R-2600 table

[tomo pauk]

R-2600-13 (red, data from latest table) vs. 1610-1 (green, data from graph from US 100K). No competition 'till 10K, with another area of large advantage from 13-17K. In other words, when P-40F arrives at a favorable altitude, 'my' P-40 is already there.
Similar advantage has R-2600 "A" series vs. contemporary V-1710s, continuing equally above 15K (unlike for V-1610).

 

[gjs238]

If the V-1710 was so much better than the R-2600 (and I'm not saying it wasn't/isn't), then why didn't they use it in lieu of the R-2600 in all applications?

 

[Shortround6]

Congratulations, you have a one trick pony. It can out climb a P-40, not exactly a ringing endorsement. It can't out run one. Will the dive be any better? It can't out turn the P-40.
And lets examine the climb part a bit more.
Engine is either 600lbs heavier than the Cyclone 9 used the Mohawk or 300lbs or so heavier than a P-40 engine and radiator. It needs a bigger prop, about 440lbs for another 60lbs or so over the P-40E. Fuel could be tricky. with 22% more drag (minimum) you either cruise slower, or for less time or you carry more fuel. A P-40 used about 100-112 G/H at max continuous power (1000hp) while the R-2600 could suck down 180G/H at max continuous (1350HP). The R-2600 could be throttled back to about 1000hp for 115 G/H But that extra drag is going to slow the plane down. Military power for the Allison (1150hp) is about 132 G/H while the R-2600, to use it's 1700-1450hp is sucking over 200G/H. If you want to equal the range or endurance of the P-40E you need 25-40 gallons more internal fuel. Another 150-240lbs not including tanks which can easily go another 75-125lbs.
Using drop tanks only gets you so far. Assuming full P-40E load of 150 US gallons (including rear fuselage tank which may be a no-no for combat) the R-2600 will suck down 17.5 gallons in 5 min for combat, it will suck down another 60 gallons in 20mins at max continuous leaving 50 gallons for about 1 hrs flight at most economical (hope you are out of the combat zone) and leaving 22.5 gallons for reserve and landing (just under 1/2 hr) We haven't added in a bigger oil system either.
Will the US Army buy the lower "G" load limit caused by the extra weight or will they insist on beefing up the structure and adding a bit more weight. Unless you really cut guns and ammo you are going to hit 8-10% heavier than the P-40E real quick. Extra drag in the climb and 10% more weight may make those climb figures look not so good. Better than a regular P-40 yes, but enough to take on a new role instead of being in the same situation?

 

[Shortround6]

If the V-1710 was so much better than the R-2600 (and I'm not saying it wasn't/isn't), then why didn't they use it in lieu of the R-2600 in all applications?

The V-1710 is better in a fighter, with a bomber you need all the help you can get taking off. You also have enough more drag (either with a twin or a naval torpedo/dive bomber) that the extra frontal area of the R-2600 wasn't that big a deal. The Avenger had a bomb bay under the crew that could house a 22.5in torpedo with the doors closed. It also had a power turret for the rear gunner and a wing with more square footage than an A-20. Sticking a pointy nose on it was like putting lipstick on a pig. A B-25 has a fuselage that will seat two men side by side, two engine nacelles that hide really big tires and gun turrets top and bottom on early ones, OK the bottom one was supposed to retract again enough drag that the engine installations were no longer the major cause of drag. Again, with a 34,000lb plane you need all the power you can get.

Fighter designers jumped over the R-2600 for the R-2800 because, if you were going to bludgeon the air into submitting, you might as well use an engine with 92% of the frontal area of the R-2600 and 250-300 more HP.

 

[tomo pauk]

Congratulations, you have a one trick pony. It can out climb a P-40, not exactly a ringing endorsement. It can't out run one. Will the dive be any better? It can't out turn the P-40.

Out-climbing another plane (even if that's P-40) is good thing in my book. I'd say it's capable to outrun the P-40, ditto for out-diving it.

