If the RAF had been defeated in the Battle of Britain (1 Viewer)

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I don't think it did.

The cannon barrel ran through the Vee in the engine. In the Merlin and V-1710 that space was occupied by the intake manifolds, and the rear blocked off by the supercharger.

If either the Merlin or V-1710 had been designed around a motor cannon, it is doubtful that the propeller shaft position would have needed to changed much.

In each case, the prop shaft is roughly centre of the frontal area of the engine.
 

Strength was added to the Spitfire wing for the VII/VIII and the XIV. So about 1942/43.
 

Times of flight from a German test at sea level by way of Anthony Williams and Emmanuel Gustin's book "Flying Guns of WW II."

round...............MV............V/300m............time/300m.................V/600m..................time 600m
7.92 Ap............810.............538..................0.453.........................348...........................1.159
13mmHEI........750.............501..................0.49...........................337...........................1.22
20mm Mine.....695.............432..................0.551.........................281...........................1.428
20mm 117g.....720.............552..................0.477.........................422............................1.101

Velocities are in meters/sec, time is in seconds. 20mm mine shell is from an MG FF/M, the 117gram HET round is from an MG 151, when fired from an MGFF/M MV was 585M/S. At 300 meters and under there isn't that much to choose, especially at higher altitudes in thinner air. somewhere short of 600meters things get weird.
Please note that all bullets fall at the same speed. They fall 16 feet in the first second of flight (and are falling at 32ftper second at the end of the first second). they travel different distances in the second though
It's the second second (really) that makes the big difference as the bullet will fall 48 feet in that second (staring at 32fs and ending at 64fps).

the MG FF fired a 134 gram projectile at 600m/s and should hold it's velocity fairly well as it has a lot of weight per unit of frontal area, even if not well shaped. The German mine shell had poor shape and poor weight per unit of frontal area.
 
Shortround6 said:
Unless you mistyped Spitfire MK.IX there is not a chance on the face of the earth of this happening without large quantities of fairy dust or magic reindeer towing the radial engine fighter.
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Well, I'll admit that my idea requires rewriting a bit of history. Reshuffling the deck chairs on the eve of the BoB wouldn't change much. Take this all for a grain of salt, because the further you diverge from the historical timeline, the more fantastical all this speculation becomes. That said...

The idea here is that Germany licenses the R1820 sometime in the mid 1930s and pours most of its development resources into this single engine family. There are three key technologies they need to figure out before the BoB. The most important is fully understanding the radial engine's torsional and linear vibration characteristics. AFAIK, the pendulum damper was internationally understood by the 1920s and patented by Wright in the early 1930s. Adding 2x and 4.5x pendulum dampers to the crankshaft gets them 80% of the way there. The other two key technologies are the two-speed supercharger drivetrain and roller follower/rocker valve train.

Yes, they would be ahead of the curve, but they need to be to win and it's plausible that they would given be the development resources allocated. The net result is a 1200hp engine running 40" MP at 2700rpm on 87 octane. I believe these numbers are conservative considering the G200 variant was producing 1200hp @ 2500rpm on 91 octane. I estimate the engine to have a high speed blower critical altitude of ~15,000ft producing 1050hp.

Please note that a P-36 with a two row radial had 22% more drag than than a P-40 long nose.
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The P-36 Hawk is deficient in power to weight ratio, wing loading and zero lift drag.

A single row radial engine does have more drag than an inline, but it is lighter (fully installed) and has less depth. I think if we play to the radial engine's strengths, we can compensate for its defects. The primary strategy is to maximize power to weight ratio and reduce wetted drag area.

Conceptually, this aircraft would most closely approximate the shape of the Polikarpov I-16. The firewall is located directly on the spar with the engine mount long enough just to clear the engine accessories. The intake and oil cooler are fed between the cylinders following Grumman FM-2 practice. The accessory section is inverted, allowing fuel gravity feed. Attached to the spar is a wing just large enough to have a loading of ~40psf at normal weight. Wing planform is trapezoidal, 0.75 taper ratio, uniform t/c ~13%, aspect ratio a bit over 5. Small wing means short tail. The landing gear is kept light by inverting the Spitfire arrangement, having it retract inwards behind the spar, like a simplified Sea Fury. Like everything else, main/tail gear retraction is manually operated by a ratcheting lever to pilots left. Split flaps operated similar.

