Bean Harvester : see Harvesting Machines, Grain.
BEA Ill NOS Hor.t.rac tar BALI, BEA RINUS.—Tho rise of rollers and halls in bearings for the purpose of converting sliding into rolling friction is meeting with success in 'omicrons special cases. The most general application of ball-bearings is in bicycles (see BICYCLE).
They have also been used to some extent for axles of mining-ears. An application of roller bearings in the main journal of the great Lick telescope is thus described by W. R. Warner (Trans. A. S. J1. E... vol. lx, p. 330). The tube is 53 ft. long, and weighs 44 tons. It is supported on a bearing near the center and at one side. It seemed almost impossible to make it move easily enough in the ordinary way by using friction-rolls; so, instead of that, the method was adopted of surrounding the axis close to the tube with a series of rolls 21 in. in diameter and 3 in. long, with a result which seemed very satisfactory. The tube when bal anced on these rolls would turn by a pressure of 4 lbs. at the end—one finger would move it very easily—so that the problem was as completely solved as could be asked. Another effort to solve a similar problem in a different position, where the rollers hardly would do, was accomplished by using hardened steel balls running in circular concave tracks, which is the same principle used in bicycle-wheels. In this problem, simply to test its working, a weight of 2 tons was placed on 40 1-in. balls in the two circular tracks, and this 2 tons was turned by a pressure of 1 lb. at a radius of 3 ft. The groove in which the balls run had a diameter of in.. so that it was practically a plane surface, bearing only on the top and lower edge, and the balls worked together so that the whole ring, when they were pressed together, left only in. between the last two balls. In the ease of the rolls, they were not together, but had their axis run on little steel balls in. in diameter. There was no lubricant. It was found safe to put on the balls something less than 1,t100 lbs. to each boll, while on a roll having its bearing surface its full length-3 in.—a much larger Fro. 1.—Bali bearing.
weight could be placed.
In the ordinary form of hall-bearings the track or tracks in which the balls roll soon becomes worn if the hearing is subjected to any considerable pressure. this seeming to be a necessary consequence of the fact that only a very small portion of the actual surface within such a bearing can be mused by the balls. It has been demonstrated that a beating dqes better without grooves for the balls to run in than with them, the plain surfaces being/not only more easily especially when hardened and ground as they should be, but actually working better in nearly every respect. This being the case, it became a problem to so
arrange the balls that all the surface within a bearing. both on the shaft and with in the box. should be made use of by the balls. thus preventing wearing in grooves. as is the ease where they are arranged in rings, separated from each other by cel lars. Figs. 1 and 2 show forms of bearings in which the balls are held in what is virtually a shell that can be removed from the bearing. handled and put in again without a single ball being displaced. it will be seen that the balls arc arranged between the coils of a helix which holds them loosely, so that they are free to turn. the ends of the helix being partially closed to prevent their running out at the ends. The sides of the strip from which the helix is formed are made con cave, as shown in Fig. 2, the object of this being obvious. The shell or helix is not held in the bearing in any way, except that collars prevent it being displaced endwise, and it turns freely with the balls as they rotate. Though arranged in a helical line, the balls do not rotate in this line, but in a direct annular direction in a plane at right angles to the cen ter line of the journal. the pitch of the helix being so proportioned to the diameter of the balls that each succeeding ball rotates in a track which is slightly at one side of that of the preceding one (usually about in.), the end play which is in most bear ings allowing for enough movement to cover the intervening spaces. so that the entire surface is made use of, both the shaft and the box be coming planished brightly and uniformly over their entire surface. Ex perience has shown that this results in decrease of wear. Fig. 3 shows another form of bearing, which embodies the same principle, so far as the distribution of the balls is concerned, they being in this case inclosed in a shell of brass, which is drilled, as shown, for the reception of the balls. a shoulder being left at the bottom of the holes, and the tops being partially closed after the halls are in place, so that they are held loose ly. as in the helical shell. One of the advantages of this form is that more balls can be put into a bearing of oiven size, and the shell can be made in two parts. joined together as shown, so that they can be put over a shaft or taken from it at any point in its length without the ne cessity of going to the ends. The two parts are joined at the irregular fins shown, and are held together by the spring hooks seen at the sides. It will be understood, of course, that not mach force acts to separate the two parts of the shell when it is in use, since its only office is to keep the balls properly separated.
Bearings: see Drilling Machines, Metal; also Cycle.
Belt Lacing: see Belts.