Sten SMG aircraft: productionized aircraft part 2, the what if

[Shortround6]

While the XP=51F/G may have been a bit lighter they weren't really much cheaper. Which was the point of many of the light or Jockey fighters.

Saving a few hundreds pounds of aluminum out of a 6-7000lb airplane is not really that big a savings as the aluminum the airframe is about the cheapest stuff in the airplane on per pound basis. Which cost more,
75lbs of aluminum airframe structure?
75lbs of radio?
75lbs of gun/s?
75lbs of landing gear struts?

and so on.

 

[tomo pauk]

There was also the Italian SAI 207 and 403. The 403 (aside from light armament) might have been formidable, but the 207 wasn't popular. It was fast, but poorly armed, had a slow climb rate, and had durability problems.

The Plane
was streamlined (although view from the cockpit?) and used a 149sq ft wing so you could get speed, or at least get close.
The Problem was you had a 750hp engine and in 1942-43 the other guys were using 1400-1500hp engines (Spitfires, Boosted P-40s, 109Gs) and the SAI 207 didn't weigh 1/2 as much.

Thing with the SAI light fighters was such that Italian aero industry was supposed to be making similar fighters in 1939, not in 1942. We can debate on how much these fighters could be considered as 'light' vs. a lot of 'continental' European fighters, but they are surely light an small when compared with Spitfire, let alone when compared with Hurricane.
By 1941, Italians might've switched to the HS 12Y-45, -49 or -51 engines on these fighters - not because these were great, but because weight of installation will be conductive to the re-engining job; again not much of a lightweight when compared with current Bf 109 or Soviet fighters, but far lighter than Fw 190, Typhoon, current Spitfires, let alone the American stuff.

Alternative engines for the 2nd half of 1930s l-w fighters might include:
- small or short-stroke 9-cyl engine (eg. Mercury, later with an improved S/C; short-stroke R-1820 that became R-1600 to 1650; short-stroke Bramo 323 or BMW 132)
- V8 liquid cooled engine, 25+- L

 

[Shortround6]

By 1941, Italians might've switched to the HS 12Y-45, -49 or -51 engines on these fighters - not because these were great, but because weight of installation will be conductive to the re-engining job; again not much of a lightweight when compared with current Bf 109 or Soviet fighters, but far lighter than Fw 190, Typhoon, current Spitfires, let alone the American stuff.

The Isotta engine was about 1100lbs or maybe about 50lbs heavier the HS Y engines (depending on variant), granted you have to count the coolant weight. But the cooling system is going to be close to 300lbs (?) so that is 2lb/sq/ft right there. More or same fuel?
At what point does just expanding production on what you are already making turn out better?

Alternative engines for the 2nd half of 1930s l-w fighters might include:
- small or short-stroke 9-cyl engine (eg. Mercury, later with an improved S/C; short-stroke R-1820 that became R-1600 to 1650; short-stroke Bramo 323 or BMW 132)
- V8 liquid cooled engine, 25+- L

A Mercury is only short stroke compared to the Pegasus.
The R-1820 used a 175mm stroke, the Mercury used a 165mm stroke and the Pegasus used a 190mm stoke. the Bramo 323 used a 160mm stroke.
How much weight do you save and how much streaming do you gain vs how much power do you loose?
water cooled V-8 does not sound like a good idea. You want to go to a 90 degree V for better vibration. Yes the crankcase and crankshaft are shorter. Each power pulse (explosion in the cylinder) is going to be bigger which means more stress which means more strength=weight.
There were valid reasons why Jumo, RR, and HS built smaller V-12s rather than try to cut down big V-12s to medium V-8s. Bolting an engine into a 20-30 ton tank is different than bolting it into a 3 ton airplane when it comes to vibration.

 

[tomo pauk]

The Isotta engine was about 1100lbs or maybe about 50lbs heavier the HS Y engines (depending on variant), granted you have to count the coolant weight. But the cooling system is going to be close to 300lbs (?) so that is 2lb/sq/ft right there. More or same fuel?
At what point does just expanding production on what you are already making turn out better?

