Red Shoes Only

[PJS1]

A couple of days ago, while in Fort Worth, I noticed that the locomotive on Number 21, which was Amtrak 51,  had a label near the front truck that said, "Red Shoes Only".  What does this mean?

[Backshop]

Sounds like it pertains to a certain type of brake shoe.

[zugmann]

https://www.wabtec.com/business-units/railroad-friction-products-corporation/products

 

[BaltACD]

zugmann

https://www.wabtec.com/business-units/railroad-friction-products-corporation/products

Here I was thinking they were for operation in Kansas to Auntie Em's house. [/sarcasm]

[JustWonderin']

zugmann

https://www.wabtec.com/business-units/railroad-friction-products-corporation/products

 

 

 

Thanks for the link.  I still don't understand.  Except for "therapeutic" brake shoes to fix malformed wheels (e.g. flat spots) what is special about a locomotive shoe as opposed to any other brake shoe (except for perhaps size and fitting)?

[Overmod]

JustWonderin'

I still don't understand. Except for "therapeutic" brake shoes to fix malformed wheels (e.g. flat spots) what is special about a locomotive shoe as opposed to any other brake shoe (except for perhaps size and fitting)?

WABTEC doesn't make it very easy to answer this question, although I would refer you to the AAR standards the Cobra TreadGuard shoes satisfy (M-926 and RP-599) for some technical information.

These are composition shoes with "inserts" (the locomotive version has two) and according to the manufacturer, these "condition and clean wheel tread, minimize turning, improve rail/wheel adhesion, and give longer brakeshoe life" (paraphrased).  I would add two potential items to this that seem to affect passenger locomotive performance: they should give the wheels more assured electrical contact for signal and PTC performance, and they should 'machine down' any small developing flat spots or other incipient tread issues before the time for scheduled wheel turnings. 

Part of the reason for the color involves the switch (many years ago) from cast-iron shoes, and the subsequent trend toward one-shoe-per-wheel rather than clasp braking on locomotive wheels.  Here is some discussion from TrainOrders (2010):

High friction composition shoes are used on locomotives with a single shoe arrangement (one shoe per wheel) and 72 psi maximum brake cylinder pressure. These locomotives have a J1.0-1.6 relay valve which takes the 45 psi max brake cylinder pressure from the 26F control valve and increases it to 72 psi (45 x 1.6 = 72)

Low friction composition shoes are used on locomotives with a clasp brake arrangement (2 shoes per wheel) with a maximum brake cylinder pressure of 45 psi and use a J1.0 relay valve.

The 2 shoe clasp arrangement originally used cast iron brake shoes and was the configuration for all locomotives going back to the 40's and 50's. In the 1960's high friction composition shoes were developed and the single shoe arrangement quickly became the standard for many reasons -- simplified brake rigging (not as many levers, pins and bushings), fewer shoes to maintain, easier to change traction motors/wheels etc. In the 1990's cast iron brake shoes became increasingly more difficult to find and low friction composition shoes were developed as a direct replacement for the cast iron shoes in locomotives with clasp type brake rigging.

The special shoes that would be used for 'Lidgerwooding' or similar procedures actually have inserts that cut the tread metal to profile.  In my opinion it would be dangerous to provide such tooling on a shoe intended for daily regular service, no matter how carefully the insert mechanism was 'interlocked' to keep it from accidental deployment.  Here are some examples of the kind of cutter used for that approach. 

If I understand the Cobra 'red shoe' construction correctly, there is iron powder in the composition structure somewhere that keeps any glaze polished off, and a carbide mix in the inserts, but I will be happily corrected if that is mistaken.

[JustWonderin']

Overmod,

Thanks for the added explanation. I appreciate it.