Bronze bushing idea

[Zumba]

Thomson linear rods are decently priced from QBC, but the bearings are killer. I'm thinking about using bronze plain bearings.

The main problem with bronze, from what I heard, is that it has a tendency to bind if the rails aren't perfectly aligned. Shouldn't this be pretty easy to solve by using set screws to adjust the angle of the bearings inside the housing blocks?

Also, I'm thinking that I could mount the bearings to the housing blocks rigidly on one rail, and then on the other rail, insert some hard rubber gasket material between the bearing and the block to give it a slight amount of play. Any forseeable problems with this?

Lastly, online metals sells 932 bearing bronze in hollow tubes for a good price. Ends up costing just a few bucks for a 1" ID x 2" bearing. I see other posts referring to sintered/oil impregnated stuff, basically premade bearings. Those cost significantly more. What's the deal?

[lakeside]

You can get oil impregnate bronze bearing that are self lubricating

[ger21]

One problem is that the rails will flex, so the alignment will change as it travels along the "curved" rails.

[Zumba]

Hmm.... I plan on using 1" shafting, fully supported along its entire length. Gantry weight will probably be about 50 lbs max. Router would be a Porter Cable. Do you think there will be enough flex to screw with the bearings?

[ger21]

How will you a bronze bearing on a supported shaft? Do you plan on cutting away the bottom of it?

[Zumba]

Yep, open just like an open thomson bearing.

[lakeside]

you may want to use an undersize bearing as it will have a little spring when spilt also you may want to encase in steel housing to pervent more springing under weight

[andy_ck87028]

I've put heaps and heaps of thought into this and my entry in this thread might help http://www.cnczone.com/forums/showthread.php?t=19524

I am confident my approach will work in principle. I will be using vesconite as my bushing but irrespective of choice of material (bronze or otherwise) if the bush is absolutely tight to the rod and binding then occurs then alignment is definitely out and to me that is an unacceptable outcome.

I believe my approach ensures good alignment and provides maximum rigidity.

Andy

[WhiteTiger]

If you use flanged bushings you can clamp them in place in the split housing with a simple screw mounted end cap. Going with the modest added expense of sintered bronze will also aid in alignment since the 80% compact is far more conformable than solid.


Tiger