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torker
10-18-2008, 09:18 AM
Hey guys! I've got the pieces I need to build my welding positioner/rotator.
I want to have a spindle bore the same size as the hole in the chuck.
It's a 2" hole.
Yup.. I could buy two big pillow block bearings and run the shaft through this.
But the shaft OD will be 2 1/2" minimum....more likey 3" OD as 1/2" wall DOM is the only suitable material I've found so far.
I'm not really liking the pillowblock idea. Those size of PB's are huge. So are flange bearings.
I'd like to streamline this.
RPM's will likely never see over 30 or 40 rpm.
Bronze or brass bushings would work....but what kind of housing?
Any ideas would be appreciated.
I know someone here will think of something I'm missing :D
Russ

Carld
10-18-2008, 09:32 AM
Will the bushes be pressed in the blocks and the DOM a running fit in the bushes?

Why not just fabricate pillow blocks to press the bushes in or run free in if the bushes are pressed on the DOM? Cold roll or hot roll will work either way.

quadrod
10-18-2008, 09:39 AM
how about front wheel bearings from a four wheel drive truck. can probably get some from a wrecking yard cheap. might even be able to use the hub as the spindle, weld and extension to the hub and turn true, thread for the chuck.

nheng
10-18-2008, 11:33 AM
Don't laugh but how about ... teak? A long time ago I did some repairs on a several tugboat propeller shaft (10" - 12" ID ??) bearings that were made of teak segments in a steel housing. May be a dumb idea but TIR should be about zero after run-in. Don't know about lube ... obviously water wouldn't be a good idea here :)

mark61
10-18-2008, 11:48 AM
Pipe for inner------round stock for bearings------pipe for outer?

We made jib cranes like that but used 8" od pipe for inner and 10" id pipe for outer with 1" solid stock for bearings. Or something like those measurements been working nicely for 15 years.

mark61

jacampb2
10-18-2008, 11:58 AM
If you can sacrifice a little bit of your through hole diameter, you could get just over 1.5" bore with the spindle, hub and bearing set from a Dana 60 front 4x4 axle, or from a Ford Dana 50 TTB (1980-1986 F350, some F250's from 1980-1996).

Rear spindle, hub and bearings from a full floating Dana 70, 80, Ford sterling 10.25, or GM 14 bolt shout get you close to 1.75" bore, but you would have to cut the spindle from an axle. Front ones unbolt :)

Good luck,
Jason

mechanicalmagic
10-18-2008, 12:08 PM
If you plan to run the welding current thru the bearing, it should be made of carbon. Rollers will arc.

I also like the Teak idea, except I use IPE/Ironwood. A taper bearing would be easy, and the wood is available as decking material 5.5" x 3/4" for about $3 per foot US.

Dave J.

barts
10-18-2008, 12:52 PM
A nice hardwood bearing here is perfect.... oak would work and is reasonable cheap. Make it of ample length and grease it heavily and you're set.

Some interesting reading via googling on "wooden bearings":

http://www.woodexbearing.com/
http://www.plantservices.com/articles/2005/469.html

ptjw7uk
10-18-2008, 03:21 PM
How are you going to earth this rotator. Fit some flanges and use some motor brushes not sure on the surafce area you will need at 100 amps.
Is the setup to run in a horizontal mode and not change orientation much if so you could support the shaft on several heavy duty rubber tyred castors or even small ball races using more on the bottom and a couple on the to pto stop it tipping. just ideas for a cheaper version as large bearings are very costly.

peter

Scishopguy
10-18-2008, 03:31 PM
Torker...A set of bearings for the US military cargo trailer M101 would do a fine job for what you want. IIRC they are about 6" diameter tapered roller bearings. If you go to a mil surplus dealer I am sure you can find something like that for a reasonable price. New ones can be obtained from Memphis Equipment Co. They deal in old surplus military trucks.

Rustybolt
10-18-2008, 06:51 PM
What about something like a lazy susan setup and drive by friction on the rim. Just thinkin outside the box.

alanganes
10-18-2008, 07:41 PM
Babbit bearings maybe? Never done any myself, but might work.

boslab
10-18-2008, 09:59 PM
Don't laugh but how about ... teak? A long time ago I did some repairs on a several tugboat propeller shaft (10" - 12" ID ??) bearings that were made of teak segments in a steel housing. May be a dumb idea but TIR should be about zero after run-in. Don't know about lube ... obviously water wouldn't be a good idea here :)
dont think it was teak, lignum vitae was the preffered wood, it also has the property of being denser than H2O [thats right it sinks] still used for carvers mallets although tufnol has replaced it on big shafts [up to 2'] like the QE2, tufnol [phenolic resin] is used in rolling mills!
regards
mark

wierdscience
10-18-2008, 10:40 PM
Full floating rear hub off a 2ton or bigger truck.That would give you bearings,seals and hollow shaft.Maybe bandsaw off the excess wheel flange to save weight/bulk.

