I am trying to discover the logic behind the use of Westinghouse manual whistle/horn valves having 3/8” NPT inlets and 1/2” NPT outlets on commuter and interurban equipment when equipped with Westinghouse Trombone whistles or their copies. I have occasionally run into this setup with powered cars and a few small industrial diesel-electric locomotives over the years, and I am wondering if someone with a broader knowledge base of these systems might have the answer.

Normal diesel-electric air horn practice would generally have pipe/tubing of the same - or decreasing - ID in the direction of the air flow, so a valve with a smaller inlet and relatively restrictive pipe leading up to it seems odd, especially considering that Westinghouse catalogued 3/8” NPT and ½” NPT valves with inlet and outlet threads of the same size.

Was this increase in pipe size between the operating valve and the air whistle an attempt to give the whistles a sort of “air reservoir” enabling a slight buildup and tailing off effect that made the signals a little less abrupt? Or was 3/8” pipe simply an early standard for pipe runs to the valve(s) in electric and IC power? Was this some sort of deliberate “flow vs pressure” manipulation, the purpose of which escapes me?

The same valve and pipe setup has been noted in CSS&SB and other cars equipped with AA-2 horns (as opposed to an aerodynamic whistle), which is just as baffling.

I don't think there is any great secret compressible fluid flow theory here. The most likely explanation is that the whistles tended to be made with the 1/2" inlet. Maybe that larger size is needed for satisfactory operation on steam vs air? The whistle cock in electric railway practice tends to be on a 3/8" branch pipe from the MR for small appliances such as windshield wipers, whistles/horns, and gauges (although 1/4" pipe is also common for that). So making a valve with 3/8 inlet and 1/2 discharge is just a convenience.

That being said, I've seen all sorts of permutations, including copper tubing

Thank you for the reply!

I am not sure how Westinghouse (or GE) arrived at the 1/2" inlet on the trombone whistles to begin with, though I suppose they had their reasons. One of the old rules of thumb was that a 2" diameter whistle needed a 1/2" pipe, but that was sort of an average figure; the trombones run a bit under 2" in diameter and do not have a particularly large amount of slot area, so I don't think they probably suffered tremendously by having 3/8" pipe somewhere in the line.

A steeplecab electric locomotive with only 90 psi in the main reservoir and a CP-30 compressor feeding it probably appreciated 3/8" lines in any event.

(I am given to understand that MP54 cars on the Pennsylvania were equipped with Westinghouse trombone whistles and these Westinghouse 3/8" NPT to 1/2" NPT whistle valves, but I have never so much as seen one of these cars personally, let alone heard one. I wonder if they were considered to be - for lack of a better term - "under-whistled?")

I would suspect that Westinghouse felt that the bulk of 1/2" pipe was needed to support the weight of the whistle, since no other attachment was provided, and providing a whistle valve with that size outlet was purely a matter of convenience.

I had completely overlooked that point! I have only seen one installation that actually used anything other than the inlet pipe to support one of these trombone whistles, and the addition was made later in the equipment's career.

Went through my stuff, and from day one (1907) through a least 1930 Westinghouse Traction Brake Company shows this 3/8" in 1/2" out scheme for whistle valves with all types of whistles it sold: clarion, trombone, and Kinsley chime. I suspect that the increased volume of the 1/2" pipe between the valve and the whistle attenuated pressure increases when blowing the whistle just enough to prevent it from "cracking" (emitting a high pitched screeching sound).

Air horns aren't designed to be operated on pressures much above 75-80 psi or the diaphragm(s) become destroyed. So if the supply pressure exceeds this, there is usually a restriction (like a 1/8" orifice) is inserted in the piping between the valve and the horn.

1907 goes back farther than I have been able to go so far, and I also haven’t pinned down exactly when Westinghouse first offered their “Trombone” air whistle… or when it went from the all-brass/bronze version having the internal partitions to the later version using a bakelite top cap and no internal partitions.

General Electric was offering their own brass/ bronze versions of these things as a “new and improved” signal around 1910, along with companion ½” NPT operating valves and cut-out cocks. Later on, GE offered a somewhat cruder, steel-bodied version of the whistle. As far as I know, these were simply referred to by GE as “deep tone air whistles.” Interestingly, one of the original selling points in an early GE catalog was the partition that separated the long bell into three chambers, keeping the wind from blowing across/ through the three “mouths” of the whistle’s bell; this predates Prof. Foley’s experiments with steam whistle placement and orientation.

Pacific Electric constructed their own version of these whistles, which would not have been a difficult task for a well-equipped shop. Like all of the “trombone-type” whistles, being a “set it and forget it” warning device with no diaphragms or nozzles to replace - and no moving parts (other than the fluttering columns of air) - I can see their allure from a maintenance standpoint.

