autogun said:

Bristol on the Hercules for low/medium altitude. The Hurricane would be replaced in production immediately after the BoB by a suitably developed Hercules-powered Bristol Type 153 in two versions: a naval fighter, and a land-based fighter-bomber without the carrier stuff but with extra armour. The other carrier plane would also be by Bristol, and would be a 2/3-seat multipurpose plane with matching controls, engine "power eggs" etc.

As previously mentioned the wright cyclone might be an alternative to the Hercules. As the engine is much more mature so early production could start in time for the first hurricanes so that they always had the engine and reduces the early demand for merlins. Also as noted noted the Soviets did an extraordinary job adapting the engine to make the ASh 82 which was 14 cm smaller in diameter.  

As a bomber, transport and Hurricane engine it would reduce the demand for merlins and serve as the basis for future low level fighter bombers.  It might also serve as a better basis for a more powerful engine like the Napier Sabre. It is a fairly convectional engine with an aluminum block and so be familiar to  R-R and Napier.  Making a British version of the ASh 82 but run on 130 or 150 octane and the same attention the Griffin saw would be an interesting question. 

All just thoughts, but it is a way to sidestep a lot of production bottlenecks in the late 30s. The hurricane is fairly agricultural design anyway so the engine would only improve it's performance in comparison to the lower powered Merlins it actually used. The R2600 is 930ish kgs compared to the 740ish of the merlin but that does not include the cooling system.  Halving demand for the Merlin early and convincing the US to make engines in 1936 could only be a good thing.  From a logistical point of view I find it very appealing,

I don't question the technical advantages of the Wright Cyclone, but this proposal collides head-on with the most basic principle of TFW: "First, do no harm". In 1940, the Hurricane was the most important aircraft in the RAF. In the Battle of Britain there were twice as many Hurricanes as Spitfires, and they shot down twice as many aircraft; the Spitfire's main practical advantage was that its pilots had a higher survival rate (due mainly to the poor location of the Hurricane's fuel tank). So no risk can be taken with the Hurricane; it has to proceed pretty well as it did historically, with its Merlin engine. It was vital to the survival of the RAF and without it, the war might have been over in 1940. So the worst-case scenario would be to redesign the Hurricane to take the Cyclone, then find for some unforeseen technical or political reasons the conversion fails, and converting back to the Merlin again would cost too much time.

On the general political side, it is worth remembering that in the 1930s the USA was strongly isolationist, determined not to get drawn into any new European war, and very unwilling to supply armaments to anyone. In fact, Hitler and the Nazis enjoyed quite a lot of popular support. If it were not for Roosevelt's strong support of the UK, it is hard to predict what might have happened. So, take no risks - stick with the solutions we know will work and be available, even if in theory they are not as good.

AIUI the main reason for fuel tank burns into the cockpit was that the culprit wing root tanks were not sealed off from the fuselage under the cockpit. (The wing structure being open into the fuselage.) The problem being that the draft from the wheel bays right in front of these tanks would force any (burning) leakage into the fuselage quite vigorously. IIRC in VVS service a simple field expedient using a lightweight sheet of ply cut to shape and sealing off this area helped considerably. A properly designed lightweight (alloy?) barrier should do much better.

The design of the Hurricane wing always seemed to me to be good for addition of folding. The transport joint just outboard of the undercarriage being a natural location for inserting a small section of aerofoil containing a side folding (like Fulmar or the Grumman cats) mechanism. The regular outboard wing section could be added on to that. So a bit more span for folding wings.

It also occurred that relocation of the oil tank from the port wing leading edge root into an under engine location like on the Spitfire would result in a slightly simpler and more streamlined under nose profile like the Spitfire and also free up space in the wing leading edge roots for another 30-36 gallons or so of fuel (2x 15-18G) total. (Relocation of the gun camera when fitted in the starboard root would also be required.)

These, to me, seem to be minimal harm improvements to what I agree is probably the most important British fighter in 1939/40. Thinning the wing down a bit would be ideal too, but that is starting to mess with the aerofoil and is not likely an insignificant (harmless) change.

You need firewalls and armour around the pilot on all sides, not just wing tanks?

(As well as self sealing tanks much earlier)

The Hurricane’s construction had made it dangerous in the event of the aircraft catching fire. As there was floor in the cockpit, flames from a burning wing tank could easily penetrate into it through the open space underneath the pilot’s feet. In addition, the gravity fuel tank which collected the fuel from the wing tanks before feeding it into the engine sat in the fuselage right in front of the instrument panel, without any form of protection between it and the pilot. If set on fire, it could sent a jet of flame right in the pilot’s face and body. To make matters even worse, the wooden construction and fabric covering of the rear fuselage meant that fire could spread through the rear fuselage structure quite easily.