And lets examine the climb part a bit more.
Engine is either 600lbs heavier than the Cyclone 9 used the Mohawk or 300lbs or so heavier than a P-40 engine and radiator. It needs a bigger prop, about 440lbs for another 60lbs or so over the P-40E.
Fuel could be tricky. with 22% more drag (minimum) you either cruise slower, or for less time or you carry more fuel. A P-40 used about 100-112 G/H at max continuous power (1000hp) while the R-2600 could suck down 180G/H at max continuous (1350HP). The R-2600 could be throttled back to about 1000hp for 115 G/H But that extra drag is going to slow the plane down. Military power for the Allison (1150hp) is about 132 G/H while the R-2600, to use it's 1700-1450hp is sucking over 200G/H. If you want to equal the range or endurance of the P-40E you need 25-40 gallons more internal fuel. Another 150-240lbs not including tanks which can easily go another 75-125lbs.
Using drop tanks only gets you so far. Assuming full P-40E load of 150 US gallons (including rear fuselage tank which may be a no-no for combat) the R-2600 will suck down 17.5 gallons in 5 min for combat, it will suck down another 60 gallons in 20mins at max continuous leaving 50 gallons for about 1 hrs flight at most economical (hope you are out of the combat zone) and leaving 22.5 gallons for reserve and landing (just under 1/2 hr) We haven't added in a bigger oil system either.
Will the US Army buy the lower "G" load limit caused by the extra weight or will they insist on beefing up the structure and adding a bit more weight. Unless you really cut guns and ammo you are going to hit 8-10% heavier than the P-40E real quick. Extra drag in the climb and 10% more weight may make those climb figures look not so good. Better than a regular P-40 yes, but enough to take on a new role instead of being in the same situation?

While I do appreciate the analysis:
Planes with substantially more powerful engines tended to be heavier, draggier suck more fuel vs. lighter cleaner ones. Yet, those planes were favored vs. lighter cleaner competition in most of the cases.

 

[davparlr]

In my opinion, the discussion is on the wrong airframe. The P-66 with a similar engine as the P-36G, was almost 20 mph faster and climbed about 500 ft/min more than the P-40. Now put in the 2600 into the P-66, which should not be any more difficult than putting in a V-1710 in place of a PW on the p-36. The added 30 to 40% power should easily off set the added 750 lbs of weight and slight increase in diameter, increasing climb and top speed. The similar designed F4U-1 with 200 more hp at altitude was capable of 417 mph. This configuration could have indeed been a formidable competition to the Bf-109 and maybe the Fw-190.

 

[Shortround6]

Tomo, go back to the Hawk 75A-4. 323mph at 15,000ft with a Wright Cyclone 9 (G205A) giving 1200hp at sea level and 1000hp at 14,200ft. using the cube law for power needed, it would have needed 1331hp to do 355-356mph. That is with absolutely no increase in drag. Considering the increase in weight and drag the likelihood of a R-2600 powered Hawk getting past 360mph at 15,000ft seems remote.
A Commercial Hawk with a Cyclone G105A engine giving 1100hp Military at 1500ft was good for 258mph at sea level. Trying for a 20% increase in speed (310mph) would require 1900hp.
Now maybe I am misinterpreting the power (no Military rating when the brochure was put out?) and the plane did 258mph with the rated output of 900hp. It still needs 1550hp to do 310mph at sea level in that case. Once again with the increase in weight and drag of the R-2600 I don't see any real advantage over the P-40.
Why don't you figure the weight of your R-2600 Hawk. Use the weight figures from the H75-A manual on this website and the figures in "Americas Hundred Thousand" for parts of the P-40, some better weight figures for the Cyclone 9 engines can be found in the Buffalo section of the book.

 

[Shortround6]

In my opinion, the discussion is on the wrong airframe. The P-66 with a similar engine as the P-36G, was almost 20 mph faster and climbed about 500 ft/min more than the P-40. Now put in the 2600 into the P-66, which should not be any more difficult than putting in a V-1710 in place of a PW on the p-36. The added 30 to 40% power should easily off set the added 750 lbs of weight and slight increase in diameter, increasing climb and top speed. The similar designed F4U-1 with 200 more hp at altitude was capable of 417 mph. This configuration could have indeed been a formidable competition to the Bf-109 and maybe the Fw-190.

P-36G or P-36C ?
The R-2600 is 6in bigger in diameter and 500lbs heavier dry. 6in on diameter isn't exactly slight. it is the difference between 12.8sq ft of frontal area and 16.1 sq ft.
a few numbers for comparison.
P&W R-1830 at 1200hp----95.2hp per sq/ft of frontal area.
Wright R-2600 at 1600hp--99.4hp per sq/ft of frontal area.
Wright R-2600 at 1700hp--105.6hp per sq/ft of frontal area.
P&W R-2800 at 1850hp----125hp per sq/ft of frontal area.
P&W R-2800 at 2000hp----135hp per sq/ft of frontal area.

Now I will certainly admit that even early war cowlings streamlined things so the actual difference was edit> NOT< edit quite as bad as these figures show but it is not hard to see why the R-2600 was skipped over as a fighter engine.

