Landships II

James H · Legend

Walter Wilson's Epicyclic Transmission.

Gwyn Evans · Legend

I'm no engineer, but my understanding is that the epicyclics in the Mark V are to assist steering rather than act as a gearbox, so you're right.

Gwyn

CharlieC · Legend

There's an old thread which addresses (in part) this question:

http://landships.activeboard.com/t48115061/mk-v-plans/

If you want a detailed but comprehensible explanation of how an epicyclic transmission works:

https://youtu.be/9sPi7DEbyI0

Regards,

Charlie

-- Edited by CharlieC on Wednesday 7th of March 2018 02:56:39 AM

James H · Legend

This is all a bit odd. There are countless references to Wilson's design, but I can't find an actual description of it. With respect, Charlie, I think that's a gearbox rather than a steering mechanism. This seems to be nearer the mark; it's OK once you get past the motorcyclists:

https://youtu.be/yYAw79386WI

Then again, I might have got hold of the wrong end of the stick altogether.

And there's this: "In 1928, Major Walter Wilson used the 16-ton Vickers A-6 tank as the vehicle for his epicyclic, or planetary, steering mechanism - a very important advance in transmission and steering design."

"1928" isn't a misprint - at least, not by me. It's from Panzer Gunner: A Canadian in the German 7th Panzer Division, 1944-45 by Bruno Friesen. Is that a red herring?

Gwyn Evans · Legend

A6 and 1928 aren't errors, though the terminology is, strictly speaking, slightly awry. A6 was the General Staff specification for a sixteen ton tank. Two tanks were built to this specification in 1928, namely A6E1 and A6E2. To quote David Fletcher's "Mechanised Force", page 15: "... although both tanks employed Wilson's epicyclics steering system they had different gearboxes for evaluation purposes."

Gwyn

vollketten · Lieutenant-Colonel

I don't know how much help it may be but in my book I typed up another very long and very in-depth report written for the Special Vehicle Development Committee in March 1942 by Major Wilson, titled “Notes of Tank Steering Gear”.
He identified and described the key differences and efficiency ranges for various methods of steering tanks with the relative advantages and disadvantages of each.
• Differential - 50% of driving force is lost before negative force is applied to the inside track. Where F is Driving Force, and N is Negative Force, the driving force during turn is ½F - N
• Clutch Brake - No drive is lost releasing drive from inside track. Therefore, Driving force is F - N
• Wilson Regenerative - No drive lost releasing drive from inside track. A portion of the negative inside track drive is applied to a positive drive on the outside track. The steering ratio is about 1 to 9, therefore, Driving force is F + 0.9N – N = F – 0.1N
• Modified Differential - Most efficient in higher gear but part of drive power is lost before drive is removed from inside track depending on gear ratio. In differential steering as track speed is doubled drive to outside track is ½F. In Merritt Brown, the increase is approximately 1 to 1.1 and drive is 0.9F. Assuming a ratio of 1 to 1.2 the drive transferred is about 80% of the negative drive. Therefore, Driving force is 0.9F + 0.8N – N = 0.9F – 0.2N
Major Wilson further noted that the lower the gear the Merritt Brown system is used in, then the lower the efficiency and that the Wilson system lost less tractive effort than the Merrit Brown regardless of issues with gear ratios. and that “the loss in tractive effort is always greater in the Merritt Brown than in the Wilson, irrespective of the difference of gear ratios.

CharlieC · Legend

1928 was an important year for Wilson's transmission designs - it was the year the Wilson pre-select gearbox was introduced.

Wilson designed a new steering system for tanks in 1938 - this could have been what he was referring to in the 1942 report.

The epicyclic gear system couldn't be patented (prior art) but Wilson did patent the control system used on the Mark V tank so that the brakes required

by the steering could be controlled by a hand lever and foot pedal alone. (1919 US1324757A). Wilson notes in the patent application that his invention

is useful for systems where steering of heavy tracked vehicles is achieved by differential drive resulting from the use of epicyclic gears. It's notable in the patent

that Wilson's drawings indicate band type brakes - exactly the type used in epicyclic gearboxes.

Charlie

Runflat · Lieutenant-Colonel

I'm not sure if we are talking about gearboxes or steering. For some gen on the epicyclic gearboxes try the Tank Museum's Matilda diaries part 11: www.youtube.com/watch

For some gen on steering, try MAFVA's Tankette 47/1.

CharlieC · Legend

According to David Fletcher's Osprey book on the Mark V the primary gearbox was a 4 forward, independent reverse thing made by Wrigley and intended for railway locomotives with internal combustion engines. The gears could only be changed when the tank was stationary. Steering was accomplished by releasing the band brakes locking the outside ring of

an epicyclic gearbox which was inside the track frame (one each side). I should note that an epicyclic gearbox is in neutral if the sun gear can rotate and the planetary gears and outer ring are unrestrained. If the turn needed to be tightened a brake connected to a foot pedal locked the epicyclic gearbox.

The attached diagram shows the general arrangement of the transmission and steering.

Regards,

Charlie