KI-84 with P&W R-2800
- Thread starter spicmart
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What version? What supercharger set-up?
(a topic better suited for the other sub-forum, IMO)
- Thread starter
- #4
Propulsion of F8F-1 and -2.
Shortround6
Lieutenant General
They used different engines.
The F8F-1 used a -34 engine which was a C series with two speed supercharger.
The F8F-2 used a -32 engine which was an E series engine with a new impeller and housing and a variable speed supercharger drive. Engine was about 300-400lbs heaver than the -34 engine. Most power ratings for the -32 are for 115/145 fuel and that is without water injection.
All of this assumes that Ki-84 can get at least the 130 grade fuel.
Climbing performance would've been far greater than with the Homare, despite the R-2800 being heavier and larger, but to about 5-6 km?. Speed might be better under 5 km, and similar to perhaps 6, and the original being faster above that because there power surplus is now gone, also the climb is better for the legacy Hayate. That is for the case the engine from the -1 is installed.
The engine from the -2 is the E-series R-2800s, and has a much better supercharger. With that, we'd see the performance improvement at all altitudes, and especially above 3-4 km.
- Thread starter
- #7
How would they be compared to the respective Bearcats in flight performance?
- Thread starter
- #9
The La-5 was tested with the heftly M-71 engine. The Bf 109 fuselage was used as part of the Me 209 fighter, mounting the heavy DB 603. Both the 109 and la-5 started out with the engines that were lighter still, the M-105 and Jumo 210.
Spitfire took the 2-stage Griffon. DB-7 took the hefty R-2600.
tl;dr - probably yes
Installing a heavier but shorter radial engine instead of a lighter but longer V12 does not require a radical change to the airframe, as the center of gravity can be maintained. However, installing the same radial engine, only much heavier, without radically redesigning the airframe is unlikely to be possible. In addition, a more powerful engine may require a propeller with a larger diameter, which would require changing the height of the landing gear struts, which is also unlikely to be possible without a radical redesign of the airframe.
The M-71 was exactly 100 kg heavier than the M-82F, and this difference could still be compensated without significant modification of the airframe, whereas the R-2800 exceeded the weight of the Ha-45 by more than 250 kg.
In my humble opinion, redesigning the airframe for the R-2800 would result in the development of a completely new aircraft.
The M-71 was exactly 100 kg heavier than the M-82F, and this difference could still be compensated without significant modification of the airframe, whereas the R-2800 exceeded the weight of the Ha-45 by more than 250 kg.
In my humble opinion, redesigning the airframe for the R-2800 would result in the development of a completely new aircraft.
- Thread starter
- #12
Counter-balance weights and structural reinforcements should be doable.
Propeller surface area can be increased with broader blades.
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The first option means unnecessary weight increase, while the second results in a complete redesign of the entire airframe. The landing gear will need to be reinforced, etc. Finally, it will be easier to design a new aircraft.
Perhaps. But apparently not always - for example, the attempt to install the M-82 on the Yak failed due to the need to use a larger diameter propeller. This required longer landing gear struts, which led to significant design changes that Yakovlev categorically refused to make. And with a smaller propeller diameter, the performance was lower than with the less powerful M-105. Perhaps this was a purely Soviet problem - the low technological level did not allow the Soviets to mass-produce propellers with broader blades during the war (propellers with broad blades were used only on a few prototypes of high-altitude fighters). It can be assumed that the Japanese aviation industry may have experienced similar difficulties.
- Thread starter
- #14
If weight increase of a Hayate with a 2800 would be about 500 kg as a rough estimate (someone correct me if necessary), it would weigh as much as an Fw 190D-12 but with almost 3 sqm more wing area.
The Germans went the way with broader blades successfully.
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Howard Gibson
Senior Airman
What should Pratt and Whitney charge Nakajima per engine?
I don't really know how much the Ki-84-N project differed from the production Ki-84, except that the wing area was 1.5 square meters larger, but the Ha219 was ~80 kg heavier than the R-2800. I might be overestimating the problems caused by the increased engine weight. However, the difference in the ratio of engine weight to airframe weight is quite significant: ~42% for the Ki-84 (810 / 1890) and ~50% for the hypothetical Ki-84-R2800 (1070 / 2130), considering that the production Ki-84 had problems with the strength of the landing gear struts, it is difficult to imagine how it would have been possible to install a much heavier engine without significantly redesigning the entire structure.
This does not mean that Japan would be able to follow the same way.
