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some, and inconvenient to apply. The belt, however, runs perfectly in either direction, and for this reason, that the two portions of belt, one on either side of each of the four pulleys, lie in the plane of that pulley: the belt therefore draws, with reference to each pulley, from a point in the plane of that pulley when moving in either direction. The same result may be attained in other arrangements. This model (Fig. 2) has the guides in the same plane, the face of one, in a vertical line with, and below the face of one working-pulley; the face of the other, in a vertical line with, and over the face of the other working-pulley: the belt drawing direct from one working-pulley to the other, on the tight side. This arrangement permits the guides to be placed on horizontal shafts, as in the last model (Fig. 10), and, without placing the guides beyond the shafts of working-pulleys, can always be used when there is distance between the working-pulleys to make the required quarter-twist in the belt; as there is always room to make the slight twist between working-pulleys and guides. The guides may be placed at any convenient height, the belt being looped over one and under the other guide, or merely deflected by each guide. The guides may also be used as tighteners by vertical adjustment, as may those of the model last shown.

We can also guide the belt in the same perfect manner by means of a single pulley (Fig. 1), or by two pulleys in the same plane (Fig. 3), so placed as to carry the slack portion of belt near each workingpulley, back in the plane of that pulley, toward the tight side of the belt. When the two pulleys are used, they may be used as tighteners by moving them parallel to that portion of the belt extending from the guide to the adjoining working-pulley. Or, we may use two guides in a manner to bring the straight portion of belt between the guides, near to, and almost parallel to, the tight side of the belt (Fig. 5). There being nearly a quarter-twist between the guides, this arrangement is applicable only where there is considerable distance between the working-pulleys; as when the belt passes through a story between those in which the shafts run. The position of the guides in all these cases, and generally in all cases that present any difficulty, may be determined by tracing by means of a cord, a path for the belt, so that the portion of cord on either side of each working-pulley lies in the plane of that pulley, then placing the guide in the plane of, and touching adjoining portions of the cord where it is deflected from the plane of one pulley to that of the other.

When it is desired to know the position of the guides before the working-pulleys are in position, every point can be determined by means of a drawing, which is of necessity somewhat complex; or, if the importance of the case demands, the position may be exactly calculated. The cases last shown will be referred to again.

When the shafts to be connected are at nearly the same height, we must always use a guide on the tight side of the belt. This arrangement (Fig. 11, which is the same model as Fig. 10, opened out) shows the ordinary overhead quarter-turn belt, arranged for working-pulleys of same size, and at the same height. In this case the guides may be placed on a vertical shaft, and the belt will run in either direction perfectly. The guides cannot, however, be used as tighteners, and the position is not a desirable one in which to run a very heavy belt. For all other cases than that of equal speed and equal height, of shafts, the position of the guides, to admit of perfect running, must be determined by means of the cord, or by drawings, as explained.

The arrangement now shown (Fig. 12) is copied from a sketch furnished me, of a belt now running, in which the two guides are on horizontal shafts, and are at about the same height; it will admit of a change of speed between the two working-shafts, which may also differ in height. The belt will run only in one direction, and has the defect of a side strain on both the tight and slack sides; while here (Fig. 13) is a model similar in arrangement, in which the belt will run in either direction, and, of course, without the side strain in the belt.

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Nearly two years ago I was called upon to arrange a belt, to connect shafts at nearly the same height, in the mills of the Appleton Company at Lowell. The agent preferred to use a looped belt rather than an open belt to a shaft in another story, and from there return with a quarter-turn belt with guides, as he could thus accomplish the result by the use of four pulleys and one belt, while the other arrangement involved the use of six pulleys and two belts. I proposed the arrangement here shown (Fig. 6), which has guides on horizontal shafts. A portion of the power may be taken off on one of the guides, thus delivering power to two stories at right angles to the driving-shaft; and the other guide may be used as a tightener. It was found that a floor-beam (T, Fig. 15), shown here in a model made to scale, interfered with the passage of the belt from one pulley to the guide to avoid this, I proposed to use a smaller guide (N, Fig. 15), and so set, that the belt should run correctly in either direction. Fig. 9 is the same arrangement, but of different proportions, to show more plainly the canted guide. I determined the position of the guide by calculation; and, when a trial belt was put on, it was found to run perfectly in either direction. It was designed to transmit 120 horse-power with an eleven-inch double belt, running about 5,200 feet per minute. It is believed that it was used to transmit 150 horse-power, always giving satisfaction, and is now to be replaced by an arrangement to transmit a much greater amount of power.

