B-29 reset
- Thread starter gjs238
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
vikingBerserker
Lieutenant General
I wonder if it could have been fitted with diesel engines for longer range.
Historically, we were within *striking distance* of having the B-39, a B-29 with Allison V-3420 engines.
In interest of full disclosure, in history the on again off again on again priority placed on the V-3420 meant that the B-39 timeline was did not work out, so historically *striking distance* maybe was not too close.
In the "could have been" universe, the B-39 had just as much development potential as the B-29 / B-29D aka B-50 timeline.
A late model B-39 with leading edge radiators, and a VDT version of the V-3420 could have been an impressive performer.
In interest of full disclosure, in history the on again off again on again priority placed on the V-3420 meant that the B-39 timeline was did not work out, so historically *striking distance* maybe was not too close.
In the "could have been" universe, the B-39 had just as much development potential as the B-29 / B-29D aka B-50 timeline.
A late model B-39 with leading edge radiators, and a VDT version of the V-3420 could have been an impressive performer.
- Thread starter
- #5
- Thread starter
- #6
From Wikipedia:
The first R-3350 was run in May 1937. Continued development was slow, both due to the complex nature of the engine, as well as the R-2600 receiving considerably more attention. The R-3350 did not fly until 1941, after the prototype Douglas XB-19 had been redesigned from the Allison V-3420 to the R-3350.
Things changed dramatically in 1940 with the introduction of a new contract by the USAAC to develop a long-range bomber capable of flying from the US to Germany with a 20,000 lb (9000 kg) bomb load. Although smaller than the Bomber D designs that led to the B-19, the new designs required roughly the same amount of power. When preliminary designs were returned in the summer of 1940, three of the four designs were based on the R-3350. Suddenly the engine was seen as the future of army aviation, and serious efforts to get the design into production started.
The first R-3350 was run in May 1937. Continued development was slow, both due to the complex nature of the engine, as well as the R-2600 receiving considerably more attention. The R-3350 did not fly until 1941, after the prototype Douglas XB-19 had been redesigned from the Allison V-3420 to the R-3350.
Things changed dramatically in 1940 with the introduction of a new contract by the USAAC to develop a long-range bomber capable of flying from the US to Germany with a 20,000 lb (9000 kg) bomb load. Although smaller than the Bomber D designs that led to the B-19, the new designs required roughly the same amount of power. When preliminary designs were returned in the summer of 1940, three of the four designs were based on the R-3350. Suddenly the engine was seen as the future of army aviation, and serious efforts to get the design into production started.
wuzak
Captain
I would think no. Because of the range requirements, the early jets being notoriously thirsty, and because the jets at the time of the B-29's development were not pwerful enough. By the time decently powerful jets started to show up the B-29 was in production.
wuzak
Captain
VDT was a P&W thing. And also problematic.
One R-4360 VDT test engine flew in a B-50 in the late 1940s. As no suitable control mechanism had been designed, the flight engineer had to constantly monitor and adjust the nozzle to control the turbo. In a V-3420 powered B-29 variant that would require monitoring and adjusting 8 turbos.
Allison's development bent was turbo-compound. Given that a V-1710-127 (-E27) turbo-compound engine could develop around 3000hp at take-off, maybe that could have been used. Would have had less power than the R-3350 version at altitude, though.
A TC version of the V-3420 could have been well over 5000hp at take-off. But it would have needed a new turbine unit designed.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Diesel engines don't do well at high altitude
wuzak
Captain
Tell that to the Ju 86P and R.
The real problem is, were there suitable and sufficiently powerful Diesel engines available in the USA?
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The problem with diesel at high altitude, is that it conceals. A diesel engine also lacks a quick throttle response-time. Otherwise, they are great for long range aircraft, like the Bv138.
As far as American diesel aircraft engines are concerned, Packard built a radial diesel in the late 20's and it was used in a variety of aircraft.
As far as American diesel aircraft engines are concerned, Packard built a radial diesel in the late 20's and it was used in a variety of aircraft.
wuzak
Captain
Quick throttle response is not usually required for long range bombers.
he Packard Diesels, were they in the 2000-2500hp class?