For grounding metallic/graphite HD starter brush,like from an old Delco starter motor.Mount it on an insulated spring loaded arm so it bears on the backside of the chuck,that way no current passes through the bearings.

Other way would be a thick wall piece of pipe for the housing bushed with bronze and a second piece of tubing for the hollow spindle.That would have more drag on it though.

I would show you pictures of the one I cobbled up at work,but it looks like Junkyard wars meets Mad Max:D

Evan
10-18-2008, 10:54 PM
Some AR steel plate running against another plate and well greased will work fine and will give plenty of support. The friction will be very low because of the low loading over a large area and the AR plate won't gall if it does contact through the grease. Sliding friction on a hydraulic film is a nonlinear function of per unit area loading so spreading the load over a larger area reduces the total friction for the same load. It's a lot like fat smooth tires hydroplane a lot easier than skinny ones.

nheng
10-18-2008, 11:13 PM
Boslab / Mark, You are absolutely right. It was lignum vitae. This was way back in '72 at a summer job as a college freshman. The tug bearing was from the NY harbor and I had to drill out some broken bolts from the end faces on a good sized radial drill. Only had half a clue at the time ... only have half a clue now but hopefully the other half :)

oldtiffie
10-19-2008, 01:44 AM
Good continuous earthing (return lead - current and arc voltage) is essential. It must not pass through the bearings due to "arcing" at the bearing/roller/ball interfaces which will really shag things up.

So it seems that some sort of connection with a fixed and a rotating part are required or a sort of "brush/slip-ring" arrangement.

Someone must have an answer or solution as this situation has been resolved before.

ptjw7uk
10-19-2008, 08:53 AM
I had the problem years ago to pass 150 amps to a wire for high speed plating experiments and came up with a copper carrier running partly submerged in a mercury bath with an oil layer on top. Did the job but we were never sure if it would last long enough in an industrial situation as \I suspect the mercury would get contaminated and fail to do its job. I suspect they wouldnt allow any mercury at all in a industial environment these days. We even tested the air around the mercury contact and never discovered any vapour.
I think Torker had better go with large graphite blocks rubbing on a slip ring or even the bare shaft if you get enough area it shouldnt arc at all.
Peter

kf2qd
10-19-2008, 09:08 AM
A relaible ground connection can be made from a spring loaded brass block against a steel plate. 1.5 inch square surface is good for 200 amps.

Materials like mercury are a hazard in their own right, not something you really want to be working around while putting a bunch of heat through it.

torker
10-19-2008, 09:49 AM
You guys amaze me!! I'd have never thought of wood. LOL...wood and welding....lol! Burning bearings!
Babbit was mentioned....ok...how bout using auto engine bearing shells clamped into a split block the same as an engine would use? Zerk to shoot grease in.
Grounding... I had planned on using the back side of the spindle. I'm thinking a big copper ring that another big piece of spring loaded copper runs on.
I run some of this dual shield wire over 200 amps sometimes so I'd like to be ready in case.
For this reason I wanted to stay away from roller bearings.
I could make the copper ring behind the chuck but it's be nicer to have it out of the way...at the back of the machine.
Russ

Carld
10-19-2008, 10:18 AM
Hmm, I like your idea of engine main bearing shells. Cheap and easy to replace.

Ian B
10-19-2008, 10:32 AM
Russ,

This any good?:

http://cgi.ebay.com/Large-Ball-Bearing-6013-ZZ-Bearings-65x100-mm-Sealed_W0QQitemZ150295364638QQcmdZViewItem?_trksid =p3286.m20.l1116

65mm bore, just over 2 1/2". About $10 including shipping. Roll up a housing ring from 1/4" x 1" steel strip, weld to a mounting plate and bore to fit the bearing's OD.

It can run at 9,000 rpm - ideal for those rush jobs...

Ian

Ian B
10-19-2008, 10:36 AM
Sorry, you wanted 2 bearings; $16.80 including postage.

