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  #11  
Old 01-19-2013, 04:56 AM
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OZWELDER OZWELDER is offline
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G,Day Clive,

Something that works well for rotary weld position units is one detailed in the drawing below.I used similar at the QAL refinery at Gladstone.

It will take in excess of 600 amps which was what was used in the sub arcing process on 150 mm diameter valve shaft / spindles.The same scaled down for your needs would work well.I doubt whether it will even get warm. Its dependent on having lathe access and getting some brass bar to part off and tap.I never had any earthing problem in those years and probably did over a hundred of them.There's a some washers in front of and behind the spring that I did not show.The basis of it is the large surface contact areas between the discs.

I Hope it helps,
Oz
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Last edited by OZWELDER; 01-19-2013 at 04:58 AM. Reason: Left some stuff out,didin I?
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  #12  
Old 01-19-2013, 05:46 AM
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Thanks to all, Oz, good news is - now I have another lathe project for Monday. I've got some phos. bronze that I am using for a cannon but I got it longer than called for, there had to be a reason. Cutter and Gerry, if the memory sparks up please post.
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  #13  
Old 01-19-2013, 03:21 PM
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I have 2 rotory ground clamps made by Lenco and Tweco..

These are pretty expensive but work great.


The lenco one has very large disks that act as the connection points. The lenco site is down.. Couldn't find the pic.

The Tweco use a rotory device with a pinch clamp and electrically conductive grease..
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  #14  
Old 01-20-2013, 04:01 AM
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Oz, I made up the bronze discs this afternoon, 50mm x 5, do you run them dry?
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  #15  
Old 01-20-2013, 10:17 AM
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Here's a picture from Diverbills thread on his positioner. He used a big brush from a generator, from a rewind shop.

IIRC, Cutters idea was to take a piece of copper and wrap it around the shaft, and bend out two ears. Then he drilled holes and put a bolt through them. This would look like a hose clamp if it were steel. The bolt had a spring to control tension, and the ground clamp hung off one of the tabs and rotated freely.

I can't find the thread.
Lubrication...if you want it, use Copperkote.

Here are some pics I saved on this and I believe digr drawing on it and these comments on the spring clamp--
Quote:
here are pics of the setup for the ground we have at work on the converted lathe.

Split brass bushing running on the shaft attached to the spindle.

The clamp around the bushing is also split and the spring provides tension.

The ground lead attaches to the clamp with a bolt and that's all covered with the plastic pipe so it can't ground out anywhere else on the machine.

This setup has a lot of hours on it with no arcing between the bushing and the shaft.
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  #16  
Old 01-20-2013, 10:25 AM
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We made one at work for large diameter shafts it will work with 8" up to 24" or bigger. It's chain driven. The only problem with it is its contact comes through the roller pads so leaves small arc marks here and there unless there is a tail we can clamp a ground clamp that free spins. Ill take some pics this week.
Btw I'm very impressed with the automated shaft welder..

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  #17  
Old 01-20-2013, 10:55 AM
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You need to modify you welding procedure, everyone wants to well
around the circumference, this is not the correct method. You
should well longitudinally and stress relieve the part or you will get
a shaft failure.
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  #18  
Old 01-20-2013, 04:05 PM
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A rule of thumb for the required contact area on a brush is 1 square millimeter per one amp of weld current.


Randy
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  #19  
Old 01-20-2013, 05:36 PM
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Quote:
Originally Posted by Shade Tree Welder View Post
You need to modify you welding procedure, everyone wants to well
around the circumference, this is not the correct method. You
should well longitudinally and stress relieve the part or you will get
a shaft failure.
Shade, I had already done that and was not happy with the results - I have visual problems and unless I have a guide of some description will weld off instead of a straight line. I have machined shafts for build up and machined them when they had been welded many times and the circular method has been the most common. I have done straight line build ups myself but that was before I had a cataract so for me it's gonna have to be circumferential.
At this stage I'm going to try it with the bronze discs - mainly because I had some bronze on hand - the whole thing will be made from what's available.
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Last edited by clive; 01-20-2013 at 05:43 PM.
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