In any event, I suspect that at least the Westinghouse version was optimized for use with Schedule 80 3/8” pipe at least somewhere upwind of its inlet, as the three air slots added together seem to more or less approximate the same area of that pipe’s inside diameter. Judged by the the limited number of examples I have gotten to see out here, the trombones are more likely to use one of these 3/8” x 1/2” valves than a 1/2” x 1/2”. Equipment with traditional 2” diameter "steam" whistles running on air seem to always have a 1/2” x 1/2” valve (of Lunkenheimer, Powell or some other make as well as Westinghouse).

In the past five or so years, I have spent some quality time near a working motor that uses an early Westinghouse trombone whistle, and while I have always sort of belittled the old clucks on various grounds, I confess that their sound carries better than many people might expect.

I forgot, some people are really, really into whistles and other noise-making devices!

From my standpoint, does the whistle cock hold air? Does the whistle cutout (if equipped) function? Check, check, pull the string, some kind of noise comes out, I'm done!

I don't think the difference in volume between 1/2 and 3/8 pipe makes any difference when it is often only a short nipple between the whisle cock and the whistle itself. As Dennis suggested, the reason why the inlets were probably made 1/2 is because that nipple was often the only thing holding the whistle on.

Much more interesting is the variety of whistle cock internal construction, with brass-on-brass seats, rubber seats, later some plastic seats, and the various ways of preventing excessive leakage past the stem when the thing is being activated. Every time I think I've worked on all of these, I'll come across a new style and sometimes have to make new tooling for it.

Have you ever seen the somewhat suggestively named "automatic cock lapping machine"? it is a device which rotates the tapered plug (or "key") back and forth while periodically lifting it in and out. OET/OERM/SCRM has one in their shop. If you are repairing these by hand, you need to use the
same motion, otherwise the lapping compound has a tendency to "dig in" and leave circular grooves which will leak. Continue lapping until there is a solid band of the same dull lapped-in color all the way around the plug and the ID of the body, preferably extending the length of the plug, but at least a respectable distance above and below the air passage slot in the plug and body.

When cock bodies were too worn, there were special tapered reamers to ream it out to the next standard size, followed by substitution of a "repair size" plug.

Been there, done that, got the t-shirt, burned myself out and "retired"... sort of. I ignored the daylights out of these old air whistles for years, considering them decidedly poor relatives to post-1949 locomotive air horns. That left a big old void in my "base for interpretation."

You bring up the subject of lapping, and that reveals a whole different skillset for people used to nothing more difficult than - for instance - normal maintenance of Viloco or Graham-White/Salem horn operating valves, where fresh rubber seals and o-rings take care of the air leaks.* My grandfather had grinding and lapping "kits" (for valves at any rate) because his business required a boiler and he had no choice but to maintain it and all the associated equipment by himself. He was comfortable and competent WRT steam, internal combustion and electric power, doing all his own maintenance until about 1970 when the last new car he purchased had one too many new-fangled electronic doo-dads.

*Now the skill would be figuring out how to make substitutes for those no longer made seals.

>1907 goes back farther than I have been able to go so far, and I also haven’t pinned down exactly when Westinghouse first offered their “Trombone” air whistle…

The farthest back I've able to track the trombone is1908, and WTBCo whistles in general, 1905, so earlier I averaged this to 1907.

> or when it went from the all-brass/bronze version having the internal partitions to the later version using a bakelite top cap and no internal partitions.

Brass, and WTBCo's design of trombone whistle has never had internal partitions, including the aluminum one I have from the 1960s.

> General Electric was offering their own brass/ bronze versions of these things as a “new and improved” signal around 1910, along with companion ½” NPT operating valves and cut-out cocks.

These are the G-1 (small, using 1/2" pipe) and KL-2 (large, brass, base connection both 1/2" internal pipe thread and 1" external thread), which sold for $6 and $41 respectively in 1922. The G-1 was single chamber and probably the steel one, while the KL-2 has 3 chambers. Both are listed in the 1922 edition of GE Railway Supplies but not in the 1911 edition. I have a catalogue flyer for GE air brake equipment, dated 1908, which lists an air whistle with no details. I suspect this is a precursor of the G-1.

>Later on, GE offered a somewhat cruder, steel-bodied version of the whistle. As far as I know, these were simply referred to by GE as “deep tone air whistles.” Interestingly, one of the original selling points in an early GE catalog was the partition that separated the long bell into three chambers, keeping the wind from blowing across/ through the three “mouths” of the whistle’s bell;

Looked it up, and these are called "windows". Usually multi-chambered whistles produced a different tone (musical note) from each chamber.

> Pacific Electric constructed their own version of these whistles,

These are longer than the WTBCo ones by about 3" and had two windows instead of WTBCo's three.

> In any event, I suspect that at least the Westinghouse version was optimized for use with Schedule 80 3/8” pipe

Which wasn't known as "schedule 80" in the 1904-1908 era. Westinghouse has been pretty savvy about air flow since about 1890, but they view the subject as somewhat proprietary.