Italians have hard time in the 'just expending production' department (especially Regianne was appalling in that regard).
A small drop tank should more that cover for the needs of the more thirstier engine once installed.

water cooled V-8 does not sound like a good idea. You want to go to a 90 degree V for better vibration. Yes the crankcase and crankshaft are shorter. Each power pulse (explosion in the cylinder) is going to be bigger which means more stress which means more strength=weight.
There were valid reasons why Jumo, RR, and HS built smaller V-12s rather than try to cut down big V-12s to medium V-8s. Bolting an engine into a 20-30 ton tank is different than bolting it into a 3 ton airplane when it comes to vibration.

Yes, the V8 needs to be 90 deg between the cyl banks. Water-cooled B8s rule

A Mercury is only short stroke compared to the Pegasus.
The R-1820 used a 175mm stroke, the Mercury used a 165mm stroke and the Pegasus used a 190mm stoke. the Bramo 323 used a 160mm stroke.
How much weight do you save and how much streaming do you gain vs how much power do you loose?

Not much of the weight is saved (10-15 kg max? for the bare engine? same for the cowling?), some streamlining is gained due to the smaller frontal area, some mileage is also gained. Mercury was down by about 5% of power vs. same generation of Pegasus on 87 oct, less on 100 oct.

 

[BarnOwlLover]

A possible "what if" is the Ta-154, since it was made mostly out of wood to try and conserve aluminum (Germany was even more up the creek without a paddle in regards to sourcing high quality aluminum than say Britain was). Of course, it and other similar projects didn't take off because of the Tego Film factory getting bombed and never being rebuilt.

The Germans also looked at the SAI 403, but also didn't go any further with it.

 

[BarnOwlLover]

I mentioned this in the other such thread, but what about using other materials (wood, steel, etc) to try and build an aircraft, even if an evolution of an existing design, to save on aluminum, even though for the most part the aluminum parts of the airframe tended to be the lesser expensive items to make?

 

[Shortround6]

Here is a partial weight breakdown for the Spitfire I (wooden prop, no protection)

Structure.....................................................pounds
Wings..........................................................820
Engine cowl................................................86
Engine mount............................................58
Fuselage & Fin........................................426
Tailplane & Elevator................................58
Rudder.........................................................18
Tail wheel....................................................28
Wheels & Brakes.....................................90
Chassis & retracting gear..................192
Controls......................................................91
Accommodations....................................23
Total Structure......................................1890

Power plant...........................................2,035

Load carried...........................................1585

Sundries un accounted for.................335
Stressing allowance................................ 30

Total weight...........................................5875

Now there are some things that take a bit of doing in order to substitute either steel or wood or ???????????????
The rudder only weighs 18lbs and that includes fabric covering. Perhaps you can change to steel or wood without too much weight gain (and might be handy for CG adjustment when you change the prop) but you are not going to save much aluminum. You also either have to decide to change all or none or you wind up with different part numbers and different hinges, etc.
You do have to be careful as to the CG as to what you put where. Having to add 50-100lbs of ballast to correct the CG is certainly possible (Spitfires used all kinds of counterweight to balance the different engines, props and other changes).
Then you have to balance weight vs the strength of the substitute parts. This is where using a few hundred pounds of wood in a bomber is no big deal Wooden floors/walkways or even wooden fuselage panels. that don't carry much or any stress/loads.
The trouble with wood is that for it's weight, it is not as strong as aluminum. You can make wooden spars but unless you are building very light planes the spars will be heaver for the same load. They will also be much bulkier (less room for fuel). A lot of times aircraft materials have to be strong in several directions at the same time. This is one reason for the fabric covering used on early planes or control surfaces. If you tried to use aluminum of the same weight per sq ft the aluminum would be strong only in two directions, but not resistant to dents or forces perpendicular to the flat surface. And once the thin aluminum dented or wrinkled it's strength is gone.
Once you start building planes to withstand high G loads you need more strength per pound of structure.

Mosquitos were stress to a light load than single seat fighters. Mosquitos used fuselage skins that were many times that of metal plane. Think cardboard mailing tube vs thin sheet metal tube.

