bearing materials

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bearing materials

Post by DaveLathrop57 on Thu May 23, 2013 1:07 pm

MaterialTennessee Valley is using on the firebox slides in 611 and 4501:
www.sepbearings.com/fluorogold-slide-bearings.html
They have proven its worth in that application - would this be a better choice than common bearing bronze for crosshead slides? Other options?

Also, consider the use of built up thrust bearings for hub liners, made of silicon or aluminum bronze wire welded fast to the boxes and hubs. GLRR 40 used this technique on the boxes, but having had new wheel centers cast, not on the hubs. The Royal Hudson had bronze liners welded to the hubs with Eutectic......

Pros / cons / comparisons?

Dave


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Re: bearing materials

Post by Overmod on Fri May 24, 2013 7:54 am

You mean 610, right?

If you have the money, I'd think the reinforced PTFE should work in crossheads,, at least as well as bronze or tinned metal. I presume the 400-degree working temperature requirement would not be exceeded in this application, and I can't imagine the deflection under load would be sufficient to compromise the seals on the piston rod. We would need to be certain that the bonding system to attach the glass fiber substrate to the crosshead would be compatible with the 'steam' environment.

Be interesting to see whether this material overcomes the problems faced by Nylatron (etc.) when used for steam-locomotive hub liners. Seems to me that it just might. On the other hand, if pressure exceeds recommended, the glass fiber might prove abrasive if the PTFE material recedes. It should be massively easier to use a bonded attachment on the hubs instead of wire-welding and then machining., provided the material and bonding agent are not susceptible to problems with lubricant, dirt, and so forth in that location. This in turn might simplify materials and machining for the box thrust faces.

I am not sure what the peak force (probably shock) on these liners would be in operation. I do not see any information on shock tolerance in the SEP material in the link, but am somewhat concerned with the inherent brittleness of glass-fiber reinforcement in general, where FRP (for example) inherently has better bonding support than PTFE substrate would provide.

I would want to see cost of machined and attached bronze hubliners vs. the cost of welded-up and then machined-in-situ -- in the particular shop environment where the work will be done. Also if some stress-relieving treatment is advisable after the wire welding has been done.

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Re: bearing materials

Post by DaveLathrop57 on Fri May 24, 2013 10:48 am

Something else that occurred to me was the idea of water as being a potential lubricant for this (or another yet to be named) bearing material. I know water works for flange lubrication - that could do a lot in terms of cleanliness around the ROW.

Dave

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Re: bearing materials

Post by Overmod on Fri May 24, 2013 3:04 pm

DaveLathrop57 wrote:Something else that occurred to me was the idea of water as being a potential lubricant for this (or another yet to be named) bearing material. I know water works for flange lubrication - that could do a lot in terms of cleanliness around the ROW.

Dave

I was not aware that these PTFE materials wanted external lubricant.

You would not use these for driver or wheel bearings, with or without water lubricant, I think. On the other hand, there are probably materials (like the ones in the enginion AG engine) that would use water, or graphite in water, for bearing tribology at comparable load -- in steady-state operation. How you would handle the situation where the engine is standing and the lube film collapses is another matter. So is precluding corrosion due to water, and the 'usual sorts' of contaminants and conditions. Personally, I'd go with a reasonable 'biodegradable' oil (doesn't Green Velvet stock some of these?) and use good compatible bearing systems that are easy to machine and easy to maintain.

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Re: bearing materials

Post by DaveLathrop57 on Fri May 24, 2013 8:55 pm

My supposition was the water would wash away grit from the crosshead slides that could otherwise abrade the surface. i think the advantage (if there is one) of this kind of material is you would only have to buy it once every few decades....but it is sold as a lubricating layer to be applied to bridge abutment slides, which don't get the amount of constant reciprocating wear the crossheads do, so I am a bit in the dark about how it would react differently.

Never thought of it for crown or hub purposes, just flat stuff that slides.

Dave

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Re: bearing materials

Post by Overmod on Sat May 25, 2013 6:50 am

I suspect the water would introduce more trouble than it solved, at least in the particular area of crossheads and guides. I think I'd prefer better seals or enclosure of the guides (more practical with this system of tribology) to keep the grit out of the bearing in the first place; on the other hand, the PTFE might tolerate a relatively high percentage of small-particle loading without producing high "machining" pressure of particles against the journal (and cause the sort of issue seen on clock pinions running against dry brass).

I would naively wonder whether something other than fiberglass or ceramic fiber could be used as a substrate for the PTFE to preclude cutting of faster-moving loaded surfaces. Copper or Monel come to mind. Likewise, a system with transverse 'membranes' in its physical structure keeping the PTFE from physically being displaced by drag might be workable for bearing liners on something this small. You might not use this for crown bearing area, but it would sure help with parts of a greater journal encirclement (right up to roller-bearing-like 360 degrees)

Can someone more patient than I am go back and provide a reference to the RyPN and other discussions of Nylatron and similar materials as hubliners? Reading that first would simplify discussion here.

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