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But this is not how a DIESEL operates. And I was referring to the V-2, which was a diesel with four exhaust valves per cylinder operated by two separate camshafts. But of course you knew that. You know everything. You know me so very well. Thank you for the lecture and condescension.
And where is YOUR evidence? You are obviously not interested in whatever I might have to say, so any further involvement on my part is fruitless. I am sorry I wrote to such eminent authorities in my attempt to contribute to a dialogue. I will not try it againI don't think that anyone went ad hominem against you. Trouble might be that you've provided next to no evidence to prove numerous points you've made, despite repeatedly being challenged to do so.
And where is YOUR evidence? You are obviously not interested in whatever I might have to say, so any further involvement on my part is fruitless. I am sorry I wrote to such eminent authorities in my attempt to contribute to a dialogue. I will not try it again
And where is YOUR evidence?
You are obviously not interested in whatever I might have to say, so any further involvement on my part is fruitless. I am sorry I wrote to such eminent authorities in my attempt to contribute to a dialogue. I will not try it again
This has gotten rather far afield. To go back to the OP's question, I think we need to see some data (not anecdotes or little quips from fighter pilots) about the actual value of through-hub vs synchronized vs wing mounted weapons. I suspect that it doesn't exist, and almost certainly doesn't exist in any meaningful form.
The questions these data should answer are:
If these data don't exist -- as I said, I suspect that they do not -- we can argue until pigs naturally evolve flight and won't have an answer.
- How much did through-hub weapons compromise engine, propeller, gearbox, and cowling design? An extreme case is the P-39. How much loss of engine and aircraft performance resulted from, for example, the location of the supercharger and inlet and exhaust plumbing for the engine? How did they effect c/g travel as ammunition was expended? Did they impair forward visibility by pushing cockpit location back or increasing cowling bulk?
- Were through-hub weapons significantly more accurate at normal combat ranges? If so, how do you quantify that? Would it take 20 rounds fired for a through-hub cannon to destroy an aircraft vs 40 with wing mounted guns? Could that difference be reduced or eliminated by training and sight design?
Why do I think the data don't exist? Simple: the air forces that used through-hub weapons had already determined they were superior and were not going to revisit that assumption., and those that did not had already determined that the through-hub weapons were not superior or at least not enough superior to wing-mounted guns to be worth the design compromises in engine, propeller, gearbox, and cowling to be worth the bother.
Simple: the air forces that used through-hub weapons had already determined they were superior and were not going to revisit that assumption., and those that did not had already determined that the through-hub weapons were not superior or at least not enough superior to wing-mounted guns to be worth the design compromises in engine, propeller, gearbox, and cowling to be worth the bother.
A lot of the automatic cannon of the 20s and 30s could NOT be synchronized which rather ruled out any sort of single fuselage mount that fired through the propeller disc.
You either figured out a way to shoot through the prop hub or resorted to something like this.
My understanding of hub cannon centers on four attributes: increased rate of fire due to no synchronizing, increased accuracy due to cannon being attached to the engine and fuselage, decreased impact on roll rate, no limitations on wing design and landing gear design. As WWII went on, the Luftwaffe's need for a 30 mm cannon became pronounced and none could be synchronized. Roll rate versus an extra 30 mm cannon is just one trade off.
Overall, it seems countries just used what they had and continued the theme. The Bf109 with its skinny little wings was happier with the big gun in the fuselage. The Russians seemed to like enhanced roll rate as they commonly stripped wing guns out of the P-39.
I'm not sure that there were any 'bad' compromises with regard to the engine, prop, or gearbox. Cowling and exhaust plumbing were same as with 'classic' V12 engines, bar the P-39 as specific case.
The main disadvantage of putting the blower on the side to allow for the prop-cannon, was not envisaged by Germany when the RLM drew up the guidelines in
something like 1930 (sadly I have never found the original document, only refereces to it). This was that if one wishes later to have a two-stage
supercharger, the packaging suddenly gets a lot more unpleasant than something like a Merlin-60. This is because you either double-stack
the blowers which is VERY difficult to then fit into something like a 109 without it poking right out into the airstream, OR you fit one
blower on each side of the engine, which then leaves you with a real birdsnest of ducts to put in. The idea of a 2-stage supercharger being
a likely service requirement in 1930 was probably not on the minds of most people - although it was not far fetched either.
Later, Germany certainly placed a great deal of store in considering gun "weave" in firing, and at least during the war produced a very lengthy report on
improving aerodynamic stability of fighters purely for the purpose of keeping the guns on target. I have this report in English as it was translated by
the R.A.E. in 1946. Its mostly full of maths, but has some practical conclusions scattered about. Directional stability of the 109 seems to have been
a bit less than pilots found comfortable so it says.
This was that if one wishes later to have a two-stage
supercharger, the packaging suddenly gets a lot more unpleasant than something like a Merlin-60. This is because you either double-stack
the blowers which is VERY difficult to then fit into something like a 109 without it poking right out into the airstream, OR you fit one
blower on each side of the engine, which then leaves you with a real birdsnest of ducts to put in.
Later, Germany certainly placed a great deal of store in considering gun "weave" in firing, and at least during the war produced a very lengthy report on
improving aerodynamic stability of fighters purely for the purpose of keeping the guns on target. I have this report in English as it was translated by
the R.A.E. in 1946. Its mostly full of maths, but has some practical conclusions scattered about. Directional stability of the 109 seems to have been
a bit less than pilots found comfortable so it says.
Jumo 213E had three-speed, two-stage supercharger, poking nastily to the right hand side airstream.
I think I have read pretty much all the German and Finnish 109 pilots bios there are. There was much to complain about the Bf109. But directional stability was not among them.
Possibly they did not read the RAE math.
Hey guys,
For anyone who is interested, modelwiz is correct in his statement:
"And BTW, when the exhaust valves open the pressure differential between the burnt fuel air mixture and outside air also create what you would call a vacuum as the piston moves upward in the exhaust stroke. In all kinds of internal combustion engines."
modelwiz used the words "as the piston moves upward in the exhaust stroke" instead of 'during the exhaust stroke' which may have contributed to a misunderstanding, but what he meant is correct.
The main disadvantage of putting the blower on the side to allow for the prop-cannon, was not envisaged by Germany when the RLM drew up the guidelines in
something like 1930 (sadly I have never found the original document, only refereces to it). This was that if one wishes later to have a two-stage
supercharger, the packaging suddenly gets a lot more unpleasant than something like a Merlin-60. This is because you either double-stack
the blowers which is VERY difficult to then fit into something like a 109 without it poking right out into the airstream, OR you fit one
blower on each side of the engine, which then leaves you with a real birdsnest of ducts to put in. The idea of a 2-stage supercharger being
a likely service requirement in 1930 was probably not on the minds of most people - although it was not far fetched either.
...