Griffon engines

[paul.mercer]

Gentlemen,
Would anyone know if the RR Griffon engine was ever used in either the Mustang or Lancaster? I believe they were fitted to some of the long range anti sub aircraft like the Shackleton right up till they were replaced in the 1990's.
Also, The Merlin had 12 cylinders for 27 litres how many did the 36 litre Griffon have?

[Dave Saxton]

The Griffon was never used in the Mustang. The light weight versions used up powered Merlins because the Griffon weighed 300 lbs more and would required cowling bumps. I don't believe the Griffon was used in the Lancaster either (perhaps prototypes), but was used by the Avro Shackleton.

The Griffon was also a V12 like the Merlin but was developed from the "R" or race series V12 engines from 1933 instead of the smaller block krestrel V12 engine from which the Merlin was developed from. Some sources indicate that the Griffon had the same stroke but a bigger bore than the Merlin (I'm not sure if this is the case why the Griffon was taller and 300 lbs heavier? likely larger heads to support larger valves and ports...) Contrary to popular believe the greater power potential of a bigger bore motor comes not so much from the greater displacement but from the greater total air flow allowed by the unshrouded and larger valves, especially with forced induction. It like most high performance aero piston engines used four valves per cylinder.

The P-51 Mustangs with the 5 blade Rotel props, usually associated with the Griffon, were the XP-51G models. This version used the fantastic RR RM.14 SM Merlin engine with 2200 HP instead of the Griffon. This was the same HP ouput as a late model Griffon but still was Merlin based.

The production version of the light weight P-51, the P-51H, used the Packard built Merlin 9 series engine instead. This Merlin produced 2200Hp (only in war emergency power) like the RM14 SM, but had to use water/methanol injection and higher octane fuel to attain this. Without water/meth injection and the lower boost pressures during normal operation; the perfomance was actually slightly less than the Merlin 60s series, and of course the Griffon. The H used a four blade prop. The reason why the RM14 SM motor wasn't used was because the USAAF refused to pay further royalties to RR. Hence the Packard built late model Merlin.

Many in the AAF really wanted to go back to the General Motors Allison V1710 but with a two stage supercharger like the Merlin. This would have been the P-51J instead of the H. The newer Allison failed to meet performance expectations despite the upgraded supercharger. Schmued had figured out how to make the Allison V1710 work better through modified induction design, but GM refused to listen.

[paul.mercer]

Thanks Dave,
I have to say the correspondants on this forum really know their stuff, how lucky we are to have such a group of experts on so many diverse subjects.
I believe that the P51 or its variation is still used for pylon racing in the US, I wonder if they still use the Packard Merlin and if so where do they get the spares from - or are they still made?

[Dave Saxton]

The Merlin's used for air racing are made up from the hodge podge of the few remaining parts world wide. RR or Ford sourced Merlin parts are prefered to Packard sourced parts, as those are usually considered higher quality, but at this stage, it's if it's a good Merlin part, then thank goodness regardless. The bomber motors, which are mostly Ford, are prefered for foundations of race builds, over the fighter motors, because they have stouter crank cases, and cylinder cases, and so forth. The stouter bomber supercharger cases and the bomber single stage superchargers are prefered for racing anyway. There is a remanfactured Merlin parts market. Sometimes engine builders simply must fabricate or have frabricated a replacement part themselves. There is a connecting rod for a particular Cat diesel engine that works perfectly as a replacement connecting rod in a Merlin. Also connecting rods from Allisons will work in a Merlin in some modified bore and stroke cases. Jack Rousch of Nascar racing fame makes specialty Merlin parts. Most of his parts are top quality, except his reputation for Merlin parts suffered briefly from the "rocker arm fiasco". Roush designed a replacement light weight roller bearing rocker arm based on auto racing rocker arm design. The part wasn't heavy duty enough and resulted in some failures.

There have been two P-51 air racers using Griffons. One is still competitive and uses a three bladed (six total) counter rotating prop. One of the problems for Griffons today is finding a suitable prop for it.

