P-40 what-if

[Elvis]

No worries, Colin. It was a fair comment. You asked, so I tried to clarify.

I think if a P-40 were to be re-engined with a Griffon, I suppose the F and L versions would be the best candidate, since mod's to use the Merlin would already be in place (and I'm thinking mostly about countering the greater weight. The Merlin's about 300-400 lbs. heavier than the Allison).

So lets start throwing some specs around.

Here's some for the Griff 58:

Model: Griffon 58
Original Application: Avro Shackleton reconnaissance plane
Engine Type: V-12 Piston Aero Engine, 60° "V" (angle between banks)
Material: Aluminum crankcase, cylinder banks and heads; Alloy pistons; Steel liners, rods, cranks, etc.
Bore x Stroke: 6.0" x 6.6"
Compression Ratio: 6.0:1
Supercharger Type: Two-speed, single-stage centrifugal 13.4" impeller
Supercharger Ratio: Medium Speed (MS) - 6.615:1, Full Speed (FS) 7.70:1
Boost Control: Automatic via Rolls-Royce auto boost regulator, w/increased boost when ADI active
Fuel System: Speed/Density type Fuel Injection (injected into eye of supercharger)
Weight: 2,000 lbs
Power: 2,450 HP takeoff at 2,750 RPM at SL with 25 psig boost using 115/145 PN fuel
Performance: 0.82 lbs/hp, 314 psi BMEP, 0.42 lbs fuel/hp/hr SFC
Max. Piston Speed: 3,025 ft/min

...and some interesting historical comments about why the engine came to be:

"Development of the Griffon Engine began at Derby, England 1939 when Harry Cantrill was assigned to develop a conventional V-12 scaled up from the 1650 cu-in Rolls-Royce Merlin. The engine was intended to produce more than 1,500 HP at low altitudes for naval torpedo bombers. For maximum utility, it was decided to keep the engine as compact as possible so it could replace the Merlin in some applications. The resulting design had approximately the same frontal area as the Merlin and was actually shorter. The bore and stroke was the same as the Rolls-Royce "R" Schneider Cup race engines of 1929 and 1931, which were direct ancestors to the Griffon, resulting in an displacement of 2,240 cubic inches.. The Merlin proportions of the Griffon were partially achieved by moving the camshaft drives and magneto to the front of the engine."

(quote and engine specs came from here)

Ok, Clay, you got me.
This is looking like an even easier re-fit than how I was imagining it a few days ago.
Sorry I doubted you.

So, I think I brought this up before, but aren't there any Mechanical Engineers in the house?....even "amatuer" ones?
I'd like to see some mock-up's (on paper is fine) of what one would look like, if you started with either the F or L version of the P-40.




Elvis

 

[Colin1]

I think if a P-40 were to be re-engined with a Griffon, I suppose the F and L versions would be the best candidate, since mod's to use the Merlin would already be in place (and I'm thinking mostly about countering the greater weight. The Merlin's about 300-400 lbs. heavier than the Allison)

Hi Elvis
don't know if it would make that much difference from the P-40E onwards. The P-40F was in fact just a re-engined P-40E and the P-40L was a P-40F in everything but name, it could be stripped/configured for different types of ops but I'm uncertain of the merits of this.
A P-40K was in turn just a P-40F re-re-engined (!) back to the Allison with the cowling, ducting and Allison carburettor intake and scoop shape re-introduced.

The Griffon II is about 240lbs heavier and the Griffon 61 about 400lbs heavier than the Allison, so

Merlin 300-400lbs heavier than the Allison
Griffon 240-400lbs heavier than the Allison

roughly similar problems weight-wise

 

[Elvis]

Gee, that's odd.
If you look at the specs I listed for the Griffon 58, it shows that its about 700 lbs. more than the Allison.
Was that a particularly heavy version?

Noting the rest of your comments, then base it on the "N"!
That was the newest version that was produced and I understand there was some structural re-engineering with that version (possibly the "M", too?).
Essentially, lighter without sacrificing reliability (how I understand it).


Elvis

 

[MikeGazdik]

Hi Elvis
don't know if it would make that much difference from the P-40E onwards. The P-40F was in fact just a re-engined P-40E and the P-40L was a P-40F in everything but name, it could be stripped/configured for different types of ops but I'm uncertain of the merits of this.
A P-40K was in turn just a P-40F re-re-engined (!) back to the Allison with the cowling, ducting and Allison carburettor intake and scoop shape re-introduced.

