 'spare' contol wires. Really, I should put an extra one in for belt-and-braces safety on the stop function.

 

[Charles Lamont]

So people feel its a marginal call then...

I had heard that some people have been running Myfords up to 3,000rpm using the newton-tesla package. Has anyone tried it? Obviously that's not something you'd want to do often, or for long, and only after making sure all the spindle lubrication is topped up, but I could see that being potentially useful for fine cuts with carbide insert tools.

AS

Done that. Tried 70Hz. For drilling tiny holes. The increased centrifugal force made the little drive engaging lever on the bull wheel flip out and break against headstock casting. Otherwise, fine. It is now set for 60Hz max. If I want to go faster any time I will have to tweak the VFD parameters.

[Don1966]

I converted my S7 over 7 years ago and love it. Motor fitted without problems mounted in enclosure on the side wall with remote select at top left side for easy selecting. I bought mine as a total package motor and drive together little over $200. My drive is a TECO and has operated very well and easily programmed. I bought my package from Dealers electric on line. I have bought three more drives and motors since to convert mill and wood lathe plus my wood cutting 14 inch Vertical band saw to metal cutting.


Don

[Allen Smithee]

Well I happened to be in the workshop and so O had a quick look at the motor. The one fitted isn't a 3/4hp one - it's only a 1/2hp one. So if it's getting tired that would certainly explain some of the raw grunt issues I've experienced. I suspect the pulley might need a hub-puller to remove it. But I have one of those somewhere.

The Newton-tesla site has an infuriating lack of data. They don't tell you the shaft size or "normal" speed of their motor, so planning the pulley size is a pain. If the shaft is a different size to mine then I can forget about getting the old one off. but I need some indication of normal speeds to give me a hint on what size pulley to buy.

I guess I have to buy the package, then measure everything and buy what extra bits I need afterwards...

AS