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Nooo...not even close!
While the DR-980 was used in some military applications, it wasn't a large engine (only 9 cyl.)
It was rated at 240hp (179kw) @ 2,000 rpm and had a power to weight ratio of .44hp/lb (.8kw/kg)
It was a good engine and I understand that the Russians even copied it.
GregP
Major
A 4-engine R-2800 B-29 would be anemic and not worth the effort. They did it the right way, persevering with the R-3350 and working through the troubles.
Had they tried a 6-engine B-29 with R-2800's ... maybe. But it seems overly complex and expensive.
The way they did it in real life sealed the deal in the Pacific and was a very capable weapon.
Had they tried a 6-engine B-29 with R-2800's ... maybe. But it seems overly complex and expensive.
The way they did it in real life sealed the deal in the Pacific and was a very capable weapon.
GregP
Major
The B-29 was always a bit underpowered. The early R-2800 developed 1,500 HP in 1939 and 1,850 some 12 or so months later. But 1941 it was making 2,000 HP at max approved boost and rpm.
The FIRST R-3350 made 2,250 HP in 1937 and languished a bit while the R-2600 was developed. It first flew in 1941 at that same HP, but was stretched to 2,800 and ginally 3,500 HP after the war. During the war it always made more HP than the R-2800.
What could have happened if they had concentrated in the R-3350 when it first came out? We already know ... it COULD have been developed as many as 5 years sooner to the same levels it was ...because it actually happened, only 5 years later.
So, say the B-29 would cruise at 60 % power, albeit not especially fast at that power, then 60% of 2,200 HP is 1,320 HP each. The R-2800 in 1941 was making 1,200 HP. If you fly THAT at 60% power you get 1,200 HP, or an aggregate of 480 HP less with the R-2800 in cruise (assuming 60% power). It's 800 HP less at max power, not inconsequential. Actually it's 10% more power than the R-2800 made and max boost.
The B-29 could make 357 mph on four 2,200 HP R-3350's and they regularly attacked Japan at 325 mph+, making them very hard to catch and shoot down for the Japanese at the time. Had they used the 2,000 HP R-2800, the top speed would likely be in the 346 mph range with a commensure drop in over-the target-speed to around 314+ mph, maybe less. That's maybe catchable even for a Zero at 20,000 feet and would render the plane a bit more vulnerable. I can't say how much MORE vulnerable, but a bit more.
Once the R-3350 developed to 2,800 HP, the R-2800 was left far in the dust as a bomber engine. Yes, I KNOW it made a lot of power in experimental models but, for WWII is was basically a 2,000 to 2,200 HP engine at war emergency power. The R-2800 wasn't going to swing the same prop at the same speed as the R-3350, so the predicted data above are probably optimistic. Basically, I don't believe a plane known for being a bit underpowered could afford to lose 480 HP at cruise and 800 HP at top speed and still have the very effective bomb load the B-29 had.
Could it have flown with R-2800's? Sure.
Would it have been as effective as what was done? That's a what-if that nobody can answer ... they never DID it, so any opinion is as good as another.
I would not have gone that route and they historically didn't, either. But I suppose it MIGHT have resulted in more B-29's to the point that maybe they could have been deployed to Europe as well as the Pacific, I don;t know. Had THAT eventuality happened, it could have made a huge difference ... but is, again, a what-if that can be argued either way.
They MAY have even considered that option and discarded it, so the opportunity was recognized and not implemented, I don't know. I DO know the B-29 was very effective and hard hitting, with the heaviest normal bomb load of the war by a bomber in large scale production.
Don't even tell me about Grand Slams ... they were never a "normal" bomb load and the Lancasters that carried them were structurally in dangerous waters. It was done out of necessity, not with any regularity. They dropped a total of 42 Grand Slams in the entire war, less than .03% of Lancaster sorties.
The FIRST R-3350 made 2,250 HP in 1937 and languished a bit while the R-2600 was developed. It first flew in 1941 at that same HP, but was stretched to 2,800 and ginally 3,500 HP after the war. During the war it always made more HP than the R-2800.
