I've read that the bevel across the face of a wheel on rolling stock is beveled so that, around a curve, the centrifugal force (I know, a pseudo force) is supposed to push the trucks outward and the bevel will give the wheel a larger effective diameter and therefore compensate for the longer distance around the outside rail in the curve.
Was that really part of the original thought in the design or was it simply someone observed and applied to the theory of operation.
The reason I has is because it seems like it would rarely work, especially for freight trains which are typically run at fairly low speed. This would be further complicated by trains on banked (super-elevated) rails which would cause the wheels to be pulled away from the outer rails except at high speeds.
Or could it have been done to simply keep the flanges centered between the rails to reduce wear and noise?
Engineers learn things over time. Over time they apply math, physics, metallurgy to the questions that get presented from an initial design as it grows over time. Suspect the first iteration of rail and flanged wheel was a straight flange on a straight cylindrical wheel - the operation of which created any number of issues for continued successful operation - Engineers weighed in to fix the problems and in the ensuing 200 or so years we have the present day designs of both wheels and rails. Those designs have manifested themselves into the various wheel profiles that are used on equipment as well as the rail profiles that are rolled into new rail and the profile that gets maintained with the use of rail grinders that have started to be used extensively in the 21st Century to prolong the carriers capital investment in the main line tracks.
I am not an engineer - so I can't even comprehend the math, physics and metallurgy that has been brought to bear on the wheel/rail interface over the decades.
Never too old to have a happy childhood!
The bevel helps keep the wheels centered on the rail - the flanges rarely come into play in normal operation. For wider curves, that bevel may help a bit, but on tighter curves (tune into the Deshler railcam sometime), the wheels still have to deal with the differing speeds between the wheels and one of the rails, leading to the characteristic squeal.
As Balt points out, experience has led to the current wheel (and rail) profile. In fact, it was found that once wheels had worn a bit, they tracked better. IIRC, that profile is turned into wheels right out of the factory these days.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Is the profile AAR-1B vs the AAR-2A the difference mentioned here.
Some railway engineers have made a religion out of tread taper. But the origin of the taper is that it is the draft angle on a cast wheel. Many passenger cars, which used lathe cut steel wheels, had (have) cylindrical wheels. Going around a typical curve, the lead wheel flange contacts the rail, the trailing wheel is mostly centered. Rear truck does same thing, but to a lesser degree. The taper usually does not last long with the wheel assuming the rail contour, particularly with the softer wheels under heavy loads, and due to brake shoe wear.
Perry Babin Is the profile AAR-1B vs the AAR-2A the difference mentioned here.
The AAR-1B was developed by AAR researchers based on study of worn freight car wheels in the mid-1980's and became the standard for freight cars shortly after. At EMD, we adopted it as well as we found it worked well on the HTCR radial steering truck. The AAR-2A takes that further in closer matching a worn wheel profile near the flange. This article compares the two profiles:
https://www.railwayage.com/freight/next-generation-wheel-profile-aar-2a/
As David1005 said above, rigid trucks do not go through curves in an ideal position. The frictional forces at each wheel cause the truck to assume a position where the lead outer wheel is trying to move toward the rail at an "angle of attack" that is measured between a radial line to the curve and the axis of the axle. The trailing axle curves in a nearly radial position. This is aggravated in a three piece freight car truck as it has a relatively low resistance to parallelogramming which allows for an increase in the angle of attack. In a 10 degree curve (573' radius) commonly found in mountainous areas, the lead axle angle of attack may be around 1 degree.
As tree68 said, the bevel, commonly called taper, on the wheel keeps the wheel flanges away from the rail as the wheels turn at the same rate since they are pressed onto the axle and they want to find a position of equal rolling radius. The taper machined new is typically 1:20. The downside of the taper is that on tangent (straight) track, higher taper causes instability (hunting) wherein the axles oscillate laterally and/or yaw at the same time trying to find the ideal running position. This is speed dependent so higher speed operation, such as Amtrak above 70mph, usually uses wheels with less taper, typically 1:40, to limit truck hunting. Cylindrical wheels are an easy way avoid hunting instability but they wear the flanges rapidly since there is no taper to center the wheels on the track so are not commonly used today but were in the past. The truck designers challenge is to get the right combination of stiffness and damping to push the hunting threshold speed to be above the operating speed while meeting all the other requirements of ride quality, strength, and (the reason the three piece freight car truck is still used after well more than 100 years) cost.
Dave
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