There may have been planes that were built out of alterative materials to aluminum for heavy duty use (fighters, bombers, heavy transports) but just about all of them had disappoint perforce. Perhaps sometimes the Designers tried to be too clever. "I can use the same engines as a DC-3 and because that is an old design and I an smarter I can get it haul more stuff!" Didn't work. If you want to use alternative you have to give up some performance. Performance can include load carried.
The Ki-106 had it's armament reduced to just two 20mm cannon in an attempt to restore performance.

This is with hindsight, I do have the advantage of tracing all of the aircraft that tried to use alternative materials and failed. The designers of WW II who were trying did not have the catalogue of failures at hand to reference.

 

[tomo pauk]

I mentioned this in the other such thread, but what about using other materials (wood, steel, etc) to try and build an aircraft, even if an evolution of an existing design, to save on aluminum, even though for the most part the aluminum parts of the airframe tended to be the lesser expensive items to make?

A fast-produced aircraft should be the one with light alloy parts in the biggest percentage? Talk Bf 109 or Il-2.

 

[z42]

The trouble with wood is that for it's weight, it is not as strong as aluminum. You can make wooden spars but unless you are building very light planes the spars will be heaver for the same load.

I don't think you can make any spars + fabric design that would be competitive with an otherwise equivalent stressed skin construction, whether you make the spars from wood or aluminum or steel tube.

Once you start building planes to withstand high G loads you need more strength per pound of structure.

That too, and also when speeds increase the aerodynamic loads start to increase, meaning you need thicker and heavier fabric and tighter frame spacing.

Mosquitos used fuselage skins that were many times that of metal plane. Think cardboard mailing tube vs thin sheet metal tube.

Of course. Not only is wood less dense than metal of equivalent strength, but the Mosquito was also more towards the monocoque end of the spectrum than the more typical stressed skin construction of metal planes of the day, so more of the loads were taken up by the skin.

Mosquito is arguably a good example of what would be needed to make a competitive aircraft using wood. Not spars + fabric, but (semi-)monocoque construction with thin veneers glued in different fiber directions. In a way it has more in common with modern composite construction than traditional wood construction, just using wood fibers rather than glass or carbon.

 

[Shortround6]

Drawing of Lagg-3 wing.

The spars are heavy and bulky, on the later La aircraft and on the later Yak's they were able to both save weight on the structure and increase the size of the fuel tanks when they switched to metal spars.
You can build planes out of wood, but expecting them to be fully the equal of metal planes is unrealistic.
Wooden planes are better than no planes but you have to give up something or several somethings. If you want speed and climb you may have to give up range and armament for example.

 

[tomo pauk]

A possible "what if" is the Ta-154, since it was made mostly out of wood to try and conserve aluminum (Germany was even more up the creek without a paddle in regards to sourcing high quality aluminum than say Britain was). Of course, it and other similar projects didn't take off because of the Tego Film factory getting bombed and never being rebuilt.

Germans have had severe problems with many things, one of them was mis-allocation of materials. They were using light alloys on tranports like Ju 52 and trainers like the Ar 96 (thousands of each were manufactured before 1945), while dabbling in wooden combat aircraft like the Ta 154.
Just make anything that-is-not-a-combat-aircraft in steel, wood and canvas, while reserving light alloys got the combat aircraft.

The Germans also looked at the SAI 403, but also didn't go any further with it.

Germans have probably had the option to emulate the SAI light fighters years earlier with the basic He 100 design that is devoid of the fancy cooling system and uses 2nd tier engines. Granted, Italians were also with possibility o make a light monoplane fighter with the I-F Delta engine already by late 1930s, not when it was too late.

Fictional He 100 with the Delta engine:



For the Soviets, Germans, Italians and British, I'd reiterate the scenario where the 90 deg V8 siblings of the big V12s are manufactured; say, manufacturers of the liquid-cooled engines want to compete with 9 cyl radials power- and price-vise.

 

[Shortround6]

Fictional He 100 with the Delta engine:

For the Soviets, Germans, Italians and British, I'd reiterate the scenario where the 90 deg V8 siblings of the big V12s are manufactured; say, manufacturers of the liquid-cooled engines want to compete with 9 cyl radials power- and price-vise.