As far as the "similar designed F4U-1 with 200 more hp at altitude was capable of 417 mph" goes the F4U-1 had a lot more than a 200hp advantage at altitude. at 16,000ft (not including ram) it was good for 1800hp for about a 375hp advantage over Tomo's chart. At 21,000ft (no ram) the F4U-1 was making 1650hp for an almost 550hp advantage. 1650hp vs just over 1100hp.

 

[elbegaio]

Hi guys, I know i'm a bit late since this conversation dates back to may, but I saw that you published the operating limit chart of wright r-2600-8. I'm working on a project of a flying boat inspired by the Boeing 314 and I need the same chart referred to wright r-2600-3. I searched everywhere on the web, so I ask you if can give me information about where to find this graph (possibly without paying 300$ dollars to buy strange manuals of 1935).

 

[post76]

i thought military rating was a 15 minute output rating, while WEP or take off power was usually considered a 5 minute rating.
The WEP rating typically gives a lower FTH.


It also had me thinking more of heat, something very relevant to the 5 minute rating.
The V engine has a water cooling system, which for overheating is going to give it a bit more time in the red.
The engine might get hot and overheat but nothing cooks until the water boils off, ie the engine becomes a pressure cooker, and usually you seea head gasket go or hose blow open before any other damage occurs. You can also warp heads and other parts by running hot.
After the water goes, then the oil cooks and the viscosity breaks down to where engine parts start grinding.

In a radial, there is no water to boil off, so the break down of oil viscosity happens much faster and cylinder heads are much more sensitive to damage. Also engine oil is a more of a mixture that burns with the fuel than something that cycles through, if i understand it correctly.
Holding your engine in the red would not be advisable. The advantage is that the engine will also cool off relatively sooner.
In a water cooled engine you'd have to wait for the coolant to reach a "normal" temperature setting which is dependant on radiator efficiency.
If overheating blows a hose, or gasket, you're screwed. A radial just needs to level out and increase airspeed.
Its not really about output, its about heat, and a combat climb is usually the most trying for radials because the output is high but the airspeed is low.

A climbing comparison might actually let the V engine climb longer at higher output but requiring a longer break to cool down, where the radial engine might not climb as long at higher outputs before it needs a short break to cool down some.
The rate of climb has more to do with the aircraft the engine goes on.

Aside from comparing horses, also compare propeller efficiency and design height.
Some planes just perform better at certain heights despite output.
It might fly faster at X,000 ft, but accelerates, zooms, and turns better at X,000 ft.
Consider drag, wing design, and acceleration and don't forget the octane rating.
Their ratings probably has more to do with octane and ram air efficiency something that was not well understood with either engine when they were first put into service.

If it says anything, the Hawk 75 or Mohawk /P-36 was said to climb with.. and had just a slightly wider turning radius than the Zero up to about 8000ft.
While the P-40 could not climb with the Zero or P-36 it out accelerated them (from 200IAS) in level flight up to 15,000ft.

 

[Shortround6]

Hi guys, I know i'm a bit late since this conversation dates back to may, but I saw that you published the operating limit chart of wright r-2600-8. I'm working on a project of a flying boat inspired by the Boeing 314 and I need the same chart referred to wright r-2600-3. I searched everywhere on the web, so I ask you if can give me information about where to find this graph (possibly without paying 300$ dollars to buy strange manuals of 1935).

I am not sure what you are asking or where you are going with this. The R-2660-3 was limited to 2500rpm and 1600hp. It used the same supercharger gears as the B series engines.

The commercial equivalent to the -3 was rated at 1600 hp for take-off at 2400rpm. It could hold 1600hp to an altitude of 1500ft as military power. power then fell off as height was gained. With a two speed supercharger the second gear allowed for a military power rating of 1400hp at 11,500ft at 2400rpm. The "normal" rating ( max continuous, not subject to 5 minute rating) was 1350hp at 5000ft at 2300rpm and 1275hp at 12,000ft at 2300rpm.

I don't know if you already had this information, I hope it helps.

 

[wuzak]

i thought military rating was a 15 minute output rating, while WEP or take off power was usually considered a 5 minute rating.
The WEP rating typically gives a lower FTH.


It also had me thinking more of heat, something very relevant to the 5 minute rating.
The V engine has a water cooling system, which for overheating is going to give it a bit more time in the red.
The engine might get hot and overheat but nothing cooks until the water boils off, ie the engine becomes a pressure cooker, and usually you seea head gasket go or hose blow open before any other damage occurs. You can also warp heads and other parts by running hot.
After the water goes, then the oil cooks and the viscosity breaks down to where engine parts start grinding.

