Part 2

A good many electrical concerns mount some of their styles of dynamos and motors (especially the light duty, small size) upon two _V_-shaped rails, Fig. 21 (the bottom of the motor or dynamo base being V-grooved for the purpose). The machine's weight and the screws _A_ are counted on to keep it in place. If the machine be properly mounted on these rails, as regards screws _A_ in relation to its drive, the screws reinforce the machine's weight in holding it down and also permit a surer adjustment through this steady holding of the machine.

Fig. 22 shows the machine properly mounted. The belt tension and pull tend to draw _B_ corner of the machine toward the shaft _C_; and screw _B_^1 is there to resist this pull. Owing to this resistance and the pull along line _D_, _E_ tends to lift and slew around in _E_^1 direction; screw _E_^2 is, however, in a position to overcome both these tendencies. If the screws are both in front, there is nothing but the machine's weight to keep the back of it from tilting up. The absurdity of placing the screws at _F_ and _G_, though even this is thoughtlessly done, needs no demonstration.

When putting a new belt on a motor or dynamo, both the driver and the driven are often needlessly strained by the use of belt-clamps, in the attempt to take as much stretch out of the belt as possible. On being loosely endlessed it soon requires taking up; and if only laced, when the time for endlessing comes the belt is botched by the splicing in of the piece which, owing to the insufficiency of the original belt length, must now be added to supply enough belt to go around, plus the splice.

The proper mode of procedure is: Place the motor on its rails or slides 5 inches away from its nearest possible approach to the driven shaft or machine and wire-lace it (wire-lacing is a very close second to an endless belt). Let it run for a few days, moving the motor back from the driven shaft as the belt stretches. When all reasonable stretch is out, move the motor back as close to the driven shaft as possible.

The 5 inches forward motion will give 10 inches of belting, which will be amply sufficient for a good splice; and, further, the machine will be in position to allow of tightening the belt up, by simply forcing the motor back, for probably the belt's lifetime.

II

SHAFTING HINTS[2]

THE bolts, set-screws, pulleys, bearings, shafting and clutches of a plant, although among the foremost factors in its efficiency, are very often neglected until they reach the stage where their condition absolutely compels attention.

[2] Contributed to Power by Chas. Herrman.

Very often this lack of proper attention is due to surrounding difficulties of an almost insurmountable and most discouraging nature. At other times it is due to a lack of proper appreciation of the damage resultant from seemingly insignificant neglects. How to overcome some of these difficulties is the object of this chapter.

Fig. 23 shows a case of a turning bolt. The head is inaccessible and the bolt's turning with the nut, owing to burrs or rust, prevents either the tightening or the loosening of the nut. One to three fair-sized nails driven through the timber as at _C_, hard up against, or, better still, forced into a tangent with the bolt, will often suffice to hold it while the nut is being turned. In iron girders, beams, etc., the nail method being impossible, a slot _E_ can easily be cut with a hack-saw through the lower end of both the nut and bolt, so that the bolt may be held by a screwdriver while the nut is turned with a wrench.

Where an extra strong screwdriver must be used, the use of two blades at the same time in the hack-saw frame will give a slot of the requisite width. Where the bolt's end projects beyond the nut and it is desired to tighten the nut, a Stillson wrench is often, though inadvisedly, called into service. This tends to spoil the lower threads of the bolt and thus prevents any future loosening, except by the cutting off of the projecting end.

As the alinement and level of shafting depend on the power of their hold, bolts, lag-bolts and set-screws should, when they are tightened, be so in fact and not in fancy.

The proper way to use a wrench, especially a screw wrench, so as to avail yourself of every ounce of power, not of your biceps only but of your whole body, is as follows: Place your shoulders on a level with the object to be tightened, secure the wrench jaws well upon it, grasp the jaws with the left hand and the wrench handle with the right, holding both arms straight and tense; swing the upper part of the body to the right from the hip, backing the force of your swing up with the full force of your legs, steadying yourself the while with your left-hand grip on the wrench jaws, which are the center of your swing. Several such half turns, at the wind-up, will cause an extremely hard jam with comparative ease.

In tightening up a split-pulley, the expedient of hammering the bolts tight, by means of an open-ended bolt-wrench and a small sledge, is often resorted to. If the head of the bolt be lightly tapped while the nut is being tightened, even a light hammering, except in the extremest cases, becomes unnecessary.

Split-pulleys are invariably better held in place by a good clamping fit than by set-screws. It must also be borne in mind that, for good holding, set-screws must be spotted into the shaft, and this defaces and often materially weakens the shaft. Split-pulleys, like solid ones, are sometimes subject to stoppage, owing to excessive strain. Set-screws, at such times, cut a shaft up pretty badly; whereas, if clamped, only a few slight scratches would result.

