Need ideas for BIG bearings???

[torker]

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
Russ

[Carld]

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]

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]

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]

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]

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]

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]

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]

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]

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.