RoadRailer brake system

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  • Member since
    March 2023
  • 163 posts
RoadRailer brake system
Posted by Perry Babin on Thursday, June 1, 2023 10:31 PM

Does anyone know what sort of brake system the RoadRailer uses? The locomotives and semis both use air brakes but in a different way. How is this accomodated by the RoadRailer system?

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  • From: Northern New York
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Posted by tree68 on Friday, June 2, 2023 7:18 AM

By no means an expert on RoadRailers, but I'm guessing that the two brake systems are/were completely separate, so the differences between truck and rail air brakes were of no consequence.

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Posted by Overmod on Friday, June 2, 2023 8:51 AM

This depends to an extent on which version of RoadRailer you're considering.

The trailer duals aren't 'air brakes', they are spring brakes pulled off with air pressure.  You'd be ill-advised to use these for service or emergency train braking, even if the lack of effective braking traction between only the inner duals and the railhead is considered.

In the "original" versions, with the rail wheels carried in a separate frame and the trailer nose equipped with a special traction pin resting on that frame, the single rail axle was separately braked, with a system that only connected to the trainline and had nothing to do with the truck brakes.  I believe the spring brakes on the duals were used to augment tie-downs, but I have no clear idea how they would have been pulled off again without using trainline charging air.

On the 'mark IV' system, the brakes were provided via cylinders on the bogies, and the trailers did no braking contact at all.  I believe part of this was to get around issues with self-guarding frogs.

Incidentally, you can save an enormous amount of time and trouble understanding what will and won't work with a RoadRailer-type system if you read about the 'Micheline' system in the late '20s and early '30s, with its several more-or-less dodgy approaches to keeping the wheels on the track, even with specialty tires optimized solely for on-rail use.  (One of my favorite issues of Trains -- the one with the Snuff Dipper and the Yellow Dog Blues -- was my introduction to this wacky and wonderful approach, although they very carefully avoided most of the specific reasons why the approach was an ignominious failure in the United States.)

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Posted by Perry Babin on Friday, June 2, 2023 9:49 AM

I don't know what I was thinking (or not thinking through) but obviously, the semi truck brakes have nothing to do with the brakes on the bogies. All they need is an air line to connect the locomotive brake system to the bogie brakes. 

As always, the amount of knowledge that's available on this forum is incredible. Even if my questions aren't answered directly (they generally are), enough information is provided to allow me to find answers to my questions (through other resources). 

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