NewtonTesla systems

Brilliant 'Factoid-busting' post, Andrew !!

MichaelG.

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[*] Despite sloppy usage in more recent years .. Norman Mailer's word is very appropriate:

See my post 03/03/2015 here: http://www.model-engineer.co.uk/forums/postings.asp?th=104837&p=2

Edited By Michael Gilligan on 11/11/2017 08:19:48

REALLY CONFUSED!

I'm more uncertain now than when I began this thread. Looking at answers here and reading other websites it seems that:

a). Never run an ML7 faster than 1000rpm at the chuck on pain of destroying the machine unless bearings are upgraded.

b). Run it at up to 2000rpm for hours on end with white metal bearings and don't listen to the doomsayers.

c). Pick an option somewhere in between.

Not sure what to do now. I've been trying to work a space in my workshop for a minilathe but not having much success without seriously inconvenient access to some other item. If it was an easy option I would have one on order by now.

Would love to run the ML7 faster as the easy option but still cannot find bronze half bearings and shaft at a sensible price.

Stephen,

There isn't a simple answer - it boils down to how much risk you're prepared to take.

a) Can you run an ML7 faster than its design speed? Yes, but there's a risk to the bearings and perhaps to other components if you crash the lathe at high speed. The faster you go and the longer you do it for the bigger the risk.

b) Can you run an ML7 for hours on end at 2000rpm? Yes but only if the guy who told that's OK also promised to replace the bearings if he's wrong.

Things you don't know:

• The current state of your bearings. Are they 'as new' or nearly worn out? If worn out then they won't last long at high speeds
• How effective is the flow of oil through your bearings? If the flow is impeded, or you're using the wrong type of oil, expect trouble.

There are a couple of things you could do to reduce the risk:

• Force feed the oil with a pump rather than Myford's gravity feed
• Monitor the temperature of the bearing and shut-down as soon as it gets hot. ( 'Full Speed and damn the consequences' in a WW2 battleship apparently involved teams of sailors cooling bearings with fire hoses.) The reason is when oil gets too hot the lubricating film collapses and the resulting metal to metal contact damages the bearing.

One thing you do know - the high cost of replacement bearings. That's the minimum pain you suffer if over speeding goes pear-shaped. If you're comfortable with that level of pain go for it. I wouldn't overrun an older lathe for long periods, but it's not daft to do it in short bursts on special occasions.

The reason I suggested a mini-lathe in an earlier post is because they're fitted with ball-bearings. Much more predictable.

Dave

Edited By SillyOldDuffer on 12/11/2017 20:30:37

I have thought of fitting ball bearings to the Myford, (two each end), at least the shaft wouldn't get hot. Not sure if they would fit in the existing clamps.

My reference to 2000rpm was not from a post on here.

Someone described converting an ML7 to roller bearings in either ME or MEW not too long ago. Looked way too ambitious for me, but it worked for him.

Perhaps that's an opening for an entrepreneurial type, new roller bearing headstock for your myford.

Duncan,

The article was in MEW about 18 months ago. As for setting up to remodel the ML7 headstocks for customers, it would be unrealistic in that far more time would be needed than can be realistically charged for, quite besides needing suitable machinery being available to do the work.

A one off by the individual was how I read the article. It did in my view also rather weaken the bearing housings by boring them out to contain roller bearing units instead, there was little meat left to contain them at the end.

Regards Brian

Stephen ... I bought a Newton Tesla VFD about 13 years ago, the small size they call CL 400 ... it is rated at 400 watts putput ... definitely the best thing I ever bought ... it has been well and truly hammered over that time ... on some days it has been run for about 10 hours and has never yet got anywhere near hot ... just hand warm ... it has never hiccupped at all ... my only minor comment is that the emergency stop button is a bit near the ordinary stop button.

Its speed range is quoted as between 200 and 1800 RPM ... I made a new drive pulley from ali. bar with a diameter of 1. 75 inches ... so, along with the large pulley on the headstock my spindle top speed is about 630 RPM ... a larger pulley on the motor spindle would give corresponingly faster speeds on the lathe spindle.

I ended up fitting the motor round by 180 degrees so it ran in reverse relative to the desired rotation ... this was simplicity itself to reverse 2 of the 3 motor wires ... I did check with Newton Tesla first.

hope this is some use ... martin

Martin,

What lathe did you fit it to? The question for me is Myford bearings, whether they will stand up to 2000rpm. Seems not according to most replies. Upgrading to Bronze costs around £330. Silly Money! I can buy a mini lathe for approx. £500, less than bearings and inverter system.

Stephen ... I fitted the unit onto a Proxxon PD 400 lathe ... lovely item but not a huge machine ... the headstock bearings are 2 opposed taper roller bearings ... I tried to find out what their maximum speed should be but it is not listed anywhere ... maybe it is quoted in the literature for some of the new machines.

martin

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I doubt if it really answers your specific question, but this is worthy of note:

[quote]

[/quote]

Taken from this excellent paper: **LINK**

http://edge.rit.edu/edge/P14453/public/Research/2-_LEADER_-_Understanding_Journal_Bearings.pdf

Frankly; I think your question is unanswerable ... simply because there are so many variables:

Myford bearings, in top condition and suitably lubricated, should take the speed if lightly and evenly loaded, BUT if you subject the bearings to heavy and/or intermittent loading then all bets are off.

MichaelG.

Stephen ... I was trying to find the fastest speeds for the Proxxon ... in one section with the original motor fitted it does quote 1400 RPM ... if I remember rightly this produced a lot of vibration at speed ... I was looking through the arc euro trade catalogue ( www.arceurotrade.co.uk ) at the taper roller bearings they sell ... they do not list the maximum speed the bearings will stand but it may be quite a bit higher than 2000 RPM ... possibly a call to them would yield the information you want ... that does assume that you want to cannibalise your lathe to fit roller bearings ????

martin