Barry Docks: Bridges
The complex infrastructure of Barry Docks included a swing bridge and two sliding (retractable) bridges survives. Large retractable bridges are rare, and one of the Barry Docks survives as a listed structure, along with its control cabin. [2]. The cabin is in very delapidated condition, while the bridge is suffering from corrosion (2019).
See photo above and here.
The bridge was traversed by wire ropes actuated by two hydraulic 'jiggers'. The arranagement of ropes and chains served to multiply the travel of hydraulic ram. In this case each ram had four pairs of pulleys. 2007 photo here.
Photo here shows a pair of rollers and the supporting structure. This photo shows a bridge rail outboard of the support structure.
Photo here shows a device which presumably acted to shut off the hydraulic supply to the rams at the outward end of the bridge's travel. Judging by the fractured casting, it wasn't always successful. It may simply be a buffer.
More photos and information via this link. The bridge was constructed in 1889 by the Darlington Wagon & Engineering Co Ltd. Photo of builder's plate and counterweights here.
1896 'As shown by the plan (Fig. 54) [see illustration above], the passage is
spanned by a roller bridge for railway and foot
traffic, and it is moved by hydraulic power. The
main girders are 154 2/3 ft. in length, 9½ ft. in depth,
with a flange width of 2 ft., and they span an opening of 83 ft. between the bearings. The bridge is
carried on 2½ft. steel rollers, a pair close together,
tandem fashion, being fitted under each main girder ;
and they travel on level steel roller paths, borne
by girders. Two 6-ft. trailing wheels, at the tail
end, run on bridge rails outside the main girders,
and carry a weight just sufficient to overbalance
the front part of the bridge. On one side of the
bridge, the treads of the wheels are grooved ; those
of the rolling carriage fit a projection on the roller
path, and that of the trailing wheel fits the bridge
rail. On the opposite side the wheels have flat
treads.
The bridge is moved by a three-cylinder hydraulic
engine, placed underneath. When it is started forward, the front end stands slightly elevated, the
rails of the trailing wheels being at a slightly lower
level for this purpose ; but after the bridge has
travelled forward 25½ ft., the trailing wheels ascend
a gradient of 1 in 60 for 75 ft. This lowers the
front part of the bridge, and brings it level. The
rolling carriage is then over a table, under which
is a large hydraulic cylinder, which pushes out two
pairs of rollers, on each side, up inclined planes,
and by this means the bridge is lowered or raised.
There are two hydraulic buffers at each end to prevent the bridge overrunning in either direction.'[3]
See Also
Sources of Information
- ↑ Engineering 1896/02/14
- ↑ [1] Vale of Glamorgan County Treasures, p.8
- ↑ Engineering 1896/02/14