August 1, 1921 



THE INDIA RUBBER WORLD 



803 



Double Grip Lacing 



and thickness, and freedom from torsion and flapping, it carries 

 macliinery along steadily. 



Other points in favor of the rubber belt are that it eliminates 

 differences between the two sides of a belt in pulling quality. 

 While leather belfing gives a gradation of strength in three plies, 

 single, double and triple, rubber-covered belting will afford a 

 range varying from 3-ply to 8-ply, or, in the case of friction- 

 surfaced belting, 3. 5. 7, 9, 11, 13, and 15-ply, Not the least 

 important feature in favor of rubber belts is that they stretch 

 less in service than those of other material and thus .save much 

 loss in the labor of tightening belts. 



FIELD WORK IN APPLYING AND REPAIRING 



The application or fastening of the ends of all belts, except 

 those made endless, was a problem that vitally interested all belt 

 makers. It was what is termed field work and any belt catalog 

 gave specific directions as to methods of lacing and of replacing. 

 Not only this, but manufacturers supplied the most tenacious 

 cements; all because the life of the belt and its satisfactory 

 work depended upon proper application. While thus teaching 

 belt users to apply belts they were actually showing them how to 

 repair them. It therefore happens that field work in belt repair 

 is well advanced, although not as yet standardized. 



The tools used are of the simplest sort : a belt punch for cut- 

 ting the holes, cement can, hand sticker, brush and a belt-stretcher. 



The stretchers 

 are to bring the 

 ends of the belt to- 

 gether, and while 

 there are a variety 

 of kinds involving 

 the use of rope 

 winds, and toggles, 

 those in general 

 use are steel or 

 wooden clamps through which two steel rods are run into heavy 

 nuts. The take-up is effected simply by turning the threaded rqds 

 as far as may be necessary. 



Efficient operation of a rubber belt is dependent much more 

 upon proper fastening than many belt users realize. Proper 

 fastening means getting the maximum amount of power trans- 

 mission, conversion, or diversion for which a belt has been spe- 

 cially selected. It means a more steady drive and freedom from 

 jerks, flapping, vibration, and side-sway, and it means for the 

 belt less wear and longer life, economic factors of no small im- 

 portance, especially where many or very expensive belts are used 

 considerably. This anxiety may not give much concern to those 

 who have their rubber belts, for high speeds or heavy drives, 

 made endless or continuous at the factories from which they are 

 bought and at which they are made up according to specifications. 



But even the best rubber belts may stretch somewhat through 

 long use or through working under adverse conditions ; or it may 

 be found desirable to shorten an original endless belt so as to 

 work it on pulleys closer together. In that event the belting 

 must be dealt with in just the same way as material bought in the 

 roll and fitted to machinery by the purchaser. Not only must 

 the utmost care be exercised with regard to fitting and measuring 

 the belt, but also as to the mode selected and the materials chosen 

 for fastening the ends of the belt together, It is a truism that a 

 chain is no stronger than its weakest link, and so, also, is it a 

 fact that a rubber belt in service is no stronger than its fastening. 



THE LEATHER LACING 



The oldest and, despite its slowness, still the most favored 

 method of fastening belt ends together is that of leather lacing. 

 While still done largely, and often successfully, by rule of thumb, 

 the lacing of rubber belts can be and to a fair degree has been 

 well-standardized. It is only by adhering to certain well-settled 

 rules concerning the fastening of belts that real satisfaction can 

 be assured. The quality and the cutting of the thongs used in 



lacing rubber belts are of primary importance. The United States 

 Xavy Department is exacting in this regard. Its specifications 

 require that all thongs for lacing belts shall be cut only from 

 green slaughterhouse hides. They must be cut lengthwise from 

 the hides and must have in the various sizes a tensile strength 

 per square inch of at least as much as that indicated in the fol- 

 lowing table : 



Widlh inches "4 -l-f H i^c 'A H H 



Strength pounds 95 125 155 165 180 205 230 



In the choosing of a lace heed should be given to the kind of 

 drive, the diameter of the pulleys, the speed of the belt, the power 

 transmitted, and the safety of workmen. .A.S a general rule the 

 lacing for a rubber belt is selected with regard to the width of the 

 belt, the thinner kinds being used for the light, narrow belts, and 

 the stouter for the broad, heavy belts. Lacing will vary in thick- 

 ness froin 1/64 to nearly % of an inch. 



Proper lacing being provided, the first step in fastening a rub- 

 ber belt is to square the butt ends perfectly. It is not safe to de- 

 pend merely upon marking the ends with a pencil and then cut- 

 ting. It is better to get a carpenter's square with which to out- 

 line the ends, and then cut accordingly. That will insure a true 

 joint. If the ends of the belt are not cut perfectly, or if the tension 

 put in the lacing is not uniform in both sides of the belt, the latter 

 will have a tendency to run crooked and by striking cone edges, 

 belt shifters, or other projections soon damage itself. 



Having squared the belt ends, and finding that they line to- 

 gether perfectly, holes should be punched just large enough to 

 allow the lacing thong to pass through them and distant in single- 

 row lacing -H to 1 inch from the ends of the belt, being careful 

 to remove no more material from the belt than is really necessary 

 in order to avoid weakening the belt. For the smaller belts a 

 'A-'mch lace will usually suffice ; for belts from 4 to 8 inches wide, 

 a >^-inch lace; for belts from 8 to IS inches, a i/2-inch lace; and 

 for belts over 15 inches, a 54-inch lace. For unusually large, 

 heavy belts a 1-inch lace is often used. 



Before lacing it would be well to verify the measurement taken 

 for the belt length by drawing a steel tape tightly around the 

 pulleys to be used, and in order to allow for possible stretch to 





Pulley Side. Outside. 



Other Ways of L.'^cing 



cut the belt a trifle shorter in about this proportion : For 3, 4, and 

 5-ply belts allow S/32-inch per foot; for 6, 7, and 8-ply belts 

 allow J/^-inch per foot; for 9 and 10-ply belts allow 3/32-inch 

 per foot, 



BEST LACING METHOD 

 While single-row lacing may serve well in an emergency and 

 even last long in some cases, the double-row or double-grip lacing 



