First put in a ridge pole out of 1½-inch pipe, starting at the face of the wheel and running in the direction of the main driven pulley, holding it firmly in place at each end with a strong iron clamp. Then solder into each edge of the strip of tin, which should be long enough to reach beyond any possible leak through the floor or oil table, a piece of ½-inch pipe, and put the tin over the ridge pole with a piece of small pipe on either side. Ordinarily the belt goes out past the cylinder; if it runs through a bricked-up runway on its route to the main driven pulley, just fasten the two pieces of 1/2-inch pipe to either wall and have the ridge about 6 inches higher than the outside ones. Then every drop of oil or water that comes through the floor will fall on to the roof and run down to the walls and be carried down to the floor of the pit and have no chance to touch the belt.
One of the most difficult things in the operation of large stations where a large number of belts are used is to keep them thoroughly clean and free from moisture and machine oil, the latter especially. One very hard problem that confronts all designers of machinery is the prevention of oil leakage from boxes. In several plants with as many as six dynamos of the same kind and the same design, at least four of the six have leaked oil every time they were run. The others did not leak as a usual thing, and all were equipped with the most modern methods of holding oil.
Fig. 80.
Now we come to the building of the belt, and we will notice only such points as interest the engineer or buyer. The first thing is to see that the laps are of uniform thickness, so that the belt will run quietly; and it should be absolutely straight when unrolled on the floor. If it has a long, graceful curve in it, look out; for it will not run straight on the pulleys until it has stretched straight, and by that time one of its edges may be ruined by coming in contact with the floor or some other obstacle. Next notice how long the leather is from which it is made. It should not show more than 52 inches, and then there will be 4 inches hidden by the point that is out of sight. Then see that the joints are broken properly. For instance, find the center of any piece of leather on one side of the belt, and then look on the opposite side and see if the joint is right under your center mark. It should be by all means, for right here lies the most important thing about the construction of leather belts. A belt whose laps are all the same length, and which has all its joints broken correctly, will put the same load on the glue throughout, and that is what must be done in order to get the best results. See Fig. 80. Here we have a belt that is 36 inches in width and a double ply. Now suppose there is a draft of 9360 pounds on this belt, that from point A to point B is 26 inches, and that the points are 4 inches long. Now we have 26 inches plus 4 inches plus 4 inches times 36 inches for the number of square inches in the glued joint. This equals 1224 square inches; the total pull on the belt divided by 1224 will equal the load on each square inch of glued joint, and will equal in this case 7.65 pounds. Now instead of assuming distance A—B in Fig. 80 to be 26 inches, let the lower joint get out of step with the upper ones, and conditions get vastly different. We will suppose that the dimensions are as given in Fig. 81, as was the case with a new belt that was measured less than one month before the observation was made and we have the following: Joint A B is now only 10 inches, and we have 10 inches plus 4 inches plus 4 inches times 36 inches which equals 648 square inches, and the lead on the joint is now 14.44 pounds. You will readily perceive what an important part in the life of the belt, and the life of everything around the belt as far as that goes, the proper breaking of the upper and lower joints is. Of course the belt maker will tell you that his glue is just as strong as the leather itself, and he is about right as long as you keep the belt free from oil and water; but when the belt becomes filled with oil the glue rots and loses its strength much faster than does the leather.
Fig. 81.
No good belt needs any posts along the sides to make it run straight and stay on the pulleys. If the pulleys are in line and the belt straight, it will run straight. All belts should be made to run perfectly straight on pulleys, first on account of the local advertisement that it gives to the man who has charge of them; second, if they do not run true, they will be on the floor or wrapped around the shaft in a very few minutes, should they ever slip. Another very important thing in the care of belts that carry heavy loads is that if any of the points do come loose so far back that they will not return to place without putting on the clamps, put them on by all means; as the restoring of this point to place means that you will still retain in service all of your belt, as you will not do if you glue it down where it is and thereby cut one side completely out of service.
How to Clean Belting
We submit the following as the best and proper way of cleaning a leather belt. It may seem simple, but it is safe and effective, as has been proved by many people who have thus restored old and dirty belting which had become almost or quite unfit for use.