This is my normal repost for this subject
A better Valentine.
Sir John Carden doesn't die in that 1935 crash, but lives.
In the test to determine a good engine for the cruiser program, the Napier Lion W-12 was tested, but not accepted, as it could not run on the low Pool Petrol of 63 octane reliably, while the Liberty V-12 could.
Sir John was not impressed with the new A.12 Infantry Tank specification that the Royal Arsenal was working on in 1936, and knew he could do a tank with nearly the same armor, but better designed and more mobile, based on his A.10, the better armored version of his A.9 Tank entering production that year.
So Vickers has a tank in 1938 as a private Venture, and updated to be a combined Cruiser and Infantry tank, all in one chassis, a 'Heavy' Cruiser 70mm armor basis on the front, 60mm sides and 25mph speed, back to what the A.9 had.
This would take more power than the 150HP 588 cubic inch AEC 'Comet' bus engine. Sir John heard from Colonel Martel at the War Office who was unable to get permission to get 600 surplus Lions from the RAF for £500. Vickers has no such financial or political limits, and acquires them
Sir John use the Lion, detuned to run on 70 Octane (as the US Army decided on in 1939 for all vehicles) It gets 400HP, and that engine is still in production at Napier for Marine uses, so has availability, but needed the rear deck had to be slightly raised and angled differently to house it and the relocated fuel tanks. Napier is contracted for making parts so the 'Sea Lion' could be used in Tanks, at a slightly higher HP rating, 500HP for later production
A Three man turret was adapted from the A.10, so the Commander could do his job unimpeded, while the gunner and loader could deal with their job
of fighting the 2 pdr or 3" howitzer, while having much thicker armor. It used an electric motor for traverse, mount balanced for the gunner to quickly adjust elevation by shoulder rest, as was demanded by the Royal Armoured Corps doctrine.
Was thought to allow better target following while on the move, think of it as Mark 0 Gun Stabilization. Had big downside, the gun had to be perfectly balanced. This meant an internal gun mantlet, that reduced the size of cannon that could be carried. The Sherman, as did most tanks, had an external mantlet and the guns trunnions located close over the turret ring itself for balance. This was balanced enough to allow easy turret rotation, even when the tank was on an elevation/slope.
BTW, OTL Valentine had a ring diameter of 1466mm , actually bigger than the T34/76 with 1420mm, so main gun has room to grow a little bit, and more than a bit, if the UK gets rid of the idea of gunners elevating the gun by it resting on his shoulder: free elevation.
The completed tank is 21 tons. It is 1938, and in trials against the A.12 built by Vulcan is found to be nearly as good protection wise, but twice the speed, but 4 tons lighter. Best of all, Vickers could build cheaper than Vulcan, and in larger quantities, if needed. It was easier to build by riveting, with few complex castings.
Some downsides were that the tracks were unreliable, with a number of pins sheared in operation, and the drivers preferred the Wilson gearbox on the A.12. It was decided by Sir John to switch from the 5 speed Meadows 'crash' gearbox to the preselector 6 speed Wilson gearbox, despite its complexity, and improving the tracks.
When War breaks out, Vickers has completed 110 Valentine tanks, while Vulcan has completed less than a dozen A.12.
Vickers could make 10 a week, and Sir John was sure that production could be raised to over 40 per week, once some of his associated facilities had orders.
