I guess many people are aware that trials of different transmission systems for rhomboid tanks were carried out in March 1917.
The winner was Wilson's planetary gear transmission which was installed in the Mark V and successors.
Has anyone found the write up of the trails? Both Daimler and Westinghouse submitted petrol electric systems presumably similar to the St Chamond transmission but I've never seen any report of these.
There are IWM images of the Mark II trial tank with Williams-Janney hydraulic transmission taken at Dollis Hill in 1918 - there's limited detail visible inside the tank but the lack of the massive differential is notable. The Williams-Janney transmission was used in the Mark VII tank.
I was looking at the Mark VII tank and note that David Fletcher says it was a stretched Mark IV with Mark V rear cupola but the "New Excaliber" says it was a stretched Mark V - anyone have a definitive answer to this? Stern's book has the Mark VII with two units per track connected by hoses but this doesn't seem right the W-J transmission could be configured as a single unit.
Regards,
Charlie
-- Edited by CharlieC on Saturday 22nd of August 2026 06:11:34 AM
I don't think the Mark VII was a stretched anything. The Mark VII was a separate design, not a Mark IV or V with an added section riveted in to lengthen it. That said, there was an Experimental Mark VII which was a Mark IV with Williams-Janney gear, but it is distinctly different from both a standard Mark IV and a Mark VII.
BTW, I have just read the article on Landships about the Mark VII. It makes some erroneous statements that need correction. The idea that no rhomboid could reverse until the Mark VII is simply wrong. The Daimler set used in Mother, and the Tanks Mark I to IV had a reverse gear. Since it was reversed in Little Willie, that in effect had two reverse gears.
I was in two minds about the Mark VII article. Documentation on the tank is thin and often contradictory. After numerous false starts I decided to just go with it and hope that someone knowledgeable would correct any eggregious errors
The Mark VII is an interesting vehicle and was the first of the attempts to replace mechanical tank transmissions with hydraulic systems. The early French Char B had a hydraulic Naeder transmission which was quite different from the Williams-Janney and, I think, required because the in hull gun had a limited traverse and the whole tank had to be turned accurately. There was an experimental 1944 German Panzer IV with hydraulic drive and steering - this was at Aberdeen and is now at Fort Benning.