The Griffon II is about 240lbs heavier and the Griffon 61 about 400lbs heavier than the Allison, so

Merlin 300-400lbs heavier than the Allison
Griffon 240-400lbs heavier than the Allison

roughly similar problems weight-wise

The K-model P-40 had a dorsal fin fillet and a deeper tail fin to aid in lateral stability. That is different than the previous P-40's and certainly something a Griffon would need. But I think you would have to go with both, the longer fuselage ( I think first out with the L model ), and deeper fin and the fillet to counter the torque from the Griffon.

I love hot-rods, and this is going to be one for sure!!!

 

[Colin1]

The K-model P-40 had a dorsal fin fillet and a deeper tail fin to aid in lateral stability. That is different than the previous P-40's and certainly something a Griffon would need. But I think you would have to go with both, the longer fuselage ( I think first out with the L model ), and deeper fin and the fillet to counter the torque from the Griffon

Ks were confusing Mike
read my Curtiss P-40 Pictorial History thread - there were long, sleek Ks and there were short, stubby Ks

 

[Elvis]

Hey guys, what about the prop?!

With substaintially more engine, more prop would be in order, to maximize the usage of the larger powerplant.

...but which way should we go?

More blades?
Longer blades?
Wider blades?
A combination of the above, or something else entirely?

What say you, people?




Elvis

 

[Colin1]

With substantially more engine, more prop would be in order, to maximize the usage of the larger powerplant.

More blades?
Longer blades?
Wider blades?
A combination of the above, or something else entirely?

I don't know

the RAF tended to go for more blades
the USAAF seemed to have a blend of add more blades and make them longer
the Luftwaffe seemed to stick with fewer blades from start to finish that just got wider

I'm not sure empirical data would reveal decisive advantages of one over any of the others which may be why the Luftwaffe stuck with 3 blades throughout but just made them wider.

I'd plump for a 4-bladed hydromatic arrangement, it didn't do the P-51D any harm but that flew with the Merlin, not the Griffon. Easy way out would be manufacturer's recommendations, so whatever Rolls-Royce and Rotol/Hamilton Standard/Aeroproducts came up with; one would have to assume that engine power/airscrew config were balanced to get the best out of each other.

 

[Shortround6]

IF you need more propellor blade area you have two basic choices, wider blades or more blades.

Increasing diameter only works if you have enough clearance which most single engine fighters did not.

Increasing diameter would mean new, longer landing gear or tricker landing gear that extended in length as it lowered. It also means a steeper ground angle with more vision problems and perhaps lift/drag problems for take off. Extra power helps acceleration but steeper ange of attack creates more drag until tai wheel lifts?

 

[MikeGazdik]

I will have to read you stuff on the P-40 Colin, didn't know there were long body ones.

Instead of a Griffon, I think Chrysler was working on an inverted V-12. Maybe that would be an interesting switch. As a matter of fact, years ago I read about this engine and it may have been tried in the P-40, not sure. I think it was fairly large.

 

[Shortround6]

Yes' chrysler was working on an engine but it was an inverted V-16. Before some bright spark gets the idea of cutting out 4 cylinders and turning it into a V -12 please see:

Chrysler IV-2220 - Wikipedia, the free encyclopedia

and

Republic AP-10 XP-47H Thunderbolt

 

[Elvis]

There was also the Continental "Hyper" inverted V-12 engine.
1600HP from only 1430 cu.in.
I understand it was overly complicated and rather heavy and thus, never entered production.
However it introduced some rather innovative ideas at the time (1932), including the hemispherical combustion chamber, a centrally located spark plug and sodium filled exhaust valves.
I believe the hemi c.c./piston shape and the sodium filled exhuast valve ideas were eventually incorporated into the V-1710.
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Colin1,

Would you have any links that alude to the recommeneded prop size for the Griffon V-12?



Elvis

 

[Colin1]

Would you have any links that alude to the recommeneded prop size for the Griffon V-12?

I'll certainly have a dig around

 

[Shortround6]

The Army gave Continental about 1/2 million dollars during the thirties to design and develop their version of the 'Hyper" engine. Unfortunatly the Army only dribbled out the money a little at a time so the first complete 12 cylinder version didn't run untill 1939. by which time it was way behind the Allison in timing.

See: Continental I-1430 - Wikipedia, the free encyclopedia

Which isn't too far of the mark, except the " At the time it was an extremely competitive design, offering at least 1,300 hp (970 kW) from a 23 liter displacement; the contemporary Rolls-Royce Merlin offered about 1,000 hp (700 kW) from 27 l displacement,..." part and a few others
At the time the Melin was in squadron service at 1000HP and in 1938 the Merlin was "OFFERED" at the 1938 Paris airshow with a 2 speed super charger at over 1200hp. The Continental may have made it through a 50 hr test at 1000hp (not 1300) in 1939.

