Brewster F2A Buffalo or P-39 Airacobra?

[Elvis]

Some export models, the Dutch B-339D's, got 1,200 hp R-1820-G-205 engines which roughly equivelent to the -40 model of the F2A-2, these engines came directly from Wright and were not refurbished like many of the R-1820-G-105's used. Thus these a/c would have had considderably better performance than the -G-105 powered models.

I had to do a little research into the differences between the 105 and 205 G series engines.
The only thing I could find (in the short time I took to do this) was that the G205 was 100HP more powerful than the G105, however, nothing was ever stated that that difference was due to the fact that the 105's were a refurbed engine.
I get the feeling the HP difference would've been the same whether the 105's were new or refurbed (my thinking is that the 205 was an improved version of the series).
Also, I noticed something interesting, in that during my research, I found that J.Baugher had written the following, concerning the Dutch 339C's and D's - "The Dutch Model 339C and D were quite similar to the British Model 339E, but did not have the oval opening panel of the British model.
Is that "oval opening panel" the glass windows seen at the bottom of the aircraft in some of the drawings?




Elvis

[kool kitty89]

Yes but the thing was that many of the 105's used were second-hand and were not even producing their 1,100 hp rated power, hoever this may also have been due to the improper fuel pressurization pumps sontimes found on the Buffalo I (less powerful pumps for P&W Hornet engines) which caused fuel problems above 18,000 ft and sometimes as low as 10,000 ft. While the G-205's were new engines from the factory, just like the US F2A's.

There was one article I reas that said thst many of the G-105's used performed about the same as the G-5's (1,000 hp takeoff) used on the B-239. Though the Finn's engines seem to have been in better condition, or it may have just been the modifications (inverting cylinder rings to improve oil flow) and the cold climat that made them more reliable. That and the planes themselves were built at a time when Brewster was still on farly good terms quality and management wise.

[Elvis]

From what I found, the 105's were "refurbed".
I take this as meaning that upon getting them back, Wright tore them all down, did a quick wash, threw a ring, bearing and gasket set in them and sent them on their way.
Unless the cylinders were really bad, they should've been performing as designed.
I understand all of those engines didn't have a whole lot of time on them, though, so I kinda find that hard to believe.
My research also noted that most of those engines came out of DC-3's, so maybe they weren't designed from the onset to work much above 18,000 feet (I think a DC-3 tops out at around 22,000 feet, if I'm not mistaken).
Personally, my thinking is that those planes were probably being converted over for military use and part of the conversion was to give them fresh powerplants, regardless of how many hours their current engines had on them.
Suddenly, Wright (or the USAAF, anyway) finds themselves saddled with a whole bunch of older model, low hour engines.
Gee, what shall we do with those?
Something also tells me the 105's and 205's were sub-varients of the 5 varient of the G series engines, thus all those "5's".
That's just my opinion, though. Nothing to back it up other than a hunch.

That's an interesting notion about flipping over the piston rings to improve oil flow.
Can you post the link where you read that. I'd like to see it.



Elvis

[kool kitty89]

Those are export designations, the G's that is, sometimes they're export specific and sometimes they have 2 designations (1 domestic, 1 export) iirc, but those cases weren't as common.

You're right on the altitude ratings for the engines (not sure for the 205), but the fuel pressurization problem would reate separate issues.

For the F2A-2 however with the -40 engine which had a high critical altitude (950 hp at 26,000 ft iirc), a high altitude carburetor was fitted as well. (hence why the F2A-2 could manage ~340 mph at 26,000 ft)

I'm not sure if this was retained on the F2A-3 since top speeds are listed for only up to 16,500 ft, though this may be for lack of data.

[Elvis]

Those are export designations, the G's that is

The following is an excerpt from that oh so famous write up of Wright engines from 1937...

"The Wright G Cyclone Series represented the latest aircooled aircraft engine developed by the company. Although of the same displacement (1,820 cubic inches) as the F and the F-50, the G Series engines incorporated many refinements and improvements in design principal. Among them was a new cylinder which has a cooling fin area of 2,800 square inches against 1,000 square inches in other Cyclone models. Advancement in foundry technique in the Wright Aeronautical foundry, made possible the casting of cooling fins on the G cylinder head as closely spaced as the teeth on a comb and nearly two inches in depth over the combustion chamber. Cylinder barrels were of Nitralloy steel, nitrided to obtain a cylinder bore with a surface with three times the wear resistance of ordinary heat-treated cylinder barrels. Five large nitriding furnaces were installed to accommodate the daily output of Cyclone G cylinders. More accurate fuel control and the improved cylinder heads on the G Cyclone engine permitted a rating of 1,000 hp at take-off with a weight in certain models of 1.07 pounds per horsepower and fuel consumption of .43 pounds per horsepower at cruising speed.

Other features of the design and construction of the G Series Cyclones were automatic lubrication of the valve gear from a built-in system devoid of all external lines or tubes, mechanism for the operation of two-position hydro-control and constant speed propellers, an accessory section provided with the driving mechanism necessary to meet all of the requirements of modern military and civil transport service, the dynamic damper counterweight which counteracts torsional vibration at all crankshaft speeds and removes all restrictions in the operating range, full pressure baffling of the cylinders, improved oil seals and refinements in the supercharger and induction systems to increase altitude performance.

