This is an interesting one. If the space existed behind the engine block and the propeller spinner large enough could it be theoretically possible to have a 20mm gatling to fire through it?
Six barrelled or three barrelled, or would that matter?
Would the jiggarypokery required for a contra-prop allow it?
Any thoughts....please say yes 'cos I really want to do it ;D.
It would be quite easy but your spinner would have to be appreciably larger to allow space for a very large, hollow prop shaft to accommodate the multiple barrels of a Gatling style gun. Your engine would have to also be placed appreciably further back, to accommodate the gun and it's ammunition supply. The same would apply with a single propeller and a contra-prop. With a contra-prop, it wouldn't be appreciably more complicated, the gearbox would just need to be further back from the props than they normally are.
There would be some engineering challenges:
- You need to have a tight fit between the Gatling barrel and the tube that goes through the prop, otherwise you get hot gases blasting out.
- The timing of the firing moment must be exact. Every bullet needs to leave the barrel when it is lined up with the prop tube, otherwise you'll shoot off your own prop.
Both can be solved by using Rickshaw's proposal to have a much larger prop tube and fit the entire barrel cluster in that.
If you have a contraprop, the gearbox would be ahead of the gun. You could place the engine below the barrel cluster, and have the Gatling machinery behind the engine for a reasonably compact installation.
A P-39/P-63 lay-out would probably assist.
:cheers:
Guy
I've been cobbling some parts together for a few day , this is very rough and gives an idea of what I'm trying to attemp. The cowling would fit a Griffon with space I hope for all the gear specified. The spinner is extra large so as to accomodate the gatling. I'm hoping to scratch a weapons bay behind the main engine body for depth charges :-\:
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi1357.photobucket.com%2Falbums%2Fq756%2Flibrarian2%2FP1050848_zps433a6cba.jpg&hash=61570dcf2bad7eefe88b73aa5f02312d51c66d6e) (http://s1357.photobucket.com/user/librarian2/media/P1050848_zps433a6cba.jpg.html)
This is very rough but it should eventually be a two seater asymetric Mustang (the port wing will be longer):
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi1357.photobucket.com%2Falbums%2Fq756%2Flibrarian2%2FP1050847_zpsc105d4c7.jpg&hash=a37398d72d287865ae7d8f2283c395807ceee13a) (http://s1357.photobucket.com/user/librarian2/media/P1050847_zpsc105d4c7.jpg.html)
Any suggestions gratefully appreciated as are all prior posts :thumbsup:.
Quote from: rickshaw on September 20, 2013, 03:36:34 AM
It would be quite easy but your spinner would have to be appreciably larger to allow space for a very large, hollow prop shaft to accommodate the multiple barrels of a Gatling style gun. Your engine would have to also be placed appreciably further back, to accommodate the gun and it's ammunition supply. The same would apply with a single propeller and a contra-prop. With a contra-prop, it wouldn't be appreciably more complicated, the gearbox would just need to be further back from the props than they normally are.
You would not need the whole gun to poke through the spinner - though that would help with the length of the installation.
Quote from: Hobbes on September 20, 2013, 03:45:44 AM
There would be some engineering challenges:
- You need to have a tight fit between the Gatling barrel and the tube that goes through the prop, otherwise you get hot gases blasting out.
- The timing of the firing moment must be exact. Every bullet needs to leave the barrel when it is lined up with the prop tube, otherwise you'll shoot off your own prop.
I would think that all barrels would fire at the same point. The blast tube could be slightly larger to allow for any discrepancy, without needing to be as big as one required to take all the barrels.
Quote from: Hobbes on September 20, 2013, 03:45:44 AMIf you have a contraprop, the gearbox would be ahead of the gun. You could place the engine below the barrel cluster, and have the Gatling machinery behind the engine for a reasonably compact installation.
The gearbox for a contraprop will be in the same place as for a single rotation prop - just behind the prop. On most ww2 tractor types the reduction gear is mounted directly on the engine. Dual rotation Merlins and Griffons had a slightly modified reduction gear housing to take extra gears.