The Continental, while it used the features you mention didn't introduce any of them. ALL high powered aircraft engines were using sodium filled exhaust valves by 1939. High powered includes the P&W R-1340 of 600HP. A few low powered engines were using them too, like 6 cylinder Rangers of 175HP.

All but the smallest (40HP or so) Aircraft engines in the US were required by law to have dual ignition. 2 spark plugs per cylinder.

By the way, it seems rather doubtful that the Continental ever came close to giving it's rated HP in an actual airplane.

SEE> http://home.att.net/~jbaugher1/p49.html

And> http://home.att.net/~jbaugher1/p67.html

 

[Elvis]

Shortround6,

I gleaned my information on the Continental engine off something I saw a few years ago on the USAF's NAtional Museum page.

"The development of the liquid-cooled Continental Hyper high-horsepower engine began in 1932. It featured cylinders with "spherical" combustion chambers and sodium cooled exhaust valves. An upright V-12 engine was planned, but emphasis was later changed to an inverted V-12 engine for pursuit planes. Continental built the inverted V engine in 1938 and successfully tested it in 1939. In 1943 the 1,600-hp IV-1430 engine, later redesignated the XI-1430, was tested extensively in the Lockheed XP-49, a modified version of the P-38 Lightning. In 1944 it was also tested in the McDonnell XP-67. Only 23 I-1430 series engines were delivered. Although more powerful and lighter than the nearest competitor, the engine was not produced because tooling capacity for large scale production was not available.

TECHNICAL NOTES:
Model: Continental I-1430 Hyper
Type: 12-cylinder, liquid-cooled, inverted Vee
Displacement: 1,430 cu.in.
Horsepower: 1,600
RPM: 3,200
Weight (dry): 1,615 lbs."

I didn't remember anything about it being installed in an actual airplane, but apparently it was.
Also, it seems I wrong about why it was never produced.
My apologies for the incorrect information in my prior post.


Elvis

 

[Elvis]

I'll certainly have a dig around

Thanks!
Look forward to reading about your findings.


Elvis

 

[gumbyk]

Elvis, it was fitted to the XP-67 "Bat"

Pictures of the McDonnell XP-67 Bat / Moonbat - Aircraft

A nice looking aircraft...

 

[Colin1]

Look forward to reading about your findings

Nothing definitive about the Griffon specificallly (yet)
but did find these interesting, various degrees of technical depth:-

Aerospaceweb.org | Ask Us - Number of Aircraft Propeller Blades

Propeller Thrust

Propeller Propulsion

Engine and Propeller Efficiency

 

[Elvis]

gumbyk,

Thanks for the info. I'm aware of the "bat" but never knew about its powerplants.
------------------------------------------------------------------

Colin1,

Great detective work!
Thanks for posting the links. I'll "wade" through those and see what I come up with.



Elvis

 

[Elvis]

So, getting back to the initial question about installing an R-R Griffon into a P-40, here's some dimension specs I pulled off of Wikipedia.

R-R Merlin 66
Type: 12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine
Bore: 5.4 in (137.2 mm)
Stroke: 6 in (152.4 mm)
Displacement: 1,648.96 in³ (27.04 L)
Length: 88.7 in (225.3 cm)
Width: 30.8 in (78.1 cm)
Height: 40 in (101.6 cm)
Dry weight: 1,645 lb (746.5 kg)

Components
Valvetrain: Overhead camshaft-actuated, two intake and two exhaust valves per cylinder, sodium-cooled exhaust valve stems
Supercharger: Two-speed two-stage, boost pressure automatically linked to the throttle, water-air aftercooler installed between the second stage and the engine.
Fuel system: Twin-choke updraft carburettor with automatic mixture control
Fuel type: 100 Octane from mid 1944 100/150 Grade Aviation fuel
Oil system: Dry sump with one pressure pump and two scavenge pumps.
Cooling system: 70% water and 30% ethylene glycol coolant mixture, pressurised.