The G Cyclone was produced in four geared models and their direct drive counterparts. These were the Cyclone GR-1820-G1 rated at 940 hp for take-off, 825 hp at sea level, and 850 hp at 3,000 feet; the Cyclone GR-1820-G2 rated at 1,000 hp for takeoff, 810 hp at sea level, and 850 hp at 5,500 feet; the Cyclone GR-1820-G3 rated at 875 hp for take-off, and 840 hp at 8,700 feet; and the Cyclone GR-1820-G6 rated at 820 hp for take-off and 815 hp at 10,500 feet.

The various G Cyclone models differ only with respect to the amount of supercharging applied. The G-1 has a blower gear ratio of 5.95 to 1; the G-2 a blower ratio of 7 to 1; the G-3 a blower ratio of 8.31 to 1 and the G-6 a blower ratio of 8.83 to 1. All the G Series engines are of the nine-cylinder radial aircooled type and have the following characteristics: bore, 6.125 inches; stroke, 6.875 inches; compression ratio, 6.45 to I; diameter, 54 1/4 inches; length, 43 1/4 inches; dry weight (geared) 1,163 pounds, (direct drive) 1,068 pounds. "

Thus the G series wasn't neccessarily an import designation, just another varient of the 1820.

You're right on the altitude ratings for the engines (not sure for the 205), but the fuel pressurization problem would reate separate issues

Agreed. Fuel pressurization would be a whole 'nother can of worms.




Elvis

[kool kitty89]

Sorry, the letter names are used for almost all normal designations (civilian, export, and the company itsself) the pure numerical designations are for the US millitary. So while a new letter would designate a new design version, this wouldn't be reflected by the millitary models' designations. Same for the V-1710, and virtually all aero engines used in the US.

Hence the major design changes that went on with the gearing of the early V-1710 for example (a couple times, to eliptical gearing, and then one with a stronger spur gear arrangement) the V-1710-33 of the P-40B/C (gearing rated for 1,100 hp), should have a new letter designation than the more powerful -39 of the P-40D/E (gearing rated for 1,600 hp), but it's more difficult to discern by the millitary designations, in less directly stated, since info on the letter blocks seem to be more common on web sites dedicated to engine data.


I found a good site with lists of lots of varients of US piston aero engins with power ratings designations weights size, but I can't seem to find it now.

[Elvis]

Under military designations, varients of a number design are denoted by letter.
For instance, the grear change you mentioned in the V-1710, would have created a "-33A" or possibly what was orignally the V-1710-33, would become the V-1710-33A, making the model with the improved gear the V-1710-33B.
After the letter comes another number. Like with the M4 Sherman tank. you have M4, M4A, M4A-1, M4A-2, M4A-3, etc.



Elvis

[kool kitty89]

Yes but those letters are different than the letter series of the engine, there are also notations like on the R-2800-57C.

THe Manufacture's latter designation series denotes an new version of the engine, while progressive millitary designations are numerical.

[FLYBOYJ]

Under military designations, varients of a number design are denoted by letter.
For instance, the grear change you mentioned in the V-1710, would have created a "-33A" or possibly what was orignally the V-1710-33, would become the V-1710-33A, making the model with the improved gear the V-1710-33B.
After the letter comes another number. Like with the M4 Sherman tank. you have M4, M4A, M4A-1, M4A-2, M4A-3, etc.



Elvis

Yes but those letters are different than the letter series of the engine, there are also notations like on the R-2800-57C.

The numbers and all letters after an engine designation meant an attachment for a specific aircraft, a component that was different or sometimes even a different engine configuration.

Here's a Type Certificate Data Sheet for the R-2800. Read all the dash numbers and notes...

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/cf0f9435e20432008525676a006759e7/$FILE/ATTIAV5I/5E-8.pdf

[kool kitty89]

Weren't there also sometimes additions like 'W' to the designation for water injection?

And for the series itsself from what I've read the manufactures designation (also used for civilian and export users) is with litters than addtional numbers for variants of the model. ie R-1820A, B, C, D, E, etc, and G-5, 105, 205, etc. With additional number/letter for specific excessories, or modifications.

But the USAAF (and USN, USMC) had separate numerical designations for the engines, ie R-1820-40, or V-1710-39, with additional letters or numbers for specific excessories or modifications.
For example, the V-1710-39 and -73 of the P-40D/E and K, were AAF designations for the V-1710-F3R and -F4R engines. (R for "right handed" iirc, clockwise when seen from the pilot's perspective)

[FLYBOYJ]

Weren't there also sometimes additions like 'W' to the designation for water injection?

Yes...

And for the series itsself from what I've read the manufactures designation (also used for civilian and export users) is with litters than addtional numbers for variants of the model. ie R-1820A, B, C, D, E, etc, and G-5, 105, 205, etc. With additional number/letter for specific excessories, or modifications.

But the USAAF (and USN, USMC) had separate numerical designations for the engines, ie R-1820-40, or V-1710-39, with additional letters or numbers for specific excessories or modifications.
For example, the V-1710-39 and -73 of the P-40D/E and K, were AAF designations for the V-1710-F3R and -F4R engines. (R for "right handed" iirc, clockwise when seen from the pilot's perspective)

Correct as well.

[Elvis]

Yes but those letters are different than the letter series of the engine, there are also notations like on the R-2800-57C.

THe Manufacture's latter designation series denotes an new version of the engine, while progressive millitary designations are numerical.

You're correct.
I was confusing manufacturer and military designations.
Sorry about that.



Elvis

[warhawk]

I have models of both planes in 1/72nd, and both of them look cool to me...