Nathan/Airchime M3 series - M3, M3H

Characteristics

Tuning

M3: A major triad (C#, E, A), with M-series bells #1, #2, #4
M3H: D# minor chord (D#, F#, A#), with M-series bells #2 (with #1 power chamber), #3 (with #2 power chamber) and #4

Sound

The M3 has the same characteristics of the M5--a pleasing and blasty sound that's not harsh--but also a marked tendancy to go out of tune. In the samples below, the M3 on LLPX 2232 has gone to a diminished chord (C#, E, A#) while the horn 2231 is halfway between a diminished chord and the intended tuning.

Samples

• LLPX GP38-2 #2231 (2001-02) - M3R1 (greeting from engineer)
• LLPX GP38-2 #2232 (2000-10) - M3R2

Appearance

The three-chime M-series shares the characteristics of the 5-chime version, the only difference being the lack of two bells above the three lower ones. The back caps and power chambers were difference sizes on each bell, which proved to be a maintenance headache. The bells of the M-series have a characteristic blunt appearance. The earliest M3's had round-based bells, which were soon converted to a "scallop-base" design on which the housings for the bolts that fasten each bell to the manifold are visible.

Classification and Use

Classification

The "H" in the M3H stands for High-profile manifold, as these horns, aside from Canadian tuning, are also built on a small "base" underneath the manifold. "R" is added in the designation when one bell is reversed.

History

The three-chime M-series was a derivative of the M5, introduced at around the same time in the 1950's. The M3H was tuned to comply with Canadian regulations for a D# minor chord, and was the horn of choice on Canadian railroads until the advent of the Nathan/Airchime K3L and K3H.

Locations

The M3 is rare today, but could be found on Denver & Rio Grande Western locomotives and those of various eastern US roads. It's possible the Canadian-tuned M3H can still be found on older Grand Trunk Western locomotives, but it is otherwise restricted to shortlines, tourist railroads and museums. Canadian National and Canadian Pacific, former users of the M3H, have long since converted to K-series horns.