Over favorable terrain, the tank is the most decisive ground weapon of
modern warfare. However, it is particularly sensitive to obstacles. A relatively
minor obstacle at a decisive point may so delay attacking tanks as to wholly
destroy the success of the attack or result in heavy tank losses. On the other
hand, one of the outstanding favorable characteristics of the tank is its battlefield
mobility. In order that the tank may take full advantage of this mobility, means
for the passage of obstacles which the tank cannot negotiate by itself must be
made immediately available. Because of a tank unit's mobility, and the difficulty
of coordination and control once the tank attack is launched, this problem of
assisting tanks through obstacle areas is extremely difficult, particularly in view
of the fact that the task must usually be performed in the face of hostile fire.
One possible answer to this problem has been produced by the British. They
have developed and standardized a so-called scissors-bridge, for the purpose
of making available to the Royal Armored Corps a tank which is capable of
laying a bridge across a tank obstacle up to 30 feet in width. It has been designed
so that the bridge can be laid under enemy fire with the tank completely buttoned
up, thus giving the crew a maximum of protection. The bridge has been designed
to take a tracked load of 30 tons.
The scissors-bridge equipment has been standardized and adapted to two
types of tanks, the Covenanter (cruiser tank Mark V) and
the Valentine (infantry tank Mark III), the latter being the newer
design and in greater numbers. A second type of tank bridge-layer is
being developed from the Churchill (infantry tank Mark IV), which
will carry a one-piece 30-foot span capable of carrying a load of about 60 tons.
The construction of the scissors-bridge is shown in the accompanying
sketches. Sketch 1 shows the bridge in traveling position; sketch 2, in
a half-opened position.
|SKETCH 1. BRITISH SCISSORS-BRIDGE--TRAVELING POSITION|
|SKETCH 2. BRITISH SCISSORS-BRIDGE--HALF-OPENED POSITION|
General data on the scissors-bridge are as follows:
|Length of bridge|| ||34 ft|
|Overall width of bridge||9 ft 6 in|
|Maximum tracked load carried||30 tons|
|Power required to operate bridge||30 hp (maximum)|
|Time required for launching||2.5 min|
|Gear reduction from engine||19 to 1|
|Weight of launching equipment and bridge||3.5 tons|
|Maximum tension load on screw||30 tons|
|Maximum load on each cable||7 tons|
The launching and recovering mechanism is operated by power taken
from the fan drive of the tank engine, through a small oil-bath clutch
and a 2-to-1 reduction gear, to a reversing gearbox directly beneath
the screw feed gearbox.
The opening of the bridge begins after the launching mechanism has begun
to pivot on the rollers of the launching frame. Since the cables are of fixed
length, they act to open the bridge as it is pivoted about the rollers. Having
been laid across the obstacle, the bridge is disengaged from the prime-mover. The
bridge is then ready for the passage of other vehicles. To retrieve the
bridge, the prime-mover crosses the bridge to the far side of the obstacle, hooks
up to the bridge, pulls it back to the traveling position, and is then ready to proceed
to the next obstacle. Safety devices have been installed on all the later models
of this equipment, and are so arranged that the power is cut off automatically
from the operating screw should the operator fail to disengage the clutch when
the bridge is fully launched or recovered.
This equipment has given good service when operated by trained personnel. In
one case 1,200 successful launchings and recoveries were made by one vehicle
without undue maintenance.
The reporting officer submits the following conclusions:
This equipment is sturdy and compact, and apparently requires very
If enough of these vehicles could be supplied to armored units, they
would afford a ready means of crossing tank barriers quickly with a maximum
of protection for those laying the bridge.
Since the bridge is recovered after the crossing has been completed, a
minimum of such bridging equipment can be carried within each division.
A decided disadvantage of equipment of this type is that it is a single-purpose
vehicle, and unless a sufficient number are provided, they will not be
available where and when needed.
When used as an organic vehicle of armored units, it should provide
a flexibility of operations that would not be possible otherwise.