AirChime/Nathan M3 Train Horns

Nathan M3 train horn was introduced in 1950, preceding the conceptualization of the M5 train horn. M3's first year of production held in its design three distinct bells that were perfectly round-shaped bells that joined the manifold (base or inlets and outlets). The next year, a modification was applied on the base, that was of a "scallop base" shaped. These common horns were popular among South Pacific, SP&S, Pennsylvania and Delaware & Hudson locomotives and several other eastern railroads, especially on locomotives from the Denver Rio Grande Western lines.

Another variation of the M3 train horn was the M3RT1. The improvement developed the 1st bell having an elliptical flare that has a horizontal angle of 10 degrees going up. This improvement was specifically created as per request from Delaware and Hudson.

The design was to harness the horn in front of the cabine of the Alco RS-3 locomotives that they produced and have the #1 bell facing behind the cab roof. Despite its design, its sound remained unscathed.

M3 had an original tuning of A major triad on the keys of C3, E and A. Factory tuning was also possible for C#, D, A, C#, E ,A#, and C#, D#, A# which were also common as a dischord variations. The horn used M-series# 1,2 and 4 bells.

A common thing among the M-series horns, is they reared out costly maintenance problems and the M3 was no exception to this demise. They were very popular though during their time,, but only a few new M3's still exist since the 1980's and the train horns are seldom in use today. One company though sought the challenge during these times. Willamette and Pacific installed the M3's on a big part of the locomotives they had in the 1990's. Only a handful still have M3's installed on locomotives. A few still exist today on Union Pacific, and a lot of them can still be heard on Rio Grande power.

The disadvantage of the train horns is their costly maintenance. M-series horns must be tuned and voiced on a six month period or so to have them in tip-top shape. Otherwise, the horns would easily go out of tune. But some M3's may still sound good even with lack of regular calibration and tuning.

AirChime M3H

Another variation of the M3 is the AirChime M3H. Its birth in the 1950's only followed the Canadian regulations to mandate the D# minor chord on all locomotive horns. Compared to its mentor, the M3 was far off tune by six keys, from A to D#. Not mentioning it transposed from a major to a minor triad. This development indeed crossed its challenges. As mandated by the Canadian regulations, thedefault tuning for the M3H train horn was a D# minor triad on keys D#, F# and A#.

The AirChime have bells#2, 3 and 4 installed following its predecessor, the M5 which had the the #1, 2 and 4 chambers respectively.

Despite of the M3H's effort to conclusively meet the market's challenges, it was still undermined by the K3H that had a low-maintenance requirement. From the early 70's to the early 80's, no new M3H's were produced because of low demand and need for the commodity. A tiny group are still evident on former Grand Trunk Western locomotives.