Assessing the Dornier 335’s capabilities as a fighter

[Shortround6]

I like the Fw-190 just fine. I don't like the BMW801 engine.

The whole point of an early Do-335 is to achieve superior performance using readily available DB601/605 engines. Dornier has experience with tandem engine aircraft going back to WWI. So why not let them enter a tandem engine heavy fighter to compete for the zerstorer role?

The Zerstorer role may have required a the standard long range radio which required a separate radio operator. In 1939-40 the Germans didn't have any reliable engine mounted guns and the only synchronized gun they had was the MG 17. With only MG 17s available for cowl/wing root positions the plane would have been rather lightly armed. Mounting MG/ffs in the wing would have limited them to 60 rounds apiece without development of a larger drum. The 110 used the radio operator as a loader to change drums on the fuselage mounted 20mm MG/FFs.

 

[davebender]

In 1939-40 the Germans didn't have any reliable engine mounted guns

That's a matter of financial priority.

Bismarck Information
KM Bismarck cost 197 million marks during 1936. Divert 10% of that amount into aircraft cannon R&D and Luftwaffe fighter aircraft will all be armed with the MG151/20 cannon by 1940. Perhaps the MG213 revolver cannon will even enter service before the end of the war.

 

[Shortround6]

That's a matter of financial priority.

Bismarck Information
KM Bismarck cost 197 million marks during 1936. Divert 10% of that amount into aircraft cannon R&D and Luftwaffe fighter aircraft will all be armed with the MG151/20 cannon by 1940. Perhaps the MG213 revolver cannon will even enter service before the end of the war.

And if the US had simply shortened the chamber of the 20mm Hispano cannon made in the US to match the British specifications the US could have had fighter planes armed with reliable batteries of four 20mm cannon in 1943.

It is not always just money, it seemed to take 4-6 years for just about any nation to develop a new aircraft gun. Making a truck load of prototypes instead of 2 or 3 doesn't speed things up if there is a fundamental flaw in the original design, you just have truck load of very expensive junk. You can't make production tooling until the design is finalized. Well you can but please look at the number of tanks and aircraft that were ordered "off the drawing board". How many were successful? How many were a disaster? how many were mediocre?

 

[davebender]

And if the US had simply shortened the chamber of the 20mm Hispano cannon made in the US to match the British specifications the US could have had fighter planes armed with reliable batteries of four 20mm cannon in 1943

It's a matter of design experience. Germany was mass producing a 20mm aircraft cannon in 1916. by 1936 they have 20 years experience. Long enough to have a bunch of engineers familiar with designing 20mm aircraft cannon.

When did the USA produce their first 20mm aircraft cannon? Fixing the 20mm Hispano cannon may have been a simple thing but not if you have no engineers familiar with such things.

 

[riacrato]

I don't think in this case it matters that much if the gun's a cannon or a heavy mg. Chamber is chamber. And the US had vast experience with heavy mgs and their ammunition.

I think the point Shortround is making is that r&d is no simple equation. You can't substitute x years with y million dollars. Not to mention that under wartime conditions, monetary comparisons are futile. Building a Bismarck costs steel and labour. Developing a cannon requires labour, but of a completely different kind.

 

[Shortround6]

It's a matter of design experience. Germany was mass producing a 20mm aircraft cannon in 1916. by 1936 they have 20 years experience. Long enough to have a bunch of engineers familiar with designing 20mm aircraft cannon.

When did the USA produce their first 20mm aircraft cannon? Fixing the 20mm Hispano cannon may have been a simple thing but not if you have no engineers familiar with such things.

OK, what was the mass produced 20mm cannon in 1916? the Becker?

You might want to check the MG 204 and the MG C/30L for some examples of German 20mm guns that didn't work so well.

The point about the Hispano was that the British had ALREADY fixed it. Just use the existing British drawings, no research, no development, no money spent, no engineers needed.

You not only want new aircraft designs but new guns to go with them, new radios and who knows what else to get your proposals to work.

