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18th Aug 2020, 10:44 PM #1Philomath in training
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How is an earth made when using a rotator?
I'm trying to make up a simple weld rotator (mainly because I can...). I've seen some with a turn of bare cable around the turntable shaft. Is that the way it is normally done or are there other methods used? (It works - I just wonder whether there is a better way to make a connection that won't spark as much. A carbon wiper like a motor brush for example?)
Michael
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18th Aug 2020, 11:10 PM #2
Hi Michael,
There are two ways that I know of.
The first is a brass round disc that is fixed to the spinning axis. There is a second brass round disc that slides under pressure from a compression spring.This round has the earth return lead fixed to it on a tab connection. The spring pressure is not heavy but just serves to butt one disk up against the other,but light enough to permit sliding as the other disk rotated. The end of the spindle is tapped and a bolt and washer puts the force on the sliding disc.
We used them on a sub arc rotator so I know they will take decent current.
The other way was with a copper woven strap much like the old type battery earth cable, say maybe 25mm wide.
As the spindle turned, the cable was looped over the spindle and kept under tension. I had not used that type but had merely seen it when the machine was idle.
Hope it helps
Grahame
spring loaded earth.jpg. Flat earth straps.jpg
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18th Aug 2020, 11:16 PM #3Most Valued Member
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Thanks for asking Michael and the reply Grahame, I've been contemplating which idea was best.
KrynTo grow old is mandatory, growing up is optional.
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19th Aug 2020, 08:03 AM #4Senior Member
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Earthing on a rotat0r
Hi from BC.
If you want to use an earth strap around a shaft, strip a mtr of earth cable and give it 5-6 turns around the shaft. The cheap way. When the bullet welders were plentiful I have seen an armature and brush assy used to good effect to earth a weld positioner. However, nothing beats an earth clamp direct to the shaft and just unwind and reclamp after each job.
Regards
BC
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19th Aug 2020, 08:20 AM #5Philomath in training
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Thanks Grahame
The type you have shown with the wire strap was similar to what I've seen but it it crackled and sparked a bit when in use so I was never sure whether they were a quick and dirty way of doing things or regarded as legit.
(mind you, that was a stripped end of a welding cable)
Michael
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19th Aug 2020, 02:05 PM #6Most Valued Member
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I was going to make mine with slip rings fitted with copper buttons as wipers, but haven’t gotten to it yet.
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22nd Aug 2020, 04:03 PM #7Diamond Member
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24th Aug 2020, 10:09 PM #8Philomath in training
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Today at semi-random I came across this -
https://www.omik.com.au/product-page...ding-turntable
If I hadn't already obtained gearboxes, motors and all the rest of the bits and pieces...
(Price is higher than I would prefer to pay, but then again, the cost of 'the doings' is not low either)
Michael
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24th Aug 2020, 11:40 PM #9
Re my post with the brass disc to disc system.
If these discs can sustain 500 amps that is a typical sub arc amps, they will easily handle whatever stick tig or mig process amperage that is used with them.
I have had literally hundreds and hundred of hours experience operating a sub-arc welder with this earth system fitted.
The brass discs never, never ever once made sparks.
The leccy types will know better than I but I believe it is a function of the contact surface area being more substantial than the other methods, plus the electrical conductivity of the brass, creates the efficiency.
Michael you should not have any trouble turning one of these up. The earth discs on the subarcs ,disc dimension would have been about 90mm diameter and about 16mm thick.
One disc was securely fixed to the rotator spindle shaft and the other one with the cable tab was pushed against the face of the other with a spring compressed by a 16mm or so bolt.
We did full shift at Gladstone and one machine could run for days at a time, stopping only to change the 2 ton valve bodies.
Never a problem at any single time with the rotating earth
I believe something around 50mm in diameter would be plenty for your needs.
Check out stray earthing and welding to understand what a poor earth can lead to.
Cheers Grahame
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24th Aug 2020, 11:41 PM #10Golden Member
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