R-1830 vs. Allison V-1710

[Clay_Allison]

While the Change from 12 to 11.5 might not be significant, changing armament to four .50s, adding armor and self sealing tanks and changing to a more powerful engine (or bigger supercharger) and bigger propeller would almost certainly change the load factors to a point where SOMETHING has to be done. I don't know how much extra weight would be involved but I would think that a Radial engine P-40 isn't going to weigh that much less than an Allison powered one. The power plant weight of an F4F was 2510lbs not including fuel system.

I'm not really looking for weight, I'm looking for an engine with a better developed supercharger.

 

[Shortround6]

I'm not really looking for weight, I'm looking for an engine with a better developed supercharger.

And what will it really get you?

even if your super dooper P&W 1830/2000 gives 1200hp at 20,000ft ,about a 20% increase over what the R-1830 really did, sticking it a 7000Lb + plane stiil won't give you the Performance of a 109F. It just might give you a similar power to weight ratio at 20,000ft to a Mitsubishi A6M3 with it's 2 speed supercharger. It might depend on how much fuel each plane had burned off.

Coming up with a superior plane to the opposition is one thing, jumping through hoops and canceling America's Best Army fighter of 1942 just to close up half the performance difference may not really be worth it.

 

[Clay_Allison]

Coming up with a superior plane to the opposition is one thing, jumping through hoops and canceling America's Best Army fighter of 1942 just to close up half the performance difference may not really be worth it.

The P-38? I don't think it ever paid off the tremendous development cost by being productive. Once it got good enough to really start killing planes it was already on par performance-wise with planes that cost half as much.

We probably disagree on this, but I'd trade the P-38 and P-39 for a radial engine P-40 with a power loading approaching .18 at high altitude, especially if Lockheed and Bell could build them under license.

Added to that, more money for the R-1830/R-2000 would result in a better performing F4F as well.

Saying the proposed radial P-40 would only make up half the difference between the P-40 and the 109 isn't telling the whole story. The radial P-40 would still have its very tough structure, a tougher radial engine (vs. the Allison) and considerable armor without the heavy cooling system. It would still be a boom and zoom fighter, just a much better one.

Further, IMO, it would retain the better flying characteristics of the generally regarded as "easy to fly" P-36. I can't prove the P-36 was easier to fly, but the French, the Finns, and our pilots generally had very positive things to say about its handling. I've also heard the P-40 characterized as "tricky" to fly.

Finally, I think that getting 2 more production lines making a single aircraft would result in more total fighter units being built than the P-40, P-39, and P-38 totals combined.

 

[Timppa]

It's 1938 and the war department has told you you have to pick one of their two 1000 horsepower class babies for further development as fighter engines at the expense of dropping the other. This move would force the Army and Navy to settle on either an inline or a radial for planes in that size category. What would you pick?

Definitely V-1710 as it had more development potential. OTOH the 2000hp R-2800 was introduced in 1939, so the War Department would have to be quite stupid.
Real history: Jun11, 1938: A contract was given to Vought for a prototype XF4U-1 airplane with R-2800.

Known engines in service or available in near future in 1938 include at least:
V-1710
R-1820
R-1830
R-2600
R-2800

 

[Shortround6]

The P-38? I don't think it ever paid off the tremendous development cost by being productive. Once it got good enough to really start killing planes it was already on par performance-wise with planes that cost half as much.

Some other peaple might disagree with you, like the General who claimed that if the Pacific got priority for P-38 deliveries then operation Torch would have to be called off.

Saying the proposed radial P-40 would only make up half the difference between the P-40 and the 109 isn't telling the whole story. The radial P-40 would still have its very tough structure, a tougher radial engine (vs. the Allison) and considerable armor without the heavy cooling system. It would still be a boom and zoom fighter, just a much better one.

If you want the tough structure you have to take the P-40s weight. the heavy cooling system (all 300lbs of it) pretty much balances out against the the heavier 2 stage supercharger and intercooler of your radial engine. ANd if you go for the R-2000 model it's extra weight will definatly push the powerplant weight higher than the Allison P40 and start heading for the Merlin P-40. It will be a boom and zoom fighter all right, just a dragger one than the inline P-40.

Further, IMO, it would retain the better flying characteristics of the generally regarded as "easy to fly" P-36. I can't prove the P-36 was easier to fly, but the French, the Finns, and our pilots generally had very positive things to say about its handling. I've also heard the P-40 characterized as "tricky" to fly.

Once you get the wing loading and gross weight up to the weight of the P-40 (and the weight of the guns out in the wings) what makes you think the radial p-40 is going to handle any different than the inline P-40?