The Griffon could not accomodate a conventional 20mm cannon, let alone a Gatling type. The issue is that the induction system gets in the way - the supercharger, aftercoolr (for 2 stage engines) and the intake pipe.
http://avroshackleton.com/rolls_files/image003.gif
http://www.flightglobalimages.com/image/rolls_royce_griffon_cutaway_drawing_1569097.jpg
A P-39/P-63 type of aircraft would be the best option. That is, have the engine remote from the reduction gear.
Interestingly, the M61 Vulcan is shorter than the 37mm M4 cannon usually mounted in the P-39/P-63, though somewhat heavier - 15kg, ~15%. But you would need more ammo to make the gun useful, so that would work out to be more.
Quote from: wuzak on September 20, 2013, 06:10:22 AM
The gearbox for a contraprop will be in the same place as for a single rotation prop - just behind the prop. On most ww2 tractor types the reduction gear is mounted directly on the engine. Dual rotation Merlins and Griffons had a slightly modified reduction gear housing to take extra gears.
The Griffon could not accomodate a conventional 20mm cannon, let alone a Gatling type. The issue is that the induction system gets in the way - the supercharger, aftercoolr (for 2 stage engines) and the intake pipe.
OK. No Griffon. But it would be feasible for an inline engine to be designed that could accomodate a gatling....a DB605 or something similar? I really want to do this but would like to stay reasonably realistic/possible.
I say go for it. In the whif world anything is possible, no ? Besides, it's too cool an idea to pass up !
I'm leaning that way. Where you in Alpha Flight ;D?
You could use a DB606 as per the He177, or any other engines of your choice,
Paired together and driving a common airscrew (contra-rotating gearbox could be added for extra complexity) :cheers:
That should give you plenty of room for a Gatling gun nestling between the engines :thumbsup:
Regards
Keith
That was initially the idea; two merlins paired but I've drifted away from that. Might revisit it though ;).
Quote from: Librarian on September 20, 2013, 07:19:19 AM
Quote from: wuzak on September 20, 2013, 06:10:22 AM
The Griffon could not accomodate a conventional 20mm cannon, let alone a Gatling type. The issue is that the induction system gets in the way - the supercharger, aftercoolr (for 2 stage engines) and the intake pipe.
OK. No Griffon. But it would be feasible for an inline engine to be designed that could accomodate a gatling....a DB605 or something similar? I really want to do this but would like to stay reasonably realistic/possible.
The Griffon couldn't accommodate a cannon within the envelope of a standard power egg, perhaps? You could always make the engine bay higher, and put an extra gear in the gearbox to make the prop sit high enough to accept a cannon through the centerline.
Quote from: Librarian on September 20, 2013, 07:19:19 AMOK. No Griffon. But it would be feasible for an inline engine to be designed that could accomodate a gatling....a DB605 or something similar? I really want to do this but would like to stay reasonably realistic/possible.
Yes, if the engine was designed around using a hub cannon, like the DB series were, then it would certainly be possible.
Or if the engine was a remote with extension drive to the reduction gear, like the P-39/P-63 or teh Rolls-Royce Flying Test Bed (which was to be Griffon powered).
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi200.photobucket.com%2Falbums%2Faa263%2Fkitnut617%2FRR%2520Mustangs%2FRRMustangFTB.jpg&hash=18987ee68c0d9913db2e251bdeeab75ca4fb85a6)
Clearly not enough space ahead of the cockpit for the cannon, but if the nose were extended, or the cockpit and engine pushed back.
Quote from: wuzak on September 20, 2013, 08:23:25 AM
Rolls-Royce Flying Test Bed (which was to be Griffon powered).
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi200.photobucket.com%2Falbums%2Faa263%2Fkitnut617%2FRR%2520Mustangs%2FRRMustangFTB.jpg&hash=18987ee68c0d9913db2e251bdeeab75ca4fb85a6)
Clearly not enough space ahead of the cockpit for the cannon, but if the nose were extended, or the cockpit and engine pushed back.
