History Of Restoration
Eight years and still going!!!
The first order of business on the Super Duck was establishing an infrastructure to restore the vehicle. By coincidence, several surplus Army 40-foot maintenance shelters became available and one was erected with the Super Duck nestled inside. S250 shelters for tools, welders, sandblasting equipment and storage bins were added as the project continued. Luckily several friendships resulted from the time at the local salvage yard including one mechanic who was an excellent welder and jig maker. His recommendation to purchase a plasma cutter was invaluable, and it was far superior to saws and cutting wheels when working with sheet metal on the scale of this project.
The most noteworthy event that occurred in the spring of 1997 while sandblasting the body was photographing the old military markings. Sand blasting is tough work, manipulating a heavy, high-pressure hose while encumbered with protective clothing and a respirator. Halfway through the four tons of sand the project would eventual consume, one of the “volunteers” motioned that some original markings had been revealed in the rear and all present were stunned! There, in faded white letters was stenciled “APG D&PS”. The Development and Proof Services was the predecessor of today’s Aberdeen Test Center, Aberdeen Proving Ground, MD. More investigation followed, through some 1950s American Ordnance Association periodicals, technical reports and other markings found on the Super Duck. It confirmed that this vehicle was at APG in 1956-57, before going to Fort Story, VA. The 347th Light Amphibious Truck Company was at Fort Story which explained the hull designation “347-38”. Some years later it was given to a Southern Maryland Fire Department and then sold into private hands.
Technical Overview
Technical specifications on the Super Duck refer to both a 2 ½ and 4 ton rated capacity. The last report dated 1959, specifically stated the capacity at 4 tons and all testing was preformed with that weight at Coronado and Monterey, CA, accordingly this is the correct rating.
The main difference to the observer when looking at the Super Duck over the WWII DUKW is the body style. The Super DUKW features the cab over engine (COE) versus the DUKW, which has the cab behind the engine. Thus the Super Duck has more cargo room, but this results in the cab also being higher. The years after WWII also resulted in the advancement of the engine and drivetrain to reflect the M-Series of trucks, the DUKW engine of 270 cubic inch displacement was replaced with the 302 cubic inch used in the M135/M211 series. The transmission fortunately was a much beefier automatic design made by GM Allison designated CTP-5 also called the “Torqmatic”. This featured three forward speeds and reverse in either a high or low range. The transmission was in excellent condition, despite the passage of 40 years. The overhaul preformed by a Baltimore Detroit Diesel Allison service center only required replacement of speedy sleeves, seals and filter.
The engine cooling system was more elaborate than the DUKW. The radiator is larger and there is a transmission fluid oil cooler. Additionally mounted under the front bow is a bronze “keel” radiator, which allows direct heat exchange between the engine coolant and seawater.
GMC made an attempt to keep water out of the rear brake drum assemblies. A bellows seal attached to the inside of the brake drum would freely rotated on a collar attached to the backing plate of the brake assembly. A vent line would provide air to each bellows to prevent water ingress. The front axle and brakes were not so equipped and appear identical to the M135. However, all three axles are equipped with a vent tube to prevent negative pressure during operation in water. The author later added a small air compressor to provide about 3cfm air at 15 psi seemed to prevent almost all water infiltration innto the bearings and universals.
The Super Duck came equipped with three bilge pumps; two were centrifugal driven, one by the propeller shaft and another by a separate power take-off and discharge on the driver’s side. The third bilge pump, a positive displacement design was powered by compressed air and discharges on the passenger side. Two electric bilge pumps and a 2kw generator were added later to enhance the dewatering capability for increased safety margin.
While the Super Duck was equipped with a Central Tire Inflation System (CTIS), the slip rings attached to the wheel hubs and exterior air hoses were missing. However, it appeared that generally the CTIS was identical to the WWII DUKW, right down to the tire pressure gage on the instrument panel.
There were some good news stories, the fuel tanks were constructed of fiberglass and were in excellent condition. The fuel pump housings, fuel pumps and sensors were decayed but M135 parts were direct replacements.
