The Air Horns of the Class M2 Locomotives
by
Gyan
Fernando
One
of the distinctive features of the General Motors EMD G12 Class M2 locomotives
of Sri Lanka are their air horns.
The triple air horns, which are mounted on top of the cab, are finely tuned with two of the “bells” pointing in one direction and the other in the opposite direction.
They are also controlled by a pull-cord, in traditional fashion.
The triple air horns, which are mounted on top of the cab, are finely tuned with two of the “bells” pointing in one direction and the other in the opposite direction.
They are also controlled by a pull-cord, in traditional fashion.
AirChime
Nathan
The horns fitted on all the M2 locos are manufactured by AirChime and Nathan. AirChime and Nathan are now
The horns fitted on all the M2 locos are manufactured by AirChime and Nathan. AirChime and Nathan are now
More......
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| 570 Alberta showing air horns |
On the Class M2 locomotives, air horns with either one, or both the company names, may be seen.
AirChime,
Ltd. traces their beginnings through the work of Robert Swanson in 1949.
Prior to the early 1950s, locomotives were equipped with air horns that sounded but a single note.
Prior to the early 1950s, locomotives were equipped with air horns that sounded but a single note.
Swanson
sought to develop an air horn which would mimic the sound of a classic steam
whistle.
Using ancient Chinese musical theory, Swanson produced the six-note
model 'H6'. This was considered impractical for railroad use, due to its relatively large
size.
 |
| AirChime logo on 626 Montreal |
 |
| AirChime logo on 626 Montreal |
In
musical terms, the triple horns play a chord which is pleasing to the ear and
this is what makes the Class M2 horns distinctive.
How
Air Horns Work
Train
air horns are operated by compressed air, typically at 125-140 psi (8.6-9.6 bar),
and fed from a locomotive main air reservoir.
 |
| 595 Newfoundland with Nathan logo |
Oscillation
in a train horn is accomplished via a diaphragm assembly enclosed within the
power chamber.
The “bell”
or the trumpet, modulates the sound and determines the pitch. In general terms,
three horns sounded together produce a musical chord.
Material
Good quality Airhorn bells are usually sand cast in aluminium. This probably explains the lack of corrosion on the M2 loco horns.
Material
Good quality Airhorn bells are usually sand cast in aluminium. This probably explains the lack of corrosion on the M2 loco horns.
 |
| How airhorns work (Wikipedia) |
 |
| Logo from pic above |
The
M2 horns are worked by means of a lanyard or cord instead of a button, and this allows
the engineer a degree of flexibility unlike with horns operated by a button.
For instance, the engineer can “feather” the horn by varying the pull on the lanyard. In musical terms this is known as a "trill".
This is not possible on button operated horns.
For instance, the engineer can “feather” the horn by varying the pull on the lanyard. In musical terms this is known as a "trill".
This is not possible on button operated horns.
Footnote: Astute readers will note that the Nathan logo
on the air horn of Newfoundland is upside down indicating that the bell has been
fitted to the chamber the wrong way. In the picture showing the detail of the
logo (above) I cut out the logo and inverted it
References and further reading:
LocomotiveHorns - How They Work
Micro Precision LLC | Model K - The best in audible signaling
Locomotive Horns
Video Links on You Tube
Great article Gyan. Very informative indeed. North American built locomotives are characterised by their triple and ocassionally five trumpet horns. (Leslie & Klaxon too make them). I distinctly remember when M2s 628 & 629 (originally the 'cement haulers') came around 1966 or so, they had a single trumpet horn much like a megaphone, fitted atop the cab door sides . Sometime 'down the track' they seem to have acquired Nathan triple horns. Keep up the good work!!
ReplyDeleteThanks for the kind comments.
DeleteThank you for the great information. I have a great fascination with these Canadian engines and specially the amazing sounding horns which were on Montreal and Vancouver. Do you have any idea what notes they were tuned to? It is obvious they had the Canadian tuning but it would be great to find out their original tuned notes. Thank you again and keep up the great work.
ReplyDelete-U.Karunaratne
I am not very musically inclined so I cannot work out the chords! Will do my best!
ReplyDelete