Where packing with paper, cardboard, emery cloth or tin becomes necessary to secure a good clamping fit, care should be taken to put an equal thickness of packing into both halves of the pulley; otherwise it will wabble and jump when running.

Emery cloth, on account of its grittiness, is preferable for packing where the duty done by the pulley is light. When the duty done is extra heavy, emery cloth, despite its grittiness, will not do; tin or sheet iron, owing to body, must be used.

The following is the most practical way of packing a split-pulley to a good clamping fit, assuming that emery cloth is to be used:

The thickness of the emery cloth to be used, and whether to use one or more folds, can readily be ascertained by calipering the shaft diameter and pulley bore, or by trial-clamping the pulley by hand. In both of these instances, however, due allowance must be made for the compressiveness of the packing used. If the packing be too thin, the pulley will not clamp strongly enough; if too thick, the chances of breaking the lugs when drawing the bolts up are to be apprehended.

Having determined the proper thickness of emery cloth to be used, place the pulley on the shaft, as shown in Fig. 24. Into the lower half _C_, in space _A_, which is out of contact with the shaft, place a sheet of emery with the emery side toward the hub and the smooth side toward the shaft. The width of the emery should be a little less than half of the shaft's circumference, and it should be long enough to project about one-half of an inch to an inch on each side of the hub.

Now turn the pulley on the shaft so that the position of the halves shall become reversed (Fig. 25), _C_ on top, _B_ on bottom. See that the emery cloth remains in its proper position in half-hub, the smooth side being toward the shaft; the projecting length beyond the pulley hub will help you to do this.

Into half-hub _B_ (space _D_) insert a similar sized piece of emery cloth, smooth side toward the hub and the emery side toward the shaft. Draw up on your bolts to clamp the pulley into position. Be sure, however, that no emery cloth gets in between the half-hubs or lugs at points 1 and 2, Fig. 25, as this would prevent their coming properly together; the width of the emery being less than half of the shaft's circumference will be a help to this end.

It often happens, owing to downright neglect or unwitting neglect, through the oil hole or oiler being blocked up, that a loose pulley, running unlubricated, cuts, heats, and finally, through heat expansion, seizes. It then becomes necessary to take the countershaft down, force the loose pulley off and file and polish the shaft up before it can be put back into place.

The following method avoids the taking down and putting back, provides an easy means for loosening up the pulley that has seized, and improvises, as it were, a lathe for filing and polishing the shaft.

In Fig. 26, _A_ is the loose pulley that has seized. Throw off both the belt that leads from the main shaft to pulleys _A_, _B_ and the belt that leads to the driven machine from the driving pulley _C_. Tie, or get somebody to hold, an iron bar in pulley _A_ at side _a_, as shown in Fig. 27, over an arm of the pulley, under the shaft, and resting against the timber, ceiling, wall or floor, in such a way as to prevent the pulley from turning in one direction, as shown in Fig. 27. Now, with another bar, of a sufficient length to give you a good leverage, take the grip under a pulley arm and over the shaft in the tight pulley _B_ at _b_, which will enable you to work against the resistance of the bar in the loose pulley _A_.

With enough leverage, this kind of persuasion will loosen the worst of cases. Take the bars out and move _B_ sufficiently to the right to allow _A_ to take _B_'s former position. Secure _B_ by means of its set-screws in its new position and, by means of a piece of cord, fasten an arm of _A_ to one of _B_'s. It is evident that by throwing the main-shaft belt on to _A_ it will, through _A_'s cord connection with _B_, which is screwed to the shaft, cause the shaft to revolve, thus enabling you to file up and polish that portion of it formerly occupied by _A_. To prevent the countershaft from side-slipping out of hanger-bearing _D_^1, get somebody to hold something against hanger-bearing _D_^2 at _E_; or fasten a piece of wire or cord on the countershaft at _F_ and the hanger _D_^1, so as to prevent side-slipping while not interfering with revolution.

Filing, polishing, a cleaning out of the oil hole or oiler, and the taking of proper precaution against future failure of lubrication will put everything into first-class order. When the loose pulley is, as it is best for it to be, farthest away from the bearing, held in its place by the tight pulley and a collar, not only is the tight pulley better adapted for carrying its load, owing to additional support resultant from its proximity to the bearing, but such matters of small repair as come up are much simplified.

Fig. 28 in some degree, aside from the cutting up and heating of the bearings, illustrates the breaking strain, in addition to the usual torsional strain, which becomes enhanced in direct proportion with the increase of breaking strain, to which an out-of-line or out-of-level shaft is subject. The bends are exaggerated for illustration.

In this instance, the fact of one hanger-bearing being out of line or level subjects the shaft to a severe breaking strain. The shaft being both out of line and level does not, if both at the same point, aggravate matters, as might at first be supposed.

