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Thanks for the link to the table rest of the stuff you've contributed here
The Japanese were able to make the Ki-45 going 357 mph at 18500 ft, on 2 x 960 HP. The wing area was some 10% greater than of the P-38, but the Ki-45 was significantly lighter.
I was not 'aiming' on the 1350 HP variant of the R-1830, but the 'usual' 1200 HP one. There is no doubt that a V-1710 powered version would've been faster.
Ki-45??
Or Ki-46?
Ki-46 later got more powerful engines (same ones as the Ki-100) but with the addition of guns (helpful for a fighter) speed only went to 391mph? No armor, no self sealing tanks? or minimal?
As a Recon plane was the Ki-46 stressed for fighter like maneuvers?
The P-38 NF should be available maybe a year earlier than the P-61, should compensate quite a bit for the lower performance of the radar. Lack of cooling system might allow for extra space for radar electronics, though it would've take a new central pod to offer both a powerful radar, space for 2nd crew member, armament and a bigger antenna - all at once. Something that would've appeared like the 'Swordfish' pod?
The problem, given even a slightly larger fuselage, isn't so much the space (cubic feet) occupied by the black boxes but the size of the radar antenna and radar dome. That parabolic dish in the photo in 29" (74cm) across and rotates 90 degrees to either side, 20 degrees down and 50 degrees up. and does several hundred times per minute in scan mode.
The earlier SCR 520 radar used in the P-70 was bulkier and heavier and there is part of the problem with using the "retrospectroscope"
You KNOW what the size of the finished radar units will be. When work started on the night fighters they had no idea how big/heavy the radars of the future (2-3 years down the road) would be. They might get smaller (they did) they may get longer ranged ( they did) but how much smaller for what range? or would a slightly bigger unit give even more range?
Ki-45??
Or Ki-46?
The problem, given even a slightly larger fuselage, isn't so much the space (cubic feet) occupied by the black boxes but the size of the radar antenna and radar dome. That parabolic dish in the photo in 29" (74cm) across and rotates 90 degrees to either side, 20 degrees down and 50 degrees up. and does several hundred times per minute in scan mode.
The earlier SCR 520 radar used in the P-70 was bulkier and heavier and there is part of the problem with using the "retrospectroscope"
You KNOW what the size of the finished radar units will be. When work started on the night fighters they had no idea how big/heavy the radars of the future (2-3 years down the road) would be. They might get smaller (they did) they may get longer ranged ( they did) but how much smaller for what range? or would a slightly bigger unit give even more range?
Here's a couple "glass nosed" P-38s...
The first one was actually built for bombing (P-38J-15-LO 'Colorado Belle', 1943-1945), the second P-38 pictured was modified for civil land surveying.
The fuselage for the P-38 was actually quite small and an adaptation to fit such a large radar in it would require extensive work like I mentioned. And once the fuselage was been modified to shoe-horn the radar system in, where would the weapons go?
This is true, the fuselage was "bigger" in the fact that it was lengthened. The radar system used, was a fixed antenna unlike the SCR-720, which was an articulated or "sweeping" type. To place the SCR-720 system in the P-38, you would have to increase the height of the fuselage and widen it, to the same dimensions the P-61 and the A-20 used for their installations.'Swordfish' featured the accommodation for two, in a longer and overall bigger nacelle.
Maybe I am missing something but it looks like you are mounting an engine that weighs 535lbs more than a P-36 engine roughly 6in further forward than the existing engine?
Seems like a lot of faith is being placed on the longer, larger rear fuselage to balance things out?
I would note that lowering the thrust line by 3.5 inches might not be the best idea either unless longer landing gear is used to regain prop clearance. And longer landing gear pushes the wheel/tires further to the rear of the wing into a thinner part. Bulges over the wheel wells?
This also assumes you can get a prop with a similar diameter to absorb the extra power. Douglas A-20 uses an 11ft 3in prop for their R-2600 engines.
Those are good points. My thoughts: The R-2600 is about 7" larger diameter and I wanted to keep the pilot to top of engine cowl relationship the same. So the engine thrust line is lower than the thrust line of the R-1830 while the top of the engine is about the same place. I used the firewall as a base line for engine installation and the R-2600 is about 3 inches longer than the R-1830. The larger engine will most likely need a larger propeller hub so the front of the engine from the firewall is about 3-6 " farther out. To compensate for the increased front weight I added structure to the rear of the fuselage by increasing its vertical cross section and lengthening the fuselage as much as might be necessary. I think this would also clean up the airflow on the bottom of the fuselage. I don't know how much that would be so I just guessed at a minimum of 12 inches. Moving the battery and radio farther aft along with increasing the strength and weight of the rear fuselage may be enough? ....I supposed more length could be added as necessary.
The length of the prop may need to be a little longer if the increase power cannot be utilized by changing the design of the propeller width/cord. The wing has a cord that could be lengthened to the rear as it extends farther out from the fuselage. This would allow for an increase in landing gear length. Also this would add a little weight to the rear of the center of gravity. It also would increase the wing area a little. This would minimize the wing loading change with the added weight.
But as someone said, The R-2600 had early development issues and seems to not have been super reliable until 1942-43? Still, it is fun to play around with ideas of re-engining these old airplanes.
More diameter is always better, but it may be constrained by aircraft geometry or tip speed, then, yes, you start increasing activity factor, by adding blades or increasing chord. Either would require changes to the hub and pitch-change mechanism or, at an absolute minimum, new structural analysis of the hub and to see if there's enough force and power from the pitch change mechanism.I am not an engineer, just a mechanic/technician. It appears one way change the propeller to use an increase in power is to change propeller area with width rather than length.
Those are good points. My thoughts: The R-2600 is about 7" larger diameter and I wanted to keep the pilot to top of engine cowl relationship the same. So the engine thrust line is lower than the thrust line of the R-1830 while the top of the engine is about the same place. I used the firewall as a base line for engine installation and the R-2600 is about 3 inches longer than the R-1830. The larger engine will most likely need a larger propeller hub so the front of the engine from the firewall is about 3-6 " farther out. To compensate for the increased front weight I added structure to the rear of the fuselage by increasing its vertical cross section and lengthening the fuselage as much as might be necessary. I think this would also clean up the airflow on the bottom of the fuselage. I don't know how much that would be so I just guessed at a minimum of 12 inches. Moving the battery and radio farther aft along with increasing the strength and weight of the rear fuselage may be enough? ....I supposed more length could be added as necessary.
The length of the prop may need to be a little longer if the increase power cannot be utilized by changing the design of the propeller width/cord. The wing has a cord that could be lengthened to the rear as it extends farther out from the fuselage. This would allow for an increase in landing gear length. Also this would add a little weight to the rear of the center of gravity. It also would increase the wing area a little. This would minimize the wing loading change with the added weight.
But as someone said, The R-2600 had early development issues and seems to not have been super reliable until 1942-43? Still, it is fun to play around with ideas of re-engining these old airplanes.
The Norwegian government had issued an order for 36 Hawk 75A-8 export versions of the P-36 just before the German occupation. These aircraft were powered by the export-model 1200 hp Wright R-1820-G205A Cyclone radial. Since Norway was under German occupation at the time these aircraft were completed in January of 1941, they were impounded by the US government.