There is no radioman. The Vanguard had the same layout as the Valentine - a driver up front with a hatch on either side.
It has a two man turret - commander/loader and gunner.
I went off faulty data: actually makes it all worse; driver trapped by Z hatch escape route, TC/gunner trapped by gun recoil safety cage, loader killed when he bails out the side hatch by enemy delousing fire. it equals 100% loss of crew in an "OMG, the tank is on fire." evolution. NTG.
My mileage will vary
British army will do themselves the favor with not designing the 2pdr, and the Treasury will be satisfied.
Vickers QF 2 pounder.
Specifications:
Mass: 814 kg (1,795 lb)
Barrel length overall: 2.08 m (6 ft 10 in) L/52...bore: 2 m (6 ft 7 in) L/50
Crew: 3–5 to serve.
Shell: 40×304 mm. R
Calibre: 40 mm (1.575 in)
Breech: Semi-automatic vertical sliding-block
Recoil: Hydro-spring
Carriage: three-leg platform or tank trunnion
Elevation: -13° to +15°
Traverse: 360°
Rate of fire: 22 rounds per minute (theoretical as aimed shots depended on gunner skill.)
Muzzle velocity: 792 m/s (2,600 ft/s) with AP shot
Effective firing range: 914 m (1,000 yd)
Maximum firing range: 1000 m (1093.6 yd)[3]
Feed system: Breech-loaded
Sights: No.24b
3 pounder: Vickers;
Specifications
Mass: 1,323 lb (600 kg) in total
Barrel length: 8 ft 8 in (2.64 m) bore (50 calibres)
Shell: 47×360mmR 3.3 lb (1.50 kg) shell.
Calibre: 47 mm (1.85 in)
Breech: semi-automatic vertical block
Carriage: three-leg platform
Elevation:-5° to +12°
Traverse: 360°
Rate of fire: 20 rounds per minute (Theoretical depends on the skill of the gunner to lay on target.)
Muzzle velocity: 2,575 ft/s (785 m/s) (HE)
Effective firing range: 2,000 yd (1,829 m)(AA)
Maximum firing range: 5,600 yd (5,100 m) at 12° elevation;15,000 ft (4,600 m) (AA ceiling)
Sights: telescopic
Sources: Wiki.
Performance: (Credit: Anthony Williams)
Source data:
http://www.quarryhs.co.uk/ammotables.htm
Anthony Williams; credit. Work is not mine.
Pick a caliber and see the results.
The 3pdr Vickers is in the warehouses, so it is it's ammo. Or, make a good APC shot to the inter-war 3pdr and it will be killing German tanks in 1940. Or, make an APC shot for the ww1 vinatge 6pdr, it will still be killing German tanks. The better HE performance of the 3pdr, and even better HE performance of the 6pdr is there by default.
Or, use the new 6pdr 10cwt that is in production by mid-1930s.
Prefer a 6 pounder NAVAL gun in production. See below.
This is before we go for tank guns that use ammo of 12lb 12cwt, 13 lb or 18lb guns that is already in the warehouses, that would've make a lot of sense for late 1930s and on.
If you have HEAT and a Foresight guy, the 18 pounder is the gun of choice. Also...
So instead of 40 rounds of 4cm bore diameter Vickers shells in the very cramped Matilda 2 tanks for France 1940, we now have 30 rounds of 4.7cm HOTCHKISS (License fee to make.) shells in Matildas and in the Cruiser Mark 1s and 2s? UK Treasury will not like that one bit.
If you go back to 1919 insist that all future tank designs use a gunner and a loader who cannot be the TC. The Tank Commander can be anywhere in the tank but must not be given a gun or loading a gun to manage his sole job is to command and be the lookout. This leads to a three man turret by default, further insist that all new designs use the 6 pounder 6 cwt or bigger guns this forces a decent size turret ring. Vickers probably has a design for a three inch low velocity smoke and HE firing mountain gun in its commercial catalogue this should be redesigned to fit a bored out 6 pounder breech and barrel.
How big a tank can the British army afford? Those guys are crying in 1935 over 12-14 tonne mass machines for an expeditionary tank. Now if 20 tonnes is the standard, a 5.7cm bore diameter/L50 is the logical weapon, since the can opener is usually rated to the likely armor (4.5 cm glacis) to be faced in corresponding equivalent enemy machines (PZKWIII for example.).
Ask Ricardo to work with a commercial engine company on the design of a new series of engine capable of being built in 2, 4, 6, 8 or 12 cylinder configuration. Air cooled and must have good filtration for Imperial use. The new engine will be suitable for commercial and passenger transport vehicles in the 4 and 6 cylinder configuration. The 8 and 12 cylinder configuration is for tanks, heavy vehicles, boats and airships.
Good luck with that one. British tank engine tech watts/kgs/reliability is fair compared to German but compared to American, Japanese, Italian or Russian is kind of CRAPPY. Filters, trained mechanics, and spare parts; based on historical record is always a big problem for period British armor. Solve those and the tank engines improve enormously and CRAPPY is not a word one should see at all. Human factors and errors is the problem, not the mechanicals.
By dictating the 3 man turret and 6 pounder you force designers to build a big turret ring. The V8 or V12 engine forces a decent size engine bay.
Too much foresight. PoD would suggest incremental improvements on the WWI Liberty with maybe a slide into RR aero engine derived powerplants NET than 1939.
One of the major problems with Crusader was the hull was made so much lower than the previous cruiser designs there wasn't room for internal air intake filters so they got put on the rear track guard just where all the muck and dust is. The cooling system was also cramped and instead of running the cooling fan off the engine crankshaft it was powered by 9 feet of motorcycle chain. The chain wasn't protected from dust so it wore, stretched and slipped result tank engine blows up.
Repeat after me... raise the engine deck 15 cms move the filters under the turret rear and exhaust through the top.
Blueprints: com, modified by McPherson (Chrysler twin-pack 8 cylinder.)
Gun wise - my opinion has been changed by this actual thread
The Czechoslovakian 47mm is the gun of choice
This had a superior AT round to the 2 pounder and had a larger HE shell - and like the BESA was ready!
Basically late 30s British tanks go Czechoslovakian for both gun and MMG (BESA) - and possibly even some Czech armour plate!
Why? Czechoslovakia is tugats (1938) and I would be looking at the USN 5.7cm/L50 (M1899) Driggs-Schroeder and Midvale Unbreakable for the plate.