Ian

jdunmyer
10-19-2008, 10:57 AM
Years ago, I wanted to build up my bulldozer rollers, so needed a "slow speed lathe" of sorts. Took 2 pillow block bearings and a hunk of shafting (about 1.5" diameter) and connected it to a little Boston gearmotor that had a DC drive. Using a timing belt between the gearmotor and the shaft, I could run it down to 1/4 RPM or maybe slower. IIRC, I needed about 1/3 RPM for the job. Rigged up a deal using an old milling vise to hold the MIG stinger and a foot pedal to control the welding machine, and went to work. I'd hit the motor Start button and the foot pedal at the same time, then stand there and watch it for 2 or 3 minutes. Give the vise screw a quick flip to move 'er over for the next pass, then relax again. Seems like it took 3 or maybe 4 passes to do the job. Running .045" wire, at whatever current that might be.

I knew that it wasn't a good thing to run welding current through ball bearings, but I had a bunch of those pillow blocks on hand, as I had bought 'em by the pound, and they were well-used. Not worn out, by any means, but many hours of operation at slow speeds. Had no trouble with the bearings siezing up, so the experiment was a success. They might be a bit rough after that treatment, but I never checked. Total welding time was well over 12 hours. I also used it later on for welding up parts on a large trenching machine, pretty much the same deal as the 'dozer rollers, but larger diameter.

If you get the bearings cheap enough and don't have to run this all day, every day for years on end, I'd forget fancy brushes, collector rings, etc.

torker
10-19-2008, 11:01 AM
Ian...those are ridiculous cheap. Don't know how they'd like a bunch of electricity going thru them tho.
Carl...my thoughts eggzactly! I can get a hockey sock full of bearing shells from the local engine rebuilder...for nothing. Lots are in near new condition.
Russ

Patch
10-19-2008, 12:35 PM
Long story short, made one, I used the brush comm end from a 40 Hp motor 800 amp capacity.
Used Enco 5/8" bearing balls, cut plate ball guides with 5/8" ballmill.
Used 1" thick material for table and bearing plate.

Patch

derekm
10-19-2008, 02:55 PM
Hey guys! I've got the pieces I need to build my welding positioner/rotator.
I want to have a spindle bore the same size as the hole in the chuck.
It's a 2" hole.
Yup.. I could buy two big pillow block bearings and run the shaft through this.
But the shaft OD will be 2 1/2" minimum....more likey 3" OD as 1/2" wall DOM is the only suitable material I've found so far.
I'm not really liking the pillowblock idea. Those size of PB's are huge. So are flange bearings.
I'd like to streamline this.
RPM's will likely never see over 30 or 40 rpm.
Bronze or brass bushings would work....but what kind of housing?
Any ideas would be appreciated.
I know someone here will think of something I'm missing :D
Russ

40 rpm and 3" + dia ~ and welding a job for plain cast iron and steel to me with maybe sprayon graphite lubricant

darryl
10-19-2008, 04:12 PM
Well, as long as there's going to be brushes, why not use say five or six brushes arranged in a circle, each spring loaded against the rotating part. They do double duty, passing the current parallelled through all brushes at once, plus they ARE the bearing surfaces.

ckalley
10-21-2008, 06:36 PM
It looks like this part of the thread is prty well done..... but I talked with with the facilites guy at the former paper mill in Pepperell, MA. They have a dam with a penstock (wood staves about 8' diam. by several hundred feet long) feeding thier power plant. He told me that the turbines are running on wooden bearings made from Black Locust. He told me that when the took the turbines down for repair, they took the bearings out and stored them in a barrel full of water to keep them from shrinking. This was all built in the very early 1900's and is still in service with new generators.

Craig

Scishopguy
10-22-2008, 02:15 PM
Ian...those are ridiculous cheap. Don't know how they'd like a bunch of electricity going thru them tho.
Russ

Torker....You don't necessarily have to have the ground lead go through the bearings if you add a slip ring and spring loaded carbon brush to the shaft, just above the bearings. Not hard to do and will save your bearings no matter what type you choose.

camdigger
10-22-2008, 03:36 PM
Russ

Large ID Timken type roller bearings suitable for this kind of service should be available as scrap from a local to you heavy truck dealer. IIRC, the KW rears had a 4" id roller bearing on the rear axles. The service co I worked for changed them based on mileage rather than condition.

Mr Cofer has alluded elsewhere on this board to a brush style suitable for welding ground made simply of a braided/stranded ground cable rubbing on a steel shaft.

My $.02 cdn

Cam