Author Topic: Spinner-mounted cannon questions (Read 1350 times)

BaldEagl · « **on:** January 18, 2008, 10:09:27 AM »

For most of this camp, I've set aside the 190's and been trying out the 109K-4. I plan on getting around to some of the others but have been having fun in this one and feel like I'm starting to really understand it (plus, I can up it and make up for a few Spit I deaths pretty easily

).

This morning I was wondering about the spinner mounted cannon. I did a search and really couldn't find anything on it.

How was it mounted? I would assume it was a solid mount to the fuselage forward of the engine? How was the ammo fed? Where was it stored?

It seems to have been a bit of technical wizardry to come up with this design as I try to think it out.

Beyond that, since a mounting of this type would seem to make such obvious sense, why wasn't it used in more applications (or even cowl mounts for that matter)?

Hoping someone knowlegable in this will have some answers.

Oops... wanted to post this in Aircraft and Vehicles forum. Skuzzy, can you move it please?

moot · « **Reply #1 on:** January 18, 2008, 10:35:52 AM »

Tony Williams had a thread going about the most efficient gun and gun platform (incl. gun position) for a prop warbird. I think it was in the AC forum.

As far as I can recall, the 109 and late 190s had the hub cannon sitting behind the engine, with the barrel fitting between cylinder heads.
E.G. On the Ta152, the engine block's front face is right around the aft end of the radiator gills. There's nowhere near enough room to fit the cannon on the front end.

FrodeMk3 · « **Reply #2 on:** January 18, 2008, 11:24:11 AM »

Quote

Originally posted by moot
Tony Williams had a thread going about the most efficient gun and gun platform (incl. gun position) for a prop warbird. I think it was in the AC forum.

As far as I can recall, the 109 and late 190s had the hub cannon sitting behind the engine, with the barrel fitting between cylinder heads.
E.G. On the Ta152, the engine block's front face is right around the aft end of the radiator gills. There's nowhere near enough room to fit the cannon on the front end.

That's what I've read, as well-the Propellor reduction gear in front has an opening through the middle, which goes' straight through the prop and hub itself.

Hornet33 · « **Reply #3 on:** January 18, 2008, 11:24:50 AM »

The hub firing cannons actually fired through a hollow crank shaft in the engine. The weapon was mounted directly behind the engine.

Greebo · « **Reply #4 on:** January 18, 2008, 11:27:35 AM »

Both Daimler Benz and the french Hispano Suiza firms designed their V12 fighter engines to allow a gun to fire through the centreline of the propeller. IIRC the Soviet Klimov engines were derived from the Hispano Suiza engine.

The gun barrel would sit in the vee of the engine with the breech and ammo behind the engine and supercharger. The engine's crankshaft drove the propeller shaft through a gear reduction and the propshaft itself was hollow to accept the gun blast tube.

One drawback of the arrangement was awkward packaging of the supercharger behind the engine compared to say the Merlin, where the supercharger casing merged into the crankcase of the engine.

BlauK · « **Reply #5 on:** January 18, 2008, 12:40:06 PM »

One interesting detail is that the 109 engines were inverted... meaning the cylinders were pointing downwards.

http://en.wikipedia.org/wiki/Daimler-Benz_DB_603

Geary420 · « **Reply #6 on:** January 18, 2008, 12:55:38 PM »

Quote

Originally posted by Hornet33
The hub firing cannons actually fired through a hollow crank shaft in the engine. The weapon was mounted directly behind the engine.

