Gatlings thru propeller spinners.

[kitnut617]

Thanks, from information David Birch gave me I built another.  This time the power unit is supposed to be a RR Crecy engine with an exhaust turbine.  David also told me that from the wind tunnel tests, they found that the tail need an extra 60% increase in fin surface so a Tempest tail assembly was issued to RR, so had the FTB flown -- it would have looked like this below



Here's a pic of the two models:

[Old Wombat]

I'd suggest going with a P-39/P-63-ish option by moving your engine further back in the nacelle with the gun placed immediately ahead of it (possibly with the barrels sticking further forward of the propellor hub), surrounded on 3 sides (maybe 3 1/2) by ammunition. For mass distribution the nacelle may need to be moved slightly forward but it shouldn't be by much.



Guy

PS: A 3-barrel gun should be sufficient to do significant damage to the target & conserve ammunition (giving a longer firing time).

[jcf]

The original gun-through-engine design was the Hispano moteur-canon of WWI, and it used
a 37mm gun.

http://www.hydroretro.net/etudegh/moteur-canonv8_hispano-suiza.pdf

The later Hispano V-12s with 20mm cannon used the same basic concept:


So an upright V-12 ( or perhaps V-16) with a three-barrelled gatling in the V that is powered
by the same turbine that drives the supercharger. 

[sandiego89]

with a three-barrelled gatling in the V that is powered
by the same turbine that drives the supercharger. 

Oh yeah! 

[wuzak]

The original gun-through-engine design was the Hispano moteur-canon of WWI, and it used
a 37mm gun.

http://www.hydroretro.net/etudegh/moteur-canonv8_hispano-suiza.pdf

The later Hispano V-12s with 20mm cannon used the same basic concept:


So an upright V-12 ( or perhaps V-16) with a three-barrelled gatling in the V that is powered
by the same turbine that drives the supercharger. 

Or just from the reduction gear.

Prop shaft should be doing ~1500 rpm, so that would be easy enough for the Gatling. For a 3 barrel version it would be 500 rounds per minute, which is slightly less than a Hispano Mk II.

[wuzak]

Thanks, from information David Birch gave me I built another.  This time the power unit is supposed to be a RR Crecy engine with an exhaust turbine.  David also told me that from the wind tunnel tests, they found that the tail need an extra 60% increase in fin surface so a Tempest tail assembly was issued to RR, so had the FTB flown -- it would have looked like this below



Here's a pic of the two models:

Thanks for the information Kit.

On the Crecy model there appears to be large bulges to cover the engine. How wide was the Crecy?

[wuzak]

A diagram showing the arrangement of the A-10's 30mm Avenger Gattling type cannon, with ammo drum.

http://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/GAU-10_Drawing.jpg/1280px-GAU-10_Drawing.jpg

The 30mm gun is somewhat bigger and heavier than the 20mm Vulcan.

[Librarian]

A diagram showing the arrangement of the A-10's 30mm Avenger Gattling type cannon, with ammo drum.

http://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/GAU-10_Drawing.jpg/1280px-GAU-10_Drawing.jpg

The 30mm gun is somewhat bigger and heavier than the 20mm Vulcan.

Oh yeah!!! That's what I wanted to put in my Vietnam B-25....Hobbyboss supply the complete deal with theit A-10 kit. I hadn't the spare cash at the time and went with the 20mm.

[NARSES2]

I don't think I've seen a pic of your Crecy engine version before Kitnut - really nice 

[kitnut617]

I don't think I've seen a pic of your Crecy engine version before Kitnut - really nice  

Thanks Chris ---

Thanks for the information Kit.

On the Crecy model there appears to be large bulges to cover the engine. How wide was the Crecy?

I have a book on the RR Crecy and I'll try to find it and see what the dimension was, but it was a 90 degree, sleeve valve V-12 two-stroke engine which was supposed to put out about 5000 hp. It was about the same size as a Griffon except for the different 'Vee' angle.   The Griffon version also has bulges too, just not so pronounced. Photos of the assembled 'mock-up' (unusually made completely of metal) in the book show the frame members around the engine bay to protrude outside of the fuselage sides and when I measured across the P-51 fuselage and compare it with the measurement across the Griffon engine covers of a Spitfire, I found that the Griffon measurement was larger.  Which could only mean one thing, the FTB had bulges too as the top of the engine cover is just under the canopy edge and almost dead flat.

[wuzak]

Re the Griffon in the Mustang, Rolls-Royce were keen, but NAA thought it would require too much redesign, so they stuck with the Merlin.

But a few Reno racers have shown that it could be done.

http://airpigz.com/storage/large/Precious-Metal-P-51-Green-Wings-On-Ground-No-Cowl.jpg

The PV fighter/FTB was a different, later project.

And here is a picture of teh mockup
http://i7.photobucket.com/albums/y282/Bomber_12th/GriffonMustangb.jpg

[kitnut617]

There's some other photos in the book other than that one Wusak, taken from different angles which show it more clearly.  The PV/FTB did come after RR converted a Mustang Mk.I into the Mk.X, their thinking was, if a Griffon installation can be done on a Spitfire it should be able to go on a Mustang, but it didn't work out that way.  The Reno guys have shown it can be done, but the engine bulkhead has had to be moved quite a bit closer to the cockpit to get the cg to work (as your pic in the link shows)