PM 38 Why the difference in prop length

[wingman]

Re: PM 38 Why the difference in prop length

Sound? Tie between Strega and Precious Metal for first, tie between Tigercat and 232 for third...

[Smee Again]

Re: PM 38 Why the difference in prop length

This one!

Ah, ok. Yeah, that was the 2005 scoop extension fashioned by MRE. But I gotta ask, is there really NO way to reroute a heat exchanger into the hell-hole of that beastie? I'm guessing it's just a lack of space with the downdraft ram intake on the Griffon. True?

Truth is, that 2005 extension was great, but the scoop MRE built for RRIII in 2009 was in a whole different class. MUCH cleaner in every way.

SA

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

Ah, ok. Yeah, that was the 2005 scoop extension fashioned by MRE. But I gotta ask, is there really NO way to reroute a heat exchanger into the hell-hole of that beastie? I'm guessing it's just a lack of space with the downdraft ram intake on the Griffon. True?

Truth is, that 2005 extension was great, but the scoop MRE built for RRIII in 2009 was in a whole different class. MUCH cleaner in every way.

SA

Pete Law says that the H-model heat exchanger can't get rid of the extra BTU's the Griffon puts out.

[wingman]

Re: PM 38 Why the difference in prop length

I sure did like that last scoop that Mike did, though. It was a work of art! It's really too bad that one cannot be used somehow.

Neal

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

There's a possibility there may be some howling coming from the pilot...

I always heard something like this over the comm 2 radio Thom.

[YT]http://www.youtube.com/watch?v=0cVlTeIATBs[/YT]

[Leo]

Re: PM 38 Why the difference in prop length

You could actually hear the engine over the prop noise this year. It sounded WICKED.
Always liked the Merlin's at full tilt. The Tigercat is just a plain sexy sound, this year PM beat it on the cool sound scale.
Nothing will ever replace, for me at least, the sounds made by White Lightnin' during Lefty's routines. Especially when it bounced off the clouds a little. Sigh.

[AAFO_WSagar]

Re: PM 38 Why the difference in prop length

There's a possibility there may be some howling coming from the pilot...

Thom, I can't thank you enough for coming in here and posting such as you are! Over the years, we've had a few racers who find it comfy enough here to sit and "chat" with the "gang" and share your experiences, your visits and posts are always greatly appreciated by all!.. In many ways, the Internet is a wonderful place!

I also gotta thank you and your crew for taking my friend who I reintroduced to the races this year "under your wing".. I think him hanging with you's guys was the high point of his visit! Did anyone gain any weight during the races..

Again, thanks to Thom, Wild Bill and the other crew and pilot "doods" who visit here!

[FlyKidChris]

Re: PM 38 Why the difference in prop length

Thom and Wild Bill,

Your posts and openness are creating a whole new and higher level of support here, I believe.

Thanks for the posts and information. I'm sure that I'm like many and I'm really looking forward to your performance at Reno 2013.

Blue skies,
Chris

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

Thom and Wild Bill,

Your posts and openness are creating a whole new and higher level of support here, I believe.

Thanks for the posts and information. I'm sure that I'm like many and I'm really looking forward to your performance at Reno 2013.

Blue skies,
Chris

Cheers to that!

[hm66sk]

Re: PM 38 Why the difference in prop length

The mk 74 and mk 65 Griffons are similar but all the nose case gearing internal is different. The Nosecase casting as well as the the crankcase is the same for both models.
The 74 typically used a 4 blade prop of longer length and ran slower. The gearing was .451 to 1. Due to the cam drives being run off the large prop drive gears the gears that drive the cams and magneto are specific to that mk of engine. IIRC the mk 58 uses the same gear ratio to drive the cams and mag. The 74 is what was used on many Fireflies with alum prop blades.
The mk 65, 66 and 67 are what was used on the Spitfires running the wooden 5 blade props. The prop gears are bit faster turning at .510 to 1. Again all the gearing that drive the cams and mag are specific to that nose case gear ratio. The gear ratio was determined by the smaller airframe of the Spit as the prop shaft is closer to the ground. To avoid contact the faster turing 5 blade prop was developed to absorb the horsepower of the engine.
The 5 blade Rotol prop on the Spit has wood blades, (actually all wood with a resin covering and metal leading edge, not just a wood core) and they can actually be cut down a bit as there is a range of diameters allowable per the book. There are a couple companies, Hoffman in Germany and an Italian Company that will make blades. I'm sure they could be made up in any configuration of airfoil and length that can be figured out and engineered.
We actually have 5 Mk 9 style blades that were made as a mirror image on the Mk XVIII Spitfire I take care of. At the time Hoffman only had approval for the Mk 9 blades and could only make them in a left handed version for the Griffon powered Spitfires. That was the early 1980s. The normal Griffon blade has an enlarged cuff at the base of the blade.
The Spitfires that used the Contra Props back in the 40s had both wood blades and metal blades during wartime and right after. I'm not sure what the Seafire mk 47 had which was the last of the Spitfire types produced in any quantity. It had the contra props.

Thanks for answering a question I asked years ago.

Are there just no non-contra rotating gearboxes available? The contra props are cool but, as others have stated, they're set up more for cruising rather than high MP settings. Couldn't a four blade be adapted with standard reduction gears? Other than rotation, is it a spline issue?

No American (IE: metal) props adaptable to the "standard" Griffon gearbox then I take it.

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

Thanks for answering a question I asked years ago.
No American (IE: metal) props adaptable to the "standard" Griffon gearbox then I take it.

Why change a program we have already proven works, and loose our coolness factor at the same time.

[hm66sk]

Re: PM 38 Why the difference in prop length

Why change a program we have already proven works, and loose our coolness factor at the same time.

No, no don't change a thing! I'm super stoked to see the contra set-up working well in the gold class environment. You just solved a riddle for me I had pondered a while back that's all.

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

No, no don't change a thing! I'm super stoked to see the contra set-up working well in the gold class environment. You just solved a riddle for me I had pondered a while back that's all.

Ah. Your post was confusing.

[eeyore]

Re: PM 38 Why the difference in prop length

To cool your working with the prop. I race model airplanes and props are the biggest area small improvement show considerable gain

[51fixer]

Re: PM 38 Why the difference in prop length

In a perfect world where many Griffon mk engines abound and Rotol Props are a dime a dozen then going to a single prop, 4 or 5 blades, with custom profiled blades could save maybe 3-400 lbs plus some ballast.
The Mk 67 Griffon was a high HP version used in the Spit. It was rated at 2350 HP at 25 lbs of boost on 150 octane fuel.
The more typical mk 65 was rated at 2035 HP at 18 lbs of Boost.
Both used the same Single 5 Blade Rotol Prop with Wood Blades.