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USS Pampanito Gyrocompass Restoration
Project Proposal revised to Project Status - Updated 1 Apr 03








USS Pampanito SS-383, a Balao class (1943 built) submarine memorial and museum in San Francisco, CA is in a unique position to restore and preserve its original Arma Corporation Mark VII gyrocompass ("gyro") navigation equipment. This gyro is now the only working example of this technology in the United States. There was a narrow window of opportunity to complete the restoration. The few remaining experts with the necessary knowledge are near retirement and the last shop equipped for this restoration is no longer used, it was held intact for a couple of years just for this project. During the restoration the knowledge of how to maintain this technology has been recorded before it was lost. Pampanito's crew gathered the needed parts and equipment, identified the key personnel and secured the cooperation of the shop; the project is nearly complete.

The Maritime Park Association operates Pampanito's preservation program with the goal of making Pampanito as complete and as accurate as possible, striving for a summer 1945 configuration. To date we have restored over 50% of her systems to working order including four of her five diesel engines, main hydraulics, high pressure air, most of the radio gear, torpedo data computer, and cipher systems. We work very closely with the US Navy as well as private sources to acquire the equipment missing from the boat.

The restoration of the gyro is of special importance to the Pampanito's mission in several ways. During the restoration, the apprenticed art of "setting up" (balancing) an Arma sensitive element has been fully documented for the first time, missing components have been replaced and damaged wiring repaired. Now that the completeness of the system has been verified through operation the system, it is being preserved with basic maintenance. Its preservation will enable the future study of not only the gyro, but also the surprisingly sophisticated WW II fire control system. The gyrocompass is used to interpret navigation technology, basic principles of physics, basic principles of navigation and fire control during educational programs. We serve over 200,000 visitors a year including several thousand children in overnight programs.

Time was a critical factor. The most pressing concern was the availability of craftsman capable of performing the specialized shop work. Virtually all the experts have retired and were no longer capable of performing the 200+ hour job. The second source of urgency was the availability of a properly equipped shop. The last shop equipped to perform the work in the United States has had not used its Arma Mk VII shop gear for many years (1972). It retained this valuable shop space intact only for this project for a couple of years while we prepared. The shop's Arma experienced staff were all near retirement age.

Pampanito is perhaps the best example of the peak of WW II submarine technology to survive. Pampanito was refit with the latest submarine fire control and navigation technology just before the end of the war and has received no significant post WW II upgrades or modifications. Her Torpedo Data Computer (the second most important part of the fire control system) is in the original WW II configuration and has been restored (the only Mk III TDC operational in the world) to operation (this includes its inputs from the gyro.) We have assembled all the other major components necessary to complete the original WW II fire control system. We believe this system has historical importance and needs to be preserved.


The gyrocompass is the most important high technology equipment aboard a submarine. Without the gyro, navigation below the seas for attack or escape is difficult and fire control systems are cumbersome. The gyro is an integral part of the fire control system that includes the torpedo data computer, dead reckoning analyzer, dead reckoning tracers, dummy log, pit log, sonars, and radars. This highly integrated system was years ahead of competitive systems and was one of the crowning achievements of WW II technology. The Arma gyro technology aboard Pampanito is particularly interesting.

During the 1930s two companies, Arma and Sperry, created competitive gyro technologies. During WW II all US submarines had Arma main gyros identical to those on Pampanito. Surface ships used either type of equipment, but more Sperry equipment was installed. It is interesting that the very largest ships, aircraft carriers, battleships and cruisers received mostly Arma gyrocompasses. During the post-war period Sperry was more successful as a company and as a result fewer Arma gyros survive today.