some, and inconvenient to apply. The belt, however, runs perfectly in either direction, and for this reason, that the two portions of belt, one on either side of each of the four pulleys, lie in the plane of that pulley the belt therefore draws, with reference to each pulley, from a point in the plane of that pulley when moving in either direction. The same result may be attained in other arrangements. This model (Fig. 2) has the guides in the same plane, the face of one, in a vertical line with, and below the face of one working-pulley; the face of the other, in a vertical line with, and over the face of the other working-pulley: the belt drawing direct from one working-pulley to the other, on the tight side. This arrangement permits the guides to be placed on horizontal shafts, as in the last model (Fig. 10), and, without placing the guides beyond the shafts of working-pulleys, can always be used when there is distance between the working-pulleto make the required quarter-twist in the belt; as there is always roo to make the slight twist between working-pulleys and guides. T guides may be placed at any convenient height, the belt being loo! over one and under the other guide, or merely deflected by e guide. The guides may also be used as tighteners by vertical ad ment, as may those of the model last shown.

We can also guide the belt in the same perfect manner by :: of a single pulley (Fig. 1), or by two pulleys in the same plane 5), so placed as to carry the slack portion of belt near each w pulley, back in the plane of that pulley, toward the tight side belt. When the two pulleys are used, they may be used as tight by moving them parallel to that portion of the belt extending fro guide to the adjoining working-pulley. Or, we may use two g in a manner to bring the straight portion of belt between the g near to, and almost parallel to, the tight side of the belt (Fi There being nearly a quarter-twist between the guides, this ar ment is applicable only where there is considerable distance bet the working-pulleys; as when the belt passes through a story be those in which the shafts run. The position of the guides these cases, and generally in all cases that present any difficulty be determined by tracing by means of a cord, a path for the b that the portion of coed on either side of each working-pulle in the plane of that pulley, then placing the guide in the pla and touching adjoining portions of the cord where it is from the plane of one alley to that of the other. When it is desire

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Fig. 8 shows an arrangement often used in woollen-mills, where the guides are calledcarrier pulleys, or, sometimes, gallows pulleys. The guides are ordinarily set at the same height, an arrangement that can never admit of a perfect running belt; although it will answer a purpose, when little power is to be transmitted. Mr. Sellers of Philadelphia has, I think, a hanger for the guides, that is applicable for one position of the driven-pulley in reference to the driver. For all other cases the position must be determined specially, by lines or drawings, as before stated, if it is important to have a perfect running belt.

The next model (Fig. 14) shows two pulleys which are not in line, are not of same size, are not square with each other. One shaft is not horizontal, and differs in height from the other, and the belt is crossed; thus presenting, I think, all the difficulties usually met with: yet the belt runs perfectly in either direction by means of two guides.

Referring again to the case of shafts at angles, having considerable difference in height. Here is a model (Fig. 19) with a cord stretched over the working-pulleys, and the ends brought together in a point of the cord between the two working-pulleys, so that the portions of cord about each pulley are in the plane of that pulley: a guide-pulley, to run perfectly, must lie in the plane of, and touch, the two end portions of cord thus placed.

It is not uncommon practice to place guides on the slack side, in positions having a resemblance to those here shown (Figs. 1 and 5), but with this important difference, that the belt draws at one edge, having the same fault as the quarter-turn without guides (Fig. 4), except that the defect is transferred wholly to the slack side of belt.

There have been in use two different schemes to guide the belt in this defective way: one leads the belt off to one side from the driving-pulley on to a guide which is at first set on a horizontal shaft, with one of its faces in the plane of the driven-pulley, and then direct on to the driven-pulley; the guide is then canted by trial until it will retain the belt. A guide so placed is in a very different position from that shown in Fig. 1, and requires constant changes in position to keep the belt in place with varying loads, and at once runs off if the motion is reversed. If two guides are used, the second (H, Fig. 16) is placed in the plane of the driven-pulley with a face in a vertical line with the face of the first guide as set before being canted. When the two guides are properly arranged in this scheme, the belt draws properly over both guides, and has a tearing strain only at the point (K, Fig. 16) where it leaves the driving-pulley. The guide in the plane of the driven-pulley can be used as a tightener, by vertical adjustment. This arrangement will run only in one direction, and, at best, gives only partial satisfaction.

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