About Education Events USS Pampanito Support Visit

History and Problem Statement
Modifications to the Non-Historic Stairs
Working Strongbacks
Acknowledgements
Concept Drawings
Drawings of the original parts (torpedo-stowage- )
Photos After
Reference (Before) Photos

The goal of this project was to allow shifting of the torpedo loading trays (also known as torpedo skids). Our immediate need was to enable the crew to get between the torpedos and pressure hull to prep and paint coatings outboard of the torpedoes. We also need to be able to move the torpedoes to measure and fit the center support rails for the sliding berths under the torpedoes. Long term we need access behind the torpedoes for maintenance once or twice a year. We wanted a system that would allow safely rigging and moving the torpedoes in less than an hour, and to restore the room to accept visitors in the same time frame.

History and Problem Statement:
When the Pampanito was converted to a reserve training boat in the 1960s, the torpedo loading hatches were cut out and the current non-historic stairs where installed. All but one torpedo and torpedo loading tray was removed, and all the berths where removed to make the torpedo rooms into classrooms. At some point three of the support tracks (also known as rails) for the torpedo loading trays in way of the stairs were cut and at least one replicated short to allow easier passage around the stairs and avoid tripping hazards. When the torpedo trays and torpedoes were installed during the museum period no system for moving the torpedoes was created. The stairs are in the way and the tracks are too short to use the original (22.5") strongbacks. Moving torpedoes with multiple chain hoists is slow and requires a large well trained crew. The ladders are very heavy, the trays about 1,000 lbs, and an empty exercise MK 14 torpedo is 2,200 lbs (a warshot is 3,200 lbs). With two torpedoes moved to center, the strongbacks will have approximately 6,400 lbs on them and are subject to shock loads as the boat moves. Three of our torpedo trays are complete with locking mechanisms, all the others are missing the locking mechanism (replicas). With the locking mechanism installed there is not a lot of clearance on either side of the tracks. We needed our design to work with all the trays.

Note that the FTR (forward torpedo room)-port-upper-track appears to be a replica and is missing any tray locking holes, or berth chain details. This is consistent with the oral history. We have an intact one of these in the warehouse that may be from Pampanito or another boat. FTR-stb-middle is cut short just inboard of the tray lock. FTR-lower tracks are intact. ATR (aft torpedo room)-stb-upper appears to be historic, and cut. ATR-stb-lower is a replica made of a block of steel with no details.

The locking pins are missing from the one original rotating strong back. We have the drawings so it can be restored.

Any plans need to minimize changes to the historic fabric, and those changes need to be documented and reversible.

If the stairs are ever replaced, they should be aluminum to be lighter, a bit narrower, and mounted just a bit to starboard so the tracks can be restored.

Completed Modifications to the Non-Historic Stairs:
The hand rails on the stairs need to be removable, but solid and quiet when installed. We cut them below the horizontal tie to the dog house, and where they attach to the stairs. We used Speed-Rail #70 slip on couplings to allow easy removal/installation.

The handrails are 1" IPS (1.31" O.D.) pipe on the top rail and verticals. The second, bottom rail is 3/4" (1.03" O.D.) pipe. So used x6 #70 couplings of 1", and x2 of 3/4" per room.

In the Forward Torpedo Room the top of the stairway was cut and had 1/4" plates bolted on both sides for a museum era torpedo loading evolution. We gave the same treatment to the stairs aft. In both rooms, we added 2" wide hinges over the cut.
CAUTION: The hinges have much more weight on them than most would think while lifting the stairs. The crew should be careful to lift both sides evenly. There must be a safety strap under the stairs near the hinges whenever the side plates are out.

We can now remove the handrails and side plates, and use a pair of chain hoists to raise the stairs up out of the way in minutes. Or remove the hinges and side pieces to lower the stairway to deck or out of the boat as needed.

Working Strongbacks:
In the FTR, forward end of the compartment the original rails and strongbacks are in place. A rotating loading style strongback is in the upper position, and we have 3-hole fixed style strongbacks in the middle and lower flats. The FTR-aft-stb-upper track is intact, the aft-stb-middle was cut short. The aft-port-upper and aft-port-middle were cut. The FTR-aft-lower tracks (below the platform deck) are intact.

In the After Torpedo Room (ATR), the aft tracks (near the torpedo tubes) are intact. There are two 22.5" strongbacks with one locking hole on deck behind the visitor proofing. Note that the rotating type strongback for loading now in the FTR will fit in either position in the ATR. The fwd-upper-port and fwd-lower-port tracks are intact. The fwd-upper-stb is cut, and fwd-lower-stb is a short replica.
CAUTION: It is not clear if the ATR-fwd-lower-stb track is attached to the boat. It looks like a simple block of steel. We need to be careful when we roll the skid off this section. We should make flanges for this piece.

