Simple, shoots torpedoes from something cleverly disguised as a roof vent
A roof vent that looks like a torpedo... looks as the venturi effect causes motion in the air to "power" the vent, which would bolt to the roof, sucking air out of a car, looks like it works equally well in both directions...
Now I will look it up after sticking my neck out:
Apparently used on coaches: (from wikipedia)
Coaches built by the LMS
The design and building of LMS coaches followed a very standardised pattern. Very many types of coaches were built to suit the various services and needs but, in general, the progression of design features was a logical one. Three quite distinct periods of design can be recognised,
[2] the last of which continued until after nationalisation of the railways in Britain.
Period I (1923–1928/9)
The general styling of LMS Period I coaches followed much the same ideas as were prevalent elsewhere in Britain. They were wooden framed and panelled, had a fully beaded body with a semi-elliptical roof, doors to all compartments of side-corridor coaches, and were mounted on a steel underframe derived from the final
Midland Railway design. Window ventilation was mainly by droplight. Roof ventilators were generally of the torpedo type. The coaches were fitted with non-automatic screw couplers and gangwayed stock made use of scissors-type British Standard pattern corridor connection (as also used on the
Great Western Railway).
Most coaches ran on two four-wheel bogies which were of a 9 ft 0 in wheelbase single
bolster design which hardly changed for the whole of the company's life. Some special vehicles ran on twelve wheel chassis and the six-wheel bogie on these vehicles was of 12 ft 6 in wheel-base, based on the
London and North Western Railway design. All coaches except kitchen cars were electrically lit and normally fitted with vacuum brake as standard.
But it looks like they don't align the way I thought:
so I wonder if someone can explain, perhaps they turn?
Ahh, some more information:
The torpedo roof vent reigned supreme for many years with only the GWR adopting the shell vent. The LMS adopted it in 1935 but only for a few years. Then they reverted to a vent that was virtually the Wolverton LNWR hemispherical roof vent of circa 1917. BR adopted it with minor mods for Mk.I stock.
Inside the coach the vents could be 'shut off' by a lever that closed the ventilation slots, although these varied from company to company. I wonder if anyone bothered. Ventilation was important in earlier times when smoking was
'normal'.