Unmitigated Woe

[Sub MandrelParticipant @submandrel]

My mini lathe has blown up. I was happily chewing down 2 1/4″ EN1A blanks to 7/16″ wide for loco wheels. Not working it hard at all really, no more than 25 thou cuts. Big pop and motor loses a couple of windings, and the machine had been cold up until a few minutes earlier.

 

I discovered some swarf had got into the control box and bridged a few connections beneath the comparator board.

 

In the hope of rapid recovery I did the very naughty trick of bridging the bad coils with solder on the commutator, it worked OK on 12V, if a little rough.

 

The blow terminated my resettable 1A cutout, which I replaced the fuse with.

 

Put it all back together and … motor didn’t turn, just popped again very loudly. I should have taken advice elsewhere on this forum and tested with a light bulb.

 

Looks like the board is putting out 216 V when it is at minimum speed.

 

There may be something to salvage, but right now I’m wondering where to find the groats to get a 0.5HP three-phase motor and inverter pack. Not a good time as next month is Christmas and MOT all together

 

Biggest annoyance is that the tangential tool holder was giving me a near mirror finish on that nice steel – best I have ever got.

 

Neil

 

[Sub MandrelParticipant @submandrel]

[blowlampParticipant @blowlamp]

Did you know that you can have your MOT done up to a month early, without losing any time from your current certificate?

 

Perhaps consider getting the car through its test now (fingers crossed) and get Santa to buy you a new motor/inverter once the MOT is a distant memory.

 

 

I’d be interested to see a 3ph motor conversion of one of these lathes, because I’m inclined to go that way myself, but would be happy to let someone else blaze the trail.

 

 

Martin.

[Les Jones 1Participant @lesjones1]

Hi Neil,

On some of the forums in the US people have used treadmill motors on their lathes and mills. I noticed a treadmill motor on ebay this morning for £35.00. If you can fix your controller board then this might be a cheaper option. The item number is 280775682007 There is also a pair of motors with controller board from a Weiss mill. The item number for these is 230703998780

 

Les.

[David LittlewoodParticipant @davidlittlewood51847]

Neil,

 

I had a similar disaster about 4 years ago with the 0.5HP motor on my Super 7 – and I think it was the same cause, swarf (but in the motor vents).

 

I took the plunge and bought a 1 HP 3-phase motor and VFD from Newton Tesla. Not the cheapest way of doing it; I’m fairly sure if you knew exactly want to do you could get all the parts and do it yourself, but you’d have to program the VFD to match the motor, make a box for it etc. The NT set came plug-and-play; just fit motor, hang box on lathe stand, plug in and everything works as it should.

 

The drive is much smoother, and I can change speed at the twiddle of a knob, even mid-cut. I hardly ever even need to do belt speed changes now. They’d have to kill me to take it away…

 

David

Edited By David Littlewood on 20/11/2011 18:39:01

[alan frostParticipant @alanfrost17805]

Worth investing in a cheapish mitigator too.

[Sub MandrelParticipant @submandrel]

Thanks for the ideas.

 

I’ve just had a look and I think that a solution is as simple as a ‘U’ bracket with the two bearings off the motor, a pulley between, and the toothed wheel on the end, fastened using the motor attachment points to allow the correct tension. The motor can sit on a hinged flap hung off the back of this bracket or somewhere else in the vicinity

 

This keeps the back gear and if I use a 2 or 3 step pulley I can have the advantages of VFD without having to worry about slowing the motor frequency too much.

 

But it looks like february at the earliest unless I do some slick xmas negotiation..

 

At least I do have a lot of non-turning tasks to do on current projects. Not many locos get cabs and running boards before they have wheels, but why not?

 

Neil

 

P.S. what’s a mitigator?

[Ramon WilsonParticipant @ramonwilson3]

Neil

Sorry to read of your plight. May you get it fixed sooner than you think and get back to square one as soon as possible. My commiserations – I’ve missed having compressed air for a couple of weeks so gawd knows what I’d do without a lathe.

 

All the best for a speedy resolution

 

Ramon

[Cornish JackParticipant @cornishjack]

Neil

Can you confirm that you are in Spixworth, Norfolk?

If so, and it is of any use, I have a spare Hobbymat which you are welcome to borrow. It all works as advertised and would only require collection from Bacton.

PM me if of any use

Rgds

Bill

[SpringbokParticipant @springbok]

Hi Bill

 

Now that is what I call a friend to someone in need

 

Bob

[Richard ParsonsParticipant @richardparsons61721]

Stub Have a look at scrapping all the electronic ‘allamagoosa’ and think about a good old fashioned countershafts, belt tensioners and multiple ‘Vee’ pulleys. They have been around since before the ‘Ark’s’ keel was laid. I have seen and read too much about electronics failing and prefer the old fashioned ‘rude mechanicals’. I can always ‘fix’ them.

