Air Brake Types

[Paul of Covington]

     In these forums and in magazines I have come across references to brake designations such as "26L" and "AB."    The number ones appear to refer to the locomotive end, and the all-letter ones to the cars.     I seem to remember from somewhere that the difference between "AB" and "ABD" has to do with quick-release or apply, but I also remember other names like "ABDW."    I've read several good descriptions of how brakes work, but I'm curious about the variations.    I would appreciate some help, either discussion or references (or both).     Thanks in advance.      ...Paul

[Paul_D_North_Jr]

Good questions - and tough to find good answers, it seems.  Here's a start: 

"(3) Types of Brake Systems." in the middle of page 2-8 briefly discusses the K, AB, ABD, and ABDW, at: 

 http://www.tpub.com/content/aviation2/P-301/P-3010046.htm 

Figure 2-10. AB/ABD/ABDW type service brake valves on page 2-11 at: 

http://www.tpub.com/content/aviation2/P-301/P-3010046.htm 

Wabco (Westinghouse) has a bunch of instructional leaflets available on-line in 'PDF" format to review and download for free, but they almost have too much information and detail for us fans, at: 

http://techinfo.wabtec.com/Aar/browseall.asp 

- Paul North. 

[Paul of Covington]

   Thank you, Paul North for those references.    Sometimes I think you are a human encyclopedia.

   I had no idea there were so many variations out.    Maybe I don't reaIly need to know about all the others, but I did find out that I was off on what little I thought I remembered:   the ABD is a revision of the innards of the AB, and the ABDW is the one with the quick-apply.   Thanks again.

[oltmannd]

Back when I started in 1978, there were WABCO AB, ABD and ABDW valves.  Shortly thereafter, a variety of form fit and function replacements from other manufactures that I took little notice of....

The basic difference between an AB and ABD was the vavles.  AB used slide valves that had to be lapped smooth at every rebuilding.  ABD used rubber diaphragms and O rings to replace the lapped surface seals.  As rubber compounds got better, it became possible to extend the rebuild cycles of these brake valves.  Where the AB valve had a two year cycle, I think there are some tests going on to extend ABDW (and the like) to 16 years.

[Jerry Pier]

The "D" stands for diaphrgm, as opposed to ring-sealed, piston. The basic functions are still accomplished with slide valves as in the AB Brake. The "W" in the ABDW signifies a mod that  minimizes undesired emergencies. The mod was invented by Dick Wilson, a highly accomplished WABCO Engineer, and it solved a major problem.  TYhe W is  for him. As far as i know, it is the only such revision ever named for its inventor, at least by WABCO

[Paul_D_North_Jr]

Paul of Covington - Hey, you're welcome.  No problem, and I'm not a walking encyclopedia - but I do enjoy a good hunt - er, search - and have the benefit of a good computer and decent recall* of where I've maybe seen things already or before, as well as the obsessive inquisitiveness and curiosity of a cat  . . .  

(*"Never memorize what you can look up." - EInstein)

Anyway, while looking for something else, I ran across this - the Simmons-Boardman / "TransAlert" bookstore page for "Rail - Brakes" - and thought I'd post it here for general information on this subject:

http://www.transalert.com/bookstore/Rail/Brakes/

I see that there are several booklets in the $10 and 30-page range as a further introduction or overview without having to buy the more expensive training manuals for car repairmen etc., as follows:

Air Brake Equipment - The AB Brake - 27 pages - $9.00

Air Brake Equipment, Basic Principles, Modern Features - 31 pages - $9.00

Air Brakes - 28 pages - $9.00

Railroad Brake Shoes -  30 pages - $10.25

- Paul North. 

[Deggesty]

Paul_D_North_Jr

Paul of Covington - Hey, you're welcome.  No problem, and I'm not a walking encyclopedia - but I do enjoy a good hunt - er, search - and have the benefit of a good computer and decent recall* of where I've maybe seen things already or before, as well as the obsessive inquisitiveness and curiosity of a cat  . . .  

(*"Never memorize what you can look up." - EInstein)

- Paul North. 

Yes, indeed, knowing where to look for the information is more than half the battle. This reminds me of when I was taking Physical Chemistry in college; the class met in the Chemistry Library, and we had doozies of tests--the first part, on theory, was closed book, but the second part, which was problems, was open book. The second part was far worse than the first part; we had to know which of the books in the library would give us help. My fellow student and I did survive.

It's a lot easier to spread the information I have on railroading.