The Super Duck came with a hard cab top also made of fiberglass while the sliding window frames were aluminum. The cab top was in good shape, but the glass was either broken or cloudy and needed replacement. The windshield was ¾ inch laminated glass for operation in the surf. In the crew area only the generator gage and tachometer were salvageable from the instrument cluster. The only wood that could be salvaged was the driver’s footboard beneath the brake pedal.
While removing the instrument panel and miscellaneous internal components, some of the parts were marked in orange grease pencil for the “XM147” Super DUKW and occasionally “XM157”. The 8x8 “Drake” was also being manufactured at the same time and some parts were apparently common to both vehicles.
The Super Duck hull was constructed of galvanized steel, 11 gage (approximately 1/8 inch) for the bow and bottom while 12 gage was used for the sides. Extensive sheet metal work was required as evidenced by the 200 square feet of new sheet metal that was ultimately used to replace corroded hull sections. Special care was taken for proper ventilation during welding due to the use of galvanized steel.
Before and after pictures of Body Work Done
The brake system is near identical to the M135, a master cylinder in conjunction with an air hydraulic cylinder activating two wheel cylinders on each hub. The original brake, vent and fuel lines were 5/16 diameter copper alloy tubing with .040 wall thickness. Corrosion resistant, copper alloy tubing specifically for hydraulic applications was selected with a stock .032 wall thickness. This was determined to be well within the operational limits of the Super DUCK brake system. Five years of actual road use and no problems have been experienced.
A particular challenge when working on the Super DUCK was the amount of time involved in just getting the right tools inside and back out. Working on vehicles like a jeep or light truck meant that you were on ground level with a tool cabinet fairly close by. In the Super DUCK getting around meant climbing up and
down a 7-foot staircase to get inside the hull. Additionally walking around a jeep is a matter of several steps compared to walking around a 34 foot long Super DUCK.
The Super DUCK as received had a mixture of 1100x18 and 900 x 20 tires. Specification sheets from Army and private sources state that the Super DUCK had 1250 x 20 tires but after much debate, 900 x 20 was selected mainly due to availability.
The bad news encountered during restoration was that most of the fasteners were hopelessly corroded and could not be saved, since safety and functionality were also a priority, current mil spec and stainless fasteners were used to the maximum extent. In regards to the body, there are vast expanses of sheet metal on the Super DUCK including dents, dings, grooves and waves that are structurally sound. They are the result of 40 years of service and are considered character features that would proudly remain in the finished product.
The selection of paint finish was also a topic of study, while it was manufactured in 1955-56 the sand blasted and disassembled parts revealed a lusterless, WWII type OD green. There was no semi-gloss OD finish as would be expected from vehicles manufactured during this period. Ultimately, due to the amount of surface area to cover on a vehicle this size 18 gallons of primer and paint were applied on the Super DUCK.
The electrical harness presented few challenges. It used the ubiquitous metal Douglas connectors, but since this Super DUCK was a test vehicle there were "cut" and unidentified wires that needed to be chased down. The entire wiring harness was removed, portions replaced where necessary and re-wrapped. The fact that the wiring was identified with a manufacturer (Packard) and date (3Q1955) confirmed that this Super DUCK was assembled subsequent to that.
The Braden, 20,000-pound capacity winch, located on the top aft portion of the Super DUCK has a rotating head, which offers 360-degree availability. Controls for the winch including a winch brake were conveniently located to the left of the driver. Like the DUKW, the winch cable can be passed through the cargo and crew compartment when winching from the front is necessary. A winch cable under strain less than an arms reach away must have caused concern to all DUKW crews!
Crew Compartment interior that shows gauges and controls as well as engine cover between driver and passenger seats. This Cab Over Engine (COE) style is one of the main distingushing features over the WWII DUKW
The front mounted surf shield was pneumatically operated using a control lever on the wall to the left of the driver. In addition the driver could also actuate the two hull drains. One drain lever for the bow section was on the lower steering column and the second for the main hull was on the floor to the left of the driver. As a safety feature, they were normally held in the “closed” position by springs.
