THE NEW PATENT SLIP.

Press, Volume XL, Issue 5830, 21 May 1884, Page 7

THE NEW PATENT SLIP.

Another convenience, a patent slip, has been added to the facilities for shipping at j this port. For vessels up to 400 tons register it was thought by the Lyttelton Harbor Board they should possess, to use a common phrase, " something handier "_ than the graving dock, and thus a contract' for the construction of a Morton's patent slip was entered into over twelvemonths since -with Mr John Stinson, at a cost of about .JE5500. The site selected is close to the graving doc?, and the slip runs parallel with the latter, the entrance to it being just westward of the dock pumping house. Mr Stinson's contract also included the closing of the water-way that existed through the western mole near to the site of the dock and the slip, and this work has been completed, like the clip, in a style that reflects credit upon the contractor. The contractor had many difficulties to contend with when making the submarine part of the excavation. The blasting of large quantities of rock by experienced divers, and the getting of it up; the fitting of «iat portion of the -ponderous platform hich at high water is 18ft below the suriace; the sawing and adjusting of I about one hundred iron bark and totara piles under the water — these may be instanced also as some of- the most trying features of the work. The whole length of the slip is 500 ft. At the seaward c nd there is, as stated, ISft of water upon it at ordinary high water springs. Tne grade is one foot in twenty f«?et. M he timber used in the platform and the ways is totara, grown in tne Wairarapa district in the North Island. For a aistance of ISOfc tbe platform rests upon concrete underways, and for 350 ft upon piles. Some of the latter were driven to a depth of 53ft. The cradle which travels upon this platform is made of kauri timber, and is ot great strength. Some exception is taken to its shape by shipwrights, who claim that were it capable of being divided into two parts it would have beiin handier ; but as to its strength and ability to hold in safety a 400-ton ship these are indisputable. The length of the cradle is 150 ft. By way of testing the work the contractor last Friday hauled up the Harbor Board's scoop dredge, the Minna Bell, upon it. Everything was, of course, stiff in the working, but the barge was finally pulled up for cleaning, of which, from the appearance of the, Minna Bell's bottom, she was much in need. The mention of the state of her bottom, and the tons of kelp, seaweed, tulip 3, ana

other marine products which fell before the scrapers of the workmen on Saturday morning last leads up to the suggestion that the shingle which f-.rms the floor of the slip should be super.-eded by a concrete floor. It is all but impossible to clear away the dirt after a vessel has been operated upon where, as in the present case, it is permitted to fall upon shingle. Besides the laf er is ill-adapted for shoring up a vessel. The slip is worked by a pair of horizontal high-pressure engines, manufactured by Messrs J. Anderson and Sons, of Christchurch. The same firm was also entrusted -with th , * making of the crab winch which the engines drive, and with the whole of the ironwork connected with the slip. Both engine and winch worked in a most satisfactory manner, doing fully ■what wa3 expected of them. The diameter of the cylinders of the engines is Biin, and the length of stroke 12in. The governor 13 fitted for 300 revolutions per minute, and with a steam pressure of 351b, should take a vessel whose actual weight amounted to 400 tons, up the slip at a speed of 15ft per minute. Steam is supplied from the boilers which supply the pumping engines of the HTaviDg- dock. The boilers are housed at a distance of 350 ft from the slip engine ehed, and the steam is consequently conducted by means of an iron pipe of 4in diameter. The pipe is enclosed in wood and well packed with sawdust, but, withal, it would seem that a loss takes place by condensation between the boilers and the slip engines, for at the trial on Friday it was foiind requisite to run two of the three lar?e boilers, and tlie steam guage on each registered an average of from 501b to 521b of steam. What the actual steam pressure was on the engines could of course be determined were there a guage at that end of the pipe. Some other means may possibly be found to economise the steam, but the opinion expressed by some engineers who were observiDg the trial was that it would be more satisfactory to get a boiler speeiallyjfor the slip werk. The winch is somewhat similar to those used on the large steamers for lifting the anchors. The power is derived by means of a worm underneath, and a wheel driving on the same shaft a spurr wheel, and on the same shaft the chain windlass is attached. The gear used for palling up the cradle consists of a piece of heavy cable which works round the barrel of the winch, the other end being made fast to the " links " or rods attached to the cradle itself. These "links" are bars of iron, each 16ft in length, and 4:n by Hin in thickness. It will readily be understood from those dimensions how the lifting , power of four able-bodied men is required to ship and unship each link, and the thought is irresistible that something lighter and simpler may ia the future be substituted. Were a cable used the whole distance from the *inch to the cradle, a receptacle being made beneath the winch for the cable to drop into, as has been adopted, it is said, elsewhere, a saving of time and labor would be secured. These and a few other matters are, however, of minor importance, and can he put right at any time should it be desirable. The slip will be found to be of great utility by the smaller sized sailing vessels and steamers, and as a cheap and ready means of overhauling that description of the shipping, the Harbor Board is to be congratulated upon it 3 completion. The contractor and the painstaking foreman, Mr Thompson, should also be complimented upon the successful issue of Ihe undertaking