II II — — ,d. III I I 3?:32’ III I A SHORT STUDY OF THE PERFORMANCES OF WATER-PROOF LEATHER BELTING AND RUBBER BELTING UNDER CONDITIONS APPROXIMATING THOSE FOUND IN MEAT PACKING HOUSES. m- Thesis for Degree of M. E. Royal Gilbert BIgelow 1 9 2 9 TH ESIS A SHORT STUDY OF THE PERFORMANCES OF WATER-PROOF LEATHER BEM‘ING AND RUBBER BEIITING UNDER CONDITIONS APPROXIMATING TH$E FOUND 1!! HEAT PACKING HUISES. Thesis for Degree of TECHANICAL ENGINEER Submitted by Royal Gilbert agent 1929. I [\ M THESIS l'llllll | I OBJECT OF THE STUDY. A great deal of detailed experimenting has been done by Engineering Colleges and industrial research organizations on the various kinds of belts used for power transmission. These tests have been comparative tests under normal operating condi- tions, for example, to show the difference in per cent of slip- page, effect of change of pulley diameter, effect of change of center distance, and the effect of speed.sariation,'using differ- out kinds of belting. Dr. Wilson of Mellon Institute of Industrial Research of the University of Pittsburgh has made many tests on all common kinds of'belting. His tests were made under normal working conditions. 1' This study of belting was limited to beltings known commercially as water-proof leather belting and rubber fabric belting. The object of this study of the above two kinds of belting was primarily to determine quickly, if possible, which of the two kinds is best adapted for use in the meat packing indus- tries. It is known that in the packing plants the room.temperar tures and relative humidities vary considerably from low to ex- tremely high, and that in may parts, the air contains a large amount of oil vapor. Under these air conditions the belts in 2. packing'houses are working under somewhat abnormal conditions. 1. Study of the Various Types of Belting, I. D. Wilson, June 14, 1919. 2. This study was made in November and December 1925. 9410-533 BEHI‘ ING USED. As mentioned above the study was confined to the so- called water-proof leather belting and the comonly known rubber fabric belting. In each case the best standard grade was used as purchased on the open retail market. The leather belting was 4-inch single ply, cemented with water-proof cement and treated with some sort of oil which is supposed to make the sur- face impervious to water. The rubber belting was what In known as 4-inch four ply. The ends of each belt were fastened together with Clipper belt hacks and pins. The Clipper belt hooks were used to Join the ends of the belts, because this or a similar kind of metal fastener is used in the packing plants, and too, because in parts of the test it was expected that the belts would have to be shortened from time to time. PROCEDURE. The study was divided into four parts as follows. 1. A horse-power slippage test on each belt Just as it came from the belting dealer.- 3. 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DESCRIPTION OF APPARATUS USED. The set-up for the horse-power slippage tests (1) and (3) as shown in Figure I consisted of an adjustable speed direct current motor, a prom brake and scales. In addition to this equipment two revolution counters were used for determining the RPM of the motor and of the brake wheel. In the 250-hour run the apparatus consisted of a 15 horse-power alternating current motor, a ventilating fan for load and an idler for uniform tension and to give reverse bend to the-belting; a mgrometer, a sight-feed steam engine lubri- catpr and a steam supply. This set-up is sketched in Figure II. The two pulleys and the belt were enclosed in a comrtment so arranged that steam could be injected to maintain a high relative humidity and acomparatively high temperature. The steam engine lubricator was shunted across the steam line so that the oil (a mixture of steam engine cylinder oil and lard oil) was carried on and blown through a nozzle with the steam, thus breaking up the oil into a vapor. I The tensile test on the belts was made on a standard Riehle tension and compression machine. Wissler dials were used to show the .elongation of the specimen under load. Special holding devices in the form of clamps made of 2" square steel were used to hold the belt for pulling. These clamps were used so as to eliminate a weakening of the belting by making holes iiililllllllll all t O _ VII III II . . n a .. , o . 5&1. I IIII.‘ ~ .. n . . . ’ . . 1"! I I. !II.. III . . 1.1 o- . . . ¢ . . Trot _ . o IJIO~ . ~ .I III: . . . 1 w. 5: IA IIQI IJIIILIII :J . a ‘I‘I -.:.:..::H_ 1:34: _:.-::. n .. _ . IIIIII‘tIIlFIIA.II.IIQI .WJI‘ . 1 " «iw .4IMI’I4I 11:11:11 11 3: _,-:r . . JIJI IIIIIOII . . 5 I. i. ill 1W. II~5I5I5 I...“ 5'_II‘I II. '1“ .IIL‘I+'H'IIHII . 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TI. 1: .. _ .. -- S-” 1.: ..-..:.F:-/.. ...-1L.-..: . . :. -.H...._:w -1: . T- -....4J_.Ifl... I:.I...I.MI. I .. . . . , . 