Finally, I think that getting 2 more production lines making a single aircraft would result in more total fighter units being built than the P-40, P-39, and P-38 totals combined.

Why would you think that? I can see the p-38 but why would a factory that could turn out several huderd p-39s a month be able to to turn out more P-40s just because another factory hundreds of miles away was making P-40s?

 

[Clay_Allison]

Why would you think that? I can see the p-38 but why would a factory that could turn out several huderd p-39s a month be able to to turn out more P-40s just because another factory hundreds of miles away was making P-40s?

If 3 companies are making one plane rather than 3, they are going to be drawing from parts suppliers that will be mass producing parts for the one plane rather than 3. Also the total man hours needed to build a P-38 would build several P-40s IIRC.

Once you get the wing loading and gross weight up to the weight of the P-40 (and the weight of the guns out in the wings) what makes you think the radial p-40 is going to handle any different than the inline P-40?

Power loading with R-2000 (1350 HP) @ 8000 lb: .17
Power loading of original P-40: .14

I also think keeping the lines it was originally designed to have over the eventually awkward-looking lines of the P-40.

If you want the tough structure you have to take the P-40s weight. the heavy cooling system (all 300lbs of it) pretty much balances out against the the heavier 2 stage supercharger and intercooler of your radial engine. ANd if you go for the R-2000 model it's extra weight will definatly push the powerplant weight higher than the Allison P40 and start heading for the Merlin P-40. It will be a boom and zoom fighter all right, just a dragger one than the inline P-40.

Draggier? I don't think there would be much difference. The huge mouth radiator of the P-40 made it draggier than most of its contemporaries.

 

[Shortround6]

Power loading with R-2000 (1350 HP) @ 8000 lb: .17
Power loading of original P-40: .14.

What does the power loading have to do with whither a plane is tricky or easy to fly?
ALthough some really high powered planes had trouble with torque.
Power loading of the Hawk 75 with Cyclone engine was .19 at take-off, .16 at 8,200ft and .13 at 19,500ft.
Did the Hawk get tricker to fly the higher it went?

I also think keeping the lines it was originally designed to have over the eventually awkward-looking lines of the P-40.

Draggier? I don't think there would be much difference. The huge mouth radiator of the P-40 made it draggier than most of its contemporaries.

Got any numbers?

Drag co-effeicients or flat plate equivelent numbers?
You do know that P-36s were 40-50mph slower than P-40s even though the P-36s had 1100-1200hp engines? and were 1000-2000lbs lighter?
Yeah, I can see how that "huge mouth radiator" really slowed the P-40 down

 

[Clay_Allison]

What does the power loading have to do with whither a plane is tricky or easy to fly?
ALthough some really high powered planes had trouble with torque.
Power loading of the Hawk 75 with Cyclone engine was .19 at take-off, .16 at 8,200ft and .13 at 19,500ft.
Did the Hawk get tricker to fly the higher it went?

I also think keeping the lines it was originally designed to have over the eventually awkward-looking lines of the P-40.




Got any numbers?

Drag co-effeicients or flat plate equivelent numbers?
You do know that P-36s were 40-50mph slower than P-40s even though the P-36s had 1100-1200hp engines? and were 1000-2000lbs lighter?
Yeah, I can see how that "huge mouth radiator" really slowed the P-40 down

you like adding criticisms but you don't like offering alternatives.

German philosopher Gottfried Leibniz believed that we live in the best of all possible worlds. Do you? You seem to think that nothing sould ever be improved about anything that was done in the allied air war effort.

 

[Shortround6]

you like adding criticisms but you don't like offering alternatives.

German philosopher Gottfried Leibniz believed that we live in the best of all possible worlds. Do you? You seem to think that nothing sould ever be improved about anything that was done in the allied air war effort.

I see, if the numbers don't back your idea up, attack the critic who points it out.

 

[Clay_Allison]

I see, if the numbers don't back your idea up, attack the critic who points it out.

not attacking, just wondering why you never debate on the positive side of anything. Most people I know with your level of knowledge about a subject feel they know how things could be done better.

 

[Shortround6]

Things that could/should have been done differently include the US getting it's head out of it's butt about the 20mm Hispano Cannon.

