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Wed Jun 17, 2020, 11:05 AM

Freight railroads reinvent the wheel.

It's still round, but the tread has a new profile.

June 12, 2020

Next Generation Wheel Profile: AAR-2A

Written by Scott Cummings, Scientist, Transportation Technology Center, Inc.



William C. Vantuono photo

TTCI R&D, RAILWAY AGE JUNE 2020 ISSUE: The AAR-2A, a new standard wheel profile recently implemented for use in North American freight railway operations, is expected to provide improved service performance for wheelsets. This assessment is based on the analysis, simulation and testing conducted by Transportation Technology Center, Inc. (TTCI).

The new AAR-2A wheel profile was designed to produce a nearly conformal contact condition with a typical rail on the high side of a curve to provide benefits such as improved steering and minimized rolling resistance, wear, fuel consumption and surface damage. Compared to the older AAR-1B profile, the AAR-2A produces a more-even distribution of wear across the wheel flange and tread such that the profile shape does not change substantially during the service life of the wheel.

Analytical evaluation, computer simulation and service testing were used over the course of multiple years to ensure that the design goals of the AAR-2A profile were met. Each method of evaluation showed improved curve performance of the AAR-2A profile compared to the AAR-1B profile. Starting with turned wheels, implementation of the AAR-2A profile has been under way since 2016, and it became the primary standard profile in North American freight operations in January 2020.



Testing in revenue service showed the AAR-2A profile better-retained its design shape and provided a reduced wear rate on both the flange and tread, compared to the AAR-1B profile. TTCI illustration.

{snip}

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Reply Freight railroads reinvent the wheel. (Original post)
mahatmakanejeeves Jun 17 OP
eppur_se_muova Jun 17 #1
Binkie The Clown Jun 17 #2
underpants Jun 17 #3
Steelrolled Jun 17 #4

Response to mahatmakanejeeves (Original post)

Wed Jun 17, 2020, 12:27 PM

1. Kicking because details matter. nt

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Response to mahatmakanejeeves (Original post)

Wed Jun 17, 2020, 12:51 PM

2. It blew my mind when I first found out...

... That the profile of the wheel and of the rail itself act together to cause the wheel to ride up to a higher diameter section on the outside rail of a curve, thus acting the same way that a car's rear end differential gear works. In other words, the inside wheel and outside wheel are solidly fixed together, yet when going around a curve, the outside wheel, turning at the same RPM as the inside wheel presents a larger circumference to the rail top, and thus travels a longer distance than the inside wheel.

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Response to mahatmakanejeeves (Original post)

Wed Jun 17, 2020, 01:19 PM

3. 👀

Marking

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Response to mahatmakanejeeves (Original post)

Wed Jun 17, 2020, 07:26 PM

4. Cool

Technology continues to advance for mature industries like freight railroads. Slow progress, but over decades it makes a big difference.

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