Rail Heads

Trains Magazine General Discussion
1

Hi. Can anyone tell me if trains in the United States use conical wheels and inclined rail heads, or are the rail heads parallel to the ties? The question came up while doing some reading. Thanks.

2

The rail heads are convex outward, and the chord of that curve is parallel to the rail base. However, the tie plates have a cant angle built into them that tips the rail slightly inward. The wheel treads are conical generally, but the form is slightly more complex than just a simple taper. Maybe somebody can post the tread and rail profile with dimensions.

3

You’re likely gonna be a little surprised by this, but . . .

Yes, the wheel treads are concial. The standard AAR wheel tread profile is a 1-to-20 slope or angle.

However, on the rail heads - neither inclined nor flat; instead, they are rounded, at a radius that varies depending on the specific rail section. For example, that radius is 10’’ for the modern 132, 133, and 136 lb. AREMA sections, 14’’ for the 100, 110, and119 lb. AREMA sections, and 24’’ for the now-obsolete flat-headed 131 lb. AREA section. See the diagrams of several rail sections and their dimensions at -

http://www.akrailroad.com/OnlineCatalog/CraneRail/RailSections/tabid/82/Default.aspx

  • Paul North.
4

Good observations. Standard tie plate cant is 1 in 40 = 1.4 degrees. However, some years ago - like in the 1960’s and 1970’s - Colorado Fuel and Iron Co. marketed a line of tie plates under the trade name of ‘‘Hi-Cant’’ or similar that had either a 1 in 20 or maybe as much as a 1 in 14 cant, so as to more closely match the plane of the rail head with that of the wheel tread surface. I’m not sure if there are any left in track - it was an idea that didn’t really catch on. Or perhaps more accurately, it was overtaken by events - the advent and wide-spread adoption of rail-head grinding, which enabled customized rail contours to be implemented to better achieve that match/ fit.

I have a tough time finding ‘on-line’ a current diagram of the AAR wheel tread profile/ contour that I’m comfortable in thinking is correct and complete, so I too will appreciate that. In the meantime, take a look at this website - http://apextoolandcutter.com/railroad.html

  • Paul North.
5

Passenger equipment is usually 1:40 taper. The shallower the taper, the higher the hunting threshold speed.

6

Paul,

European wheel treads are cylindrical as are the wheels on the RTL Turboliners. Truck design elininates hunting. The cylindrical wheel runs on a different part of the rail head than does the standard AAR profile wheel. As a result, a cylindrical wheel running on a section of rail that has been worn in by AAR wheels will see it as slippery new rail. We discovered this when performance testing the first RTL at the Pueblo Test Center. After the triain had been run on the track for some time the condition corrected itself. (I wrote a detailed report to Amtrak explaining the phenomena.) To the best of my knowledge, the problem never occurred in the NYC-Albany service.

7

Here’s an article that explains the profile. No claims are made regarding said article - it’s just one I found with a search.

I could swear reading a some time back that the profile of wheels had been changed as the result of a discovery that wheels with some 'experience" rolled better than new wheels. What I don’t recall is what that change was. It could be that wheels at one time were cast/machined flat, instead of with a slight slope.

8

Thanks everyone for the replies so far. They have been very helpful.