Trouble is the I-F Delta engine was 750hp at 4,000 meters. So you have less than 70% of the power.
The engine is light (510Kg?) but it is large, over 10cm wider. It is has around 18% more frontal area, granted it doesn't have a radiator.

You could just keep the Jumo 210 in production
680hp at 4200 meters?
Use the time between 1938 and 1940 to figure out how run the Jumo 210 a few hundred rpm faster?

The big V-8 doesn't work well. Unless you switch to 90 degree V angle you wind up with vibration problems. You have 2/3rds the power with equal or greater frontal area and you do not save 1/3 of the weight. Maybe close but not the full 1/3. You also get 4 power impulses per revolution of the crankshaft instead of 6 with also has vibration problems.

Commercial aircraft are quite happy with 9 cylinder Radials as they don't have liquid cooling systems to deal with. Wright Cyclones vibrate a bit but they are light, reliable and offer about as much power for take-off as the V-12s, dropping to the V-8 means under 800hp in 1939 and that is not going to get many takers.

We are back to the "cheap" fighter which always going to be a looser. If you cut the engine to V-8 you still have the cost of the supercharger and the gearbox and the other stuff. close to 2/3rds but not quite. Instruments and radio are going to cost the same and so on. You are not going to get a 2/3rds cost fighter. maybe 75-80% if you are lucky but then it won't do what the full fighter will do.

 

[tomo pauk]

Trouble is the I-F Delta engine was 750hp at 4,000 meters. So you have less than 70% of the power.
The engine is light (510Kg?) but it is large, over 10cm wider. It is has around 18% more frontal area, granted it doesn't have a radiator.

You could just keep the Jumo 210 in production
680hp at 4200 meters?
Use the time between 1938 and 1940 to figure out how run the Jumo 210 a few hundred rpm faster?

RR made a much better job with Peregrine, than what Jumo did with the 210 (even when we have the 10% displacement deficit in mind), so there was a lot of headroom left to the 210 IMO. Not just better RPM, but also the better supercharger might be needed ( that was - inefficient as it was - still served as the pattern to the Jumo 211s before the F version).
Granted, every extra manhour in improving the 210 is a manhour less in tweaking the 211.

I'd use the time between early 1939 and late 1939 to figure out how to install the HS 12Y on the He 100, if the DB 601s can't be had for it.

IIRC Italians were toying with the idea of a supercharged sibling of the Fiat A.30, that came to naught due to the switch from the liquid-cooled engines towards the radial engines. At 24L and 2900 RPM, and a decent S/C, there is an Peregrine equivalent with a bit of luck by late 1930s for them? Not just the power surplus vs. the Delta - and vs. the A.74, plus less drag - but also a few years earlier.

The big V-8 doesn't work well. Unless you switch to 90 degree V angle you wind up with vibration problems. You have 2/3rds the power with equal or greater frontal area and you do not save 1/3 of the weight. Maybe close but not the full 1/3. You also get 4 power impulses per revolution of the crankshaft instead of 6 with also has vibration problems.

I've noted that 90 deg is needed.

We are back to the "cheap" fighter which always going to be a looser. If you cut the engine to V-8 you still have the cost of the supercharger and the gearbox and the other stuff. close to 2/3rds but not quite. Instruments and radio are going to cost the same and so on. You are not going to get a 2/3rds cost fighter. maybe 75-80% if you are lucky but then it won't do what the full fighter will do.

Thread is about the fighters of high 'producibility'.
Engine can save just so much, both in weight and price, and some engines can save manufacturing time (thus no big suggestion by me of 2-row radials - they make sense for the USA - let alone the multibank engines, or sleeve-valve engines). A smaller and/or lighter engine allows for a smaller airframe, that means reduced weight and drag, as well as smaller number of parts (both bigger, like ribs and formers) as well as small (rivets, mostly), again improving the time required for manufacture of the fighters required. Not every fighter needs to be as big & draggy as Hurricane.
(yes, if the Italians are their old selves, the fighter still gets manufactured very slowly with a forest of small bits and pieces to make a single rib)
A captured engine is a boon, reduces not just the cost, but also the time required for production.

