A Novel Type of Drawbridge. (Specially Contributed by our Californian Correspondent.)

Progress, Volume IV, Issue 6, 1 April 1909, Page 205

A Novel Type of Drawbridge. (Specially Contributed by our Calif ornian Correspondent. )

The longest one known, and the first of its kind, built west of the Rocky Mountains, is the new Salt Lake drawbridge recently built and just on completion by the Llewellyn Iron Works at Los Angeles. It is known as a Scherzer rolling lift bridge, and ib being erected over the San Gabriel Eiver at Long Beach, Calif, and connecting that

part with Terminal Island, for the Southern Pacific Los Angeles and Salt Lake Rail Road. It is a single track bridge 18 feet wide, and the longest single span roller bridge yet built. The weight of the bridge is approximately 700 tons, and it is a fine steel structure. Its draw is one that raises instead of swinging on a pivot. When open, it will leave a clear channel of 180 feet, and the highest point of the bridge when in that position will be 240 feet above high tide

mark. Operation will be by electric power from the Long Beach end, furnished by the Pacific Electric Railway Company. There are three piers designated A. B. and C. Pier C is at the Long Beach end. Piers B and C are 4 feet apart, and from B to A is the moving span of 180 feet, said to be the longest of its kind known. At the Long Beach end is the counterweight tower, or box, filled with concrete. So delicately is the balance fixed that this weight is exactly that of the moving span to be raised, and if the machinery gets out

of order one man can raise or lower the draw by hand. This is what will be done in case of an emergency. When the draw is up, the counter-weight will go down. It is much as though one were to take a huge triangle like a carpenter 's square, with a heavy base, build a huge box and place it on the top of the hypothenuse to make the latter 's weight equal that of the base, fasten the right angle to a pivot, then raise the base by the weight of the box on the end of the hypothenuse, and swing the base

back into place by its own weight, just setting the whole in motion by a very slight exertion of power. In this box will be also about 25 tons of pig iron additional, so as to be able to adjust the counterweight in the event of such being required in the future, owing to a possible change of the centre of gravity .of the bridge. On a level with the counterweight box is a platform, known as the machinery floor, on which are placed two twenty horsepower motors. The ladder shown in the

picture, like a fire escape at one side, affords access to the machinery floor and counterweight box. When lowered, the bridge is locked in place at the Terminal Island end. A set of automatic signals will notify engineers of approaching trains to stop when the draw is raised, or to go ahead with a clear bridge. The total height from the floor of the bridge to the top of the counterweight box is 225 feet. The bridge is being equipped with all the

latest safety signals, interlocking and derailing devices, together with all necessarysignals for both railroad and channel requirements. The working drawings and details were all worked out by the engineers of the Llewellyn Iron Works, and the fabricating of all the material and the erecting of same is being done by them. All the parts were made at the local plant and brought to the ground, carefully numbered and marked, each for its exact place. The contract called for completion on December 1, but unavoidable delays have occurred, and extension of time has been allowed. The piers of the old bridge have been used as false work. They will be taken out when the structure is finished. During the building the trains have used a temporary trestle. At present the bridge merely crosses a dry or almost dry bed of sand. Sometimes there is water there, but very little. Inside there is water, and it is the intention to dredge it all out and make a harbour for Long Beach. For this end the Government has forced the railroad to build the drawbridge. Until the dredger is at work there will be little practical use for the draw. The site is about a quarter of a mile beyond the Pacific Electric s terminal at Seaside Park. The power for manning the huge crane that lifts the heavy girders and plates to their places is electric. The total cost of the bridge will be between £50,000 and £60,000.