USS Pampanito Depth Gauge Replacement
USS Pampanito is a WW II submarine museum and memorial on Fisherman's Wharf in San Francisco. Our preservation goal is to make the submarine as complete and accurate to our summer 1945 restoration date as possible. This note is a description of the project to replace the missing depth gauges, and a heartfelt thank you note to the individuals and corporations that helped make it possible.
During WW II Pampanito the depth gauges in the Control Room and Conning Tower where critical to the safe underwater operation of boat. In addition, the After Torpedo Room, Conning Tower and Escape Trunk in the Forward torpedo room had depth and compartment pressure gauges needed for emergency escape. Although the submarine will never dive again, our goal is to restore the gauges as a museum worthy reference examples of the technology whenever possible. Our priority is always to prevent any changes to the historic fabric that cannot be easily reversed.
During the 1960s when Pampanito was used as a reserve trainer, a simulator control station was mounted on the aft deck. Wires led to electronic (selsyn) replacements for the shallow water depth gauges on the dive station and the conning tower. Many other gauges and controls were replaced so the crew could simulate operating the submarine without ever leaving the dock or diving. After the reserve period and before she became a museum, other gauges were removed and/or vandalized. During the early museum period additional changes were made without documentation.
To create a restoration plan, we first studied a gauge list from 1944 we found in microfilm from the National Archives and Records Administration, the original gauge boards and flanges, the gauges on the boat, the couple of photos from WW II, and the few photos we have from the early museum period, and photos from the other museum boats.
* The dive station in the Control Room had two 16", 15-165 depth gauges used by the dive planesmen. These were replaced by two simulator gauges during the reserve period. During the 1990s, these were replaced by two real depth gauges from other boats. One is on loan from the US Naval Historical Center, and the other was donated from the collection of USS Alabama & USS Drum. Each gauge was checked and the radium dials and needles where emitting very low levels of radiation (below unmonitored exposure standards). We confirmed that the normal vent holes were clear (to prevent radon buildup) and did not open the gauges before installation.
Follow-up work is needed to plumb the gauge lines into the gauges and maybe to add a reference needle (for decks a wash, periscope, radar, etc. depth.)
* Also on the dive station in the Control Room was an 8.5", 0-600 depth gauge. There was a gauge here, but without a dial or needle when Pampanito became a museum. For as long as current crew can remember there was a 450 foot depth gauge in place. This would have been appropriate for an earlier Gato class submarine, but not for a Balao class submarine like Pampanito. During 2011 a vandal managed to open this gauge and dropped its needle (visitor proofing has been improved). The needle was recovered and stored. In 2014 we decided to create a replica dial for this gauge with the correct 0-600 foot scale and re-install the needle. The needle has radium paint, but with a very low level of radioactivity (below the normal unmonitored safety levels.) We top coated it with paint being very careful not to disturb the radium paint and verified the normal vent holes in the gauge are open. We hired CAD Graphics Inc. to draw the 0-600 dial, and then used the Techshop laser cutter to etch and cut a replica dial in laminated plastic. Note that "Replica 2014" is etched at the bottom of the dial.
Only then did we open the gauge and we were surprised to find that the 0-450 dial plate had only one screw in place because its mounting holes did not line up. The dial plate is etched, painted, brass that is almost surely real, but from another gauge body. Similarly, the needle had a mounting hole much bigger than the stem of the bourdon tube mechanism. It also is real, but not from this gauge. The instrument and gauge body itself look correct and included a temperature compensation bulb broken at the bellows and the ability to zero the gauge without disassembly (advanced features). We were also surprised to see the gauge had been modified for internal backlighting. If this gauge body is original to Pampanito it solves the mystery of how the deep gauge was lighted. We restored the emergency gauge light power during the bubble clinometer restoration project in 2011. However there were no external lights visible in the WW II photos, or mounting holes on the gauge board. There are examples of etched laminated plastic being backlighted on small indicators during the war. This gauge would be a larger version of the same concept, or maybe there were holes in the dial. If backlit, we just got lucky that we chose the laminated plastic rather than trying to etch brass. At this point we think the gauge is original to Pampanito without our replica dial and replacement needle.
We installed the replica laminated plastic 0-600 foot dial and stored the found 0-450 dial in our collection. The needle found in the gauge was reinstalled.
Follow-up work is needed to re-power the emergency lighting, replace the needle with a new old stock one that fits better, possibly repair the temperature compensation bellows, and blacken the heads of the dial plate screws.