Small fighter, at least in continental European parlance in the 2nd half of 1930s, was required to carry a pair of LMGs, or a pair of HMGs, or one cannon + two LMGs, or two light cannons + two LMGs, and it was done with 60-80% of the Merlin III power. So it is not outrageous what I've suggested above.
Problem with historical designs was lack of producibility (MS.405-406, Italian fighters), outdated layout (many times open cockpit, fixed U/C, even biplanes were produced), low power of radial engines coupled with inefficient/draggy engines' installation. 1st problem = not suitable for the requirements of this thread by default, 2nd and 3rd problem = performance was far lower than what a fighter of modern appearance can offer on similar or same power.

 

[Shortround6]

Thread is about the fighters of high 'producibility'.
Engine can save just so much, both in weight and price, and some engines can save manufacturing time (thus no big suggestion by me of 2-row radials - they make sense for the USA - let alone the multibank engines, or sleeve-valve engines). A smaller and/or lighter engine allows for a smaller airframe, that means reduced weight and drag, as well as smaller number of parts (both bigger, like ribs and formers) as well as small (rivets, mostly), again improving the time required for manufacture of the fighters required. Not every fighter needs to be as big & draggy as Hurricane.

If you want the speed/performance of the Hurricane and you want to use that boat oar propeller and you want the armament of a Hurricane and you want to use the size air fields the British used you are going to windup with something between the Spitfire and Hurricane if you are designing the thing in 1934-35.

109 was designed to use 1/4 of the guns and maybe 1/3 of the ammo? And didn't go as fast as the Hurricane. This changed with the 1938 engine but such is progress.

I'd use the time between early 1939 and late 1939 to figure out how to install the HS 12Y on the He 100

The HS 12Y should have been carted off to the coast and been offered as boat anchors to French Fishermen.
The 12Y dates back to at least 1928 and the 12N, how much was common to an even older engine with dry cylinder bores and a 140mm bore I don't know. Adding a supercharger and a few modifications to the 12N gave you the 12Y in 1932. At some point you have design new production tooling and start producing a new engine and not keep doing the least amount to the old engines to stay near the front. The H-S engines had a good run but at over 12 years by the time 1940 came around they were out of date. The advent of 100 octane fuel and higher bmep and higher rotational speeds meant the end of the HS engines. Now this should have been seen in the very late 30s. Without a substantial overhaul the 12Y was about to hit the wall.

1st problem = not suitable for the requirements of this thread by default, 2nd and 3rd problem = performance was far lower than what a fighter of modern appearance can offer on similar or same power.

If you want high performance you not only need a good engine but you need the manufacturing infrastructure to go with it. Most (all?) British airframe manufacturers did not build their own landing gear, well maybe DH with the rubber springing on the Mosquito. They did not build their own retract mechanisms. They did not build their own brakes, or hydraulic systems for flaps. If they used electric motors for such things they bought the electric motors from outside suppliers.

This only has a small bearing on the ability of a design team to design such systems. The problem is manufacturing such systems in quantity. Even quantities of a few score and not hundreds.
Maybe the "sten gun" fighter can make do with had crank undercarriage retraction, or small, manually operated flaps. Or perhaps other stuff can be left out.
The Gladiator carried 786lbs of military load. That includes the Pilot, flying suit and parachute. It also included guns/ammo, fuel/oil, instruments radio and a few other bits.
This was for a plane that weighed 4646lbs. with 3 blade fixed pitch prop.

You can use smaller engines, you may decide to use few guns or smaller guns. You cannot shrink the pilots by much or the volume they take up in the aircraft (Spits and 109s were close to the minimum) and starting to leave out instruments ? (the Soviets did, flying through cloud was lot more dangerous) and some countries didn't think radios were really necessary. But then you need to train more pilots.

 

[z42]

For the Soviets, Germans, Italians and British, I'd reiterate the scenario where the 90 deg V8 siblings of the big V12s are manufactured; say, manufacturers of the liquid-cooled engines want to compete with 9 cyl radials power- and price-vise.

