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Does barbette size shrink when gun number goes down?
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Author:  dy031101 [ September 28th, 2014, 9:55 pm ]
Post subject:  Does barbette size shrink when gun number goes down?
Long story short, I am thinking of messing with the 381mm gun used by the Littorio class battleship..... but in two-gun turrets.

Since such an arrangement never existed (AFAIK, at least not with the same guns as used by the Littorio class), I figure I should enlist some expert opinion on where I can start.

Is there a general guideline as to whether and/or how a turret barbette would shrink if the turret gets reduced to a two-gun or twin turret from a three-gun or triple one? Or would the ballpark really vary from one particular model of gun to another?

Thanks in advance.
Author:  eltf177 [ September 28th, 2014, 9:57 pm ]
Post subject:  Re: Does barbette size shrink when gun number goes down?
Yes, a smaller turret will use a smaller barbette. Which in turn means a smaller, cheaper hull.
Author:  dy031101 [ September 28th, 2014, 10:03 pm ]
Post subject:  Re: Does barbette size shrink when gun number goes down?
eltf177 wrote:
Yes, a smaller turret will use a smaller barbette. Which in turn means a smaller, cheaper hull.
Is it reasonable to assume that the length of the turret depends solely on the recoil distance of the guns, or does the barbette size also play a role here?
Author:  apdsmith [ September 28th, 2014, 11:53 pm ]
Post subject:  Re: Does barbette size shrink when gun number goes down?
Hi dy031101,

Barbette size will be defined by the recoil distance of the guns, unless the maximum elevation is very low - the slide has to drop into the barbette at high elevations, no? As I understood it, the back part of the turret is generally used for rangefinders, the mount captain and mount crew (as opposed to gun captain and gun crew), manual loading bins and cranes and also for balance, though this last point can also be worked out by using thicker-than-necessary armour on the turret back plate.

Regards,
Adam
Author:  heuhen [ September 29th, 2014, 12:49 am ]
Post subject:  Re: Does barbette size shrink when gun number goes down?
does this one answear you'r question:
[ img ]
[ img ]

The Barbette have to fit the recoil of the guns.

KGV with 3 quad:
https://dl.dropboxusercontent.com/s/6gs ... in-v-3.png

KGV with 2 quad and 1 twin:
http://www.shipbucket.com/Real%20Design ... 201940.png

http://padresteve.files.wordpress.com/2 ... turret.jpg
http://www.donnan.com/images/NJ10.jpg
http://www.navweaps.com/Weapons/WNUS_14 ... ch_pic.jpg
http://www.navweaps.com/Weapons/WNUS_16 ... on_pic.jpg
http://www.navweaps.com/Weapons/WNUS_16 ... et_pic.jpg
http://www.navweaps.com/Weapons/WNBR_16 ... r2_pic.jpg
http://www.navweaps.com/Weapons/WNBR_15 ... et_pic.jpg
http://www.navweaps.com/Weapons/WNBR_15 ... el_pic.jpg

one of the KGV's guns:
http://www.navweaps.com/Weapons/WNBR_14 ... or_pic.jpg

note on how far down the gun elevate on this one:
http://www.navweaps.com/Weapons/WNUS_14 ... de_pic.jpg
http://www.navweaps.com/Weapons/WNUS_16 ... al_pic.jpg
Author:  smurf [ October 31st, 2014, 3:17 pm ]
Post subject:  Re: Does barbette size shrink when gun number goes down?
Lots of interesting pictures, but it is not easy to see what is happening unless you look at a plan view.
IIRC the distance between the guns in a RN 6in triple was about 6ft. That means the outer guns lie on lines 6ft from the centreline. Assuming that the gun separation can be the same, in a twin the guns both lie on lines only 3ft from the centreline. What fixes the minimum barbette size is the distance needed to accommodate the recoiling gun between the forward and rear points where the straight line along the gun meets the circular barbette. This distance (all things, especially the gun, being equal) will be the same in both triple and twin turrets, so the twin turret barbette can be smaller.
Draw the diagrams: gun separation L in both turrets, gun offset from centreline is L in the triple of radius R, L/2 in twin of radius r.
length needed for the recoiling gun is 2x in both turrets
Pythagoras theorem in both turrets. [but I don't know how to do "squared"]
Triple: Rsquared = Lsquared + xsquared
twin: rsquared = (L/2)squared + xsquared
Assume L = 6 then Rsquared - rsquared = Lsquared - (L/2)squared = 36 - 9 =27
Suppose the twin turret diameter is about the same as the barrel length. Then for a 6in L/45, 2r is about 22ft, put r = 11
Then Rsquared is about 121 + 27 = 148; R is about 12 and the triple turret is about 24 ft diameter, or up about 10% on the twin.
The numbers are very rough, but it gives an idea. Sorry I couldn't draw the diagram. Much easier to see what I mean with one.
John Roberts' "British warships of the second world war" has [reduced] official plans of Southamptons, Leanders and Arethusas to check if anyone has it, but you will be measuring distances of about 1cm.
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