4.. .... - . o _ n A IWLI. I I- .I I I VI 1 I m. l 9 . .05: I o I. o I 5 . I‘k‘ rbfllllvvt vatl'll . . c 1 u . C. . . -:T+....... .. _ . .. 1 .1 . . _ I "1V.OmI 'm.‘.‘.O-.tlorlI“I.“.5IMl II. I”? ‘14. . I‘Ti ill. I II ‘4‘ . ., r J ... IA 4 .' “vi . It {I l6 s I. .J . . m4. 0 ‘Q‘OIIIJIW'JII . . 1'3... 4* L.tnfi . u . 4. through it. A sketch of the clamps is shown in Figure III. THE HORSE-EVER SLIPPAGE TEST. The belts were each in turn placed. on the pulleys as shown in Iigure I. A pull was put on the belt by turning the hand wheel nut (N). The pull was transferred from the horizon- tal to vertical by the right angle member, thus making it pos- sible to use a regular laboratory platform scale (A). The not pull used for each belt was 240 pounds, or 60 pounds per inch width of belt. The transmitted horse-power was measured with the prom brake and scale (B), using increments of not load of 2; pounds. The horse-power was computed by the brake horse-power formula, BHP,§_XE3.1416 x R 1M 33,000 where R is the length of the brake an, IV is the net load on the scale, and H is the RPM of the brake wheel. The slip was determined by the difference in RP! of the motor and the brake wheel. The per cent slip was computed by dividing the slip in RPM by the RPM of the motor. Horse-power slip tests were made on each belt before and after the 250—hour run at different driving speeds. The re- sults of these 30 tests are shown by the curves, Figures IV, V, 5. VI, VII and VIII. The curves were made by plotting per cent ' slip as abscissa and horse-power transmitted as ordinates. BESUIES OF THE HORSE-POWER SLIPPAGE TEST ON THE NEW BELTS. On examination of the curves of the belts before the 250-hour run it is seen that at all speeds the leather belt showed a somewhat earlier slip than did the rubber belt. The slip of the leather belt was very noticeable as the test was being run. As the load was increased and the increased slip slightly warmed the belt the odor of what seemed to be fish oil was detected. This oil probably was the cause of the excessive slip on the part of this belt. However, it is also very noticeable from the curves that when the rubber belt began to slip, the slip increased very rapidly. When the slip of the leather belt reached around 4 or 5 per cent it usual- 1y slipped entirely off the pulleys, expecially so on the higher speeds, while the rubber belt remained on the pulleys longer, although int increase in horse-power transmitted was but very little. This performance of the rubber belt is probably due to the softening of the rubber coating by the heat of friction. This effect, of course, would disappear when the rubber coating were off, thus exposing the fabric to the pulleys. Of course, at this point the belt would begin to disintegrate very rapidly. It will be noticed, however, that at all'speeds and at the lower loads, the belts perform about alike. 6. THE 250—EDUR BUN. The two belts, rubber and leather, equal in length were Joined together making one complete belt 30 feet, 6 inches long. This belt was placed on the pulleys as shown in Figure 11. The belt was run under load (about 12 HP) for 10 hours per day, until the 250-hour run had been completed. Readings on the thermometer and hygrometer were taken twice per day. The temper- ature for the 250-hours of run averaged 92° 1., while the relative ' humidity averaged 91%. Enough oil was injected with the steam to give a slight oil deposit on the inside of the compartment, and likewise on the belting. Every day the condition of each belt was noted. Both belts stretched considerably, necessitating shortening. The leather belt stretched about 2.2%, while the rubber belt stretch- ed about l.5$. 0n measuring the cross-section of the belts at the end of the run it was found that both.belts were narrower, the leather belt having decreased about 1.26% in width.and the rubber belt about 0.75%. The thickness of the belts did not, how- ever, show the same relative change. The leather belt decreased about 2.17% in thickness, while the rubber belt increased about 4%. The surface of the leather belt was in very good shape and showed no noticeable signs of disintegration except that where the sections of the belt were Joined the laps were slightly 7. cracked and peeled. The surface of the rubber belt was very spong and sticky. This was apparently due to the effect of oil on the rubber. The effect of the oil in linking the surface spongy also probably accounts for part of the increase in thick- ness. The moisture absorbed by the fiber of the belt probably caused a small part of the increase in thickness. It is a well known fact that cotton fiber like most vegetable fiber swells when dampened. The idler or tightening pulley had the effect of giving the belts a reverse bend and also to subject the out- side of the belts to wear. Of the two belts the rubber seemed .to suffer the most from the workout given them. TEE RESUIES OF THE HORSE-Pm SLIPPAGE TESTS OBI THE USED BEUI‘S. This horse-power slippage test was made in exactly the same manner as the one on the new belting described earlier in this thesis. The results, however, are not the same as those obtained in the earlier test. On referring to the dotted curves in Figures IV and V it will be noticed that on the lower speeds thfifibber belt performed much better than the used leather belt. This, probablymas due to the fact that the softening of the rubber by the oil made the surface of the belt very sticlw. The belt functioned like a belt that bad Just had an application of a very good belt dressing. It will also be noticed that both belts " '11: - .a—Lla 5.4 1 .4...” RNA... 5 up '-:;f .4 KEUFFCL A [59!