Performance
Power output: (Note: 100 Octane fuel, +12 lb boost)
1,315 hp (981 kW) at 3,000 rpm at take-off.
1,705 hp (1,271 kW) at 3,000 rpm at 5,750 ft (1,753 m) (MS gear)
1,580 hp (1,178 kW) at 3,000 rpm at 16,000 ft (4,877 m) (FS gear)
(100/150 Grade fuel, +25 lb boost)
2,000 hp (1,481 kW) at 5,250 ft (1,600 m) (MS gear) (bmep = 320.2psi)
1,860 hp (1,387 kW) at 11,000 ft (3,353 m) (FS gear)
Specific power: 0.95 hp/in³ (43.3 kW/L)
Compression ratio: 6:1
Power-to-weight ratio: 0.80 hp/lb (1.76 kW/kg) take-off; 1.21 hp/lb (2.69 kW/kg) 100/150 grade fuel/MS gear.
--------------------------------------------------------------------------------------------------------------------------------

R-R Griffon 65
Type: 12-cylinder supercharged liquid-cooled 60° Vee aircraft piston engine
Bore: 6 in (152.5 mm)
Stroke: 6.6 in (167.6 mm)
Displacement: 2,240 in³ (36.7 L)
Length: 81 in (2057 mm)
Width: 30.3 in (770 mm)
Height: 46 in (1168 mm)
Dry weight: 1,980 lb (900 kg)

Components
Valvetrain: Two intake and two exhaust valves per cylinder with sodium-cooled exhaust valve stems, actuated via an overhead camshaft.
Supercharger: Two-speed, two-stage centrifugal type supercharger, boost pressure automatically linked to the throttle, water-air aftercooler installed between the second stage and the engine
Fuel system: Triple-choke updraft carburettor with automatic mixture control
Oil system: Dry sump with one pressure pump and two scavenge pumps
Cooling system: 70% water and 30% ethylene glycol coolant mixture, pressurised

Performance
Power output: 2,035 hp (1,520 kW) at 7,000 ft (2,135 m) 1,820 hp (1,360 kW) at 21,000 ft (6,400 m)
Specific power: 0.91 hp/in³ (41.4 kW/L)
Compression ratio: 6:1
Power-to-weight ratio: 1.03 hp/lb (1.69 kW/kg)
--------------------------------------------------------------------------------------------------------------------------------

Allison V-1710-85
Type: 12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine
Bore: 5.5 in (140 mm)
Stroke: 6 in (150 mm)
Displacement: 1,710.6 cu in (28.032 L)
Length: 98.53 in (2,503 mm)
Width: 29.28 in (744 mm)
Height: 41.18 in (1,046 mm)
Dry weight: 1,445 lb (655 kg)

Components
Valvetrain: Two intake and two exhaust valves per cylinder with sodium-cooled exhaust valves, operated by a single gear-driven overhead camshaft per each bank of cylinders.
Supercharger: Centrifugal-type, single-stage, impeller 10.25 in (260 mm) in diameter with 15 vanes.
Fuel system: Bendix Stromberg carburetor with automatic mixture control
Fuel type: 100 octane
Oil system: Dry sump with one pressure and two scavenge pumps.
Cooling system: Liquid-cooled with a mixture of 70% water and 30% ethylene glycol, pressurized.

Performance
Power output: 1,325 hp (988 kW) at 3,000 rpm (bmep=204.5 psi)
Specific power: 0.77 hp/in³ (35.25 kW/L)
Compression ratio: 6.65:1
Power-to-weight ratio: 0.92 hp/lb (1.51 kW/kg)
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I'm quite surprised by how close in physical dimension all of these engines are, considering the wide range of displacements listed.
The only thing that concerns me here is weight.
The Griffon that is listed is 553 lbs. heavier than the Allison and 353 lbs. lbs. heavier than the Merlin, with the Merlin coming in at 200 lbs. over the Allison.
I suppose one could extend the fuselage and maybe move the pilot back a little, but I wouldn't want to move him far, lest we fall into a "P-37" situation again.
I wonder how much extension (of the fuselage) would be needed to counter that increase in weight?
...maybe if the radiator were moved rearward, ala P-51, then the chin could be shrunk, OR, part of that space could be used to help contain the slight increase in size of the engine and part of it could be used to house the aftercooler.
That might balance things out, right there.
Changes to the tail would in order, as well, to counter the increased torque of the larger engine....hmmm....




Elvis

 

[Elvis]

Nothing definitive about the Griffon specificallly (yet)
but did find these interesting, various degrees of technical depth:-

Aerospaceweb.org | Ask Us - Number of Aircraft Propeller Blades

Propeller Thrust

Propeller Propulsion

Engine and Propeller Efficiency

Colin,


Still looking into the links you posted, but a quick check at Wiki says the Griff-powered Spit Mk. IV used a four bladed Rotol prop of 10.5 ft. diameter.
The P-40 was already using an 11' Curtiss-Electric prop, so maybe upping the blade count from 3 to 4 would be all that were needed.......ah, back to the research.



Elvis