50 years ago
NSC 31
May 20
road deck is designed to BS 153 HA loading
plus 45 one-ton units of HB. The towers are
12ft square and withstand all loads from the
operating racks as well as supporting the top
booms and counterweights.
The lifting racks are activated by driving
pinions which are driven by hydraulic pumps
powered by two 70 HP electric motors. The
combined pump and motors are situated
immediately behind the main trunnions on
which a cam is mounted so that the delivery of
the pumps is always related to the inclination
of the deck, thus ensuring complete control of
its angular movement and dispensing with the
more usual electric limits and inching motors.
The deck is raised or lowered in approximately
one minute.
Erection of the superstructure was effected
rapidly as the components were few in number.
To lift them into position use was made of the
PLA’s 200 ton lifting crane.
In order to eliminate the risk of any accidents
operation of the bridge is manually controlled
by remote push buttons (all controls are
electrically interlocked to ensure that they are
operated in the correct sequence). The control
cabin is large in area and has a clear view of
both the road and the lock. It will be possible in
the future to operate all lock gates and sluices
from this position though this is not done at
present.
Maintenance of the bridge is the
responsibility of the PLA and to keep costs
down care has been taken to ensure that work
can be carried out as easily as possible. To this
end the external surfaces of the superstructure
are easy to paint while bearings should need
no more than occasional packing with grease.
The pump/motor sets are duplicated so that
the bridge can be operated while one set is
being serviced.
The bridge is a good example of the unique
properties of steel, no other material being
suitable for the purpose.
The 200 ton Goliath crane
lifting in the top beams
Main contractors for the superstructure
Sir William Arrol & Co Ltd
Sub-contractors for the operating
machinery
MacTaggart Scott Ltd
Contractors for the civil works
John Mowlem & Co Ltd
Design and erection supervision
Engineering department of the Port of
London Authority (Chief Engineer J. F.
Stanbury C.Eng, FICE)
The deck being swung
into position