AN OLD UPRR 33 WHEEL DRAWING

33" FREIGHT CAR WHEEL

1895 33″ FREIGHT CAR WHEEL

1840 WHEEL DESIGN PATENT DRAWING

Wheels have been around for a long time; so have railroad wheels and the history of the railroad wheel is a subject I have been pursuing for some time now. I have included an 1840 Patent drawing as an illustration of the longevity of railroad wheel design. It looks a lot like modern wheels, except, there is no indication of the wheel tread design. The design of the wheel tread is vital to a successful wheel application. The link to a 1849 wheel tread design is:

http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=0006042

1849 WHEEL TREAD DESIGN PATENT

1849 WHEEL TREAD DESIGN PATENT

The importance of wheel tread design cannot be overstated for the following reason. The conical shape of the tread is what keeps the train on the track. As the wheels roll on the rails, the wheels and axles (the wheel set) will  find a position relative to the rails such that the average angular velocity of each wheel is identical; a requirement of the solid axle of the wheelset. As the train speed increases, the wheelset will begin to “hunt” for the right position by moving back and forth in the direction transverse to the track. The magnitude if the “hunting” increases as the train speed increases. At what is known as the “critical speed”, the transverse motion of the wheelset is such the flanges of the wheels ride up onto the railhead and the train derails. This is the start of a bad day for all concerned.

Even when the train is on curved track, the two wheels of the wheelset must have identical average angular velocities, if wheel sliding is to be avoided – a good thing. This is achieved by the wheelset moving in the transverse direction such that each wheel finds a position on the conical tread in which the effective diameters of the wheels compensate for the lessor distance traveled on the inner rail of the curved track and the greater distance on the outer rail. The conical shape of the tread is what keeps the train on the track.

Here is a link to an analysis of wheel tread design which has the details of modern design methods:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&cad=rja&uact=8&ved=0CDgQFjAEOAo&url=http%3A%2F%2Fpolach.ch%2Fdata%2Fobject_5%2FCM-2009_Paper.pdf&ei=DGRMVLSbAYqiyQSuyoGwDw&usg=AFQjCNGx_fkDbI200IvXNfufvMvBdCbaIA&sig2=7KXMZWXbU77cJLu5_RyLRg&bvm=bv.77880786,d.aWw

An examination of the 1895 tread will yield insight into the state-of-the-art at that time. As a comparison, I have included images of modern UPRR freight car wheelsets. These were obtained from the display provided at the recent UPRR family day picnic held at the ORANGE EMPIRE RAILWAY MUSEUM. The larger one is used on the center truck of articulated intermodal cars. They appear to be cast steel.

 

About THE OLD MACHINIST

I am 82 years old and wed for 65 years. I am a retired engineer and spent 35 years developing INS gyroscopes. I am a High School mentor in physics, mountaineer, model builder, machinist and have a degree in Physics. My interests include railroad history and photography, science history, cosmology, interesting people, and old engineering drawings. I place a high value on my friendships. I enjoy life and am looking forward to the future with my usual sense of anticipation and curiosity.

Posted on October 25, 2014, in ART AND CRAFTSMANSHIP OF THE DRAFTSMAN, RENDITION OF DETAILS OF DRAWING, TRIVIA FROM THE UNION PACIFIC RAILROAD DRAWING COLLECTION, UNION PACIFIC RAILROAD HISTORY IN DRAWINGS, UNUSUAL DRAWINGS IN THE UPRR DRAWING COLLECTION and tagged , , , . Bookmark the permalink. 2 Comments.

  1. Here is a Youtube video about making wheels:

    Don Strack

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