We spent an awful lot of money on Curtiss planes that just weren't any good. THe P-40 was good or at least nesassary in it's day but it's day was over, production wise by Jan 1944. Given that it could take several months to get a plane from the factory to an overseas operational unit and given the fact that the decision that no US units combat units weer going to get anymore P-40s had already been made the Manufactrure of several thousand more is hard to figure. The Helldiver didn't become an acceptable airplane until hundreds if not thousands had been built. ANd perhaps the less said about the Seamew the better

THe whole unescorted bomber thing needed a rethink. In the 1930s when intercepters carried a pair of rifle caliber MGs and the bomber could mount pairs of rifle caliber MGS in each defensive postion maybe one could argue that the bomber could fight it's way through. Once interceptors started carring 6-8 rifle caliber MGs or multipule cannon the Idea that a bomber could carry enough armament to fight it's way to the target needed a rethink, even using close formations.

The US might have been better served, at times, if we had taken a bit longer to straighten something out rather than rushing some things into production and then getting almost as obsessed with numbers as any German political hack or Russian factory manager

For example, Lockheed knew very early that their intercooler was too small to support the power levels that the Allison could reach. This wasn't rocket science. THe P-38 was designed in 1938 for Allison engines of about 1000hp. The Intercoolers weren't changed for years. They could measure the inlet temperture of the planes using 1150hp engines and knew it was too high and they knew that Allison was planning on introducing higher powered engines months before they became production items. By the time the H model P-38 came along with 1425hp engines the intercooler was WAY TOO SMALL.

Why did some American fighter planes carry so much ammunition? THe American .50 cal had roughly 3 different rates of fire during the war. 600rpm in wing guns and free mounted guns in the early part of the war rising to 800-850rpm near the end of the war. But the Syncronized guns firing through the propeller were good for 400-450rpm according to some sources. How many early P-40s ran ou of ammo for those nose guns with 380rpg? and how many seconds earlier had the wing .30s run dry?
The P-39 may have been screwed up by it's armament more than some peaple might want to admit. With 1000rpg for those wing .30s they were going to keep firing long, long after the 37mm and the .50s had stopped. Now you have a 4 rifle caliber MG fighter flying around carring several hundred pounds of dead weight. ( the now silent 37mm and .50guns ) Maybe somebody had a reason forall that ammo but short of pulling the guns entirely like the Russians, limiting the ammo boxes to around 300rpg could have saved almost 200lbs of loaded weight and had the .30s run out of ammo just a little before the .50s.

THe Brewster Buffalo was another plane saddled with way too much ammo. would it have made much difference? I don't know but there are stories of the British limiting ammo or changing to lighter guns.

We have the benifit of looking back with hindsight. Predicting the future is a lot harder and that is what many of those generals, engine and aircraft designers were trying to do. In 1938 (with 100 octane just coming into service in America and still a year to two years from being in service in England) predict what grade of fuel will be availabe in 1942 and plan your country's engine production program and as a relut of that what types of aircraft might be available 3-5 years in the future.

DO you want to bet a 100 million on what the electric car market will be in 2013?

And if you are wrong, just to spice things up, you not only loose the money, but part of your country will be ruled by somebody else.

ANd just to add something extra, you have no control over the price of oil. It could be $35.00 a barrel in 2013.

 

[Clay_Allison]

See? That's good stuff. A reliable P-38 could change everything. I had no idea that the ETO reliability issues for the P-38 were both fixable and FORSEEABLE. That's amazing. If high altitude escorts could be had for B-17s from day one, if as you suggest they could be armed with 5 cannons, the bombing raids would have hit Germany twice as hard. Fewer bomber crew casualties, more bombers reaching the target.

 

[krieghund]

I just posted a P-36A&C flight manual in the reference section to help this thread along.

 

[krieghund]

With a speed comparison the drag of the radial is clear:
Both at 10000ft
MPH BHP
P-36A 313 1050 R-1830-17
P-40B 329 1040 V-1710-33

 

[Shortround6]

I just posted a P-36A&C flight manual in the reference section to help this thread along.

Thank you.

 

[Shortround6]

See? That's good stuff. A reliable P-38 could change everything. I had no idea that the ETO reliability issues for the P-38 were both fixable and FORSEEABLE. That's amazing. If high altitude escorts could be had for B-17s from day one, if as you suggest they could be armed with 5 cannons, the bombing raids would have hit Germany twice as hard. Fewer bomber crew casualties, more bombers reaching the target.

I am not suggesting 5 cannon. Perhaps 2 20mm and 2 50.s or Three 20s or maybe even four. it depends on how much ammo you want. THe weight of the Hipspano is a bit decieptive because it actualy needed a rather heavy mount in order to be reliable (after all, it was designed to be bolted to an 800-1100lb engine)and with a firing rate about the same as an early .50 it will run through an equel weight of ammo much quicker.

