Nathan/Airchime M5

Characteristics

Tuning

A major dominant 7th (C#, E, G, A, C#), with M-series bells #1, #2, #3, #4, #5

Sound

The M-series horns were known for a pleasing sound that was blasty but not harsh, and not imitated by any other horn type. The horn pitch tended to drop noticeably as air was gradually applied, sometimes creating a very interesting effect. Chords were often varied, even when the horns were new. A common chord was an A major sixth (C#, E, F#, A, C#) which is a similar chord to the Nathan/Airchime K5LA.

Appearance

The M-series can be told by later horns by the blunt shape of the bells and different-sized back caps and power chambers on each bell. The manifold on the M5 featured three bells in a lower row with two above. Early M-series horns had round bases where the bells meet the manifold; later ones had "scallop base" bells which were more lightly built and had protrusions from where the fastening bolts entered the bell from the back.

Classification and Use

Classification

The M series started the straightforward classification system that characterizes most Nathan/Airchime horns. "R" is added for reversed bells. A common arrangement was to have bells #2 and #4 reversed, resulting in the designation "M5R24".

History

The M-series horn was among the first multi-chime air horns, offered as an alternative to early single-chime "honkers" (such as the Leslie A-200) found on early diesel locomotives. The M-series was fairly maintenance-intensive, requiring tuning every six months or so (which railroads often neglected to perform). Despite its initial popularity, it was eventually supplanted by newer horns (the P-series and K-series).

Locations

Although the M-series horns were common in the earlier decades of dieselization, they are now quite rare and are mostly restricted to shortlines and tourist railroads.