Volume Ten - Pre-Victorian to the present day - even more aspects - The Patent for the Penarth Slipway - 1881 . . .

Mr. G. B. Godfrey cont'd :

The excavation was first pushed ahead, so as to set the work free for pile-driving, which, when once commenced, was carried on continuously. As the tide ebbed, the pile-driver was allowed to go down upon the traveller by gravitation. The piles were then driven in each successive row, two and four alternately, the engine being worked across the traveller, from side to side of the slipway, by means of the under pulley and chain.

When the tide flowed, the same means were adopted for hauling the traveller and pile-driver above high-water level. The piling was then continued on the upper portion of the slipway until the ebb allowed operations to be again commenced at the lower end. By these means the works were continuously carried on, and the great cost of tidal work was to some extent neutralised.

The piles varied from 25 to 50 feet in length, and were driven into the clay until their set for the last blow was ¼ inch, with an 8-feet fall of the ram. The work at the lower end of the slip, where the working time was only one half-hour to one hour at lowest spring tides, had to be performed by hand-engines, the piles being of an extra length, and they were subsequently cut off when the tides permitted.

The whole of the machinery and cradle was constructed by Earle’s Shipbuilding Company, similar in many respects to that described by the Authors, but there were three rams, 15 inches in diameter, so arranged that either one, two, or three might be used, and were supplied by two double-acting pumps working up to a maximum pressure of 1,250 lbs. per square inch. All parts taking the strain, such as the rods, &c., were of “ Siemens-Martin ” steel.

The slipway and machinery had been so constructed that vessels of from 2,500 to 3,000 tons deadweight might be taken up ; but the largest hitherto “ slipped ” was the “ Othello,” a Wilson liner, with a length of 316 feet, 36 feet beam, 10 feet 6 inches mean draught, displacing 2,300 tons. The time occupied in slipping vessels varied from half an hour to one hour.