USS Pampanito Magnetic Compass Project 2011
This note is a description of the project to replicate the foundations and brackets that hold the magnetic compasses on USS Pampanito. It is also thank you note to the many individuals and corporations that helped make it possible.
The magnetic compasses where used as a backup for when the main gyro-compass (Arma Mark 7) and the auxiliary gyrocompass (Arm Mark 9) where not available. This might occur due to damage to the gyrocompasses, to save power during difficult situations, or during the long time it takes for a gyrocompass to stabilize after powering on.
When Pampanito opened as a museum in 1981, no magnetic compasses where aboard and no one knew what type and where they were located. In 1996 we found installation instructions for magnetic compass installations at the US National Archives in San Bruno, CA. This showed what type of type of compass (Pioneer 1829 Armored Vehicle type) was likely used and how to swing (calibrate) it. We later found a paper drawing showing the mounting bracket at the US National Archives in College Park, MD. This matched one half of one of the brackets that was still in the conning tower. Volunteers bought and donated three of the compasses from different sources to be sure we had all the parts to create two good compasses. In 2008 we found another drawing of the compass mounts in the USS Pampanito microfilm and a third version of the drawing in some GUPPY II microfilm. Finally, we found a single photo from before the summer of 1945 refit that has a fuzzy view of the compass at the conning tower helm.
We started by creating a full 3 dimensional model of the brackets in Autodesk Inventor CAD software. The software was then able to calculate the correct bend radius adjustments and create unfolded drawings of the brass parts. Because of the full 3D model we were confident enough to take the donated brass (Sequoia Brass and Copper) directly to commercial CNC waterjet cutting. All 12 sheet metal parts where cut (parts for both USS Pampanito and USS Cod). This saved us a huge amount of time and created better parts than we inexperienced metal workers could have created. We used he mill at TechShop to countersink the mounting holes. The accurate bends were made by a commercial sheet metal shop. Ralph Waller silver soldered the mounts and then the parts were sand blasted.
The parts were not painted because the one piece of the original brackets in the conning tower was not painted. We hope to find a photo some day to see if this guess was correct.
The last step was creating simple plexiglass boxes to protect the small, easily removable parts from curious visitors. In Oct 2011 the compasses were mounted on Pampanito and the second set of brackets shipped to USS Cod.
It is hard to express how much we appreciate the advice, help, donations and discounted products and services from individuals and companies along the way. We had the help of an very talented team. We could not have succeeded without the incredible generosity of these people and companies:
ADVICE AND HELP:
Sequoia Brass and Copper, http://www.sequoia-brass-copper.com/store/SBC-Metal.html
PROVIDED PRODUCTS AND SERVICES AT DISCOUNT:
Joyce Brothers Metal Works Inc.
Rich Pekelney, Pampanito Volunteer was the project manager.
Empty flange at the auxiliary helm in the control room.
Compass submarine installation instructions, nara-compass-install.pdf (10.7 MB PDF file).