I've always taken it as read that the Mk V had a major ventilation problem because the fans drew air from the outside rather than from the interior. Now someone has put this on Wikipedia:
The only ventilation for the crew compartment, other than the driver and gunner view-ports, located on all sides of the tank, was a roof-mounted Keith fan.
The source is given as Tanks in the Great War 1914-1918 by J.F.C. Fuller. What Fuller actually says is:
The engine was completely enclosed in a sheet-iron casing, from which the hot foul air was exhausted through the roof of the tank by means of a Keith fan.
That's not quite the same thing. This is what a Keith Mine Fan is. All of this is news to me, but I can't see that they would put a fan in the roof - it would be asking for a grenade or a Molotov to be dropped in. If there was a fan, wouldn't it be just ducting air from the engine into the exhaust? Anyone explain?
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Aha. That's most interesting. I've never noticed that before. I must have a look at some more photographs.
This is what D. Fletcher says in the Osprey book, p14:
Despite the fact that the engine was totally enclosed by concertina folding panels, and equipped with a fan cooling system for the exhaust pipe, conditions for the crew are said to have been far worse than in the Mk IV. This appears to have been due to tne new ducted cooling system for the radiator, which drew in air from the outside, so that fumes built up rapidly inside the tank . . . . A sliding shutter had been incorporated in the ducting, which was supposed to supply fresh air to the interior of the tank, but it appears to have been fighting a losing battle. Later, and extra shutter was fitted, which drew contaminated air out of the crew area, and this appears to have made a difference.
In his Tank Chat on Youtube, DF says just, "They altered it after a while, to get better ventilation."
I can't say I can fully picture the set-up here.
__________________
"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.