Question

[Charles S]

I apologize for posting this 'non-home built' question here.
But I believe here is where I am most likely to discover the answer.
My question involves how the Germans in WWII fired cannon through the
propeller hub of V-12 engines.
I cannot see how this is accomplished, since to my knowledge there were no
gear reduction units on these planes..
I can only suppose that the diameter of the 'throw' journal was large
enough,
that it always included the centerline of the crankshaft. This would be a
hugh diameter.
Thus a hole bored through the centerline of the crank,
would also be through each 'throw' journal. Thereby making a continous
bore,
with no exposure to the crankcase.
This seems unlikely, as it would add tremendous amount of weight to an
engine.
And, those ME-109 cranks I have seen on TV do not seem to have that feature.

So, I am still confused.
Again, sorry about posting here, and thanks.

[Jan Carlsson]

They was geared!

/Jan Carlsson

"Charles S" > skrev i meddelandet
link.net...
> I apologize for posting this 'non-home built' question here.
> But I believe here is where I am most likely to discover the answer.
> My question involves how the Germans in WWII fired cannon through the
> propeller hub of V-12 engines.
> I cannot see how this is accomplished, since to my knowledge there were no
> gear reduction units on these planes..
> I can only suppose that the diameter of the 'throw' journal was large
> enough,
> that it always included the centerline of the crankshaft. This would be a
> hugh diameter.
> Thus a hole bored through the centerline of the crank,
> would also be through each 'throw' journal. Thereby making a continous
> bore,
> with no exposure to the crankcase.
> This seems unlikely, as it would add tremendous amount of weight to an
> engine.
> And, those ME-109 cranks I have seen on TV do not seem to have that
feature.
>
> So, I am still confused.
> Again, sorry about posting here, and thanks.
>
>

[Corky Scott]

On Mon, 05 Apr 2004 12:27:26 GMT, "Charles S"
> wrote:

>I apologize for posting this 'non-home built' question here.
>But I believe here is where I am most likely to discover the answer.
>My question involves how the Germans in WWII fired cannon through the
>propeller hub of V-12 engines.
>I cannot see how this is accomplished, since to my knowledge there were no
>gear reduction units on these planes..
>I can only suppose that the diameter of the 'throw' journal was large
>enough,
>that it always included the centerline of the crankshaft. This would be a
>hugh diameter.
>Thus a hole bored through the centerline of the crank,
>would also be through each 'throw' journal. Thereby making a continous
>bore,
>with no exposure to the crankcase.
>This seems unlikely, as it would add tremendous amount of weight to an
>engine.
>And, those ME-109 cranks I have seen on TV do not seem to have that feature.
>
>So, I am still confused.
>Again, sorry about posting here, and thanks.
>
>
Ah but your premise is wrong: ALL high performance WWII military
engines used gear reduction to swing the props. That includes the
radials and the inline liquid cooled engines.

The Bf 109 used a Daimler Benze DB601 2,070 cubic inch displacement,
fuel injected inverted engine. The canon used in the models F and G
but not the E used during the Battle of Britain, nestled between the
banks of the inverted V12 and fired through the hollow gear that spun
the prop. It wasn't a terrific idea but given that the wings were
never designed to handle canon within the airfoil (The Bf 109 was
designed in 1935 when most fighters used machine guns mounted in their
nose and Messerschmitt did not want to spoil his wings with wing
mounted armaments). So he designed them very thin. The wing design
proved difficult to put canon into which is why you see canon mounted
on blisters under them, rather than in them.

Corky Scott

PS, google Bf 109 and you'll find lots of information.

[Corky Scott]

On Mon, 05 Apr 2004 17:10:28 GMT,
(Corky Scott) wrote:


>The Bf 109 used a Daimler Benze DB601 2,070 cubic inch displacement,
>fuel injected inverted engine. The canon used in the models F and G
>but not the E used during the Battle of Britain, nestled between the
>banks of the inverted V12 and fired through the hollow gear that spun
>the prop.

>Corky Scott
>
>PS, google Bf 109 and you'll find lots of information.
>
>
Sorry, I re-read that and it looks a little confusing. To elaborate,
the DB 601 had a spur gear type reduction drive with the drive gear on
the end of the crankshaft driving a hollow propshaft gear. It is
through the propshaft gear that the canon fires, the propshaft gear
was offset enough to allow the barrel of the cannon to fit between the
banks of the engine.

The reduction ratio was either 1.55 to 1 or 1.88 to 1, depending on
the model and use.

My understanding is that it was a tough gun to keep working correctly
and it must have been fun to open the cowl to get to it to clean and
re-arm when the engine was nice and hot.

Corky Scott

[Bob Kuykendall]

Earlier, "Charles S" > wrote:

> ...My question involves how the
> Germans in WWII fired cannon through the
> propeller hub of V-12 engines.
> I cannot see how this is accomplished,
> since to my knowledge there were no
> gear reduction units on these planes..

There were, in fact, gear reduction units on the DB601 and similar
engines. The cannon was oriented through a tunnel between the two
cylinder banks. The tunnel opened through a bore in the center of the
drive hub of the propeller.

This page pretty much describes the system, and has a diagram that
shows the cannon tunnel:

http://www.aviation-history.com/engines/db605.htm

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com