Rare Bear question

[Fred41]

What is the hole at the end of the fuselage ?
What is its function ?

http://wingshots.foxalpha.com/2009/RENO/IMG_9562s.jpg

More picts here:

http://www.foxalpha.com/forums/viewtopi ... sc&start=0

[mdwflyer]

(simplified version) Rear Bear has gone to a boil-off system for oil cooling. By that, air is no longer run through the oil cooler, the cooler is now submerged in a tank filled with liquid. As the oil cooler heats up the liquid boils off. The hole in Rare Bear's tail is the vent for the boiler tank.

Advantage no air running in and out of the airframe for cooling, disadvantage, weight of the liquid that must be carried for cooling.

[Fred41]

Thank you for this clear explanation !

[lestweforget]

Awww. And here was me thinking it was a rocket engine!!!

[jet1]

Awww. And here was me thinking it was a rocket engine!!!

so I wouldn't be surprised if it does produce a few lbs. of thrust at speed...

[P51Mstg]

How much water does it boil off during a race then??

Mark H

[PbyCat-Guy]

Awww. And here was me thinking it was a rocket engine!!!

so I wouldn't be surprised if it does produce a few lbs. of thrust at speed...

Something similar to what the P-47s where the pilot could inject water into the cylinders to cool them off real quick, then get a good increase in power?

[P51Mstg]

Thats different......... The WWII was ADI Anti Detonation.... Kind of cooled the engine from the inside when producing max power by injecting water and alcohol into the cyclinders......

In the Bear, they are basically immersing the oil cooler in a tank of water to cool it.... In your car, the engine water circulates through the radiator and back into the engine..... In the Rare Bear, as the water boils, the steam is vented out the tail and fresh cool water refills the tank. Hence no radiator (less weight) and there is the potential (as I see it) to run cooler.....

So how much water does it use?????

I saw the oil cooler spray bars running on RIFF RAFF and I can say they put out a LOT of water.......

Mark H

[MX304]

Thats different......... The WWII was ADI Anti Detonation.... Kind of cooled the engine from the inside when producing max power by injecting water and alcohol into the cyclinders......

In the Bear, they are basically immersing the oil cooler in a tank of water to cool it.... In your car, the engine water circulates through the radiator and back into the engine..... In the Rare Bear, as the water boils, the steam is vented out the tail and fresh cool water refills the tank. Hence no radiator (less weight) and there is the potential (as I see it) to run cooler.....

So how much water does it use?????

I saw the oil cooler spray bars running on RIFF RAFF and I can say they put out a LOT of water.......

Mark H

ADI is a mix of alcohol and water and can be used for the water injection and boil off fluid. I believe the Bear uses one main water tank for both things. There is a resivoir that the oil coller sits in that has a level valve in it. It re-fills from the main tank as needed. The main tank probably hols upwards of 75 gal.

[Jack]

Check here, plenty of good info from Pete.

http://www.enginehistory.org/Convention ... ooling.pdf

[Tim Adams]

Here is a better pic of the boil off working.

[b29flteng]

ADI cools the air charge down. When air is compressed as in a supercharger its temperature goes up causing the air to be less dense and when mixed with fuel in the cylinders it tends to detonate. The air is cooled with fuel by running the carburetor in full rich to a certain point. ADI cools it better and you can lean the mixture of fuel out to save the fuel for better range. Most airplanes with ADI had about a two minute supply before running out.