Minutes of Proceedings of the Institution of Civil Engineers, Volumen99,Parte1

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Página 168 - ... be exactly equal to the moment to turn the casing round the shaft. This can be readily and absolutely measured by suspending weights at a definite horizontal distance from the shaft. The first published account of this form of brake having been made use of for dynamometric measurement was by Hirn*, in his investigation for the verification of Joule's mechanical equivalent of heat, and was subsequently adopted by Joule in his second determination. In neither of these cases, to the Author's knowledge,...
Página 170 - ... During the twelve months they have been running the brakes have demanded and received no attention whatever. They are easily tested for balance. They have neither fixed nor spring attachment, except the bearing on the shaft. They are loaded on a 4-foot lever, with 2-inch play between the stops. When the speed of the engines reaches about 20 revolutions per minute, the levers rise (whatever load they have on), and, though always in slight motion, they do not vary £ inch until the engines stop...
Página 170 - These conclusions having been verified on a model, it was decided to arrange the engines with the shafts in line, with three brakes on the shafts ; and the brakes, with 18-inch wheels, were designed according to the resistance given by the model. The brakes promised all the attributes desirable, except that of running with a constant load under varying speeds. This matter was considered during their construction, and an automatic arrangement was devised acting on cocks regulating the supply and exit...
Página 287 - The compartments of 24 feet depth or more form 80 per cent, of the whole section, and occupy a width of 3,000 feet, with maximum depths close up to 70 feet. In the new channel between the jetty-heads, where the hydraulic radius is 39.71 feet, it may be expected that the area of depths of more than 24 feet will constitute a very large proportion of the total area of the gap, and that maximum depths of 75 feet and upward would be maintained in mid-channel.
Página 289 - HARBORS. nine feet of water, where the figure 3 indicates the present depth. The vessels were placed checker-wise, in such a manner as to impede navigation, while interfering least with the discharge of the water. The effect, nevertheless, was the formation of a shoal in a short time, and the scouring out of two channels, one on each side of the obstructions, through which twelve and fourteen feet can now be carried at low water. The increased water-way thus given to the ebb-tide caused it to abandon...
Página 153 - All engines to be of the inverted-cylinder type, with the walls and covers separately jacketed with steam at boilerpressure, and so arranged that they could be worked with or without steam in any or all of the jackets. Each engine to work with steam at any pressure up to 200 Ibs. per square inch, to run at any piston speed up to 1,000 feet per minute, and to have expansion-gear to cut off from zero up to § of the stroke. One engine to be supplied with air-pump and surfacecondenser, the other two...
Página 289 - On the accompanying diagram is seen the "stone fleet" sunk in the main channel, which at that time had twelve feet of water at low tide where the figure 7 indicates the present depth. There was, moreover, another channel making out more to the southward, with nine feet of water where the figure 8 indicates the present depth.
Página 297 - The 3 following conditions appear to be necessary to create a bore : — • 1. A swiftly flowing river. 2. An extensive bar of sand, dry at low-water, except in certain narrow channels kept open by the outgoing stream. 3. The estuary into which the river...
Página 289 - The increased waterway thus given to the ebb tide caused it to abandon the old nine-foot channel on the less direct course to deep water. We have here the total obstruction of a channel, which was of considerable importance to the southward trade, by new conditions introduced at a point four miles distant from where the effect was produced, and we are warned how carefully all the conditions of the hydraulic system of a harbor must be investigated before undertaking to make any change in its natural...
Página 286 - The approved project is to obtain a least mid-channel depth across the bar of 15 feet at mean low water, by the contraction of the stream by two long jetties starting from the opposite shores of the entrance and converging until near their outer extremities on the bar they shall be 1,000 feet apart.

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