288 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[September, 



be provided with a jam nut outside, to prevent any dripping of 

 water, or escape of steam. It is common with some engineers to let 

 the packing project beyond the face of the valve an inch or two, 

 little pieces being cast on the cylinder to continue the circle of the 

 valve, and afford a support for the packing beyond the face. Messrs. 

 Maudslays make the packing merely to abut against the face, without 

 going beyond it. This method requires the length of the packing to 

 be determined with great exactness previous to its introduction ; and 

 if it swivels the least on the back of the valve, there will be a vacant 

 space at the one corner, and a double thickness of packing at the 

 other. 



The packing port should always, if possible, be opposite to the 

 port of the cylinder, and when it is not opposite it is very important 

 that the valve, if short D, should have the upper and under portions 

 connected by three rods ; indeed, in all large engines three rods are 

 best. When there are only two, the valve at the extremity of its stroke 

 is apt to bend back from the face, and will generally wear taper. 

 The valve rod is often, in the case of short D valves, attached not 

 immediately to the diaphragm of the valve, but to a malleable iron 

 jaw, which is secured to the valve diaphragm. But we think it the 

 simplest way for the valve rod to go at once through the valve dia- 

 phragm, with nuts upon the under side, and for the square pin by 

 which the valve is moved to be supported by two brackets cast on the 

 valve diaphragm, there being a little play left fore and aft in the 

 square eye of the valve rod, to admit of the valve being pressed 

 forward as the faces wear, without interfering with the stuffing box 

 above. 



Paddle centres. — We do not think favourably of the plan of boring 

 out the eyes of the paddle centres, turning the bosses on the shafts, 

 and fitting the centres on with a single key. When once the centres 

 get rusted in their seats, when fitted in this way, it is next to impossi- 

 ble to start them, and if the vessel has to go into dock, it will some- 

 times be necessary to break the centres before the paddle rings can 

 be drawn towards the sides of the ship. Nor do we think well of the 

 plan of putting the centres on in two halves. It is almost impossible 

 to prevent such centres from becoming slack upon the shaft, unless 

 they be encircled by a malleable iron hoop. We like best to see the 

 bosses on the shaft, and the eyes of the centres square ; each centre 

 made in a single piece, and fixed on the shaft by means of eight good 

 thick and wide keys. A cut should be made with a chisel at the head 

 of each key, so as to raise a projection on the shaft against the end 

 of the key, to prevent it from working out. These burs can be easily 

 cut off at any time the centres require to be shifted, and the keys, if 

 made of proper strength and taper, may always be started without 

 any very great difficulty. The heads of the paddle arms should be 

 secured in sockets in the paddle centre, with keys. We do not at all 

 like the plan of fixing the arms with bolts to the sides of a centre 

 indented to receive them ; we have never known any of this kind of 

 centres to be in use for any considerable time without the arms 

 becoming loose. 



Crank pins should always be made much larger than is required for 

 strength, else they will be very apt to heat. The crank pin of Messrs. 

 Miller and Co.'s West India packets is llj ; of that of Messrs. Scott 

 and Sinclair's about 71. We like the crank pin to be put in from the 

 inner side, that is, through the eye of the paddle crank, and secured 

 by a strong screw tapped into the pin pressing upon a washer of 

 adequate strength, which rests on the crank pin eye. We do not 

 approve of large cutter holes through the eye and pin, by which they 

 are much weakened ; and think a single steel pin of moderate dia- 

 meter, driven through the crank pin and eye, sufficient to keep the pin 

 firm, assisted with the screw at the outer extremity. 



Drag links are a useless incumbrance : the end of the pin in the 

 loose eye of the crank should, of course, be rounded, to admit the 

 fall of the outer end of the shaft without snapping the pin, and should 

 be steeled, so that it may not wear very fast. There should be a 

 removable steel or brass block in the loose eye for the pin to press 

 against, rounded to the shape of the pin, and slipping into its place 

 in a dovetail. This should be on the driving side : on the backing 



side there should be a small square block fitted into a recess in the 

 crank eye, and pressed against the pin by a screw with a jam nut, so 

 that there may be no back lash in the loose eye, when the sea strikes 

 the paddle-wheel. The screw should always be on the backing side, 

 else the continual pressure on the point of the bolt will be apt to 

 rivet it in. 



Different modes of Propulsion. — Up to the present time the common 

 paddle-wheel is undoubtedly the best; but we have high expectations 

 from a very novel plan of propulsion devised, and now in the course 

 of being matured, by the Messrs. Whitelaw, of Glasgow. Mr. Smith's 

 screw has succeeded far better than most engineers ever expected ; 

 but it is certainly as yet less efficient than the paddle-wheel. Yet we 

 understand the Great Western cognoscenti have adopted the screw in 

 their iron leviathan, and intend to drive it with a belt. A thousand 

 horses' power and a belt! Who, after this, can refuse to put faith in 

 Indian rubber ? We know not if this be an emanation of Mr. Brunei's 

 genius, or a device of the chivalrous Mr. Guppy ; and we think it is 

 to be regretted that the public is not more specifically informed to 

 whom the brilliant thought is principally due. Our grandmothers 

 certainly had but little idea of spinning-wheels on so magnificent a 

 scale, else they might have bequeathed some hints of very material 

 import. They might perhaps have told us that belts are apt to stretch 

 and slip, when there is much strain put upon them, and that salt water 

 and heat and steam do not act beneficially upon leather. But as no 

 such legacies have been left us, and the days of spinning-wheels are 

 gone, we must now make up our minds to wait with resignation the 

 issue of the Great Western experiment, though we question much 

 whether it will be brought to an issue for ten or twenty years to come. 

 We really think it would have been well for the Great Western 

 people, had they gone to Messrs. Maudslays and Field for another 

 Great Western. Had they done so, they would have been sure of an 

 excellent vessel, she would have been afloat long ago, and would now 

 be earning money. 



PROFESSOR MOSELEY'S CONTINUOUS INDICATOR. 



We think upon the whole very favourably of this contrivance, but 

 it appears needlessly complicated and expensit-e, and perhaps some- 

 what liable to get out of order. The friction cones, we consider, are 

 not sufficiently safe and certain in their action. A little oil falling 

 upon them, and a little undue friction in the machine — accidents likely 

 enough to occur, especially in a steam vessel — would cause the cones 

 to turn round, without carrying the wheel-work with them, and thereby 

 vitiate the indications. These evils in our estimation are susceptible 

 of a remedy, and we should propose a form of indicator something 

 after the fashion of that figured in the subjoined rude sketch, as less 

 objectionable, perhaps, than Professor Moseley's, though without any 

 pretensions to the character of a matured or unobjectionable scheme. 



A A are the springs; BB 

 the links connecting them; 

 C is the cylinder of the in- 

 dicator; D the cock for in- 

 serting it in the cylinder 

 cover; E a ratchet wheel, en- 

 circled by a ring, with a num- 

 ber of internal palls, as in the 

 patent windlass, and termi- 

 nating in a lever, F, with a 

 long slot, in which the end of 

 the rod, G, may be, by the 

 bell-crank, H, moved either 

 towards F, or towards E; G 

 is connected with the engine, 

 and if the pin moving in the 

 slot of the lever, F, were 

 always stationary, it would always carry round the ratchet an equal 

 distance. But when the pressure in the cylinder is increased, the 

 piston of the indicator is forced farther up, and the rod, G, is drawtt 