[Byron Angel]

Very interesting thread. And some fascinating info from David.

B

[Dave Saxton]

Paul and Byron or anybody interested,

You may be interested in this correspondance (I have permission to share this here) between a Power and Airframe Mechanic associated with unlimited air racing and myself. I was asking questions about the P-51 racer Voodoo:

Voodoo comes in right behind Dago as the 3rd fastest of the highly modified P-51s.

According to Skip Holm, who has raced them all.

Strega is the fastest - Built by David Price with the lessons he learned on Dago

Dago is 2nd Fastest – Built by David Price and a team from Lockheed (Basically a skunk works after hours project)

Then Voodoo – I believe it’s mods were designed by a mid level engineer at General Dynamics.

Destroyed are Miss Ashley – a P-51 Fuselage with Learjet Wing and tail. Skip says this was the fastest of them all. The tail came off in a race with owner Gary Levitz flying. The tail was little more than hacked in and harmonic fatigued caused the failure. A different length and spacing of the longerons would have prevented it. The airfoil on the Lear and Mustang wing is the same NACA series but the Lear wing is much thinner. Skip says Miss Ashley took full power and twice the runway to takeoff.

Now look at the race records and it is obvious that the team is more important than the aircraft. When Dago got parked its team core went to a Sea Fury and they won the gold.

You can have the hottest ship in the field but if you can’t turn the laps without breaking then it doesn’t matter

[Byron Angel]

Very interesting post, Dave. Thanks for sharing. It never really struck me that aeronautical engineers would be moonlighting on such projects, but it seems so obvious when you read about it actually happening. Reminds me of the Chrysler engineers in the mid-60s building and racing their hemi drag cars on weekends - those were the days.

Byron

[Sunbury2]

The Australians developed a long range fighter prototype the CA-15. It was essentially a Griffon Engined Mustang.

http://en.wikipedia.org/wiki/CAC_CA-15

http://www.raafwarbirds.org.au/aircraft.htm

It's development never went past the prototype stage, but its performance was apparently fast. In a test flight it achieved 502 mph in level flight. The jet era had already arrived so it was quietly scrapped. It does show what a Griffon engined Mustang might have been like.

[sandym]

May be worth pointing out that the Griffon rotates in the opposite direction to the Merlin.

Caught Spitfire pilots out during the war as the Griffon engined ones 'swung' in the 'wrong' direction on take-ff.

[Ken Thompson]

May be worth pointing out that the Griffon rotates in the opposite direction to the Merlin.

Caught Spitfire pilots out during the war as the Griffon engined ones 'swung' in the 'wrong' direction on take-ff.

Why is that is it, because of a double reduction gear box?

[tommy303]

Engine torque through the large props creates quite a gyroscopic effect. Why the designers chose a different rotation, though, is beyond me.

[Dave Saxton]

The different rotation may of had to do with some multi engine applications (Shakleton) and/or prop combinations. A counter rotating prop helps overcome some of the tourqe roll issues with the higher tourqe engines.

Here's a Griffon powered Spit with counter rotating prop:

http://www.youtube.com/watch?v=VZ8BUNJYtOo

Some of the late model BF-109s with big Junkers Jumo 213 motors were nick named the Mule because of the nasty tourqe aspects. BTW, some of those Czech built late model 109s played a pivitol role in Israel's War of Independence.

Here's a lang nase 190D with a Jumo (eventually) being started followed by some Merlin Mustangs:

http://www.youtube.com/watch?v=4Y5LBUVS ... re=related

Here's a Griffon powered Spit with the 5 blade Rotel (Wood) prop:

http://www.youtube.com/watch?v=MiCI8xeb ... re=related

Just a touch rougher idle than a Merlin as can be heard on the counter rotating vid as well.

[Byron Angel]

Here is a case of a Merlin engined craft that requires judicious use of throttle to avoid unpleasant torque effects.

Go here - http://www.youtube.com/watch?v=SIj2GVfua84

B

[tommy303]

So too did the Mosquito, as it did not have right and left turning engines to counteract torque.