Plans for calendar year 2006 include rebuilding of the brake cylinders with brass sleeves and stainless steel pistons plus addition of an independent bilge pump alarm.
A fair amount of time was spent researching the two distinct types of body styles for the Super DUCK. Photographs from 1953-54 show an exterior body style with two lateral reinforcing ribs per side. Photographs from 1956-1959 show a body style with three ribs per side. There are many other details that evolved on the body such as the bow shape, bumpers, lights and mirror locations. The following illustrations show the different sets of registration and hull numbers on the Super DUCK among the two different body styles. Based on the limited information and available photos of Super DUCKs, the author tracked down five Super DUCKs survivors as of December 2005. Informal postings on the internet indicate that 3 prototypes and 13 Pre-Production Super DUCKs were made for a total of 16.
Early Body Style, 2 Ribs 1953-54
Registration/Hull Identifying numbers from available photographs and reports
USA 7042378
USA 7042379 (and also US Army 7042379) 347-50
USA 7042380
*Note that from available photos the 8x8 DRAKE identifying numbers followed in sequential order e.g. 7042381 and 7042383
Later Body Style 3 Ribs 1956-59
Registration/Hull Identifying numbers from available reports and photographs
USA 4A2310
USA 4A2309 On display at 45th Division Museum
US Army 4A2307 347-38 Authors at Aberdeen, MD
Later body style showing three reinforcing Ribs on each side. Stencil on side reads “USA 4A2310” photographed at Aberdeen Proving Ground 1956. (Note: photo was “flipped for comparison purposes with restored Super DUCK below)
Authors Super DUCK at the May 2001, 28th Annual East Coast Rally, Aberdeen Proving Ground, MD. The APG, D&PS designation 4A2307 and Fort Story registration 347-38.
The Super DUCK is street legal, with historic tags and insurance and often catches the public’s attention during trips around the Chesapeake Bay area. The author is a member of the Ordnance Association and the Super DUCK is often used to help bring awareness to the Ordnance Museum expansion project at APG, MD. Besides the historical aspects of the Super DUCK, when it comes to parades it can haul at least 40 close friends and MVPA members around.
Truck, Amphibious, 4-Ton, 6x6, XM-147 (Super DUCK) Specifications
Weight: Empty 18,000 lbs
Rated 26,000 lbs
Towing: Capacity 60,000 lbs
Winch, Braden Model 36000 20,000 lbs
Dimensions:
Length Overall: 34 ft
Height: (top of M36 mount) 11 ft
Width Overall 105 inches
Wheelbase: 164 inches
Cargo Space
Length 182 inches
Width 88 inches
Engine
GMC, 302 cid, 145 hp at 3600 rpm
Transmission
GM Allison Division, Model CTP-5,
Part # CEX10673, Torqmatic
3 forward, 1 reverse, hi and low range
Suspension Leaf Spring
Steering
Saginaw, model H-12472
Tires Original 1250 x 20 12 ply
Electrical 24 volt
Ground Clearance 12 inches
Angle of Approach 40 ½ deg
Angle of Departure 22 deg
Fuel Capacity 120 gal
2 tanks each 60 gal
Crew 2
Water Propulsion
Propeller, 3 Blade, 31 inch, D 28 inch P
Hull Material Galvanized Steel
Water Turning Diameter 50 ft
Water Speed, Calm water 6.2 mph
Bilge Pumps: 2 Centrifugal; Detroit Marine Co.
1 Positive Displacement; Unknown
Max ground speed 47 mph
Manufacturer GMC
Select References:
- Joint Comparison of U.S Army Amphibians, Final Report 21 Nov 1959, LARC-5 Transportation Corps, SUPERDUCK Ordnance Corps, Camp Pendleton Monterey and Coronado, CA UC320.J6
- Aberdeen Proving Ground, XM-147 SUPERDUCK, Data Sheet, Page 529, 1 March 1954
- Military Vehicles, Gun Carriers, Mechanical Mules, Ducks and Super Ducks, C.B. Colby, 1956, Library of Congress 56-9949
- American Ordnance Association Magazines November-December 1957 and November-December 1959