I have tried, and failed, to figure out if there's some general trend in price (or man-hours to produce) of a liquid cooled inline vs. a radial of roughly equal power. For German engines it seems the Jumo and DB engines were considerably cheaper than the BMW 801 (around 30k RM vs. 45-60kRM), but that's a single example that doesn't prove a general trend. It's of course difficult to do in general due to differences between companies and countries.

I would imagine the engine block itself of an inline would be cheaper to produce and assemble, assuming it's of a monoblock style construction. Only a few castings for the major parts of the engine. OTOH the valve gear with 4V/cyl is probably more expensive, and you need the cooling system and radiator. For a radial I'd imagine the cylinder barrels with their cooling fins could be pretty complicated and time consuming to manufacture.

 

[SaparotRob]

If you want the speed/performance of the Hurricane and you want to use that boat oar propeller and you want the armament of a Hurricane and you want to use the size air fields the British used you are going to windup with something between the Spitfire and Hurricane if you are designing the thing in 1934-35.

109 was designed to use 1/4 of the guns and maybe 1/3 of the ammo? And didn't go as fast as the Hurricane. This changed with the 1938 engine but such is progress.

The HS 12Y should have been carted off to the coast and been offered as boat anchors to French Fishermen.
The 12Y dates back to at least 1928 and the 12N, how much was common to an even older engine with dry cylinder bores and a 140mm bore I don't know. Adding a supercharger and a few modifications to the 12N gave you the 12Y in 1932. At some point you have design new production tooling and start producing a new engine and not keep doing the least amount to the old engines to stay near the front. The H-S engines had a good run but at over 12 years by the time 1940 came around they were out of date. The advent of 100 octane fuel and higher bmep and higher rotational speeds meant the end of the HS engines. Now this should have been seen in the very late 30s. Without a substantial overhaul the 12Y was about to hit the wall.

If you want high performance you not only need a good engine but you need the manufacturing infrastructure to go with it. Most (all?) British airframe manufacturers did not build their own landing gear, well maybe DH with the rubber springing on the Mosquito. They did not build their own retract mechanisms. They did not build their own brakes, or hydraulic systems for flaps. If they used electric motors for such things they bought the electric motors from outside suppliers.

This only has a small bearing on the ability of a design team to design such systems. The problem is manufacturing such systems in quantity. Even quantities of a few score and not hundreds.
Maybe the "sten gun" fighter can make do with had crank undercarriage retraction, or small, manually operated flaps. Or perhaps other stuff can be left out.
The Gladiator carried 786lbs of military load. That includes the Pilot, flying suit and parachute. It also included guns/ammo, fuel/oil, instruments radio and a few other bits.
This was for a plane that weighed 4646lbs. with 3 blade fixed pitch prop.

You can use smaller engines, you may decide to use few guns or smaller guns. You cannot shrink the pilots by much or the volume they take up in the aircraft (Spits and 109s were close to the minimum) and starting to leave out instruments ? (the Soviets did, flying through cloud was lot more dangerous) and some countries didn't think radios were really necessary. But then you need to train more pilots.

…boat anchors…

 

[z42]

I've noted that 90 deg is needed.

Yes. Which means a considerably wider engine than a V-12 of equivalent power. It probably needs more displacement too than the equivalent power V-12, to the extent the MPS is a limit, the V-12 with its smaller cylinders can rev higher. I don't think going down to a V-8 is attractive for the engine sizes we're talking about. Maybe if you're doing an engine smaller than 12L (1L/cyl in a V-12 configuration) the V-8 could be attractive; at that point the width of the plane maybe starts to be dictated by the cockpit rather than the engine? But at that point we're talking about a trainer and not a frontline fighter anyway.

Maybe instead think how to go about reducing the cost of a V-12? 2V/cyl instead of 4V? Cheaper and heavier construction? Monoblock constructions seems like an obvious thing to do, but most newer inline engines in that era were already going that way so maybe not a particular advantage for the cheap version.

Thread is about the fighters of high 'producibility'.

I think the history of air combat shows that if you can't afford a large number of good fighters, it's better to have a smaller number of good fighters rather than a large number of mediocre fighters. So I think a more fruitful approach would be to see what you can do to reduce the manufacturing cost of a good fighter. E.g. forget elliptical wings.