* The Conning Tower had a 26-176 foot gauge according to the microfilm. All the other real Conning Tower gauges on the other museum boats are 15-165 foot. We have early museum era photos of the empty flange, and a second bracket with a gauge body installed on the air conditioning evaporator mount. A cylinder that is probably a selsyn is seen sticking out the back of the gauge body. There is also a photo of the removed gauge body that shows gears not part of a pressure gauge. The original gauge line piping is in place by the original flange, and also the lighting power wires. Together this leads us to we believe that the original gauge was removed, and possibly modified (or replaced) with a simulator mechanism on the new bracket during the 1960s. With the selsyn out the back of the gauge body it makes sense that it have been easier to add the extra bracket than use the original center mounting flange.
The simulator gauge body was removed in 2000 and sent to Ashcroft/Dresser for restoration. Unfortunately, in spite of their goodwill, during large changes in their business the gauge body was lost before being returned.
We decided to remove and store in the collection the extra mounting bracket we think is from the 1960s simulator. We then created a replica gauge mount to fit the gauge to the original mounting flange. The details of the gauge mount including felt washer shock mounts that match the other gauge mounts on the boat and microfilm drawings. We found an 8-1/2" pressure gauge with a poor quality photo replica of a 0-450 depth dial on aluminum, and no needle in our collection. It is a normal bourdon tube type gauge with no temperature compensation or external zero adjustment. So we created 15-175 foot replica laminated plastic dial and installed it over the existing dial. Technical Service Group donated a new old stock needle.
Follow-up work includes plumbing up the sea and vent gauge lines, and figuring out how the lighting was installed. I.e. the unusual backlight found in deep water gauge on the dive station, or an external light? We also do not know if it had a reference needle, or painted reference lines for decks awash, periscope sheers awash, periscope or radar depths. We are also continuing to look for a real depth gauge from a Fleet submarine to replace this replica.
* During WW II the Commanding Officer's Stateroom had its own 0-600 foot, 8-1/2" depth gauge according to the microfilm. We found a 960 foot gauge body improperly installed with a hard pipe segments. It had no bourdon tube, and had a big hole and screw holes for a selsyn mount that make it look it might have been part of the 1960s simulator system. We are fortunate to have a 13' 11-3/4" to 650 foot depth gauge that was donated to us by USS Cod. It is very similar to the gauge in the C.O.'s stateroom on USS Razorback. The gauge was tested and does not have radium paint. This gauge had a broken needle hair-spring, the temperature compensation tube was broken at the bellows, the dial paint was badly abused, and the lens was deeply scratched on both sides. Even so, this is the best example of an original 8-1/2" depth gauge we have. Technical Service Group repaired and calibrated the gauge. We polished the lens clear, painted the bezel, and did very minimal paint touch up on the dial face.
Follow-up work includes piping this in with soft pipe and flare fittings.
* Emergency Escape Gauges. To open a hatch for an emergency escape, the pressure inside the submarine has to be the same as outside the hatch. So a compartment (inside) pressure gauge of 0-600 foot, 0-266.29 lbs and an outside 0-600 gauge are needed near each escape hatch. Pampanito has what we think are the original set of 6" gauges in the emergency escape trunk in the forward torpedo room. The gauges were missing from the After Torpedo Room and the Conning Tower. The mounting brackets were intact in the Aft Torpedo Room, but the gauge piping was bent and pulled back. In the Conning Tower the external depth gauge mount was complete, the compartment pressure mount had two of its legs broken off. The sea and vent gauge valves are also missing in both the Conning Tower and Aft Torpedo Room.
We had one real compartment pressure gauge in the collection, after replacing a degraded yellow plastic lens with modern acrylic lens it was mounted in the Aft Torpedo Room. We bought two liquid pressure gauges from a collector and installed replica 0-600 foot dials in each. We did not attempt to calibrate these or straighten the bent needle shafts. One of these was mounted in the Aft Torpedo Room.
We repaired the Compartment Pressure gauge mount in the Conning Tower with two replica legs. We found an air pressure gauge in the Susuin Bay Reserve Fleet and replaced the dial to create a replica compartment pressure gauge. We did not attempt to calibrate this gauge. The second replica 0-600 foot gauge was mounted here.
Follow-up work includes finding and installing appropriate valves for the vent and sea pressure lines. We will continue to look for three more of the missing gauges so we can replace the replicas with real depth gauges.
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:
Technical Service Group, Alemeda, CA
Rich Pekelney, Pampanito Volunteer was the project manager.