Gatlings thru propeller spinners.

[Librarian]

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 .

[rickshaw]

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.

[Hobbes]

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.

[Old Wombat]

A P-39/P-63 lay-out would probably assist.



Guy

[Librarian]

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 :



This is very rough but it should eventually be a two seater asymetric Mustang (the port wing will be longer):



Any suggestions gratefully appreciated as are all prior posts .

[wuzak]

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.

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.

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.

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.

[Librarian]

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.

[Captain Canada]

I say go for it. In the whif world anything is possible, no ? Besides, it's too cool an idea to pass up !

[Librarian]

I'm leaning that way. Where you in Alpha Flight ?

[TallEng]

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)
That should give you plenty of room for a Gatling gun nestling between the engines

Regards
Keith

[Librarian]

That was initially the idea; two merlins paired but I've drifted away from that. Might revisit it though .

[Hobbes]

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.

[wuzak]

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.

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).



Clearly not enough space ahead of the cockpit for the cannon, but if the nose were extended, or the cockpit and engine pushed back.

[kitnut617]

Rolls-Royce Flying Test Bed (which was to be Griffon powered).



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.

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.

[Librarian]

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.