I may have gotten my nomenclature off a bit, as the ones I am referencing as having "partitions" were constructed with one bell, having the "three-lobed inner divider" (as Ed Fagen termed it in his book "The Engine's Moan") inside that bell.

(While the book is about steam whistles, he did include some information on the Westinghouse air whistles.)

The view of the bakelite cap has triggered a long forgotten memory. A long time ago, I serviced a #6 distributing valve which had a bakelite bushing instead of the usual brass in its application cylinder. During WWII suppliers had to make do with alternative materials, and that cap is an example of this, which means your whistle dates from the WWII era. The #6 was from a logging RR, which may have made the substitution on its own, and I doubt the class 1s (or class 2s) would have found this type of substitution acceptable.

> the ones I am referencing as having "partitions" were constructed with one bell, having the "three-lobed inner divider"

WABCo trombones were always manufactured as single chambered whistles. How a purchaser may have modified them with dividers after buying them is another story.

Well, in any event...

If someone has cab photos of the original - or at least close - valve/plumbing setups for trombone-equipped electric cars or GE/Davenport/Plymouth "critters," I would sure like to see some.

I just don't get out enough these days.

I believe that the above two explanations are the primary reasons for the specific valve that has puzzled me. The old timers responsible for these setups were apparently practical men, and they got reasonable results given the state of the art at that time. After rummaging around in some scrap and struggling with my agonizingly slow mathematics, I have to conclude that the trombones were adequately supplied with air via either 3/8" or 1/2" piping.

Thanks to all.

Does anyone know of a source for replacement coil springs and thimble seats for the 1/2" x 3/8" Westinghouse whistle valves (Part # 31422) under discussion? I believe that the correct descriptions are:

Part # 3503 - "Spring"

Part # 31416 - "Thimble Seat".

If there are acceptable commercial equivalents easily had, a source for those would be just as appreciated.

In the time since I originally posted this topic, I have had the chance to examine quite a number of these Westinghouse valves (both the 1/2" x 3/8" and 1/2" x 1/2" outlet/inlet versions). They were a common commodity for many years, and are still to be found in service to a surprising - at least to me - degree. They aren't the ideal flow control device by any stretch of the imagination, but they had the attractions of being inexpensive and dead simple.

One thing that I found of interest was a small number of examples that had a fully-threaded, fine thread fillister-head screw used as the lever pivot... while the majority used a fillister-head pivot with coarse threads, and which was not fully threaded (the lever pivoted on an unthreaded section of the fastener). Since there was no evidence indicating that the valve bodies had been stripped and/or rethreaded or otherwise messed with, I believe they may have been a (cheaper) late-production manufacturing variant (these fully fine-threaded machine screws were all found on valves having the conical final-style "cap nut").

The PRR and probably LIRR used WH Trombone whistles on their MP54 MU Cars. Some PRR MP54's flowed to SEPTA and were still around in the early 1980's. The original Broad St, Subway cars have Trombones too.

The Reading MU cars, Budd Silverliner I and II, St. Louis Silverliner III and GE Silverliner IV cars and current BSS cars have WH AA-2 two note air horns. Melodious in my opinon.

The PRR Trombones were quite audible on the railroad cars.

Phil Mulligan

By the time I had exposure to trains of MP54s (going to Swarthmore 1973-1976) the whistles were barely audible at station arrivals -- more like someone blowing into a bottle than a functional warning device.

Compressed air whistles (true aerodynamic whistles) were definitely a mixed bag. They were not helped by inadequate air systems cursed with relatively low pressures and small-diameter pipes; when these Westinghouse valves were used, they themselves added some restriction for air... at least compared to most of the equivalent commercial steam whistle valves of the day.

With no moving parts or diaphragms to replace, air whistles were an install-it-and-forget-it item, but the air horn kicked them to the curb WRT efficiency. One can appreciate why interurbans were removing whistles and replacing them with horns as time went on. Not that Westinghouse AA-2 horns or the like were audibly awesome in themselves, but they made far better use of the air on hand.

We have a P&W interurban car (St. Louis Car 1907) with chime air whistles. It's been out of service for a couple decades and is now in the main display bay.

It has automatic (RR type) train air with a 70# trainline.

Back when we ran it, a few of our members took it out for a ride, tooting the whistle up and down the line. Then the brakes applied. It seems the trainline is the whistle feed and they had blown the whistle so much the brakes set!

Phil Mulligan

Whistles will use up all the compressed air you can shove through them at an alarming rate. Westinghouse advised a "whistle reservoir" for good reason.

The P&WV had single chime horns on the caboose cupola roofs for signaling the head end. There was a small reservoir plumbed in that I can only assume was there so as not to accidentally set the brakes if one was a bit enthusiastic with their tooting. IIRC, it was in the electrical locker.

If the system uses a "control pipe" trainline held at a constant (nearly) pressure by the feed valves on each car feeding into it from local MR, then the whistle should never be piped from that. It is usually a smaller pipe since its function is to charge the BP and keep it charged. Drawing a lot of air from the control pipe can cause the BP to be reduced, resulting in a nuisance application.

Of course, the whistle is not meant to be used continuously. If the CFMs that the whistle is pulling exceed the capacity of the compressor(s) on the car(train), you will eventually run out of air.

I've seen this first-hand. Dallas Area Rapid Transit still uses a variant of the classic trombone whistle on all of their trains. If I was ever trying to purposefully trigger the air compressor, I'd just lay on the whistle for a few seconds. Compared to the air horns also mounted on the car, the whistles were absolutely thirsty for air.