07/29/2012 - Fuse Settings & Kw

Today started wet and rainy I didn't get a chance to walk my 4 mile loop.   After a little while it cleared up, and it turned out to be a nice day. I managed to conduct three tours.

During one of the tours I was asked about the kw rating of the Main Propulsion Generators. The answer turned out to pretty easy. It was detailed on the USS Slater Web site - Description of B-2, The generators were Allis-Chambers, 1200 KW, 525 VDC, 750 RPM, The USS Slater has four.  The picture above is the main generator in the forward motor room.  In the description of the aft motor room B-4, there is a panoramic view.

The USS Slater has a power plant arrangement that is similar to fleet submarines.  There is a detail description of WWII US Navy submarine generators on the Historic Naval Ships Web Site.

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At the 3" 50 cal I was asked what was the minimal time setting of the mechanical time fuse (MTF)?  A mechanical time fuse is used for shooting at airplanes.  This minimal time is referred to as arming delay (a safety feature).  It is the minimal setting from the time a gun is fired, until a projectile can detonate.

The short answer is 0.60-second for the 30-second mechanical time fuze.  There appropriate projectile (3" Mk26) is detailed in the US Explosive Ordnance Manual (OP1664, May 28, 1947). The fuse referenced is Mk21 MTF (same manual, OP1664 page 105). 

At a muzzle velocity of 2700 ft per second, the .60 delay, means that the shell will travel somewhat less than 540 yards (2700 * .60 / 3).  The muzzle velocity is the highest rate of travel for a projectile but it will slow the further the projectile travels.  The rate is influenced by the gun elevation.  You need range tables to determine the exact value for a given elevation.

btw - Detail Information of the 3" 50 cal. is available in OP 811, 1943