 

[davebender]

Was it acceptable to U.S. methods of mass production? We spent a lot of design effort on the RR Merliin engine and Bofors 40mm cannon before they could be produced in American factories.

A similiar re-design effort failed when the U.S. attempted to copy the German MG-42 machinegun. A weapon that worked just fine in the original German version.

 

[Shortround6]

Was it acceptable to U.S. methods of mass production? We spent a lot of design effort on the RR Merliin engine and Bofors 40mm cannon before they could be produced in American factories.

A similiar re-design effort failed when the U.S. attempted to copy the German MG-42 machinegun. A weapon that worked just fine in the original German version.

Just how does shortening the chamber length make the entire gun different to produce by mass production? You just don't run the reamer in all the way or you use a slightly shorter reamer.

Just what did we do the Merlin engine to make it producible in American factories? Just about ALL major parts were interchangeable with the British built engines. We may have used different manufacturing techniques to build the parts but that is not quite the same as modifying the parts.
By the way, some American factories used different manufacturing techniques to build American engines than the parent factory did. It depended on the expertise of the particular company/factory involved.

Speaking of expertise, that was part of the problem with the American effort to copy the MG-42. The company involved had never built a gun a before. As the story goes, they forgot (failed to understand) that the American 30-06 case was 6mm longer than the German 8mm case and failed to make the ejection slot big enough. Machine guns don't work very well if the empty cases can't get out of the gun. By the time the goof was caught not enough time was left to the war to make adopting a new gun worthwhile.

 

[davebender]

Just what did we do the Merlin engine to make it producible in American factories?
Packard V-1650 - Wikipedia, the free encyclopedia

The initial Packard modifications were done on this engine by changing the main bearings from a copper lead alloy to a silver lead combination and featured indium plating. This had been developed by General Motors' Pontiac Division to prevent corrosion which was possible with lubricating oils that were used at that time. The bearing coating also improved break-in and load-carrying ability of the surface. British engineering staff assigned to Packard were astonished[citation needed] at the suggestion but after tear-down inspections on rigidly tested engines were convinced the new design offered a decided improvement.

The real improvement Packard incorporated into the Merlin was adopting the Wright supercharger drive quill. This modification was designated the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51. The two speed, two stage supercharger section of the -3 featured two separate impellers on the same shaft which were normally driven through a gear train at a ratio of 6.391:1. A hydraulic gear change arrangement of oil operated clutches could be engaged by an electric solenoid to increase this ratio to 8.095:1 in high speed blower position. The high speed gear ratio of the impellers was not as great as the ratio used in the Allison but speed of the impeller alone was not the factor that increased the engine performance at altitude.[clarification needed] The double staging of the compressed fuel/air mixture provided the boost pressure through a diffuser to the intake manifolds which increased the critical altitude of the power plant.

The ability of the supercharger to maintain a sea level atmosphere in the induction system to the cylinders allowed the Packard Merlin to develop 1,210 horsepower (900 kW) at 25,800 feet (7,900 m). The two stage impeller created extreme heating of the fuel/air mixture during the compression process and in order to prevent detonation of the compressed charge, it was necessary to cool the mixture prior to entry into the cylinders. This cooling was accomplished by the casting of an intercooler passage into the wheelcase housing between the first and second stage impellers.

Ethylene glycol coolant was circulated by a pump through this passage to carry off the excess heat generated by the impellers. Without the intercooler the temperature of the charge could be as high as 400 °F (204 °C). The intercooler in itself was not adequate to deal with the high temperature and an additional cooling fin and tube core was placed between the outlet of the blower and the induction manifold to the cylinders. This radiator was known as an aftercooler and served as a reservoir for the system.[clarification needed] The glycol mixture used for the supercharger cooling was independent of the main engine cooling system and used a centrifugal pump driven by the engine to circulate the coolant through an aircraft radiator system at a rate of 30 gallons[clarification needed] per minute.