Official RAF pilots’ instructions warned that at an altitude of 15,000 feet, cockpit temperature in a fighter suffering fuel fire rose from cool room temperature to 3,000 degrees Centigrade in the space of ten seconds. Even given the limited protection of his flying suit and gloves, the pilot had to get out immediately – or risk not being able to get out at all.

In contrast, fuel tanks of a Spitfire were located in the forward fuselage, protected from the rear and above by armoured plate and by the bulk of the engine from the front. Also, a sealed firewall separated the tank from the cockpit. In statistical terms, the Spitfire’s construction translated into much lower rate of burn injuries on Spitfires than on Hurricanes.

http://spitfiresite.com/2010/08/battle-of-britain-1940-burning-hurricanes.html

One last numberwang post, based on re-skimming the first half of TFW. Incomplete timeline attached if anyone interested. Some numbers that jumped out:

• British have 8 armoured divisions equipped with TFW Crusaders in 1940.
• Germans plan to have 25 armoured divisions fully equipped with TFW Panthers for spring 1941 (though it later appears they have mostly Panzer IIIs?), plus 1000 heavy and 1000 medium bombers and 2000 fighters (mostly FW 187s and 190s).

The numbers seem just possible but the quality does not. E.g. in OTL:

• The British got to this level a lot later and only with significant US tank production. The 36 division army plan pre-Dunkirk required 7,000 tanks and the 55-division plan post-Dunkirk 10,000.* Even on paper these would not be ready until late 1941, and actual production was even less.  I don't think this is something foresight can wave away while respecting historical budget constraints (yes tanks deserve a higher priority but you haven't said what gets a lower - see my previous post on naval tonnage).
• Germans started Barbarossa with 20 armoured divisions (>3000 tanks) that were roughly 2/3 Panzer III/IV and 1/3 older models. The number of aircraft also appears roughly comparable but of older and smaller types (e.g. they kept the Bf 109 until 1945 and it was their most produced fighter because it was cheap). So you're replacing 1-engined planes with 2-engined and 2-engined with 4-, making all the tanks bigger and newer - what are you building less of? (Capital ships for the Germans but I thought those resources were going into U-boats?)

There used to be an idea from the postwar bombing surveys that the Germans were just sitting around with their thumbs up their a***s (economically speaking) until after Stalingrad, but Overy and Tooze have put that to bed (see also this on the aircraft industry). And the British war economy was always considered pretty well run (shadow factories, rationing etc.) even if weapon quality is a different story.

*This looks like about 1000 tanks per armoured division (i.e. several times establishment strength): "In the summer of 1940 Mr. Churchill laid it down that the Army should, to begin with, contain not less than seven armoured divisions, and the programme of August 1940 was based on the assumption that the equivalent of about ten armoured divisions would be formed."  

P.S. not doing this to have a go particularly, just find this stuff fascinating and would like to see a bit more of it in the book. IMHO you mainly need to introduce the newer types in smaller numbers, although the British navy/army tradeoff needs to sacrifice some quantity as well.

Thanks for this - I do need to address those issues in more detail, I think. I have dug out my copies of "Design & Development of Weapons" and "British War Production" for some refresher reading...

dskellogg said:

) having saved-to-pdf many of your articles, including the alternative WW2 gun one on 57mm and 75s, would you still consider this to be the proper direction, or start from scratch altogether (perhaps pushing the 3-pdr/47mm caliber in various service configurations, closer to the aircraft P-gun in performance but years earlier

47mm 3pdr vickers is an option?

In production till 1936, it would be perfect as a "balanced" gun for tanks and a good size for an AT gun. It can use the heavy HE that Mr Williams suggest. A 3 pound AP and 4 1/2 pound HE.

The 47mm could be used as the Bofors round? Much more streamlined than separate 40mm and 57mm Bofors? 

The old pom-pom can be recycled as powered twins, and forget about 20mm peashooters!

You can skip the 57mm and pussy 75mm and head straight for a 15 pounder 77mm Comet tank. Fix the vertical armour and have a good all round 35 ton in 1943. It too can have Mr Williams heavy HE, a 22 pound smasher.

By 1944, have the Centurion with a 20 pounder with 30 pound HE, and HESH. 

