Need specialty material for high PV bushing. 1

[Schroyer]

We are trying to come up with a solution to a bushing problem. We have a bushing in an reversing application where a sleeve rotates +/- 15° within a bushing continuously. The sleeve has a 2-3/4" OD for reference.

I need something that will withstand a Velocity of V=210 fpm, P= 2000 psi (force that pin puts on projected area of bushing), and a pv value around 450,000.

An initial attempt was Mag-bronze with grease. After running through these numbers I can see why it didn't work.
Mag Bronze Max P=8,000 , Max V = 100, max PV=150,000
Any ideas?

Thanks,
Schroyer

 

[rnd2]

Am I correct that V = 210 feet per minute = 1.067ms-1 & 2000 psi = 13.605 MPa?
Kryptonite is what you need! Let me know when you get it.

 

[RikuY]

I don't have a source, but I have a similar problem with similar geometry, just a whole lot slower...
I found Acetal impregnated with Moly Disulfide and also an Acetal with PTFE blend. These were definite overkill for my application, but the numbers seem close to yours. Depending on costs though, you can go from a Nylon w/moly disulfide on the low side to a PEEK with multiple fillers to the high.
If costs run high enough, what about a sealed roller bearing?
Hope this helps...

For sources near you, I suggest a search on google once you know what you want.

RikuY

 

[rnd2]

RikuY
Please be kind enough to specify your speed because speed + load = rapid temp build up + load = eliminates ALL thermoplastics because they extrude under heat and pressure.

 

[RikuY]

My speed for the shaft is only 5.75 rpm...

Use is max of 10 minutes per cycle, with max of 6 cycles per day. Not really high use...

 

[rnd2]

Thanks Rikuy. Your shaft speed is dead slow so very little heat is generated. That supports the point I am making. For ANY thermo-plastic bearings, unless there is a continuously flowing liquid that can remove the heat faster than is being generated, the rubbing surfaces experience rapid and intense temperature rise and entire the bearing will experience thermal runaway and melt/disintegrate/fail.

 

[RikuY]

rnd2,
You have a very valid point. Acetal with some choice fillers are turning that point around though. If you get a chance, check some of the new specifications out...

http://www.dupont.com/fluoroguard/en/literature/H-79796-1.pdf.

(I have seen it more in the higher pressure applications than the higher velocity applications, for what it's worth.)

 

[rnd2]

A few years back we built a rig to test so-called self lubricating sleeve bearings for dry run operation.
The rig is simple. 1" diam. shaft turns at 1100 rpm. varying axial loads are applied to the bearing. The bearing test piece is a 1/2" shell, 1"id x 1 3/8"od x 1" long. The maximum load applied was 50Kg (approx 110 pounds).
Some of the sleeve bearing materials we test are strong and have high temperature integrity for plastic materials. They can resist static loads above 450 Mpa and temperatures above 200 deg. C.
So far, no commercial thermo plastic bearing material running unlubricated we have tried has ever lasted more than 10 minutes without showing clear signs of distress. There is a marked improvement with some materials when oil or water is allowed between the sliding surfaces.

Schroyer's sliding speed at 1.067 ms-1 is a little slower than our rig at 1.46ms-1 but his loading at 13.6 MPa MPa is more than 8 times the rig at 1.64.

 

[RikuY]

rnd2,
What was the material with the best results for the least amount of money? I am curious to say the least.
Sounds like a really good set of testing, but your PV seems a little high for anything you have tested, what is the material of choice for the application?
I am just curious is all. If confidential, I understand.
Thanks in advance...

RikuY

 

[rnd2]

RikuY,
You may wish to contact maritex@upnaway.com

 

[RikuY]

rnd2,
You got mail.

Thanks

RikuY