You found my FTB (actually it's the RR Private Venture Fighter) --- when I made this model I found that the forward fuselage as it comes in the conversion is too short. However, I was able to confirm that with the nose length corrected (as it is in the pic) a 20mm cannon will fit in the space between the spinner and cockpit. I did this on information provided by David Birch, who is the Official Rolls Royce Historian. BTW, the 1/10 scale model used for wind tunnel tests still exists and it was getting measurements from the test model that I arrived at my solution where I added 8mm to the forward fuselage in front of the wings.
Quote from: wuzak on September 20, 2013, 08:23:25 AM
Rolls-Royce Flying Test Bed (which was to be Griffon powered).
BTW, the FTB was to be powered by any engine RR wanted to put in it. which was the reasoning behind the mid-engined placement, it's set on the cg point. This came about after RR had problems converting a P-51 to have a Griffon engine.
That is very nice, a sort of cross between the Me 509 and Attacker. I might have a go at that sometime. Thanks for the info.
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
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi200.photobucket.com%2Falbums%2Faa263%2Fkitnut617%2FRR%2520Mustangs%2FDSC00340.jpg&hash=c93f63694a0ba885ec39473563d0c6ee674a21b8) (http://s200.photobucket.com/user/kitnut617/media/RR%20Mustangs/DSC00340.jpg.html)
Here's a pic of the two models:
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi200.photobucket.com%2Falbums%2Faa263%2Fkitnut617%2FRR%2520Mustangs%2FRRMustangwithTempestTail003.jpg&hash=27cbd8c8ae0c80f6b3057195ee7075296ef6e546) (http://s200.photobucket.com/user/kitnut617/media/RR%20Mustangs/RRMustangwithTempestTail003.jpg.html)
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.
:cheers:
Guy
PS: A 3-barrel gun should be sufficient to do significant damage to the target & conserve ammunition (giving a longer firing time).
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:
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fwww.bibert.fr%2FJoseph_Bibert_fichiers%2FMS406_fichiers%2Fimage005.jpg&hash=5e2a02e6393674624f67018a0182b11744e590b2)
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. ;D
Quote from: joncarrfarrelly on September 20, 2013, 11:39:21 AM
with a three-barrelled gatling in the V that is powered
by the same turbine that drives the supercharger.
:thumbsup: Oh yeah!
Quote from: joncarrfarrelly on September 20, 2013, 11:39:21 AM
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:
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fwww.bibert.fr%2FJoseph_Bibert_fichiers%2FMS406_fichiers%2Fimage005.jpg&hash=5e2a02e6393674624f67018a0182b11744e590b2)
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. ;D
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.
Quote from: kitnut617 on September 20, 2013, 09:12:04 AM
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
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi200.photobucket.com%2Falbums%2Faa263%2Fkitnut617%2FRR%2520Mustangs%2FDSC00340.jpg&hash=c93f63694a0ba885ec39473563d0c6ee674a21b8) (http://s200.photobucket.com/user/kitnut617/media/RR%20Mustangs/DSC00340.jpg.html)
Here's a pic of the two models:
(https://www.whatifmodellers.com/proxy.php?request=http%3A%2F%2Fi200.photobucket.com%2Falbums%2Faa263%2Fkitnut617%2FRR%2520Mustangs%2FRRMustangwithTempestTail003.jpg&hash=27cbd8c8ae0c80f6b3057195ee7075296ef6e546) (http://s200.photobucket.com/user/kitnut617/media/RR%20Mustangs/RRMustangwithTempestTail003.jpg.html)
Thanks for the information Kit.
On the Crecy model there appears to be large bulges to cover the engine. How wide was the Crecy?
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.
Quote from: wuzak on September 20, 2013, 10:09:39 PM
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.
I don't think I've seen a pic of your Crecy engine version before Kitnut - really nice :thumbsup:
Quote from: NARSES2 on September 21, 2013, 02:38:51 AM
I don't think I've seen a pic of your Crecy engine version before Kitnut - really nice :thumbsup:
Thanks Chris ---
Quote from: wuzak on September 20, 2013, 06:06:46 PM
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.
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
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)