In a radial, there is no water to boil off, so the break down of oil viscosity happens much faster and cylinder heads are much more sensitive to damage. Also engine oil is a more of a mixture that burns with the fuel than something that cycles through, if i understand it correctly.
Holding your engine in the red would not be advisable. The advantage is that the engine will also cool off relatively sooner.
In a water cooled engine you'd have to wait for the coolant to reach a "normal" temperature setting which is dependant on radiator efficiency.
If overheating blows a hose, or gasket, you're screwed. A radial just needs to level out and increase airspeed.
Its not really about output, its about heat, and a combat climb is usually the most trying for radials because the output is high but the airspeed is low.

A climbing comparison might actually let the V engine climb longer at higher output but requiring a longer break to cool down, where the radial engine might not climb as long at higher outputs before it needs a short break to cool down some.
The rate of climb has more to do with the aircraft the engine goes on.

Aside from comparing horses, also compare propeller efficiency and design height.
Some planes just perform better at certain heights despite output.
It might fly faster at X,000 ft, but accelerates, zooms, and turns better at X,000 ft.
Consider drag, wing design, and acceleration and don't forget the octane rating.
Their ratings probably has more to do with octane and ram air efficiency something that was not well understood with either engine when they were first put into service.

If it says anything, the Hawk 75 or Mohawk /P-36 was said to climb with.. and had just a slightly wider turning radius than the Zero up to about 8000ft.
While the P-40 could not climb with the Zero or P-36 it out accelerated them (from 200IAS) in level flight up to 15,000ft.

WEP does not necessarily mean overheating. The 5 minute rating is due to mechanical considerations also - running higher boost and/or higher rpm.

Not sure that an overheating liquid cooled engine needs "a longer break to cool down" when climbing. I would think that climbing would generally be performed at engine settings where overheating does not occur.

I have a NACA document which compares several different propellor profiles on both liquid cooled and aircooled engines. The results are that the propellors are generally more efficient, by a few percent, when sitting in front of a liquid cooled engine. Something to do with the great big lump behind the props with an air-cooled engine.

 

[elbegaio]

Thank you very much, but I need something more technical. I need to know the trend of available power with altitude for R-2600-3, since I have to compute Pénaud diagrams. So I need a graph similar to that published by tomo pauk.

 

[Shortround6]

Try modifying the published one. You have the start points. Flat line of 1600hp to 1500ft in low gear and then a very similar slope downward as altitude increases. like wise in high gear. flat line from gear change to 11,500ft for 1400hp and then an almost identical slope to the published chart. All sloped lines would have a common end point at around 55,000ft.

In fact if you take the published chart and extend the sloped 2400rpm line in high gear to the upper left it comes very close to the 1400hp at 12,000ft.

Some differences for a -23 engine in a Boston IV are that the -23 was limited to 45in boost for take-off and 45in boost for combat (military power) in low gear, and 44 1/2 in in high gear. the 1 hour limit was 41 1/2 in and the max climb was 37in. Both of the latter were at 2300rpm and the combat take off power were at 2400rpm. Differences between a -3 and a -23 seem to be the carburetor and perhaps the cylinder compression. try putting the different pressures on the published chart.

Depending on the year of this project the available fuel may limit things.
The original Boeing 314 and A314's used single speed superchargers on their engines. 7.01 gears instead of the 7.14 gears in the low gear of the two speed engines but this should not change things much, less than 2% on the impeller speed.


edit>>
Found this link which may be helpful.

http://www.hq.nasa.gov/office/pao/History/SP-468/ch8-6.htm

It has zero lift drag co-efficients and lift to drag ratios for the 314.

Also data from Juptner's "U.S. Civil Aircraft" vol 8. Boeing 314 at 82,500lbs with GR-2600-A2 engines 1500hp for take off and 1200hp max continuous was listed at a max speed at 193mph (this may be using the 1200hp rating) and a cruise at 2000ft of 175mph using 75% power. climb is 565fpm for the first minute at sea level. service ceiling is 13,400ft.

Data for the A314 with the GR-2600-709C14 AC1 engines, 1600hp take off and 1350hp max continuous, is 199mph max speed. Cruising speed of 184mph (75% power) at 2000ft. climb 600fpm first minute at sea level and a service ceiling of 14,000ft. Gross weight was 84,000lbs provisional for airline use with 87,000lbs allowed for wartime use. The book doesn't say which gross weight was used for the performance figures.