Griffons and Allisons

[MARK SHANE]

Here was a question I had are Rolls Royce Griffons more rare than the Merlins? Are parts harder to come by for them? And are there many people that know how to work on them and the gear box for the contra rotating propellers I was told they can be trouble. As far as Allisons go aside from Polar bear and the P40s that race in the Bronze and Silver class is there a reason why race teams wont use Allisons in Gold racers can't they be souped up just like a Merlin or is it just a availability issue. Thanks Mark.

[Big_Jim]

Re: Griffons and Allisons

Here was a question I had are Rolls Royce Griffons more rare than the Merlins? Are parts harder to come by for them? And are there many people that know how to work on them and the gear box for the contra rotating propellers I was told they can be trouble. As far as Allisons go aside from Polar bear and the P40s that race in the Bronze and Silver class is there a reason why race teams wont use Allisons in Gold racers can't they be souped up just like a Merlin or is it just a availability issue. Thanks Mark.

I'm sure Sparrow will ultimately chime in here, but bottom line even though the Allison has more cubic inches and stronger rods, the bottom end and supercharger on the Merlin is much better. To quote a dear friend of mine "a Merlin in a box is faster than an Allison on a Mustang". That's why the Mouse Motor (aka Allison-rod Merlin) is the best of both worlds...you take the strong points of each and combine them together.

As for the Griffon, even though there weren't nearly as many produced, I'm sure there is still a bigger stash to pull from than what is left of the Merlin. And while Rolls Royce didn't make a worse engine with the Griffon, it came along at the beginning of the jet age and wasn't produced in the mass quantities as it's younger sibling.

The Shackelton prop setup isn't inherently "trouble"...no more than any other setup, except you have twice the fun to play with. If you lose oil pressure the blades to to flat pitch, the props overspeed, and it's like a huge six-blade boat anchor out on the nose. Airplane goes 400 knots to 50 knots in a real hurry. It's happened twice in the racing Mustangs, both resulting in crashes.

But the thing to remember is that the system (at least on the Shackelton version, not necessarily on the Spit/Seafires that used them) was designed to go out on a 12 hour mission and loiter around at 35 inches of manifold pressure all day long. In the racing Mustang, you're trying to stuff 100+ inches of mercury down it, and that oil/prop system is running WAY above what it's comfort zone is.

And anyone who saw Skip lose the prop governor in Jeannie back in '82 will testify that the same thing happened to the 4-blade Aeroproducts prop, so it's kind of unfair to tag the Shackelton counter-rotating system as trouble...as I said, it's no different than any other system that is running such huge manifold pressure and RPM's.

[tow-3]

Re: Griffons and Allisons

I think one of the biggest "problems" with the griffon is since there where so few aircraft using the contra-rotating set up, there is not a lot of props to choose from. I think, and I'm sure the experts here will correct me if i'm wrong, that the shackelton blades just are not the right airfoil and profile for racing. As big jim said, it was made to hang around all day at a low power setting. there is only so much re-profiling and re-pitching you can do to them.
I think that a lot of speed could be found on PM with a blade more optimized for racing, if such a prop could be found.

[JCP]

Re: Griffons and Allisons

"A Merlin in a box is faster than an Allison on a Mustang"

I believe what you meant to say was:

"You can fly an Allison farther than you can ship a Merlin"

JC

[Big_Jim]

Re: Griffons and Allisons

"A Merlin in a box is faster than an Allison on a Mustang"

I believe what you meant to say was:

"You can fly an Allison farther than you can ship a Merlin"

JC

Yeah, but JC, you're straddling the fence there....and perhaps I'll remind you that if you bring the Bee to Reno this year and see just how much faster it goes than the Parrothead.

[Bob]

Re: Griffons and Allisons

quick question. Can you use an electric pump to control the prop pitch? That may negate the increased oil pressure?

[Smee Again]

Re: Griffons and Allisons

quick question. Can you use an electric pump to control the prop pitch? That may negate the increased oil pressure?

That would be the general idea behind an Aeroproducts prop/governor system. Aeroproducts uses a hydraulic governor system which is completely independent of the a/c's oil supply. The Achilles Heel for Aeroproducts systems in years past was always the failure of prop torque seals, which were routinely compromised by running very high power settings. The leaky seals would then lead to fluid-streaked back plates, glare shields and windscreens, and if left unchecked, failure of the governor due to lost hydraulic pressure. We experienced this very failure on Ridge Runner III in 2005 while running an Aeroproducts P-51H propeller.