It is true that the full torsional strength of a shaft is only equal to the weakest portion of it, so that three weak spots more or less can, theoretically, make no difference one way or the other. But, practically, there is the undue strain and wear of the bearings at these points, and if a pulley transmitting any considerable amount of power is situated anywhere along the length _A B_ it is sure to be unpleasantly in evidence at all times.

Only an eighth or a quarter out, but oh, what shaft-breaking stories that fraction could tell!

The following is a simple method for testing the alinement and level of a line of shafting that is already up.

As in Fig. 29, stretch a line _C_ so that it is exactly opposite the shafting. Set it equidistant from the shaft end centers _G_ and _F_ and free from all contact along its entire length except at its retaining ends _A_ and _B_. Now, it is self-evident, as line _C_ is straight and set equidistant from the shaft end centers _G_ and _F_, that if you set the entire center line of the shafting at the same distance from line _C_, as _G_ and _F_, you are bound to get your shafting into perfect alinement.

In leveling a line of shafting that is already up, you can, by the use of a level and perseverance, get it right.

Placing the level at _A_, you are just as likely to raise the first hanger as to lower the middle one. Look before you jump, even if compelled to climb to the top of the fence to do so. When you find a length of shafting out of level, try the two adjacent lengths before acting, and your action will be the more intelligent for it.

On exceptionally long lines of shafting the following method, in which the level and a line constitute a check upon and a guide for each other, can be used to great advantage. Stretch a line so that it is exactly above, or, if more convenient, below the shafting to be leveled. With the level find a length of shafting that is level and adjust your line exactly parallel with this length. Your line now, free of contact except at its retaining ends, and level owing to its parallelism to the level shaft length, constitutes a safe _hight level_ guide while the level itself can serve to verify the accuracy of the finished job.

In lining, whether for level or alinement, unless the shafting line consists of the same diameter of shafting throughout its entire length, though of necessity measuring from the shaft circumference to the line, always base your calculations on the shaft centers. The figures in Fig. 29 will make this point clear.

The manner of securing the ends of the line under different circumstances must be left to individual ingenuity. Only be sure that the line is so placed that the shafting adjustment shall not affect its original position with reference to the end shaft centers.

Coupling clutches, _i.e._, those joining two lengths of shafting into one at option, will fail, utterly or partially, if the respective shafts which bear them are out of line or level with each other. Such a condition should not be tolerated on account of the danger entailed by the inability to shut off the power in cases of emergency.

As a general rule, it is most advisable to set a clutch to take as hard a grip as it can without interfering with its releasing power. Where a clutch grips weakly, it is subject to undue wear owing to slippage, whereas a strongly regulated clutch absolutely prevents slippage wear.

III

SHAFTING HINTS[3]

ENGINEERS, machinists and general mechanics are often called upon to turn their hands to a shafting job. We recognize that all of the following cannot prove new or even suggestive to most of our readers; still, some of it for all, and, mayhap, all for some, may not come amiss.

[3] Contributed to Power by Chas. Herrman.

We all know that to have belting run rightly on pulleys located upon parallel lines of shafting the shafting must be in absolutely correct parallel. The slightest deviation, even to a 1-16 inch, often imparts a marring effect, through poorly running belts, to an otherwise faultless job.

Fig. 30 shows how to line a countershaft as regards parallelism with the driving shaft when the countershaft's end-centers are availably situated for thus measuring. _A_ is the countershaft, _B_ the main shaft, _C_ is a stick of proper length about 1-1/2 inches in thickness and width, _D_ a heavy nail--about 20-penny will do--driven into _C_ far enough from its end _E_ to allow of _C_'s resting squarely upon the top of the shaft _B_.

Rest the measuring rod upon the main shaft, keeping the nail in touch with the shaft, so that when the _F_ end is in contact with the end of the countershaft the stick shall be at right angles to the main shaft, and then mark the exact location _a_ of the countershaft's end-center on the stick. Do the same at the other end of the countershaft. If both marks come at the same spot, your counter is parallel; if not, space between these two marks will show you how much and which way the counter is out.

It may only be necessary to shift one end in or out a little; and then, again, it may be that to get into line you will have to throw one end all the way in one direction and the other all or some in the opposite direction. But, whichever it be, do not rest content until you have verified the correctness of your adjustment by a re-measurement.

The nail should be well driven into _C_, so that its position will not readily change, and it should, preferably, be slant driven (as shown in Fig. 30), as it thus helps to keep the stick down in contact with the shaft.

Where an end-center is not available or where there is no clear space on the main shaft, opposite a center, the method shown in Fig. 31 can generally be used.