Behind the firewall sit two self-sealing fuel tanks, one above the other. The top is shallow and extends further aft to the instrument panel, over the pilot's legs. The other has less depth and sits in front of the rudder pedals. Combined fuel ~90 gallons. Behind the fuel tanks and above the landing gear sits the pilot, whose cockpit slightly bulges upwards to afford ~6 degrees view over the nose. Simple blown canopy resembling the Me163 sits at wing trailing edge, turtle-deck extending aft to tail. Minimal seat back armor affording .30 protection only.

To each side of pilot are belt-fed synchronized HS.404 cannon (assuming German license/development, if not use equivalent) with barrels extending forward between engine cylinders. Manually charged via foot-operated lever on each side. ~200 rounds of ammunition for each stowed below pilot behind landing gear.

10ft, 3 blade hydraulic constant speed, lightweight wooden-blade propeller. Engine nacelle curves inwards on sides perpendicular to top wing surface at a rate slightly beyond attached flow, somewhat similar to SU-26 practice. Flat, straight fuselage sides from wing maximum thickness to trailing edge. Three exhaust stubs / variable outlet on each nacelle somewhat like a simplified Sea Fury. Oil cooler exhausts upstream inside nacelle.

Maximum weight <5000lbs. Wetted area ~50% of a Grumman FM-2. Still in conceptual design stage. Basic weight/performance analysis suggests plausibility. Germany needs lighter radios...
 

It's hard to tell, so you may be right. I tried dimensioning out a motor cannon on a V1710 once and and I remember the propeller sitting a bit high after putting in a 50mm blast tube. I may not have pushed the tube as close to the cylinder liner as the db601? I think the effect is more pronounced on the Hispano Suiza 12Y owing to its larger stroke/bore ratio... but that too may be an optical illusion.

Regardless, the propeller shaft doesn't sit perfectly in the center of any of the major V12 engines. It clearly sits low on the DB601. Notice the upper left-hand image how the propeller shaft doesn't bisect the vertical dimension line. Some other day, it might be interesting to compare thrust lines between the Spitfire and BF-109.




I was using the velocities for the MG FF cannon (585m/s) as I'm under the impression the E3 was the most common variant during the BoB. Since I don't have any better technical data, I threw some best guess weights/BCs in a ballistic computer and calculated ~1ft difference in drop at 250yd. Not huge, but appreciable for an aircraft size target.

KiwiBiggles said:
I believe the HS.404 wasn't capable of being synchronized.
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It wasn't belt-fed in 1940 either. I'm hoping the German's are smart.
 
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Nice theory, falls down a little in practice.

Wright eventually got the R-1820 to 2800rpm, at some point in the late 40s. they did hit 2700rpm around late 1942 or early 1943.

trouble is it required an entirely new engine that just kept the bore and stroke of the R-1820 G200.

Wright did this trick to a greater or lesser extent 3-4 times during the "development" of the R-1820.

The older engines used a forged aluminium crankcase, the G100s used a forged steel crankcase, the G-200s used a brand new forged steel crankcase.
The number and size of the cooling fins changed with every model. This can be a real hiccup to your plans. The H versions used forged cylinder heads and sheet metal fins rolled into groves machined into the steel cylinder barrels. They also used 20 studs on each cylinder compared to the 16 used on the Fs and Gs (really old cyclones use 12 studs per cylinder)
Using roller followers on the cam rings was pretty standard practice.

as was using a roller on the valve stem.
Wright was one of the first engine makers to offer 2 speed superchargers. Trouble is that most Radial engine makers used the two speed feature to improve low altitude power. They actually didn't have much choice. Most people's superchargers in the 1930s weren't very good. The one on the RR Merlin was as good as there was in actual service and that is before Hooker took over. everybody else was in 2nd or 3rdplace.

Radials have trouble with high RPM because you are running 7 or 9 cylinders on one crank throw and that is a lot of metal flying around. stress loads go up with the square of the speed. 200rpm doesn't sound like much but it is a 16% increase in stress loads gong form 2500rpm to 2700rpm.
Please note that that on the FM-2 WIldcats the difference between the the 1300hp Cyclone on the first ones and the 1350hp Cyclones on the later ones was a new crankshaft. not a tweak on the carb or a twist on the boost control.

They were using new manufacturing techniques on these engines (1940 Allison's used plain steel crankshafts, by 1942 they used the same steel alloy but they were shot peened and nitrided for a tremendous increase in both strength and fatigue life).

An R-1820 running at 2700rpm has a piston speed of 3,093fpm. There was one engine running at that piston speed in 1939/40. The Bristol Pegasus and it wasn't running the pressure in the cylinders that you need.


You better give up on the Hispanos, they were never synchronized by anybody ever. They are also heavy and the ammo is heavy. two guns with 200pg weigh around 540lbs. And there were no production belt feeds in 1940 for them, those came later.
 
