Have some background information on the British use of Air Cleaners that might be of interest.
This is from a report titled Armoured Fighting Vehicles in the Mediterranean Theatre 1939 - 1945. It was completed in 1945 based on Mediterraneen Area AFV Technical reports nos 1 to 27, covering Libya and Italy from 1939 to 1945:
As a result of unfortunate experiences near Mersa Matruth in 1935, during the Abyssinan crisis the British Army were alive to the dust menance and was provided with fairly effective air cleaners for its vehicles. These were the 'concertina type' and consisted of a series of felt rings sewn together along their inner and outer peripheries to form a concertina-like tube. One end was closed and the other connected by pipe to the carburettor intake. All aspirated air had to pass through the felt and periodical cleaning was effected by pumping the concertina and thus blowing the accumulated dust off the outer surface.
For ordinary use these cleaners were reasonably effective but it was found that the finest type of alluvial dust would pass the felt and thus led to oil contimination and heavy cylinder wear.
In consequence, the M.E. authorities condemed the felt element type of cleaner anf themselves began various experiments with oil-bath types. Despite the inventors fondness for his child, none of these locally made cleaners proved in the long run to be really satisfactory, mainly owing to oil carry-over and it was not until the vokes 2-stage cleaner was introduced on Crusader that the situation was brought properly under control.
The objection to the simple type of oil bath cleaner such as fitted to the Matilda and some Valentine was that on test, it did not give as high an efficiency figure as the felt element pattern and, furthermore, when the oil became saturated with dust it ceased to clean and gave no warning of having done so.
The Vokes 2-stage cleaner put an end to the argument and was generally accepted as the best to date. This appliance consists of an initial vortex which deposits the larger granules by centrifugal action: the air then passes over a succession of weirs in an oil bath which trap the finer grains. The efficiency was high and there was little or no trouble from oil carry-over. However, such was the volume of dust which had to be dealt with that these cleaners required clearing every 50 miles.
An interesting sidelight of this period was the capture of an enemy document in which the writer complained about the oil bath cleaners fitted to German tanks and asked why they could not have something similar to the excellent felt cleaners used by the British.
U.S tanks all had oil-bath cleaners of varying degrees of efficieny, the precise merits being somewhat obscured by commercial propoganda on the part of theatre representatives of the manufacturing firms.
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