The ETO reliability issues had little to do with the size of the intercoolers. In fact it was partialy the opposit. The Newer P-38s intercoolers worked a little TOO good in cruising flight. THe pilots were being taught in the US to cruise at high RPM and low boost, which was wrong not only for fuel economy but on the P-38 it ment that the turbo was doing very little work and so was heating the intake air very little. After this low heated air went through the intercooler and was partially reheated by the engine supercharger it was still too cold and raw fuel condensed out in the intake manifolds, mixture distribution was poor and other problems. Changing the cruise settings to lower engine RPM but higher boost cured most of the problem with NO mechanical changes. The temperature problem is why it was an ETO thing only. Med and Pacific temperatures were warm enough that the problem didn't occur.
Bigger/better intercoolers earlier means the P-38 could have used higher WER settings earlier
Changing the intercooler space to fuel tanks also increased internal fuel by just over 33%. SO, While the P-38 might not have quite equeled the Mustang, Fighter escort could have been provided over more of Germany months earlier than was done.

 

[Clay_Allison]

I am not suggesting 5 cannon. Perhaps 2 20mm and 2 50.s or Three 20s or maybe even four. it depends on how much ammo you want. THe weight of the Hipspano is a bit decieptive because it actualy needed a rather heavy mount in order to be reliable (after all, it was designed to be bolted to an 800-1100lb engine)and with a firing rate about the same as an early .50 it will run through an equel weight of ammo much quicker.

The ETO reliability issues had little to do with the size of the intercoolers. In fact it was partialy the opposit. The Newer P-38s intercoolers worked a little TOO good in cruising flight. THe pilots were being taught in the US to cruise at high RPM and low boost, which was wrong not only for fuel economy but on the P-38 it ment that the turbo was doing very little work and so was heating the intake air very little. After this low heated air went through the intercooler and was partially reheated by the engine supercharger it was still too cold and raw fuel condensed out in the intake manifolds, mixture distribution was poor and other problems. Changing the cruise settings to lower engine RPM but higher boost cured most of the problem with NO mechanical changes. The temperature problem is why it was an ETO thing only. Med and Pacific temperatures were warm enough that the problem didn't occur.
Bigger/better intercoolers earlier means the P-38 could have used higher WER settings earlier
Changing the intercooler space to fuel tanks also increased internal fuel by just over 33%. SO, While the P-38 might not have quite equeled the Mustang, Fighter escort could have been provided over more of Germany months earlier than was done.

I have a lot of respect for what concentrated armament can do when deployed in a good fighter. Even with 5-6 50s, it would have a pretty impressive range advantage vs. Luftwaffe interceptors. Nose guns in a pusher or twin engine aircraft can have good accuracy out to 1000 yards versus 200-300 yard ranges for wing guns. Delivering long range escorts in 1943 would change the war dramatically.

 

[wuzak]

If it came down to R-1830 vs V-1710 the powers-that-be would have chosen the V-1710 simply because it gave them a credible liquid cooled engine. They needed to hedge their bets on air-cooled vs liquid cooled in case one or the other proved to be far superior as they developed.

The fact that we still discuss these things now shows that it wasn't a simple or obvious choice.

 

[Readie]

If it came down to R-1830 vs V-1710 the powers-that-be would have chosen the V-1710 simply because it gave them a credible liquid cooled engine. They needed to hedge their bets on air-cooled vs liquid cooled in case one or the other proved to be far superior as they developed.

The fact that we still discuss these things now shows that it wasn't a simple or obvious choice.

You have hit the nail on the head there.
As mentioned in a previous post we now have the luxury of hindsight,Shortrounds bet on the future is tempting...but, I'll pass as we still have to pay our debts and canot afford another world war just yet !!
Cheers
John

 

[billswagger]

R1830 displacement = 30L. 567 kg dry.
V1710 displacement = 28L. 633.5 kg dry. This engine requires a liquid cooling system.

I'll go for the R1830. It has a bit more displacement and is significantly lighter.

Basically a P-36 vs a P-40B

Despite the added weight of the cooling system, the P-40B was said to be significantly faster despite having the same "rated" output.
Basic performance only favored the P-36 in turn seeing as it was a tad lighter.
The streamlining of the V engine allowed another 20-40mph in top speed at the same output.
I'd be leaning toward the V1710.

OTH, comparing the P-43's use of the R1830-49, it might be up for consideration but it still required a turbo charger to reach 1200 hp.
The AVG used the plane, but had originally rejected it because it lacked self sealing tanks.
That decision speaks volumes considering the better ceiling and climb over the P-40.