Nathan M5

The picture illustrates a common arrangement of the horn bells with the #2 and #4 bells reversed (turned backward). In this configuration, the horn is designated an M5R24.

Other Views (click for larger image):
Side view of the M5R24

The M5 was first produced in 1950 as a refinement of the H-5. Gone were the external copper tubes supplying air to each bell, replaced by a more substantial manifold. The placement of the bells and design of the back caps were also different. The chord and the beautiful timbre remained, however.

The first M5's made in 1950 looked like the one at left. The horn bells are perfectly round where they meet the manifold (or base). Subsequent refinements in 1951 resulted in so-called "scallop base" horns such as the one at the top of the page. Horn and photo courtesy Brent Lee.

The M5 was the common horn on the Western Pacific, Southern, Atlantic Coast Line, Seaboard Air Line, Richmond Fredricksburg & Potomac, Baltimore & Ohio, Chesapeake & Ohio, and other eastern railroads. Southern Pacific had M5's on many of their passenger service locomotives. The Western Maryland Railroad had pairs of M5's on many of their cab units.

No railroads are known to have purchased M5's in recent years, but they can still be purchased new...for a price. The horn pictured at left was bought new from Nathan in 1999. Horn and photo courtesy Brent Lee.

Here's what an old, round-base M5 looks like when it has been almost completely disassembled. Note how the power chambers and diaphragms are different sizes for each bell. This was a liability for the M-series horns, as it required the railroads to stock many different sizes of diaphragms. On later horns such as the P-series, all horn bells used identical power chambers and diaphragms. Click on the picture to learn the names of the parts. Horn and photo courtesy Dennis McCurry.


Original tuning was: A major dominant 7th (C#,E,G,A,C#).

Many other variations were possible, though, even from the factory.
These included A major dominant 6th (C#, E, F#, A, C#),
and D# minor 7th (C#, D#, F#, A#, C#)

The horn used the M-series #1, 2, 3, 4, and 5 bells.


The M-series horns turned out to be relatively high-maintenance items, and with the development of lower-maintenance horns from both Nathan and Leslie, the M's fell out of favor. Few if any railroads have acquired new M5's since the early 1980's. There are virtually no M5's in regular use on major freight railroads, but some can still be heard on excursion and tourist railroads and a handful of shortlines.


M5 sound samples:

Western Pacific GP40:
Sample 1...211kB...9 seconds

Simpson Lumber SW1200 (horn courtesy 5CC):
Sample 1...437kB...20 seconds
Sample 2...247kB...11 seconds

Oakland Terminal GP7 (horn courtesy 5CC):
Sample 1...332kB...5 seconds
Sample 2...332kB...10 seconds
Sample 3...232kB...10 seconds

Niles Canyon Railway, various locomotives (horns courtesy 5CC):
Sample 1...281kB...13 seconds
Sample 2...135kB...6 seconds
Sample 3...207kB...9 seconds
Sample 4...239kB...11 seconds
Sample 5...319kB...14 seconds
Sample 6...544kB...25 seconds



The M-series horns were tunable, and were supposed to be retuned and voiced every six months or so to keep them sounding properly. Unfortunately, many railroads neglected to maintain the M's properly. Left to fend for themselves, the horns soon went out of tune. Sometimes they managed to sound good, if different, despite deferred maintenance. Other times they did not.

Modesto & Empire Traction GE 70-ton:
Sample 1...65kB...3 seconds
Sample 2...310kB...14 seconds
Sample 3...177kB...8 seconds
Same horn two years later:
Sample 4...270kB...12 seconds
Sample 5...119kB...5 seconds
Same horn a year later:
Sample 6...453kB...21 seconds
Sample 7...200kB...9 seconds
Sample 8...173kB...8 seconds

New Georgia (ex-Southern) EMD FP7:
Sample 1...221kB...10 seconds
Sample 2...373kB...17 seconds

Southern Pacific H24-66 "Trainmaster:"
Sample 1...135kB...6 seconds
Sample 2...216kB...10 seconds
Sample 3...65kB...3 seconds
Sample 4...245kB...5 seconds
Sample 5...173kB...3 seconds

Southern Pacific, others:
Sample 1...340kB...15 seconds
Sample 2...151kB...6 seconds




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