Where the original tracks are intact our longer replica strongbacks fit in the 1" wide slot that the original strongbacks used. That leaves five other interfaces. After examining several alternatives, we welded a 3/4" deep, 1" I.D., 2-1/4" O.D. U-shaped end flange on the existing rail ends that had been cut short. We then created long strong backs to fit.

Acknowledgements and Thanks:
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:

Autodesk, CAD software, http://www.autodesk.com
Bayshore Metals, steel, http://www.bayshoremetals.com
Dean Lewis Associates and Southco, hinges, http://www.deanlewisassociates.com
Hougen Manufacturing, mag drill, annular drills, http://www.hougen.com
Techshop, shop, http://www.techshop.ws
Walter Surface Technologies, https://www.walter.com
Luke Stevens
Rich Pekelney

The drawings of the original parts are located at:
https://maritime.org/tech/drawings/index.htm#torpedo
Look at the drawings that start with torpedo-stowage. For example the original removable strongbacks:
https://maritime.org/tech/drawings/torpedo-stowage-ftr-removable-track_basic386853alt6_32429-15-0409.jpg
Rail arrangement:
https://maritime.org/tech/drawings/torpedo-stowage-atr-tracks-at-fr-110_basic386883alt6_32429-15-0427.jpg
https://maritime.org/tech/drawings/torpedo-stowage-ftr-tracks-fr-31-arrangement_basic387465alt4_32429-15-0461.jpg

Concept Drawings:
The first three U-channels were identical, and strong backs in each room are identical except for length. The deeper channel for FTR-aft-port-middle accommodates the flip up tray lock when the strong back is not installed, and FTR-aft-port-top was also 3-1/2" deep. It is unclear if we will want to add the cross flange for mid support on the forward middle (~2.43") shown in the concept drawings. Edge chamfers, lightening, and extensions for the 1-1/16" holes to lock trays are not shown in the drawings.

The outboard, storage position lock holes are two 1/2"R hemispheres with an 1/8" gap allowing 1/8" vertical play, but not the ones at the tube and ship centerline we are replicating. Ship centerline holes are 24" from loading position (tube centerline) holes. The centerline of the holes are 1-9/16" from the top. Fwd. room strongbacks also have two extra holes 9" from centerline hole. The strongbacks will need to be extended to provide room for the holes.

We created the strongbacks from a 1" x 2" center bar with with two 5/8" x 2" pieces welded on each side. The as built dimensions reflect a little extra length of tab on the historic un-modified flanges, and a minimum of 1/32" clearance on each end.
ATR Top 48-1/4" center overall, 46-1/2" shoulder, 1/4" extra on port tab
ATR Bot 49-3/4" center overall, 48-1/8" shoulder, 1/8" extra on port tab
FTR Top 47-1/4" center overall, 45-1/2" shoulder, 1/4" extra on starbord tab
FTR Mid 50-1/2" center overall, 48-3/4" shoulder, centered
FTR both have a 1" x 1.5" x 2" extended tab on Stb. because of the deeper U-flanges

They have been welded, welds ground flush, and test fit. At some point in the future we might mill or file the tops flat, and extend and drill for the locking holes. If we plate or paint these, we will need to take a bit more off the shoulder clearance because they are snug fit.

One of the removable couplings we used to make the hand rails easy to remove.

These added flanges (on both sides) hold the weight during normal operation. They can be removed and the stairs lifted on the hinges. Or the hinges un-bolted, flanges removed, and the stairs lowered to deck.

Another view of the hinge.

Aft, port, lower track with added flange.

Aft, port, upper track with added flange.

Fwd, port, middle, track with added flange.

Fwd, port, upper, track with added flange.

Fwd, starbord, middle track with added flange, the original tray stop down.

Fwd, starbord, middle track with added flange, the original tray stop up.

Luke Stevens TIG (GTAW) welding the flanges. This was the first use of our updated welding infrastructure inside the boat, it worked great.

Working strong backs welded, but before test fitting, milling and holes. They can be used in this functional, but not elegant state.

Test fit forward torpedo room top.

Test fit forward torpedo room middle.

Test fit after torpedo room top.

Test fit after torpedo room bottom port.

Test fit after torpedo room bottoms starboard.

Ladder raised for the first time on the hinges.

Torpedo trays with torpedos shifted to port for the first time.

Room to work on starboard while the torpedoes are shifted.