- Thread starter
- #17
IIrc the landing gear strut issue was a metallurgical one and the weight increase I mentioned includes structural reinforcement.
Some fighter designs gaining fat of a ton during their evolution was not too extraordinary either.
A Ki-84 with an R-2800 is a thought experiment, so Japan being able to produce broader bladed props and better landing gears should not be more challenging to imagine.
Some fighter designs gaining fat of a ton during their evolution was not too extraordinary either.
A Ki-84 with an R-2800 is a thought experiment, so Japan being able to produce broader bladed props and better landing gears should not be more challenging to imagine.
Shortround6
Lieutenant General
I am not sure what this is trying to prove.
The Japanese seem to have done a rather creditable job with the Ha.45 engine claiming 1620hp at 6400 meters (21,000ft). and doing this in very late 1944 (?).
Almost a year before any F8F-1s could have shown up. These had engines rated at 1700hp at 16,000ft military power. Not sure what they could get out of them with water injection as the supercharger was already maxed out. Water injection would help out with more power down low. but not 5000ft higher than rated altitude.
The engines in much later F8F-2 was good for 1600hp at 22,000ft. Not seeing where the big increase in performance at altitude is going to come from. Down low a big increase but then 2-3 years will do that for you.
Just about all of the late war R-2800 two speed engines that were rated at 2000hp for take-off (late B-26s, PV-2s, A-26s, etc) were rated at 1600hp at 13,500ft military power. Using one of the these may well have been more reliable but it sure wasn't going to give any better performance above 15,000ft if the Ha.45 was running right.
Engine in the F6F would make more power high up but now you have to deal with the auxiliary supercharger and the intercoolers and all of the ducting. No longer a 'simple' engine swap.
The US great at making high power engines for take-off, they had trouble making engines that made good power at 20,000ft without fancy supercharger set ups.
The Japanese seem to have done a rather creditable job with the Ha.45 engine claiming 1620hp at 6400 meters (21,000ft). and doing this in very late 1944 (?).
Almost a year before any F8F-1s could have shown up. These had engines rated at 1700hp at 16,000ft military power. Not sure what they could get out of them with water injection as the supercharger was already maxed out. Water injection would help out with more power down low. but not 5000ft higher than rated altitude.
The engines in much later F8F-2 was good for 1600hp at 22,000ft. Not seeing where the big increase in performance at altitude is going to come from. Down low a big increase but then 2-3 years will do that for you.
Just about all of the late war R-2800 two speed engines that were rated at 2000hp for take-off (late B-26s, PV-2s, A-26s, etc) were rated at 1600hp at 13,500ft military power. Using one of the these may well have been more reliable but it sure wasn't going to give any better performance above 15,000ft if the Ha.45 was running right.
Engine in the F6F would make more power high up but now you have to deal with the auxiliary supercharger and the intercoolers and all of the ducting. No longer a 'simple' engine swap.
The US great at making high power engines for take-off, they had trouble making engines that made good power at 20,000ft without fancy supercharger set ups.
Howard Gibson
Senior Airman
An R2800 powered Ki.84 would be bigger and heavier than a Nakajima Homare powered Ki.84. It would be faster. Given Japanese design practise, it would have better acceleration and climb, and would be a bit less manoeuverable. The Ki.84 was reasonably well armed. The extra power would allow better armour protection.
An important question about any alternate history is how would this happen? Do American pilots complain that the war is not glorious enough, and that the Japanese need Double Wasps? Engines could be parachuted down from B29s.
How do the USA and the Japan wind up as allies in WWII? This affects all sorts of things, including supply chains. The Japanese were making decent engines. A lot of their quality problems were due to attacks on their supply chains, and bombing by the USA. The USA generally does not bomb allies. Do the Japs need R2800s badly enough to buy foreign engines?
The only foreign WWII use of Pratt and Whitney R2800s as far as I know is Great Britain's Vickers Warwick, a twin engined heavy bomber. None of Britain's 2000HP engines were reliable and available (for non-critical aircraft) until 1945, when they finally switched to Bristol Centauruses.
Most American engines in foreign hands were exported in American aircraft. Packard V1650 Merlins were installed in Canadian made Hurricanes, Lancasters and Mosquitos. Some P&W R1830s would up in some Vickers Wellingtons and some Australian made Bristol Beauforts. Great Britain was designing and building good engines.
The French were investigating Wright R2600s for their Leo45s. The Germans shut down their engine development (and Leo45 development) after 1940. If they had survived the German onslaught, would they have needed American engines?
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SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Infrequently.