One of the problems is that the accountants (who know the cost of everything and the value of nothing) insist on the cheapest of the cheap components. These have a very high risk of failure but so long as they do not fail under the 5 minute in house test they are acceptable. The customer does not matter. He has bought the thing and is stuck with it. We have his money.-Ha Ha Ha! The retailer is stuck with the irate customer and any bills. Beside we can sell him a new bit of electronics costing 10 times the ex works costs.

Ok I have a 60 year old motor on the Myford (I bought it second hand, reconditioned 35 years ago.). Two years ago it went ‘pop’. I trotted it down town where the little man rewound it and put in new bearings (which I asked him not to do as I had a pair of brand new (top of the range) SKFs ). He charged me 4,000 HUFs (about £12 in ‘London money&#8217. I was back ‘on-air’ two days later.

[adyParticipant @ady]

Stub Have a look at scrapping all the electronic ‘allamagoosa’ and
think about a good old fashioned countershafts, belt tensioners and
multiple ‘Vee’ pulleys. They have been around since before the ‘Ark’s’
keel was laid. I have seen and read too much about electronics failing
and prefer the old fashioned ‘rude mechanicals’. I can always ‘fix’
them.

—-

 

Plus have backgear on whatever lathe you choose.

I prefer a retro approach too, it just seems to go on and on forever once you get it set up.

Seventy years young with not a hint of any problems and munching through the metal.

 

Even without the ingress of swarf higher load electronics can’t last more than what? 15 years tops?

[wheeltapperParticipant @wheeltapper]

Neil,

Is that right that you live in Spixworth?

If so we are neighbours. I’m in Park Road.

 

Roy.

[Richard ParsonsParticipant @richardparsons61721]

There is a solution to all these problems. Have a look at the transmission on the DAF Daffodil motor car. This was derived from the Zenith ‘Gradeo’ motor bicycle. It is rude mechanicals but it works.

It might be an interesting idea to get the clutch and pulley from an old twist and go 50cc scooter. You might be able to fit your lathe with a (limited range) variable speed and a clutch.

I suppose the Electronic ‘gubbins’ can be put together by a ‘bot’ for a few micro dollars with the chips etc costing about 5-6 Dollars (wholesale). This would be about 1/10^th of the cost of a 4 cone pulley.

[Sub MandrelParticipant @submandrel]

I’m feeling more cheerful now, especially touched by Cornish Jack’s offer. Sadly I don’t know where Spixworth is, I’m near Burton upon Trent!

 

No matter, rather than moping and feeling sorry for myself I should use some Model Engineer’s ingenuity and take up a few of your suggestions.

 

I was given a Hoover fractional motor by a colleague (our former book-keeper Roger, who used to work with electric motors – as in ones the size of cars) a year or two ago; I’ll go and dig it out. If I make my countershaft bracket on the mill and bodge/get a pair of 3-2-1 pulleys, with the 2:1 gear built into the mini lathe I should get a reasonable range of speeds .

 

And as Guy at work pointed out, if I lurk around Ebay for a while there’s agood chance of getting a deal on a motor and/or inverter in due course.

 

Neil

[Cornish JackParticipant @cornishjack]

Neil and Roy – apologies for my mental confusion!!! I had made a note of one of the forum ‘regulars’ being a county neighbour and wrongly attributed it to Neil. Just have to keep taking the tablets, I suppose.

Anyway, it sounds as though you are well on the way to getting sorted.

Back to the topic

Rgds

Bill

[Ray LyonsParticipant @raylyons29267]

If you decide to buy an inverter and 3 ph. motor, can I suggest Gavin Oseman who advertises on the Home Workshop site. I bought 2 inverters from him several years ago and both still going good. He usually supplies all the bits, switches etc.,and a manual on disk to get you started. His Phone No is : 01684574966. EMail hpdrifter@sky.com.

 

He supplies used, tested at about half price of new.

[Sub MandrelParticipant @submandrel]

I’ve just tried out Roger’s motor (photos below).

 

It is quite lovely, I popped a few drops of 3-in-1 in the oil cups(!) on each end bearing, and fitted a plug. I was wary of the external capacitor which looks victorian and the lack of earth.

 

I read the resitance across L and N as 8 ohms, which seems about right, and the earth to live was over 2 megaohms (the max my DVM goes up to, so I switched on.

 

It made a scary click (I realised this must be a centrifugal switch) then it hummed quietly and without any sign of vibration. I ran it for several minutes, switched off and it slowly ran down, and the centrifugal switch tripped out just before it stopped.

 

The wires look like they could do with replacing (and an earth would be nice) but I am happy that I should be able to do something with this. I can’t think how I forgot this motor – thanks Roger!