Each Armored division have a heavy tank battalion, like the post war Ivan's T-10. 

hobbes154 said:

Can you afford a much bigger armoured force while building a similar naval tonnage to OTL (even if recycling 15-inch turrets and copying the Ark Royal makes the BB and CV builds quicker, that actually increases the demand for steel for the hulls in the short run)? Also if you are building faster turbine-powered corvettes to counter the electroboats (instead of the OTL reciprocating engines), what turbine-powered ships are you building less of (the gearing for turbines was a production bottleneck)?

No, the 4 mount design would have come out longer and heavier with less protection than the 3 mount design. Speed wouldnt have changed I believe as the longer finer waterline would counter the greater weight. The extra 60 feet of length iirc would have cost 2 inches of deck armour (to counteract the high up weight of C mount and the aft director which would need to be 2 decks higher than in the 14" ship) and a shallower torpedo defence, also the 5.25 battery would have had to be mounted closer together and a deck lower to counter blast from C mount. The only way to get the same protection in the 4 mount was to break the Washington treaty big time and that wasnt politically or economically possible when the design was sealed in 1936.

So you need more than 35,000 tons, more like 41,000 to 45,000 tons of Hood or Vanguard, and an extra six months of construction and 1000s of tons of steel. 

Spearthrower said:

47mm 3pdr vickers is an option? In production till 1936, it would be perfect as a "balanced" gun for tanks and a good size for an AT gun. It can use the heavy HE that Mr Williams suggest. A 3 pound AP and 4 1/2 pound HE. The 47mm could be used as the Bofors round? Much more streamlined than separate 40mm and 57mm Bofors?  The old pom-pom can be recycled as powered twins, and forget about 20mm peashooters!

From the point of view of Don, the planning would be to keep the tanks and their armament effective, maintaining an edge over the OTL German Pz III and IV as they evolve, but not excessively so otherwise that would just encourage the Germans to accelerate their development of heavy tanks, thereby making all of the earlier ones obsolete. That would be undesirable, as it would disrupt tank manufacture in the UK.

The 40mm Bofors is definitely one of the "untouchables" given its significance in OTL, so using the same ammo for the first generation of AT and AFV guns is an obvious rationalisation. The 57mm Bofors is a "nice to have" rather than a "must have", but the same applies.

The 20mm Oerlikon remained a significant weapon throughout the war, until the Japanese kamikaze tactic was adopted.

Spearthrower said:

hobbes154 said: Can you afford a much bigger armoured force while building a similar naval tonnage to OTL (even if recycling 15-inch turrets and copying the Ark Royal makes the BB and CV builds quicker, that actually increases the demand for steel for the hulls in the short run)? Also if you are building faster turbine-powered corvettes to counter the electroboats (instead of the OTL reciprocating engines), what turbine-powered ships are you building less of (the gearing for turbines was a production bottleneck)?

No, the 4 mount design would have come out longer and heavier with less protection than the 3 mount design. Speed wouldnt have changed I believe as the longer finer waterline would counter the greater weight. The extra 60 feet of length iirc would have cost 2 inches of deck armour (to counteract the high up weight of C mount and the aft director which would need to be 2 decks higher than in the 14" ship) and a shallower torpedo defence, also the 5.25 battery would have had to be mounted closer together and a deck lower to counter blast from C mount. The only way to get the same protection in the 4 mount was to break the Washington treaty big time and that wasnt politically or economically possible when the design was sealed in 1936. So you need more than 35,000 tons, more like 41,000 to 45,000 tons of Hood or Vanguard, and an extra six months of construction and 1000s of tons of steel. 

The first point to bear in mind is that the much earlier MAC ships and carriers (including smaller ones based on cruiser hulls) is a huge "force multiplier". Having aircraft constantly patrolling over convoys was proved to be so effective in OTL that hardly any ships were lost when so protected, compared with the carnage without air cover. So fewer escorts would be needed, and they could mainly be deployed as "hunter/killer" groups. This would of course be countered by the improved performance of the electroboats, but the general principle of aircraft doing the "spotting" would still apply.

Similarly, the high demand for RN cruisers (they wanted 70) had a lot to do with the need to patrol sea lanes to keep the merchant ships safe from surface commerce raiders. But a small force concentrated around a cruiser-hulled carrier with recce and strike planes would be able to protect a vastly greater sea area with fewer ships. 

As far as the battleships are concerned, ones with only six 15" guns would be unacceptable - OK for a couple of fast battlecruisers, but not as a replacement for battleships. Given that the major threats to battleships turned out to be torpedoes, followed by bombs, the main belt was actually the least significant aspect of protection. Building-in the ability to absorb punishment and cope with it, eg through more of a focus on a combination of compartmentation and protected pumps for each compartment, would be of more value and allow weight economies to be made in the vertical armour.