We located the last Arma gyro repair shop in the United States: Gyro Systems Inc. in Virginia Beach, VA. As Arma gyros became more and more obsolete the market for their repair and maintenance diminished. Fewer and fewer gyro repair shops stayed in the business and Gyro Systems Inc. slowly acquired their stocks and the few remaining customers. The last of these gyros is long gone and we were fortunate to contact Gyro Systems Inc. as they were preparing to dispose of the last of this long obsolete equipment. They have very generously donated all the spare parts and equipment we have used. Further, they still have all the shop tools, gauges, equipment, etc. needed to setup an Arma gyrocompass sensitive element (including the delicate rotor mechanisms). They provided the use of these facilities for free before they are dismantled. We were hoping to get a 72-year old former Navy expert on gyros to perform the 200+ hour job of setting up the sensitive element. Unfortunately health problems made this impossible. When we could not get the skilled labor for free, Gyro Systems president, Buddy Creakmore generously donated the skilled labor. These are the most qualified people available to perform this work and quite probably the only ones not yet retired.

The existing Arma documentation barely captures the process of setting up the sensitive element to a level that would allow repetition after the current generation of experts are gone. Servicing any mechanical gyrocompass has always been more an art than a science. The reason is that the forces at play to make the compass work are very small and are dependent on a delicate balance of all components to be expressed accurately. This was an apprenticed skill that was never completely captured in writing. Among those servicing these gyros, craftsman of greater skill were known an respected among their peers. Gyro Systems Inc. has two such men still working who are skilled in the servicing of the Arma gyros and all the specialized shop equipment. When they retire, this art would have been lost. We were able to restore this system and document the sensitive element setup by last skilled craftsmen available.

We understand that the operation of most types of equipment is a necessary component of a long term preservation plan for many reasons. First, idle equipment frequently deteriorates faster than operating equipment. The operation distributes lubrication, dries components, discovers incremental problems in their nascent stages, and avoids material creep. Second, although Pampanito has had no post WW II additions, modifications and removals did occur during the 1960s and 1970s when she was used as reserve trainer and then opened for stripping by other Navy units. As a result, wiring was modified and parts were removed from many systems on the boat. No system can be assured complete and accurately assembled until it has been operated at least once. Third, our experience has shown that many safety problems are found and corrected during the restoration of equipment to operational status. Fourth, in restoring equipment to operation, the skills of repair and operation are themselves preserved in a way not possible with static displays. Finally, operating equipment inspires respect and care not offered inoperable equipment. This is true not only of its caretakers, but also those that might be inspired by it. There is a magic to teaching with a complete and operable system that is not possible with equipment of unknown condition. Of course, when long term operation is not sustainable, equipment is brought to operable state and then properly laid up.


Restore Pampanito's main gyrocompass to operable condition. Operate it on an scheduled basis as needed for preservation. Create a gyrocompass binnacle emulation device for system testing and demonstration of the system. Implement a plan for long term preservation. Implement a plan of education and interpretation.

Priority Goal
Nearly Completed, final balance is not completed. One rotor has a slow leak. Restore the gyrocompass binnacle. This consist primarily of balancing the sensitive element. Repair the spider and follow-up mechanisms.
Underway. All except follow up amplifier are fully working. Follow up amp is working, but not to specification. Restore main control panel.
Completed Restore and install replacement gyro motor generators.
Completed. All except forward torpedo room. Restore gyro repeaters and its cabling.
Completed Create a Own Ships Course emulation device to drive an Arma repeater. This is used to test individual repeaters, and to supply a simulated signal for emulating the function of the gyro itself. This allows running simulated attacks testing the rest of the fire control system including TDC. It may also be used during interpretive programs.
Ongoing Document all work. Especially the art of setting up the sensitive element of the gyro. Capture detailed photographs of all process steps, video of particularly dynamic steps, and textual notes.
High Visitor proofing for side of Gyro control panel so it can be powered up with visitors aboard.
Med Replace the Alarm Flasher (if we can find one).
Completed The gyro circuits are OK from the TDC to the control panel. The own course synchros are good in the TDC. A replacement follow-up amplifier has been installed and wired to the main control panel.
Completed Restore high current 120 VAC and 120 VDC to IC Switchboard. Restore power supply wiring from IC Switchboard to the main gyro control panel.
Completed Restore Bendix Dummy Log. This supplies ships speed correction to gyro and speed data to the TDC.

