Nylatron
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Nylatron is a tradename for a family of nylon plastics, typically filled with molybdenum disulfide lubricant powder. It is used to cast plastic parts for machines, because of its mechanical properties and wear-resistance.
Molybdenum disulphide (MoS2) filled nylon offering improved strength and rigidity. With a lower coefficient of linear thermal expansion than Nylon 101, Nylatron GS parts maintain better fit and clearances, and have less tendency to seize as bearings.
Bearings
From "Norman Gracy's Atlantic", Live Steam Magazine, December 1976:
- John and Norm have been doing some experimenting with a new bearing material - molybdenum disulphide impregnated nylon (trade name Nylatron). It is available in round rod of various diameters. Norm and John have machined various journals and sleeves from it and found it almost unreal. For example: installed in the crosshead to main rod bearing, it showed no noticeable play or wear after six months whereas oilite bronze bushings have had to be replaced after six weeks of heavy running. This material requires no oil; in fact DO NOT oil.
- Paul Brien (Mid-South Live Steamers) installed Nylatron bearings and bushings on his first locomotive (7.5 inch gauge 0-6-0) in the late 1960s. Due to Paul's background as a tool & die maker, and later QC manager, he was inclined to make things to close fits. What he learned was that Nylatron has a relatively high coefficient of expansion and on it's first test steaming, as soon as his bearings and bushings heated up, the loco locked up solid. He discovered that anything made of Nylatron needed expansion clearance and once that was determined the Nylatron, and the loco which is still running, performed very well. Read about Paul Brien's experience with Nylatron.
- I used Nylatron in the crosshead rod bearings of all my locos for 30+ years and have never had a problem. Do not BORE the holes...DRILL them and be sure that the stuff is COLD when you drill it.
and:
- Nylatron works very well in non-rotating situations - like the crosshead bearing. In pure rotation, it can overheat and 'smear'..had a bad experience with that.
Regarding contamination, Bill Shields wrote:
- Properly applied, Delrin, Delrin AF, Nylatron, Rulon, etc, will all work.
- The problem with any of these bearing types is how badly they can be torn up by contaminants...get a bunch of crap in there and they can dissapear in a hurry.
- I have been using Nylatron (molydisulfide nylon) and Delrin AF bearings in my crossheads for decades - but they are in a location where I can fit them tight and not worry about dirt getting in - and their use in reciprocating load applications is far superior to bronze alloys.
- Keep 'em clean and give them enough clearance so that they can grow properly under load, and there is no reason why these newer bearing materials shouldn't work very well.
- I have used Oil Impregnated Cast Nylon as well as Nylatron. The problem with the OICN is that it tends to be green in color, which won't look very good on your locomotive if the bushings are not hidden. I also think the Nylatron is a better material to use, in addition to the color, but there is more than one that will work acceptably. I always machined them with a running fit clearance (3 to 4 thousands of an inch) and they've always worked very well for me. I do actually oil mine, but only once per day just to wet them a little bit. Haven't had any problems with it. Just a few drops of oil on the rods in the morning when I fire it up, and then I leave it alone.
Note: Soft steel or stainless steel, as well as all non-ferrous metals do not run well with plastic bearings, even those with a so called "self-lubricating" filler. Metallic bearing surfaces mating with plastic bearings should be hardened, and preferably polished, steel.
Other Parts
- I could not maintain grease between the spring loaded plungers (of my OS Mogul). No matter what I tried, any lateral movement of the pony truck wiped away the grease. I've made a new pair of plungers from Nylaton GS, they're the ones in the center with the springs. Heck, Nylatron works for pedestal liners on 6,000 HP diesels, why not here. The Nylatron was less that $8.00US from Online Metals.
OS Mogul pony truck spring loaded plungers made from Nylatron.
Physical Properties
Nylatron GS
- Color Gray-Black
- Durometer Hardness, Shore D: 85
- Tensile Strength: 12,500 psi
- Water Absorption 24 hrs: 0.30%
- Tensile Elongation at break: 25%
- Shear Strength: 10,500 psi
- Specific Gravity: 1.16
- Continuous Service Temperature (Max in air): 220° F
- Dielectric Strength: 350 v/mil
- Coefficient of Linear Thermal Expansion at 73° F: 4.0E-05 inch/inch/°F