The Home Machinist!

I remember that there are several members who are fans of Delrin for valve gear and rod bushings. I can't remember seeing a discussion of using it for journals. The drivers on my Consolidation use the same ball bearings that LE uses on the Pacific. A decision I made many years ago. I'm about to decide what to use on the lead truck for my Consolidation. Any thoughts on Delrin?

Any of the plastic materials don't like to be in compression, as they will flow over time.
So Rod Bushings seem OK, but I would worry about weight-bearing use.

Others here hopefully will have more precise info from actual usage.
~RN

I think they are talking about Delrin AF, which is impregnated with teflon.

Steve

What? Delrin... Plastic?!! I thought we were building a steam engine here..... Cast iron, bronze bearings, STEEL!!! Next thing you know people will want to use crazy materials like Aluminum n such... Isn't that stuff intended for airplanes!!!

In all earnest, I really enjoy my Allen 10 wheeler because all of the bearings and such are brasses and require oil just like the real thing. To me, if you start down the path of removing / reducing the things that make a steam engine a steam engine, then you might as well be building a battery powered diesel... First delrin for bearings, then run on propane cause coal is dirty, next we'll just get rid of they pesky boiler and run on an air compressor instead... etc,...

I would just used 660 bronze and lubricate appropriately.

JP

Delrin AF will out live all of us put together in either main or rod service unless someone puts a torch to it.

The only drawback to it is that you cannot Loctite it in place, so us 'progressive steamers' have to decide which modern material to use: Delrin AF or Loctite -> not both.

I did an overhaul on an engine that had run hard for 25 years with Delrin rod bearings. They were worn badly and the crank pins too but they held up for all that time.

Why not use needle bearings running directly on hardened, or semi-hard axles? That's what I use on my lead truck, and they've run for years. I took them apart about 3 years ago, and they looked just great. I just put them back together without doing anything to them.

What I do is to drill the axle ends and give it a lube hole for oil. I then hardened and ground them, although you could use a pre-hardened material that would last a long time and work great too, and that you could turn and polish on the lathe. The technical book says that the races for a needle need to be 58-62 Rockwell C hardness, but for the speeds and loads you are going to be using, just about anything harder than a mid-30's Rockwell is going to last a long time. I got needles that had a seal on one side and I turned that to the inside of the locomotive. That way,when I put oil in there, the excess will run out on the wheel side and lubricate the thrust surface of the axle box and the back of the wheel. Needle bearings like these will absorb no thrust.

Fred_V wrote:I did an overhaul on an engine that had run hard for 25 years with Delrin rod bearings. They were worn badly and the crank pins too but they held up for all that time.

The question is, was the material Delrin AF, or just plain old Delrin? There's a huge difference in how each would hold up in service.

If you don't know, AF is a light chocolate brown color, unlike other types of Delrin.

H

johnpenn74 wrote:What? Delrin... Plastic?!! I thought we were building a steam engine here.......... Cast iron, bronze bearings, STEEL!!!

So, I suppose you're also opposed to 3D printing a boiler?

Nylatron is another alternative that some Live Steamers have used successfully.

See http://ibls.org/mediawiki/index.php?title=Nylatron

Regards,
Daris

Dick_Morris wrote:

johnpenn74 wrote:What? Delrin... Plastic?!! I thought we were building a steam engine here.......... Cast iron, bronze bearings, STEEL!!!

So, I suppose you're also opposed to 3D printing a boiler?

Please don't give anyone that idea... I cant even imagine...

"Surely this sintered material will work, right?"

There's also Vesconite that some of the SAR preservation groups have used to replace bronze bearings on full size locos:

http://www.vesconite.com/

A few people are experimenting with it on model locos for rod bushings. I've got a couple of samples of it but haven't done anything with it yet.

I have used bearing grade PEEK ( PEEK loaded with PTFE and graphite) with success for rod and valve gear bushings.

John