Nicholas Straussler, inventor of the Duplex Drive amphibious
tank was born in Hungary in 1891. He made his name as a
designer of revolutionary vehicles and in the years leading
up to World War II established a relationship with Alvis
in Coventry who built armoured cars, to his design, for
the Royal Air Force. This is his account of the design of
the Sherman DD.Nicholas Straussler died in 1966, having
become a naturalised Briton in the meantime.
My research led me to the conclusion that fighting
machines could only be floated by the provision of temporary
additional floatation. This problem was attacked in 1927/1928
by me designing outside floats which collapsed for economical
transport. At about the year 1934 I abandoned this line
of development and attacked the problem from an entirely
new angle. Apart from the basic idea the solution was extremely
difficult from the technical and design point of view as
it had to contend with the existing design of the tank and
all details and arrangements had to be so designed that
they would not be costly and would not necessitate lengthy
or substantial alterations to the structure of the hull.
Tank Museum photo No.
The design was commenced by putting a continuous rigid
deck right around the tank at approximately mudguard level,
that is to say just above the top of the tracks. A number
of tubular frames were made, the contour of which generally
corresponded to the outer rim of this decking. A very heavy
rubberised canvas screen was constructed to connect these
tubular frames to the decking. The tubular frames were spaced
at suitable intervals so that when the canvas attachment
was made the structure formed a hull, flexible in an up
and down direction in a concertina manner. A number of compressed
air tubes were placed on the deck and attached to the screen.
Inflation of these tubes raised the screen. Since each tube
exerts an upward pressure of some 600 lbs when the screen
is raised it is held upright by the total upward pressure
of some 12 tons.
Tank Museum photo No.
next problem was the provision of efficient propulsion.
It was quite impossible to break into the tank in order
to obtain a power drive from the engine for driving the
two propellers. Hence it was decided to use the idler roller
as the motive power.
A crown wheel gear was attached to the idler and the mating
pinion drove the propeller. Thus, each re-designed idler
drove a propeller of some 28 inch diameter capable of absorbing
a total of some 350 horsepower.
An entirely new system was designed which permitted the
propellers to swing from side to side around a vertical
pivot for steering, and lifting about a horizontal axis
right out of the way.
photo No. 2498/D/2
Museum photo No. 2918/B/2
This system of floatation resulted therefore in enormous
economy of manufacturing speed as witnessed by the conversion
of some2,000 tanks in this country alone, and of some 300
in the U. S. in the course of a very short period of time.