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andy_b
12-08-2003, 12:15 AM
my parents asked me to make them one of those porch gliders that looks like a bench suspended in a frame. the bench swings back and forth kind of like how those glider rocking chairs work. i was wondering what to use for the pivot points. since the glider only has a short range of motion (i'm guessing maybe 10 or 15 degrees) i don't know if a ball bearing is needed. what would you folks suggest that would hold up the best? should i look for some bearings, or should i just make up bronze bushings? heck, maybe even some type of nylon bushing would work.

andy b.

Paul Gauthier
12-08-2003, 12:45 AM
I would use stainless steel hardware and bronze bushings.



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Paul G.

Al Messer
12-08-2003, 02:13 AM
I "second" what Paul advised.

Joel
12-08-2003, 02:19 AM
Yep

docsteve66
12-08-2003, 12:45 PM
needle and ball bearings repeatedly moving in small distances tend to brinell. go for bushings if you need longer life.

Evan
12-08-2003, 03:26 PM
Steve is right. Rolling contact bearings don't work well for repeated short partial rotation. That has always been a major problem in the design of helicoptor rotor heads as the blades change pitch every rotation of the rotor but only over a fairly small angle.

winchman
12-08-2003, 04:04 PM
Why not use a slightly larger bushing made of a plastic? Seems like either Teflon or ultra high molecular weight (UHMW) polyethylene would be a good choice here.

Roger

Evan
12-08-2003, 05:01 PM
I don't think teflon would be entirely suitable as it tends to cold flow under load. Better would be Nylatron which is nylon filled with moly. It is also known as "black" nylon even though it is gray. Readily available at a plastics shop. There is also available nylon filled with graphite which makes excellent bearings but is harder to find.



[This message has been edited by Evan (edited 12-08-2003).]

JCHannum
12-08-2003, 06:05 PM
The glider we have had for 10 plus years simply has 1/4" carriage bolts through the wood frame suspended on plated flat stock. It is still in good shape. It has been outdoors it's entire life. If the bolts wore out, I guess I could replace them.
My grand parents had one made of steel that used a sort of rod end bearings that were basically cheap unground bearings. That lasted at least 50 years.

docsteve66
12-08-2003, 07:00 PM
JCH: you are a spoil sport- correct on all counts ,but you got too practical http://bbs.homeshopmachinist.net//smile.gif.

Those "gliders" not only used (by my observation) bolts and wood (and yes the bolts did wear thin), bolts on strap iron, bolts through chains, leather hinges. I remember one with "knife" edge bearings (except the edges were round). I suspect that if it does not squeak or bind it will satisfy.

One very comfortable used rubber from old inner tubes (real rubber) as lacing in the seat and back. When the "lacing" was removed the seat and back kind of fell apart until new rubber (from modern inner tubes) was added.

In Texas, they once grew Willow in the wild. Migrant workers would make furniture of it. Some was good, some would not last. I THINK they made gliders and the bearings were just ten penny nails through a hole.

If the parents are old enough to remember any of the old contraptions used for comfort before WWll, you might do some research and make from scratch (including design).

WE have some nice rattan stuff, bought in Philippines. Findlay (40 years) some joints loosened. They (filipinos) used soft iron nails through center grain to hold the stuff together. Joints were wrapped with rattan. I want to used raw hide to repair. Wife is too stubborn to compromise and do it my way so the joints just get looser every year. Raw hide strips might make good hanger bearings.

andy_b
12-08-2003, 10:39 PM
thanks for the many ideas!!!!
i guess whichever material i find first will be what i use.
there is a plastics place near me and i think i'll see if they have any pieces of that moly or graphite filled nylon laying around that i can get for a buck or two.

andy b.