Perhaps there aren't many of you having locomotives with blind drivers, but on the Mt. Rainier Scenic Railroad we encounter them frequently on our logging locomotives. The problem with blind drivers is that they wear hollow down the center of the tire, wear occurring at a greater rate than the standard tires. As you know, blind drivers are wider than normal, flat across the center, and tapered a short distance on both edges.

During rebuilding of a Baldwin 2-8-2 with both the main and intermediate wheelsets (the two in the middle)we are altering the wheel profile. We are applying the standard 1:20 wheel taper up to the point where the flange would begin on a standard tire, where we cut straight across the tire. It's like a wider standard tire with the flange removed.

We are hoping that the long taper will allow wear to be spread across a greater area, and that stress on lateral motion will be relieved because the wear groove in the center of the tire will be eliminated, allowing the drivers to float across the rails instead of being caught by the rail in the groove.

We modified the one blind driver on a 2-6-2 rebuilt and returned to California, but it has very few miles on it to date.

All crank pins on the Mikado are being replaced. We are considering reducing the diameter of the crank pins where the bearings are and locktiting case-hardened bushings, which should wear more slowly and could be replaced in the future. With the pin's reduced diameter to accept the bushing, there remains a safety factor of 7 with full boiler pressure applied to the smallest pin.

Many are aware of the process of "rolling" the journals of their axles for a fine finish, done with a heavy ball or roller bearing in the lathe toolpost pressed heavily against the journal. An article from the 40's from Railway Mechanical Engineer magazine cautions against such practice, claiming that the hard and soft spots in the steel axle will not compress equally, therefore producing a poorer (but nice and shiny) finish. They based their findings on microscopic evaluation. The Mikado journals were machined at a slow speed with a stoned, flat, high speed steel cutter (giving us better results that with carbide, which is never really sharp and require greater tool pressure), then polished. Using a 36" American lathe built just after War II we achieved dimensions within half a thousandth.

steamrr@mashell.com

> Many are aware of the process of
> "rolling" the journals of their
> axles for a fine finish, done with a heavy
> ball or roller bearing in the lathe toolpost
> pressed heavily against the journal.

This is called "burnishing" and work hardens the outer surface of the journal, which grinding and/or using a fly cutter won't do. The burnishing wheels (in the lathe) are usually polished.

> This is called "burnishing" and
> work hardens the outer surface of the
> journal, which grinding and/or using a fly
> cutter won't do. The burnishing wheels (in
> the lathe) are usually polished.

Have to agree with Jack. The microstructure (with the emphasis on micro) of steel will reveal a collection of crystalline grains elongated and oriented in the rolling direction. Within these grains there are layers of hard and soft sections. All these different regions of "hardness" are averaged out by the "macro" size of the Brinell ball.
Truly high speed bearings such as ball bearing races or crankshaft journals are finish ground, not burnished, with wonderful results and amazing life.


lamontdc@adelphia.net

A simple way to burnish is to tip your tool and shove the face of the tool against the bearing surface using a decent supply of cutting oil. Beats hours of flapwheeling. Just one of the tricks an old lathe hand taught me years ago.....wish I could remember them all. He had some good salty stories too.

Anybody use a tool post grinder for a fine finish?

Somebody installed hardened bushings and pins in the valve gear on 14 before my tenure at GLRR. The bushings wallowed out the holes in the valve gear and became loose. Instead of just doing the usual simple new brass and polish the pins, we had to bore out all the valve gear holes, machine new oversize brasses, and make new pins. I hope this sort of thing doesn't result with this experiment Jack, and very interested to hear how it withstands the test of time.

Blind driver tapers make sense. Wonder why it wasn't standard?

Dave

irondave@bellsouth.net

> Blind driver tapers make sense. Wonder why
> it wasn't standard?
> Dave

Such tapers defeat the purpose of the flangeless tire which is to remain on the rail over its entire 6" width on sharp curves. Tacoma Rail, over which Mr Anderson's tourist railroad runs, does not have such sharp curves. The partly tapered tire may not do any harm.

johncb@u.washington.edu

>Thank you for your response, John.

The tire remains at its original width of 6 1/2" which will certainly stay on very curved rails even with the taper, don't you think?

The biggest problem with wide wheels is encountering self-guarding frong, over which the wide tire must lift and ride on top of the guards (they actually lift part way up until the flair of the quard widens enough to accommodate the tire, causing quite a bit of shearing on the sides of the tire. We have found that other railroads which we have visited have gotten away from self-guarding due to other reasons.

Thank you,
Jack

steamrr@mashell.com