What could have happened if they had concentrated in the R-3350 when it first came out? We already know ... it COULD have been developed as many as 5 years sooner to the same levels it was ...because it actually happened, only 5 years later.
So, say the B-29 would cruise at 60 % power, albeit not especially fast at that power, then 60% of 2,200 HP is 1,320 HP each. The R-2800 in 1941 was making 1,200 HP. If you fly THAT at 60% power you get 1,200 HP, or an aggregate of 480 HP less with the R-2800 in cruise (assuming 60% power). It's 800 HP less at max power, not inconsequential. Actually it's 10% more power than the R-2800 made and max boost.
The B-29 could make 357 mph on four 2,200 HP R-3350's and they regularly attacked Japan at 325 mph+, making them very hard to catch and shoot down for the Japanese at the time. Had they used the 2,000 HP R-2800, the top speed would likely be in the 346 mph range with a commensure drop in over-the target-speed to around 314+ mph, maybe less. That's maybe catchable even for a Zero at 20,000 feet and would render the plane a bit more vulnerable. I can't say how much MORE vulnerable, but a bit more.
Once the R-3350 developed to 2,800 HP, the R-2800 was left far in the dust as a bomber engine. Yes, I KNOW it made a lot of power in experimental models but, for WWII is was basically a 2,000 to 2,200 HP engine at war emergency power. The R-2800 wasn't going to swing the same prop at the same speed as the R-3350, so the predicted data above are probably optimistic. Basically, I don't believe a plane known for being a bit underpowered could afford to lose 480 HP at cruise and 800 HP at top speed and still have the very effective bomb load the B-29 had.
Could it have flown with R-2800's? Sure.
Would it have been as effective as what was done? That's a what-if that nobody can answer ... they never DID it, so any opinion is as good as another.
I would not have gone that route and they historically didn't, either. But I suppose it MIGHT have resulted in more B-29's to the point that maybe they could have been deployed to Europe as well as the Pacific, I don;t know. Had THAT eventuality happened, it could have made a huge difference ... but is, again, a what-if that can be argued either way.
They MAY have even considered that option and discarded it, so the opportunity was recognized and not implemented, I don't know. I DO know the B-29 was very effective and hard hitting, with the heaviest normal bomb load of the war by a bomber in large scale production.
Don't even tell me about Grand Slams ... they were never a "normal" bomb load and the Lancasters that carried them were structurally in dangerous waters. It was done out of necessity, not with any regularity. They dropped a total of 42 Grand Slams in the entire war, less than .03% of Lancaster sorties.
Last edited:
Greg,
Under what conditions the R-3350 was making 2800 HP in the ww2? The R-2800-57 in the P-47M and N was making 2800 HP (war emergency power) and 2100 HP for take off. The 1st such engines were in service in late 1944 on P-47Ms and often problematic, bugs were ironed out by the time P-47N entered combat (May 1945). OTOH, it took some time to get R-3350s to be dependable.
The bomber designed around the R-2800s should be tad a smaller than B-29, so the speed should be in the ballpark.
The usual bomb load for the Lancaster included the 12000 lb cookie (three 4000 lb cookies 'glued' one after another) and bunch of small incendiaries, the Fat Man weighted 10300 lbs, Little Boy was at 9700 lbs. The Tallboy, another Lanc's bomb, was at 10000 lbs.
Under what conditions the R-3350 was making 2800 HP in the ww2? The R-2800-57 in the P-47M and N was making 2800 HP (war emergency power) and 2100 HP for take off. The 1st such engines were in service in late 1944 on P-47Ms and often problematic, bugs were ironed out by the time P-47N entered combat (May 1945). OTOH, it took some time to get R-3350s to be dependable.
The bomber designed around the R-2800s should be tad a smaller than B-29, so the speed should be in the ballpark.
The usual bomb load for the Lancaster included the 12000 lb cookie (three 4000 lb cookies 'glued' one after another) and bunch of small incendiaries, the Fat Man weighted 10300 lbs, Little Boy was at 9700 lbs. The Tallboy, another Lanc's bomb, was at 10000 lbs.
Users who are viewing this thread
Similar threads