The Mustang is probably a good example of this. Despite being on the of the very best fighters of the war, it was explicitly designed also for manufacturing efficiency, leading it to be relatively cheap.

 

[tomo pauk]

If you want the speed/performance of the Hurricane and you want to use that boat oar propeller and you want the armament of a Hurricane and you want to use the size air fields the British used you are going to windup with something between the Spitfire and Hurricane if you are designing the thing in 1934-35.

Not everything is about the RAF

The HS 12Y should have been carted off to the coast and been offered as boat anchors to French Fishermen.
The 12Y dates back to at least 1928 and the 12N, how much was common to an even older engine with dry cylinder bores and a 140mm bore I don't know. Adding a supercharger and a few modifications to the 12N gave you the 12Y in 1932. At some point you have design new production tooling and start producing a new engine and not keep doing the least amount to the old engines to stay near the front. The H-S engines had a good run but at over 12 years by the time 1940 came around they were out of date. The advent of 100 octane fuel and higher bmep and higher rotational speeds meant the end of the HS engines. Now this should have been seen in the very late 30s. Without a substantial overhaul the 12Y was about to hit the wall.

I don't see an easy way for the Germans to send the Czech production HS 12Ys to the French fishermen.

If you want high performance you not only need a good engine but you need the manufacturing infrastructure to go with it. Most (all?) British airframe manufacturers did not build their own landing gear, well maybe DH with the rubber springing on the Mosquito. They did not build their own retract mechanisms. They did not build their own brakes, or hydraulic systems for flaps. If they used electric motors for such things they bought the electric motors from outside suppliers.

Soviets managed to manufacture more than 10000 (ten thousand) of retractable U/C sets just for the needs of the I-16 production, so let's not make a mountain out of the anthill.

This only has a small bearing on the ability of a design team to design such systems. The problem is manufacturing such systems in quantity. Even quantities of a few score and not hundreds.
Maybe the "sten gun" fighter can make do with had crank undercarriage retraction, or small, manually operated flaps. Or perhaps other stuff can be left out.

The F4F soldiered through the ww2 with the U/C that was operated by hand crank, so this is a good start until the mechanized system is produced.

 

[tomo pauk]

I have tried, and failed, to figure out if there's some general trend in price (or man-hours to produce) of a liquid cooled inline vs. a radial of roughly equal power. For German engines it seems the Jumo and DB engines were considerably cheaper than the BMW 801 (around 30k RM vs. 45-60kRM), but that's a single example that doesn't prove a general trend. It's of course difficult to do in general due to differences between companies and countries.

Here is what the Americans were paying:

 

[Shortround6]

Not everything is about the RAF

No but you said nothing everything had to be the size of a Hurricane. There was a reason the Hurricane was as large as it was. Because of the poor choice of propeller it had a rather similar take-off and landing performance as the Gladiator.
So somethings depend on requirements other than speed-climb-armament.
Another air force may well have specified a constant speed prop to begin with and been happy with a 75mph stalling speed and used a smaller wing to begin with.

I don't see an easy way for the Germans to send the Czech production HS 12Ys to the French fishermen.

Trains
The Czechs were building a 1934 version of the Hispano engine. The big question is how many engines per month were they producing. If you average the 568 Avia 534 fighters over 3 1/2 years and add 25% spares you get about 17 engines a month. Plus whatever else they stuck them in.
Next question is what the engine factory doing after they stopped making H-S engines? sitting vacant or building something else.

Soviets managed to manufacture more than 10000 (ten thousand) of retractable U/C sets just for the needs of the I-16 production, so let's not make a mountain out of the anthill.

It is not such an anthill. The Soviets planned to build all those landing gears, perhaps they should have designed a new aircraft instead of build late model I-16s.
The Problem is adding hundreds or thousands of landing gear sets to the ones they were already producing for the existing Soviet aircraft.
The landing gear for Lagg's, Migs and Yak's may have been a bit bigger but did they cost in proportion to the weight of the plane or were the bigger struts cheaper per pound of weight? You need more material but is the machining time that much longer?

A lot of parts don't scale that well on a cost per pound basis unless you really design the plane to be easy to build, which a lot of them weren't.