SA

[JCP]

Re: Griffons and Allisons

Yeah, but JC, you're straddling the fence there....and perhaps I'll remind you that if you bring the Bee to Reno this year and see just how much faster it goes than the Parrothead.

I know! I'm having a hard time breaking that habit of ragg'in on the Merlins. I must say that the 724 we have in the Boise Bee is the smoothest engine I've ever been behind. I absolutely LOVE that thing!

JC

[Matt58]

Re: Griffons and Allisons

JCP, not trying to steal the thread here, but you put on one impressive performance today in the P-40! In fact, I was rather impressed with the enitre airshow. very nicely done!

[MARK SHANE]

Re: Griffons and Allisons

I'm sure Sparrow will ultimately chime in here, but bottom line even though the Allison has more cubic inches and stronger rods, the bottom end and supercharger on the Merlin is much better. To quote a dear friend of mine "a Merlin in a box is faster than an Allison on a Mustang". That's why the Mouse Motor (aka Allison-rod Merlin) is the best of both worlds...you take the strong points of each and combine them together.

As for the Griffon, even though there weren't nearly as many produced, I'm sure there is still a bigger stash to pull from than what is left of the Merlin. And while Rolls Royce didn't make a worse engine with the Griffon, it came along at the beginning of the jet age and wasn't produced in the mass quantities as it's younger sibling.

The Shackelton prop setup isn't inherently "trouble"...no more than any other setup, except you have twice the fun to play with. If you lose oil pressure the blades to to flat pitch, the props overspeed, and it's like a huge six-blade boat anchor out on the nose. Airplane goes 400 knots to 50 knots in a real hurry. It's happened twice in the racing Mustangs, both resulting in crashes.

But the thing to remember is that the system (at least on the Shackelton version, not necessarily on the Spit/Seafires that used them) was designed to go out on a 12 hour mission and loiter around at 35 inches of manifold pressure all day long. In the racing Mustang, you're trying to stuff 100+ inches of mercury down it, and that oil/prop system is running WAY above what it's comfort zone is.

And anyone who saw Skip lose the prop governor in Jeannie back in '82 will testify that the same thing happened to the 4-blade Aeroproducts prop, so it's kind of unfair to tag the Shackelton counter-rotating system as trouble...as I said, it's no different than any other system that is running such huge manifold pressure and RPM's.

Oh ok cool thanks Big Jim I didnt know they did that with the Merlins as far as using Allison rods thats cool! Thank you for the Griffon info as well.

[JCP]

Re: Griffons and Allisons

JCP, not trying to steal the thread here, but you put on one impressive performance today in the P-40! In fact, I was rather impressed with the enitre airshow. very nicely done!

Thanks Matt...we had lots-O-fun for sure!

Mark Peterson (Diamondback and Hell-Er-Bust) is the spark plug and driving force behind the re-vitalization of the Caldwell Show called "Celebration of Flight Idaho". He and his team really are working hard to put and build a first class Air Show.

JC

[Bob]

Re: Griffons and Allisons

Any video available?

[Matt58]

Re: Griffons and Allisons

Any video available?

I got some on my i-pod; let me see if I can upload any of it tonight when I get off work!

[Matt58]

Re: Griffons and Allisons

Thanks Matt...we had lots-O-fun for sure!

Mark Peterson (Diamondback and Hell-Er-Bust) is the spark plug and driving force behind the re-vitalization of the Caldwell Show called "Celebration of Flight Idaho". He and his team really are working hard to put and build a first class Air Show.

JC

Well from a spectators view-point, I can say that he is definately heading in the right direction. I was very impressed with the show. And Mark's demonstration in Hell-er-bust was just plain awesome! Great job to everyone invloved and I can't wait for next year!

[kiwiracefan]

Re: Griffons and Allisons

Heading back on topic.. the late production seafires the Mk 46/47 used a contra-prop setup infront of griffon 81 or 85 series, but with only a 115 odd airframes produced and with 185 shackletons which used the 50 series griffons, there are a lot less with contra setups but there were a lot of fairy fireflies, spitfires and earlier mk seafires there were a lot of other griffons out there that used either 4 or 5 blade props, but again there are less around than the total of merlins built.