Related Future Projects:

- Restore the Arma Dead Reckoning Analyzer, Arma Mk 5, Mod 0 for Submarines
- Restore the Dead Reckoning Tracers. Arma Class 3, Mk 7, Mod 1.
- Restore the Target Designation System
- Restore the Auxiliary Gyro. Arma Mark 9, Mod 2 Gyrocompass
- Create operable shore side display.


Resource Purpose Status
Shop Time, 200 hours donated. Set-up sensitive element and spider. Labor, shop and parts donated by Gryo Systems.
Shipping, $1,000 Shipping of sensitive element to and from VA. Donated.
Spare parts and equipment. Includes not only gyro, but also other very rare fire control systems spare parts Equipment donated by Gyro Systems Inc.
Shipping of donated spare parts and equipment. Approx. $1,500 Shipping of 5 palates (4'x4'x4'), 3,000 lbs. as class 85 machinery  
Storage of donated materials Storage of 5 palates of material  
Misc. Fluids, Misc. Parts, Vacuum Pump & Gear, Synchro Test Gear, Photocopy expense, Other supplies, Travel Expenses, Other shipping.   Donated.
Ongoing maintenance Very, very little is needed. Gyro must be spun up periodically if it is to retain calibration. Volunteer crew.


USS Pampanito is in a unique position to preserve and restore a fine example of a WW II, Arma Mk 7 Gyrocompass. Outside of the unique technology of this device, the Arma gyrocompass has a unique place in history.

The practical gyrocompass was invented by the creative genius Elmer Sperry ca 1904. A gyrocompass measures the movement of a ship around small wheels turning at high speed to track the movement of a ship. Historically this invention was more important than the invention of the present day global positioning system. For the first time in history it was possible to instantaneously and accurately determine your vessel's location at all times no matter what forces caused its motion. It worked in all weather, was less prone to local anomalies, and could be used no matter how much steel was used to build the ship. When during the 1930s it was extended to three dimensions it was the basis not only of navigation, but also fire control.

Elmer Sperry and his company held a monopoly on this critically important technology through its patents. However, Germany's Aunshutz company created its own version of the gyrocompass before WW I. Sperry sued Aunshutz in those pre-WW I years in the international court at the Hague. We have extensive correspondence between Sperry and his lawyers showing his deep personal interest in the progress of the case. At the end of WW I the US Navy took the Aunshutz gyrocompass technology from Germany as a prize of war. The Navy immediately turned this technology over to the Arma corporation in an effort to create a competitor to Sperry. Arma improved the Aunshutz design with its own innovations a produced a gyro. Sperry then sued Arma, however it was quickly resolved by the US Navy.

The Aunshutz compass had several advantages over the Sperry design, most importantly the refinement of putting the gyro wheels at an oblique angle to each other. This approach was inherently more stable than the orthogonal Sperry arrangement. This allowed creating smaller, more accurate gyros. The trade off was that in order to read the course it was necessary to adjust the frequency of the wheels rotation based on the latitude. This adjustment was simple to implement and with uniquely Arma improvements a very fine gyrocompass was created.

As part of the arrangement between the US Navy, Arma and Sperry, it was agreed that Sperry would remain the primary gyrocompass supplier. However, because of its critical importance to modern warfare, the Navy would insist on two suppliers. The same was true of the critical fire control equipment and stable elements.

The Arma equipment was supplied to all submarines for several reasons. First it was inherently smaller, more stable and required less maintenance. Second, it was easier to adjust during operation. Third, it had lower power consumption. Lastly it was easier to start and stop, an important advantage in a submarine that was trying to evade enemy acoustic detection.

Because Arma was the secondary supplier, fewer Arma gyrocompasses were made. Of those produced, most were in submarines and few of these have been preserved.

As the Arma corporation slowly decayed until it ceased to operate in 1976, support for the equipment underwent a consolidation among the third party vendors. Gyro Systems Inc, a leader in the repair of this technology slowly acquired the market of customers and inventories of parts and equipment until it remained as the last remaining repair center for Arma gyros. The last of these gyros was removed from active service in the late 1980s.


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Version 2.00, 11 Sep 2006