Have you ever seen a crank shaft before? Unless they have magical bullets I don't see that one working out so well.

jab116 · « **Reply #7 on:** January 18, 2008, 01:13:09 PM »

From a book I have about the Bf 109
Engine: DB601A ( DB 605 ACS or DB605 DC for the K 4)
Year: 1937
Type: 12 cylinder inverted 60 degree Vee supercharged liquid cooled engine
Bore: 150 mm
Stroke: 160mm
Total swept capacity:33.9 liters (2069 cubic inches)
Compression ratio: 6.9:1
Fuel: 92 octane
Maximum RPM: 2400
Reduction gearing: 1 : 1.55
Dry weight: 610 kg (1,344.7 lbs)
Lenght: 1352 mm (4 ft. 5 1/4 inches)
Width: 705 mm (2 ft. 3 3/4 in)
Height:1,027 mm (3ft. 4 1/2 in)
Takeoff power: 1,100hp.
Max continuous power: 960hp @ 5,000m (16,400ft)
The inverted V engine allowed the spinner hub cannon to fire between the cylinder heads, and the cowl mounted MG's to fire alongside the crankcase.
Impressive, but it must have been hell on the ground crews.

BaldEagl · « **Reply #8 on:** January 18, 2008, 01:22:14 PM »

Interesting. I always thought one of the drawbacks (in accuracy) of the wing-mounted 30mm cannons was supposed to be their relatively short barrels in the FW varients.

This would indicate that the 109's used much longer barrels and should, therefore, be more accurate. Does anyone know if this is true?

I also find the inverted engine interesting. It makes me wonder how they kept it from flooding the (normally) upper engine with oil.

Lusche · « **Reply #9 on:** January 18, 2008, 02:04:00 PM »

Quote

Originally posted by BaldEagl
Interesting. I always thought one of the drawbacks (in accuracy) of the wing-mounted 30mm cannons was supposed to be their relatively short barrels in the FW varients.

This would indicate that the 109's used much longer barrels and should, therefore, be more accurate. Does anyone know if this is true?

The barrel is not longer in engine mounted guns.

stockli · « **Reply #10 on:** January 18, 2008, 02:14:02 PM »

Quote

Originally posted by BaldEagl
Interesting. I always thought one of the drawbacks (in accuracy) of the wing-mounted 30mm cannons was supposed to be their relatively short barrels in the FW varients.

This would indicate that the 109's used much longer barrels and should, therefore, be more accurate. Does anyone know if this is true?

I also find the inverted engine interesting. It makes me wonder how they kept it from flooding the (normally) upper engine with oil.

Side oilers.

Think of motor cycles. Older ones have dry sumps, a pump pumps oil from a seperate tank through the engine and back to the tank.

No oil flooding that way.

Same on some of the 427 "side oiler" Ford motors.

moot · « **Reply #11 on:** January 18, 2008, 02:30:08 PM »

Lusche, are you sure about that? The MK108 was designed (IIRC) as short-barreled as it was to adress issues with the original longer barrel version's barrel related problems.

BaldEagl · « **Reply #12 on:** January 18, 2008, 02:38:51 PM »

Quote

Originally posted by Lusche
The barrel is not longer in engine mounted guns.

Can you explain this? If the gun (striking mechanism) is actually mounted behind the engine and the muzzle is in the front of the spinner, wouldn't that then be a barrel traversing the distance from the actual gun to the muzzel? Unless the part about the gun being behind the engine is wrong.

Which brings up another question... was this entire span rifled?

Lusche · « **Reply #13 on:** January 18, 2008, 02:57:22 PM »

Quote

Originally posted by BaldEagl
Can you explain this? If the gun (striking mechanism) is actually mounted behind the engine and the muzzle is in the front of the spinner, wouldn't that then be a barrel traversing the distance from the actual gun to the muzzel? Unless the part about the gun being behind the engine is wrong.

Which brings up another question... was this entire span rifled?

No, because it wasn't the barrel.
The actual barrel muzzle is not at the spinner.. it's inside the plane:

BaldEagl · « **Reply #14 on:** January 18, 2008, 03:11:50 PM »

Thanks Lusche. Great diagram.

One last question then. Was there something to guide the bullet to the spinner? Surely it didn't "free-fly" from the muzzel. That would seem pretty dangerous while manouvering but it would also seem that any type of "guidance" would also have an adverse effect and would have to be within pretty close tolerences.