Description of Richards' Improved Steam-engine Indicator with Directions for Its Use

Longmans, Green, 1868 - 134 pagina's
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Pagina 21 - This is owing to the difference in the speed of the piston at the opposite ends of the cylinder, which is, at the outer end of a direct-acting engine, from 35 per cent to 66 per cent greater than at the crank end, the difference varying according to the degree of angular vibration of the connecting-rod. In side-lever or beam-engines, these proportions are reversed, and the speed of the piston is greater at the upper end of the cylinder. Often also there is a difference in the lengths of the thoroughfares,...
Pagina 26 - ... To fix the Paper. — Take the outer cylinder off from the instrument, secure the lower edge of the paper, near the corner, by one spring, then bend the paper round .the cylinder, and insert the other corner between the springs. The paper should be long enough to let each end project at least half an inch between the springs. Take the two projecting ends with the thumb and finger, and draw the paper down, taking care that it lies quite smooth and tight, and that the corners come fairly together,...
Pagina 10 - The diagram thus described shows on inspection the following particulars, viz. : what proportion of the boiler-pressure is obtained in the cylinder — how early in the stroke the highest pressure is reached — how well it is maintained — at what point, and at what pressure, the steam is cut off — whether it is cut off sharply, or in what degree it is wire-drawn — at what point, and at what pressure, it is released — in a non-condensing engine, whether it is freely discharged, or what proportion...
Pagina 54 - Table the logarithm of the number nearest to the quotient, and to this add 1 ; the sum is the ratio of the gain. Then find the terminal pressure, by dividing the initial pressure by the proportion of the stroke during which the steam is admitted, and multiply it by the logarithm + 1 found as above ; the product will be the mean pressure through the stroke. EXAMPLE.
Pagina 36 - ... pressure will come a little above the atmospheric line, but it is more convenient, and answers all the purposes of the diagram better, to measure each way from the latter. The space above the steam line and between this and the line of boiler pressure shows how much the pressure is reduced in the cylinder by throttling, or by the insufficient area of the ports, proper allowance being made for the difference of pressure necessary to give the required motion to the steam in the pipe ; whilst the...
Pagina 26 - ... one to fix the paper very readily. The marking-point should be fine and smooth, so as to draw a fine line, but not cut the paper. It may be made of a brass wire ; the best material is gun-metal, which keeps sharp for a long time, and the line made by it is very durable. Lines drawn by German silver points are liable to fade. A large-sized common pin, a little blunted, answers for a marking-point very well indeed ; a small file and bit of emery cloth used occasionally will keep the point in order.
Pagina 25 - ... way of obtaining the required motion is to use a kind of weigh shaft, supported in two bearings, and placed exactly over the cross-head and fitted with two arms, one longer than the other, the long arm being connected by the cord to the cross-head, and the short arm to the indicator. The short arm must be keyed in such a position that when the piston is in the • middle of its stroke it will stand at right angles with the direction of the cord. The direction of the cord may form any necessary...
Pagina 26 - ... length, and taken up from time to time, as it may become stretched by use. On high-speed engines, it is as well, instead of using this, to adjust the cord and take up the stretching, as it takes place, by tying knots in the cord. If the cord becomes wet and shrinks, the knots may need to be untied, but this rarely happens. The length of the diagram drawn at high speeds should not exceed four and...
Pagina 36 - What is known as the Admiralty rule for the nominal horse power of engines is (1st), Multiply seven times the area of the cylinder in inches by the mean velocity of the piston in feet per minute, and divide the product by 33,000. (2nd), Square the diameter of the cylinder in inches, and multiply by the mean velocity of the piston in feet ner minute, and divide the product by 6,000.
Pagina 30 - ... the former being applied to the size of engines, irrespective of the pressure or speed employed, and the latter to the power which they exert. The term " nominal horse-power " has, moreover, acquired a variety of significations in different localities, and it has become difficult to tell, in any case, precisely what is meant by it ; but fortunately, we shall have no occasion to make any further reference to it, as it is entirely a commercial expression.

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