Todays update from Bodgers Lodge

I like the lateral thinking, I will store that one away in the idea bank.

Mike

Hi John,
I must try to remember that trick for future use. In the last video clip it looks like the section of shaft between the steady and the armature is running eccentrically. Is this an illusion as I assume this section of the shaft was in the steady when you machined the section now in the steady so they must be concentric ?

Les.

Nice work, John

You certainly have this "remake it out of weld" technique off to a fine art.

Any hints & tips on technique [and choice of kit] ?

... or is it all down to years of practice ?

MichaelG.

Very clever stuff John, most ingenious

I do have a relevant question. On a weld that deep there will be a lot of weld to rebuild the section and therefore a lot of weld shrinkage.

Do you compensate for that by welding on a rotating job, albeit very slowly and secondly would you apply any post weld stress relief to get the run out results you measured?

Brian

Answers in some semblance of order - i think.

Les looks like that doesn't it but it does run concentric. Only answer I have is You tube came up with an option because it has recognised shake and did I want it to correct it ? Guessing it was the dial gauge movement but I said yes and this is the result. Need to look at the original video on the camera card to check.

Michael, think the tips and kit have been covered in previous posts, noting special at all.

Brian, I start off slow and do a bit one side, then the other, rotating by hand as I go to try and keep the pull even.

Go as fast as I can as I want as much heat into the weld as possible because when it is put back in the lathe in soft jaws and steady and centres it has the maximum support and the lathe is run at about 100 revs [ not critical just need to keep rubbing speed down on a hot shaft with the steady.]

The gradual cooling whilst running in line performs the stress relief or that's the way I see it.

With MiG welding there is no flux but you get an oxide layer on the top of the weld and you often see this flaking off as it cools which I put down to the stress's working out ? Not sure if this is true, I'm no rocket scientist, but it seems to work for me.

End of the day some of these jobs are bodges forced on us by cost / time restraints and lack of spares. In this case the proper answer would have been to press the shaft out and make a new shaft. However unlike AC rotors you cannot press the shaft out of a DC motor without wrecking the windings as the laminations are separate to the comm and it just squashes the windings up. The windings in this case are not wire but strip which has to be folded to shape. Not many rewinders have the facility to do this and most send away to specialised companies to have this done and so cost and time again come into it.

The rewinding companies that can pull repair jobs off like this, [ remember no one knows who I am, as far as the customer is concerned it's the rewind company pulling rabbits out the hat, they get all the praise ] manage to get good working relations with the customer. Most of these companies are household names and their maintenance department is also accountable and pulling a rabbit out the hat ticks everyone's boxes which means more work, a better working relationship and another sixpence at Christmas.

Another ,I hope, sesible question- I have assumed you are welding in the lathe, maybe wrongly. Where do you put the earth wire ? If on the lathe bed this will put a lot of amps thru' the bearings. Maybe you have a myford and brass bearings so will be ok.

Thanks for the answers John, pretty much as I expected.

The flaking oxide layers on successive runs are I'm afraid just that, it isn't stress relieving as it goes. It would be hard indeed to do it properly where it needs soaking at temperature, you don't have the luxury of that so as my old boss used to say--" It's muck or nettles" The argon blanket is most effective at the arc point, not round the back where it will still be hot enough to oxidise.

I still like your solution, a proper rabbit from the hat. The re-winders must love you.

Brian

Gordon,

No, welding in simple vee blocks on the welding bench.

Welding in the lathe is a big no-no unless you have a trash lathe just for this reason. That lathe that features in many of my pics is a TOS lathe 360mm swing and 1000mm between centres. It doesn't look pretty but it does some serious work.

Bought new it's about 15 years old and after about a month I was very disappointed in that loads of paint was coming off the saddle and apron due to one spray coat being applied over bare castings, no filler etc.

Then I realised that it had been bought solely as a work horse and not to polish. Even after 15 years it's deadly accurate and I rely more on the dials than the DRO

Gordon, JS's welding fixture can be seen on the first page of this thread

Eye there John done a good few DC amature reshafts a Stanton its a huge job com de soldered tails lifted com off the IE and Lams off the DE

Then sweat the whole lot back up its OK with wires but a pain in the butt with tape copper 1/2 X 1/16 was normal up to 100 hp

It was about a weeks work on a 50 hp . So I can see why you put it back to true

Stuart

Thanks for that, just did not realise you used the same V blocks as before, makes sense now. Still can't figure out how you keep it straight after all that welding, just my lack of experiance.

If you build the weld a little above shaft diameter, it will be straight by the time it's turned down to size.

Ian S C

This is why JS puts it back in the lathe while still red hot, the metal will still be able to flex slightly so the ctr pulls it straight and holds it there while it cools, still need to balance the welding by doing a bit on each side at a time.

Not sure if this is going to work ??

Got a tall 3HP motor her thats too tall and also a bit to powerful, so thought I'd try this and see if it works.

Carefully cut it into 1/3rd - 2/3rds, just need a new shaft now.

Reckon it will work ?

Hi John,
You'll have to remove a few laminations to expose the ends of the copper or aluminium bars to allow you to short all the ends together. I think the fun bit will be rewinding the shortened stator sections. You should have saved this one until April 1st.

Les.

Edited By Les Jones 1 on 21/11/2014 22:43:08

Has to be said, you're a clever bloke John.

Obviously just a result of a caffeine 'high'!!!

Rgds

Bill

Hi John, should work, now I've fixed it for you.

Regards Nick.

Now tidy up the bench

Neil

I can't stand this sort of thing - Coffee cups dirty and swarf in them!.