Rest _C_ on top of both shafts and at right angles to the driving shaft _B_. With _D_ pressed against _B_, place a square on stick _C_, as shown (stock in full contact with the top of the rod, and the tongue running down the side of it). Slide along _C_ toward _A_ until the side of the tongue touches the shaft the other side of _A_. Now mark a line on the stick down tongue. Do the same at the other end of your countershaft and the two resultant marks will be your parallel adjustment guides.

It often happens that a counter, or even line shaft, is end driven from the extreme end of the main or jack driving shaft with its other end running beyond the reach of the driving shaft, as shown in Fig. 32.

It is evident that neither method 1 nor 2 can here be applied to solve the alinement problem. If the driving pulley _B_ and the driven pulley _A_ are both in place, the following method can be used to advantage.

Fasten, or let somebody hold, one end of a line against pulley _B_'s rim at _B_^1; carry the line over to _A_ at _A_^2; now sweep the loose _A_^2 end of the line toward pulley _A_ until the line just touches pulley _B_'s rim at _B_^2. When the line so touches--and it must just barely touch or the measurement is worthless--_A_^1 and _A_^2 of pulley _A_ must be just touched by or (if _B_ and _A_ are not of a like face width, as in Fig. 32) equidistant from the line.

A single, two-hanger-supported length of shafting thus lined is bound to be in parallel; but where the so adjusted shaft line consists of two or more coupling-joined lengths supported by more than two hangers, only pulley _A_'s supporting portion of the shaft between its immediate supporting hangers 1 and 2 is sure to be lined; the rest may be more or less out.

To make a perfect job, fix a string in parallel with shaft length 1 and 2, stretching along the entire length of the adjusted shaft, and aline the rest of the shaft length to it.

When there are no pulleys in place to go by, or when, as occasionally happens, the wabbly motion of pulley _B_ (when running) indicates that, having been inaccurately bored or bushed, or being located on a sprung shaft length, its rim line is not at right angles to the shaft line, the method shown in Fig. 33 can be resorted to.

Instead of the nail used in methods 1 and 2, use a board about 8 to 12 inches long and of a width equal to considerably more than half of shaft _B_'s diameter. By nailing this board _x_ to the measuring rod _c_ at any suitable angle, you will be enabled to reach from the end _a_ well into the shaft _B_, as at _b_, and from _b′_ well into _A_, as _a′_. By keeping the board _x_ along its entire length in full contact with the shaft _B_ at both 1 and 2, the angular position of rod _C_ is bound to be the same in both instances, and you will thus (by the use of a square, as in Fig. 31) be enabled to aline _A_ parallel with _B_.

In all instances of parallel adjustment here cited it is assumed that both the alined and the alined-to shafts have been, as to secure accuracy of result they must be, properly leveled before starting to aline.

The above methods apply to cases where the shafting is already in place. Where, however, shafting is being newly installed before the work can be proceeded with, it is necessary, after determining on the location for the shafting, to get a line on the ceiling in parallel with the driving shaft to which to work to. Mark that point _A_ which you intend to be the center line for the proposed shafting upon the ceiling (Fig. 34).

Rest your measuring rod upon the driving shaft and at right angles to it, with the nail against it. Hold your square with the stock below and the tongue against the side of the measuring stick, so that its tongue extremity touches the ceiling mark _A_, and then mark a line on the rod along the tongue side _A_. Move your rod along the driving shaft to the point where the other end of the proposed shafting line is to be, and, squaring your stick to the driving shaft with the tongue side _A_ on the marked line of the stick, mark your section point on the ceiling. Draw a line or stretch a string between these points, and you have a true parallel to work to.

Owing to the supporting timber _B_'s interference, a square had to be used; but where the ceiling is clear the rod can be cut to proper length or the nail be so located as to allow of using the stick extremity _C_ for a marking point.

When a pulley is handily situated on the driving shaft, the method shown in Fig. 35 can be used to advantage.

Let somebody hold one end of a line at 1, and when you have got its other end so located on the ceiling that the line just touches the pulley rim at 2, mark that ceiling point (we will call it 3). In the same way get your marks 4 and 5, each farther back than the other and, for the better assurance of accuracy, as to just touching at 2, remove and readjust the line separately each time. If now a straight line from 3 to 5 cuts 4, your line 3, 4, 5 is at right angles to the driving shaft and a line at right angles to this will be parallel to the shaft.

The plumb-bob method is so familiar and, where not familiar, so easily thought out in its various applications, that we deem it useless to touch upon it.

The stringers or supporting timbers of drop hangers should be equal in thickness to about one-fifth of the hanger drop.

Where the stringers run with the hangers and crosswise of the shaft, both feet of a hanger base are bolted to the same stringer, and this should be from 1-1/4 to 1-1/2 times the width of the widest portion of the hanger base. As the hanger is securely bolted to its stringer, this extra width is in effect an enlargement of the hanger base, and thus enables it the better to assist the shaft's end motion.