This combined system reduced the charge temperature to suitable levels. The throttle valves in the updraft carburettor throat were controlled by an automatic boost control through the pilot's linkage to maintain the selected manifold pressure during changes in altitude. These valves were only partially open during ground and low level operation to prevent overboosting of the engine. As air density decreased with an increase in altitude, the throttle valves were moved to an open position by boost pressure corresponding to aircraft altitude. This system provided full power within engine boost limitations up to the critical altitude of 26,000 feet (7,900 m). This was the improvement Packard brought to the Merlin

 

[parsifal]

In the overall scheme of things this is not a major redesign of the merlin engine. They used different bearing and a different supercharger. This is not a big deal...they did not have to change the engine geometry, the crank, the pistons, the ignition timing even.....have done similar modification to car engines myself in a previous life.....

 

[Glider]

I cant think of the Do335 w/o the Shinden jumping to mind...

They had similar numbers.. from what I read, the Do 335 was faster but the Shinden had a higher ceiling..

which was a better climber?

For some reason I hadn't realised what a big aircraft the 335 was. That soldier looks tiny by comparison

 

[davebender]

In the overall scheme of things this is not a major redesign of the merlin engine.

It depends on how you define "major". The Japanese copy of the DB601 engine (Ha-40) failed because of problems manufacturing reliable crankshaft bearings. Most nations except Britain and Germany appear to have had serious problems with aircraft engine supercharger systems.

Packard got both of these items right when they copied the RR Merlin engine. IMO that's a noteworthy achievement.

 

[Shortround6]

Just what did we do the Merlin engine to make it producible in American factories?
Packard V-1650 - Wikipedia, the free encyclopedia

Packard used different bearings and a different supercharger drive system, nothing there about different manufacturing techniques is there? and using a different bearing material, while an improvement, isn't really HAVING to adopt different manufacturing techniques is it?

The last three paragraphs have nothing to do with any differences between American Merlins and British Merlins and the second paragraph aside from the first sentence could equally be describing a British 60 series Merlin.

Packard was the first to manufacture a separate cylinder head Merlin but the engineering had already been done, Packard was just in a better position to incorporate the change without a disruption in manufacturing/delivery schedules.

 

[davebender]

The romance of engines - Google Books

Here is the information on the Ha-40 engine problems. I miss-spoke concerning the reason for Ha-40 engine failure. Apparently the Japanese had difficulty heat treating the engine crankshaft. This caused excessive wear within 100 running hours.

Packard had a well deserved reputation for building high quality engines. Their copy of the RR Merlin was as good or better then the original. It's a good thing they weren't located in Japan or the Pacific skies might have been full of Ki-61s powered by reliable DB601 engine clones. 8)

 

[drgondog]

OK, what was the mass produced 20mm cannon in 1916? the Becker?

You might want to check the MG 204 and the MG C/30L for some examples of German 20mm guns that didn't work so well.

The point about the Hispano was that the British had ALREADY fixed it. Just use the existing British drawings, no research, no development, no money spent, no engineers needed.

You not only want new aircraft designs but new guns to go with them, new radios and who knows what else to get your proposals to work.

Dead on Shortround - IIRC the RAF had to scrap a lot of 20mm ammo we sent them, in addition to the problem that our 20mm had headspace problems that they kept telling us about.

I wonder if Adm King was the prob on our side?

 

[drgondog]

Packard used different bearings and a different supercharger drive system, nothing there about different manufacturing techniques is there? and using a different bearing material, while an improvement, isn't really HAVING to adopt different manufacturing techniques is it?

The last three paragraphs have nothing to do with any differences between American Merlins and British Merlins and the second paragraph aside from the first sentence could equally be describing a British 60 series Merlin.

Packard was the first to manufacture a separate cylinder head Merlin but the engineering had already been done, Packard was just in a better position to incorporate the change without a disruption in manufacturing/delivery schedules.

NAA did have to go outside to also fix the radiator core oxidation issues with the new Packard Design IIRC