Germans were working on the MG 151 at least as early as 1938, went into service (not operational trials) in small numbers in the fall/winter of 1940, increasing in the spring/summer of 1941.
Building aircraft guns that worked took almost as long as making aircraft engines.
 

One foot is actually negligible. Please remember that the machine guns and cannon could be adjusted for elevation and a common impact point at the desired combat range would be used. Please note that a 300mph aircraft is moving at 440fps or moving 44ft in 1/10 of second. unless you are sitting exactly on the targets 6 you need to figure out where the target plane is going to be at some point in the future (deflection shooting) at which point high velocity/short time of flight becomes much more important than 1 foot of trajectory height.
 
Using two engines instead of one in a country that was always strapped for engine supplies is never good in the numbers game. Replacing established types with new technologies close to a campaign is going to affect your serviceability rates on two grounds, availability of spares and teething problems in bedding down the new technology. a FW187 introduced say in early 1940 is not going to be a reliable platform from which to fight a difficult campaign.

Moreover up to 70% of losses suffered by aircraft are due to non-combat related causes. You lose your aircaft for reasons unrelated to enemy actions and unrelated to aircraft performance. Far more losses are due to technology failures, like engine problems, or human error.

I am unconvinced that the FW187 offered any kind of panacea to the problems faced by the LW in 1940.
 


wuzak said:
In each case, the prop shaft is roughly centre of the frontal area of the engine.
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InlineRanger said:
My point was that the inverted engine, motor cannon and landing gear geometry individually compromised the design.
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Just to be pedantic, the first Bf 109 to be fitted with the motor cannon to be put into production was the Bf 109F - there were no production Emils fitted with the motor cannon. The Emil was designed for it, but contrary to many publications having included such a detail, none were so fitted that went to war in the summer of 1940.

I am unconvinced that the FW187 offered any kind of panacea to the problems faced by the LW in 1940.
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Correct; it wasn't their aeroplanes that let the Germans down in the Battle of Britain and changing them won't make a lick of difference to the outcome, not if they don't change their strategy and tactics.

Here's the one thing I always ask the Fw 187 guys; if Fw are building 187s, what is the LW not receiving that it did traditionally? Fw 190s? Highly likely, so the Butcher Bird, being the terrific aeroplane it was would have been much later to the party, if at all, given the development of the 187 and let's face it, (sigh, here we go again) if the Fw 187 was as good as everyone says it was going to be, do its supporters really believe that the British would have sat back and done nothing? The Spitfire IX was created out of a hasty need to redress the losses suffered in 1941 at the hands of Bf 109Fs and eventually Fw 190s, so if the Fw 187 was to sweep all before it away in 1940, would the British really sit on their hands? Not likely. We could have expected to have seen Merlin and Griffon development accelerate to have met any advanced threat.

Nad here's the big thing, as Steve pointed out, the LW didn't want it, so how could it have made such a difference? The Fw 190 was the right choice of fighter; it was a brilliant design, but it was too late for the BoB.
 
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The most common cannon during the BoB was the MG FFM, that fired the Mine shell at 700 m/s. The MG 17 fired the SmK projectie at 755 m/s.
Bf 109 have had far smaller wings, the torsion applied to the spar will be smaller than what is applied with a big wing.




Landing gear for the Bf 109 was a carry-over from the Bf 108 Taifun. Plus it allowed for lighter wing. The legs of the U/C that are close to fuselage allow for shorter legs, not longer.

I don't understand what you mean.
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I mean that going with Wright Cyclone and it's derivatives would've decrease performance of German fighters from 1938-41, while increasing the fuel consumption per mile travelled. Own goal, or self-inflicted wound.

InlineRanger said:
It wasn't belt-fed in 1940 either. I'm hoping the German's are smart.
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Germans were smart, but some things are easier to engineer than others.
They can buy a license for the .50 Browning in the 1930s and scale it up for 20mm - can be syncronised, it is belt fed. Or steal/copy the Soviet ShVAK.
 
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Typically

One need only examine the French fighters of the era: upright V-12, cannon mounted between the cylinder banks. The Hispano 12Y and 12Z were largely designed around the gun installation
 
parsifal said:
Using two engines instead of one in a country that was always strapped for engine supplies is never good in the numbers game.

I am unconvinced that the FW187 offered any kind of panacea to the problems faced by the LW in 1940.
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to go with your post.

