The AirChime M Series Train Horns

M Series Train Horns

The AirChime M Series was the company's first ever series of train horns that experienced a large running in production. It was brought in 1950. Still, if you want to buy one today, you can do so, of course for a price. Originally produced by AirChime, the M series was also licensed to Nathan, Holden, and Burnette, thus more than a few variations got created. Of all these companies (including AirChime), Nathan was the only firm that continued producing the M horns even well into the 1960s.

In terms of sound, M train horns are said to be the best ever created. An M train horn can really produce a mellow tone that is at the same time commanding, and the chord tones are pleasing. Unfortunately though, this horn needed serious maintenance and its replacement parts were costing heavily so its makers had no choice but to pull the plug for its production. It was replaced by easily maintained and more affordable horns- K series, P series, and SuperTyfon (Leslie). There was a placement of a large order for M horns in the 70s but this was the last. Ever since, Nathan has cast a few horns. In 2001, an M5 special was ordered from Nathan and this seems to be the last cast. The M5 was bought by Brent Lee and it cost a whopping $6600. In 1950, it was just a mere $100.

Nathan M5 Features and Identification

A train horn with a wide-mouthed bell plus a highly minimal flare of the bell length is easily identifiable as an M horn. An easier identification though is that M horns have varied-sized diaphragm housings or heads. Moreover, they have a back cap that is a screw-on type and diaphragm tension can be adjusted with it. 2 holes can be found on the back cap. This will be utilized by a spanner wrench for cap adjustment purposes. Another unique M train horn feature is that its manifolds are cast with the bell number for every position. Because each bell is varied in size, the placement of the bells must be done as suggested because of not, they simply would not fit. Still, there are no problems reversing the bells.

Other M train horns, for example Leslie SuperTyfon has its bells and heads separated. They are bolted on opposite sides of the manifold of the horn. The inside of an M horn head though is anything but like that of the Leslie power chamber. Instead, within the head is a diaphragm assembly (multi-leaf phosphor-bronze). The 5 bell utilizes 2 leaves and the rest, 3 leaves. The assembly is bolted down together. On one side of the horn's diaphragm assembly is a clapper disk (separate). This is because the seat cannot be found on the same plane where the diaphragm leaves are. In fact, the way the diaphragm assembly is created is very similar the way the diaphragm of a Westinghouse E-2 is constructed. It has fewer parts though.

The clapper of the M horn seals against a nozzle. This nozzle is also cast bronze. It is seated above an O-ring. Partly, the heavy bronze clapper is what creates the mellow tone of an M train horn. This is because it vibrates against the horn's bronze seat. Bronze is actually good in making the tone mellow. Other reasons that made the tone of the M horn the way it is include the heavy castings as well as the bells that were made to have wide throats. Heavy castings mean that when the horn is giving off sound, there are more metal the sound can resonate with. The wide throats allow the creation of a tone that is more open and pure.

Nathan M3H

One M train horn common variation is the one named as M3H. It was specifically designed for Canadian engines to use. This train horn plays D minor chord – D F A. This was the chord mandated by the government. Using bells 4, 3, 2, and 1 along with heads 4, 2, and 1 is how it is achieved. The M3h was commonly sold by Holden, Nathan, AirChime, Burnette and it even saw some Grand Trunk service and was also released through other US lines.

The other variations were few and rare. Burnette was mainly manufacturing them. With reasons unexplained, Burnette cast some train horns that deviated from the specifications given by AirChime. Some bells were slightly shorter or longer. The result was the production of different chords. The Burnette M5H was believed to play C# F G A# C#. This was possible by making the 4 bell shorter and the 2 bell longer. Other famous Burnette M5 chords include C# E G A# D#, C# D F# A C#, and C# E G A D. there was also a non-standard M3H offered by Burnette that was tuned to D# F A.