06/20/2010 - What is that switch for?

Over the last two weeks we had a steady flow of visitors. I understand that attendance has been very very good. One weekend we were a little pressed for guides. Typically smaller cohesive groups are the best. When you have few guides and heavy attendance you are forced to have larger tour groups. This takes a little longer and makes it a little difficult to get the groups into all the compartments. It seemed to me that the groups were always of reasonable size.

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What is that switch for?

On 1st glance it is simple - It is that the power switch for the elevation power drive. Next question - Why does to have a Fast and Slow Button? That's very difficult to answer. I didn't know the answer two weeks ago when I was asked, and I don't know today (after spending many hours of research). I asked Tin Rizzuto (the Ship's Superintendent) and Eric Collin (Restoration Coordinator) and they didn't have an answer either. The initial consensus was that we just used a non-standard button during the restoration. During subsequent investigation I found that this wasn't true. I checked other 3" mounts on the Slater that still had the original buttons. I also pulled the design prints (The Slater has a complete set of prints for the 3" mounts). They both indicate a three button configuration.

What I currently BELIEVE: the switch is a quick fix to a problem with the Arma Elevation Power Drive (Mark 31 Mod 0). I believe in the fast setting the elevation drive would respond quicker under director control but it would loose accuracy. With the slower setting the elevation drive would be more accurate, but it's response would be slower. The Trainer position (moving the gun from right to left) does not have this setting. This leads me to believe that in certain situations, perhaps when the ship was rolling heavily, the normal setting of the drive failed to keep the gun on target. When a gun is under director control, it moves quite a bit to compensate for the roll of the ship. Most of the movement is in elevation. When they tried to speed up the drive the accuracy suffered. Rather than scrap the program, someone though of the dual setting as a quick fix.

Unfortunately, I have no documentation to support this theory. I do have a great deal of circumstantial evidence.

I reviewed the 3" Gun Manuals (ORDNANCE PAMPHLET NO. 811, December 22, 1943 which is available on line; and NAVORD OP811, 2nd revision, January 1, 1968, which is available in the Slater's Library). According to the 1943 manual, the 3" guns do not have a power drive. The later manual appears to reference Elevation Indicators - Mark 21. The description of these Indicators seems to be different that the configuration on the Slater.

The manual in the Slater Library (rev 2) refers to Ordalt 2227A (Ordnance Alteration) - "...To provide installation of power drive equipment with automatic control, firing stop mechanism, and hydraulic buffer stops on manually driven mounts MK 22 Mods 0, 4, 17 and 20 converting them to mounts MK 26Mods 0 and 1. ..."

The name plate on the drive has the following details:

• Elevation Power Drive, Mark 31 Mod 0
• Arma Corp, Brooklyn NY
• Serial #177
  
• SK 93744

I ran across this this note on upgrading 3" 50cal with Arma Drive units in the Guide to United States Naval Administrative Histories of World War II. The following excerpt is from the Ordnance Section, Chapter VII: "... The design of 3"/50 power drives was completed in the spring of 1944 by the Arma Corporation, at that time, the bureau of Ordnance was authorized by a directive summary to procure 2,000 power drives for installation on U. S. ships having a battery of three or more 3"/50 guns.[9] However, in the fall of 1944, when the program reached a directive stage for authorization of actual procurement it was decided that 1,000 drives would be sufficient to start the program and the contract for this number was placed with the Arma Corporation. Initial deliveries of power drives were expected during this first quarter of 1945 but due to the difficulty of obtaining a satisfactory design of certain components and to procurement difficulties with subcontractors, the initial supply of 3"/50 power drive equipment was not available until August 1945. Following VJ Day, procurement of drives was reduced to 600; of these, 500 were to be used on 3"/50 caliber mounts Mark 22 scheduled for ships of the post war fleet In which 3" 50 caliber guns are a part of the ultimate approved armament. The remaining 100 units were reserved for the 3M/50 single rapid fire development. ..."

I believe that the USS Slater was one of the 1st ships to be equipped with this Drive, and the difficulties with the program related to the power drives. Those problems led to the power button with the fast/slow setting.