A large part of the Luftwaffe troubles is that they simply didn't have enough of any type of aircraft, or putting it another way, they didn't have enough aircraft in total, to get the job done. Substituting one type for another was not going to change the total numbers and as Parsifal says, substituting at twin for a single is going to make things worse.

People often talk about P-40s in the BoB for the British. Flip it, give the Germans P-40s. Since they were just a P-36 with a new engine there is no secret technology. There is nothing the Germans couldn't build or substitute, and yet they could have fighter with six 7.9 machine guns (two in the cowl and two in each wing) and around 540 liters of internal fuel plus a drop tank and it would be faster than 109 with the same engine. Wouldn't climb well though and would have a lower ceiling than the 109.
It can penetrate further in England but over all, would it have really changed things if 60% (to be conservative) were lost due to take-off and landing accidents, other engine failures or bad navigation?
 
Me 109 pilots who had flown the Spitfire thought the 109 had better visibility forward. They sat further forward (didn't have a fuel tank in front), could see over the wing better. The inverted arrangement of the engine meant the pilot was looking over a relatively narrow crankcase rather than a wide V. They were both crap really.

Me 109 had 5 wing spars. The big one with the big bolts that held the wing to the fuselage that could be called the main spar detoured around the undercarriage. I imagine that it was formed in a single pressing operation, at least on the Me 109F onwards which was adapted to true mass production and automation rather than small family sub contractor supplied components.. Torsional rigidity of the wing was never an issue on the Me 109. Ailerons lost effectiveness due to compressibility increasing control forces on the ailerons, deflection was limited by the pilots strength.. Regarding the Spitfire: After replacing fabric covered ailerons to improve the issue on the Spitfire was twisting of the wing at high speeds. It was dealt with by a new stiffer wing in F.22 Spitfires which also received balance or servo tabs on the ailerons. MK XVIII Spitfires used stainless steel spars and stringers for added strength and stiffness but otherwise had the "old" wing.

The Me 109F and G received Friese ailerons to reduce aileron forces. This clearly wasn't enough as speeds grew. On the Me 109 there were attempts to install spring tab servo ailerons, apparently successfully on WNF built Me 109G6s. The occupying allies, including American forces confiscated all private cameras from German households so no one had a camera to document anything including in the aircraft wrecks post war. The NACA developed something called geared servo spring tabs that limited the tendency for over deflection at high speed due to low force feed back.

The proper way to do this is hydraulic boost of the ailerons, something which made late war P38s among the fastest rolling aircraft of WW2. The only German aircraft that I'm aware of using these are Do 335. Rumors of Ju 290 and even He 162. In many cases these turn out to be servo tabs not hydraulics.

Back to the Me 109. It was a fast rolling aircraft at low to medium speeds. At high speeds it did roll, the speed depend on pilot strength. In the BoB period the Me 109 had the roll advantage.

The forearms of Me 109 pilots never look wussy.

Dietmars Book mentions the Fw 187 had spring tabs on the early prototypes.

These Me 109 tabs look like balance or geared tabs.
 
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While what you say is true it is also true that the engines (jumo 210, perhaps the 211 and certainly the DB 600 series) were all designed to have a gun firing through the prop hub from the start. Gun development faltered. Badly.
The Germans had tried a 20mm gun through the prop on an He 112 in Spain (let alone on the proving grounds) but being related to the Flak 30 AA gun, while powerful, it was large heavy and slow firing, not a good combination for air to air combat. They also tried using a 3rd MG 17 through the prop hub as a substitute on some early Jumo powered 109s but the gun didn't like the heat of the location and jammed more often than the cowl guns, this was to be a re-occuring theme until the 109Fs, experimental aircraft with guns firing through the prop hub suffered an unacceptable number of jams/malfunctions. This failure of the prop hub gun quickly lead to a gun bay being put in each wing for a MG 17 so the firepower could go to four 7.9mgs.
The intention to use a prop hub gun was always there.

I don't like the term motor cannon even though the Germans used it. I don't really like the term prop hub gun either. The French and Russians actually bolted the gun to the engine and so are more correctly motor cannon. The Germans mounted the gun to the fuselage and just had the barrel sticking into the tube with no actual connection. You could remove the engine and leave the gun (of whatever type) behind.




This is harder to predict as in the late 30s and 1940 the Germans had everybody building everybody else's designs. A bit of an exaggeration but Fiesler built about 90 109Bs and 80 109c/ds which is more than the Augsburg factory did. Focke-Wulfe built 123 109C/Ds and Arado built 144, there were other companies/factories involved in 109 production before the DB engines showed up. I believe there were a number of sources for the He 111?
 
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