P-51 engine runup- Counter Rotating Props?

Jaybird180 said:
https://www.youtube.com/watch?v=3Cf3EA-JQY0

First thing I notice is that it has 2 props on the same shaft (What?!??!) and they rotate counter to each other.

Lucy, joos gots some sesplaining to do....

How do they work?
Click to expand...

The amazing part of that video is watching the exhaust valve stems glowing red hot, up inside the exhaust ports.... Just WOW....:yikes:
 
So if you have a bird strike - will you have sliced lunch meat?
 
Something tells me that engine run was much louder than the video makes it out to be.
 
Here are a couple of photos of them working on Precious Metal in the pits from the Reno Air Races this year. They were pretty serious about keeping the secret a secret. Must be an amazing gearbox.

They used two people to very carefully turn the props. Which they did to polish them. Incredible setup, and the crew was friendly and tolerant.

When flying, it makes a unique and terrific sound. Looks like a spinning fishing lure, too. My Reno Air Races video/slideshow has more at: http://youtu.be/Ds1YV_7v2cw
 

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G-Man said:
Here are a couple of photos of them working on Precious Metal in the pits from the Reno Air Races this year. They were pretty serious about keeping the secret a secret. Must be an amazing gearbox.

They used two people to very carefully turn the props. Which they did to polish them. Incredible setup, and the crew was friendly and tolerant.

When flying, it makes a unique and terrific sound. Looks like a spinning fishing lure, too. My Reno Air Races video/slideshow has more at: http://youtu.be/Ds1YV_7v2cw
Click to expand...


You would think the forward prop would cavitate the air going into the rear prop... Probably that " unique and interesting" sound..;)
 
Ben, is it possible the valve stems you mention are actually EGT probes glowing?
 
ronnieh said:
Ben, is it possible the valve stems you mention are actually EGT probes glowing?
Click to expand...

Maybe.... But they look about in the correct location for the valve stems... The stacks on that V-12 are VERY short


Edit.... After looking closely.... You might be right....:redface:
 
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A lot of boats have similar prop setups. I never understood how the second one could actually get a good bite of the wash from the first one.
 
Sad that one a**hole judge decided that he didn't like the race results and suddenly magic-ed up a non-contestable safety violation to disqualify Precious Metal from this year's Gold race.
 
Jaybird180 said:
https://www.youtube.com/watch?v=3Cf3EA-JQY0

First thing I notice is that it has 2 props on the same shaft (What?!??!) and they rotate counter to each other.

Lucy, joos gots some sesplaining to do....

How do they work?
Click to expand...

They CONTRA rotate, yes they spin opposite directions on the same axis. This would be on a Griffon engine. Counter rotate is what some twins do when the axis are split.
 
StinkBug said:
A lot of boats have similar prop setups. I never understood how the second one could actually get a good bite of the wash from the first one.
Click to expand...

The accelerated wash plus the axial energy actually increases the efficiency of the drive, much like a stator improves the efficiency of a turbine.
 
N801BH said:
Damn.... I should have used that trick on my "slightly overpowered" experimental...
Click to expand...

Yes, if possible you should build such a drive as it would eliminate your torque control problem.:yes::yes::yes:
 
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