> Equipment with traditional 2” diameter "steam" whistles running on air seem to always have a 1/2” x 1/2” valve (of Lunkenheimer, Powell or some other make as well as Westinghouse).

One thing is for sure, you can't operate an air whistle on steam or the steam's heat and high-speed corrosion effects will ruin it.

> In the past five or so years, I have spent some quality time near a working motor that uses an early Westinghouse trombone whistle, and while I have always sort of belittled the old clucks on various grounds, I confess that their sound carries better than many people might expect.

Many decades ago, when I worked for the SP in Oakland, we had one of the "PE-ized" EMD switch engines which was equipped with a home made PE "trombone". One day I had it on the Emeryville job, which used a lot of the former IER trackage being to serve industries (the IER red electrics used WTBCo trombones). So I used the whistle instead of the air horn, and on one crossing I saw two older guys standing in the street, hands on hips, staring at us. A couple of years later the whistle disappeared.

Photos please?

Wesley
Study Hall
Trombone Horns 101

I did have a brass-capped Westinghouse Trombone with thin sheet brass internal partitions come into my hands back in the 1990's; it looked factory to me, but it had obviously been around the block a coupe of times. I remember it mostly because of two things: the partition assembly was a bit loose so that it "rattled" if you gave the whistle a light shake, and the whistle body was dappled with off-white/cream paint here and there.

The only example of a Westinghouse air whistle that I ever bothered keeping for myself is a bakelite-capped Trombone with no partitions, and it came to me from a gentleman in Pennsylvania who threw one of the 3/8" x 1/2" valves into the deal. I still have it somewhere in a box. Around the same time I acquired it, I was cleaning up another Trombone which I thought was identical, but unlike the one I had just gotten, this one had a transverse brass pin of about 3/16" diameter to apparently help secure the bakelite top cap. I have no idea if that was a factory variation or a field modification, but in any event I cleaned the caked sludge out of the thing for its owner and made a mental note of that pin.

I never dealt with what would be called a large amount of air whistles, but from the 30 years I was messing with noisemakers out here on the prairie, I concluded that there were plenty of variations in just the Westinghouse-made Trombones, let alone the General Electric version(s). Like A-2 and AA-2 Westinghouse horns, there were a lot of them made and sold over a long enough span of time to keep me from being too surprised at whatever oddities would pop up.

Of the air whistles I HAVE seen that made it past the scrapper, most are without "context," so to speak, and thus my curiosity about the valves and associated piping. The photographic record is basically one showing some Trombone variant on the outside of a car or engine, either sticking straight up on a piece of pipe or in a reclining position courtesy of a 1/2" elbow... but interior/cab shots of the plumbing are far fewer.

> I did have a brass-capped Westinghouse Trombone with thin sheet brass internal partitions come into my hands back in the 1990's; it looked factory to me,

To be considered "factory", it must have the WA symbol on it somewhere: cast into the cap in raised letters and/or stamped into the base. WABCo/WTBCo's trombones have always been single chamber, which means those internal partitions you mention can be only "after market", not factory equipment.

> The only example of a Westinghouse air whistle that I ever bothered keeping for myself is a bakelite-capped Trombone with no partitions,

While it might strongly resemble a WTBCo whistle, it can't be considered one unless it bears the WA symbol. The original cap was lost (post manufacture) and a bakelite one substituted. The cast brass caps were either a press fit or soldered in, which is the reason for that pin: retention.

> there were plenty of variations in just the Westinghouse-made Trombones,

The only variation in Westinghouse made trombones between 1911 and 1966 has been with the material used: brass or aluminum. This is based on personally examining parts catalogues dating from 1911 through 1966.

> there were a lot of them made and sold over a long enough span of time to keep me from being too surprised at whatever oddities would pop up.

The oddities of which you speak are all after-market modifications made by users, not factory production. The parts catalogues all list two whistles: the single chamber "trombone" type (WTBCo's term) and the "clarion" type, which had two separate single chambers mounted in a T shape on a (cast brass) base. "Clarion" is also WTBCo's term.

> The photographic record is basically one showing some Trombone variant on the outside of a car or engine, either sticking straight up on a piece of pipe or in a reclining position courtesy of a 1/2" elbow... but interior/cab shots of the plumbing are far fewer.

My comments about pipe sizes are based on looking at the line diagrams in the parts catalogues and that 1906 instruction book. Photographs of cars which also show the air whistle are too low resolution for making definitive determinations of whistle types because there were other manufactures which made whistles that closely resembled the WABCo ones, particularly the trombone design. NYAB also produced the clarion type, under a different name. From more than 6" away the differences between it and a WTBCo/WABCo made one is indistinguishable.

I have always been under the impression that examples like this bakelite-capped, no partition one were prototypical latter-day Westinghouse Trombone whistles.

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