 

Finally this is the sort of thing I was facing off when the motor blew, but not a finishing cut I was winding the handle as fast as it would go without slowing the work down. Tempting to say this is how pins are made…

Neil

[AESParticipant @aes]

Stub Mandrel,

 

This may be too late to help you now, sorry (been overseas on a job n only just got back), and also this may be out of date. But ……….

 

On one of the “main” minilathe websites there’s some stuff about a US guy called Gerling who has specialised in reparing/ replacing/upgrading minilathe electronics. The link is:

 

http://www.mini-lathe.com/Controllers/Repair/Gerling.htm

 

As you’ll see, it’s dated 2009 so perhaps he’s no longer around, but before things get TOO drastic for you it may be worth a visit?

 

And BTW, it’s too late for this time but based on info from these various minilathe sites, I took a bit of time building an extra full size “swarf plate” out of 30 thou plastic card which covers the whole of the electronics area (inside) and is specifically placed to stop bits of swarf getting in amongst the “wiggly amps”. Very quick n simple to do and maybe worth doing before you put it all back together again, whatever solution you finally end up?

 

If I may end with a Q – in your original post you mention getting good results with a tangential tool holder. Would this be the Australian device advertised on this site? If so how is it please, and what size did you buy for your minilathe?

 

Krgds

AES

[Sub MandrelParticipant @submandrel]

Thanks AES,

 

I mistakenly thought the clear plastic shield was doing that job – I hadn’t realised the comparator board poked out underneath.

 

The board is probably repairable – no signs of major damage, I’m guessing one of the LM324s is blown and giving a wrong signal and causing the output to be ‘off’. It’s the loss of another motor that irks me. I had already replaced it once. I did have a spare which I bought off an elderly advertiser in the classifieds. They added on enough for postage to make it almost as expensive as a new motor, but I went through with the deal. I was assured it was OK, but when it arrived, I discovered that two of the coils on the mtor were blown. Ripped off by a pensioner

 

The tangential tool is a homebrew one:

 

Tangential Tool Holder

 

I haven’t finished drawing it yet.

 

Neil

[AESParticipant @aes]

Thanks Neil,

 

Having now read your posts (and the other connected ones) thoroughly I now realise your motor went “phut” too. Really sorry about that. And to be ripped off by an internet “spiv” just adds insult to injury (even more so as he was as a pensioner!).

 

I assume you’re going ahead with a 3 phase set up now? That’s something I’ve been toying with, especially as here in Switz 3 phase is virtually a standard in all houses, inc my own (amongst other things, used for dishwashers, washing machines, etc). But at present I’m waiting for my own minilathe standard electronics set up to go bang before I do anything on that idea. But so far so good. “Touch wood”.

 

But just in case the motors and inverter idea doesn’t work for you, I’m sure you already know that Little Machine Shop in USA (plus, I think Arc Euro in UK) can both help with an “original” replacement motor. As above I’ve not bought a motor from either but loads of other stuff and found both excellent in every respect. Usual disclaimers; here are the links, just in case:

 

http://www.littlemachineshop.com

 

http://www.arceurotrade.co.uk

 

Thanks for the info on the tangential tool holder, very interesting. But for now I think I’ll buy (not enough time at home to get all I want to do done, never mind making tooling).

 

I can’t imagine that you’ll need it, but if you want some pix of that “electronics protector” (plus a cut up kitchen seive to protector the motor itself), just ask.

 

Best of luck

 

Krgds

AES

 

 

[Sub MandrelParticipant @submandrel]

Hi AES,

 

Finances dictate it will be the new year for a 3-opahse motor, but I think I’d raher go down that route and have something I can expect to last a few decades, rather than a few years. The mini lathe is quite capable of decent cuts and big workpieces that the motor, in all honesty, is not up to handling.

 

In the short term I’ve made a countershaft which will let me use the old hoover fractional (see above). All I need to do is bodge up a pair of pulleys now:

 

 

 

OK it looks a bit rough , but I’m in a hurry! Luckily my Mill is OK so I tidied up some edges on a couple of bits of thick checker plate and bored out some housings. I have to cut a keyway for the toothed wheel.

 

Unfortunately without the lathe I had to drill out the wheel so it wobble a bit, but once the lathe is working I can make some proper pulleys and a replacement toothed wheel.

 

When I get a 3 phase motor, it can be a drop in replacement for the single phase one.

 

Neil

[Richard ParsonsParticipant @richardparsons61721]

Stub seriously now you are at it. I suspect that there is a Moped fixer near you. Pay them a visit and see if they have a wrecked ‘Twist and Go’. They do this. You could probably modify it.

Another idea is have a look for an old Sturmy Archer 3 speed. The My Dad once fitted one to drive a 3 ½” Xyto lathe which he carried in the back of an old Dormobile. It was driven by I think a JAP stationary engine. The Min of Ag & Fish were so impressed that he was given a ‘priority allocation ticket’ to buy an arc welder (it only took 5 months to be delivered). They were all wanted for the Ground Nut Scheme.

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