“ CO.. H. 7. NO. 3604‘ Mluifiwtbr", 114th hm". blunt“). _L_A— NL'. n52b" NY KEUFFEL A ESSER CO, us hm ~ . h E‘, 1U”! 11 into- 31 M; _. 1... L». OII.,9.I .I‘ .Ll is.. u. .. Lisle. w. t..|. » 101.01, . $0+4173 4 . . Lyell-1V! _ .Lt. no. 163-} Y . Milfimctcr, liyih “mm |.ra\',‘. N KEUFFEL A ESSER CO Kturm ‘ [36:9 C°.. N. Y. N0. 359.?4 Millimeter, lUih hum heavy, \ . u s..“ sllll.|. it .|.. c . ‘1‘1: 6‘ II IIIoa . '2" I II \ i. ‘O‘1 2.1. I .{0’.“l€'|.l\ .sill‘lc'.1tl\0n .-..b I‘I .1“Otl| IVtIl.lIlI I lit}. I 1‘..th.III l‘l‘ 1 . . . . . . . . . . . _ . ' . O . U . a . . p . . . . . . ..I y . . ~ . p I . ~—.‘ . . a . a u s . -. . R . . . . -. . . . . . W s .I. _ . . . . . . .. . . _ i . . . If, . . I I v I I . I. .. .. . .. .A .. . e I. . I eIIl I . . V I I. . . . 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Figures VI, VII and VIII show that at the higher speeds the leather belt clung to the pulleys much better than the rubber and delivered more horse-power without slipping entirely off the pulleys. The fish oil odors were not noticed in this test, probably due to the mixing of the vaporized oils with the fish oil on the surface of the belt. The rubber belt seemed to pull about as well as the leather up to and around 16 or 17 horse-power. Above that point the rubber belt seemed to slip more rapidly and finally left the pulleys while the leather belt continued to pull for several more horse-power before slipping off the pulleys. This peculiar per- formance of the rubber belt at the higher speeds seemed to be due to the fact that when the belt began to slip the heat developed softened the spongy and sticky surfhce and increased the slippage. The odor of heated rubber was very noticeable. 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I I 7 I ‘. | 2‘7?“ 4‘1 4 -7 | 0 “7 I -T I" L l I 71. ‘ -7 ‘ 6751171 . .7- T7 ..IT 7.77.,7. . 7 .-m . .7L J.IIIM.I.7.7._L7 77eI 4I 4I0 ”I.|_. 7.7 7 . HIM _ . _I7« .«7 7Iw777LI_77 l ..777 - . . , r . 7-77.fi77.-.7_77 . . _ _ . 9. THE TENSILE TEST. In this test- three samples of each belt; before and after the 250-hour run, were used. The loadings were divided into increments of 200 pounds each. After each increase of loading the Wissler dials were read to obtain the exact elonga- tion of the specimen. The mean of the elongation readings for each increase of load on the three samples was remiced to per cent. These values were plotted as abscissa and the loadings as ordinates. These curves are plotted to get an idea of the performance of the two kinds of beltingmder tensions much greater than ordinary running tensions. To obtain the breaking load the samples of each belt were loaded grachially until rupture occurred. To get a basis for future comparison these values were reduced to pounds per square inch of section, as shown near the curves of Figures Ix and 1. RESULTS OF THE TENSILE TEST. By referring to Figure II it will be seen how the rubber belting acted under the tensile test. It will be noted that the curve of the used belt shows such less elongation per increment of load than does the new belt. This is probably due to the stretching that took place in the used belt while it was being used on the 250-haur run. 10. The average load at the breaking point or stress at rupture for the used belt of rubber was 3520 pounds per square inch and for the new it was 4280 pounds per square inch, show- ing an average decrease in ultimate strength of 15.495. This shows that the belting was appreciably affected by the presence of the oil and moisture during the 250-hour run. Rf referring to .the curves on Figure 1: it will be seen how the new and used leather belts acted under the tensile test. It will be noted here that at the beginning the used belt showed less elongation per increment of load than did the new belting. This, too, is very likely due to the stretching of the used belt during the 250-hour run. It is also noticeable that after the load reached 800 pounds on each belt the new belt seemed to stretch uniformly with the loading, while the used belt began to stretch at a slightly increasing rate. In all probability this is due to the moisture and the oil absorbed by the used belt and the soften.- ing of the fibres. It will be remembered at this point that the cross-section of the used belt had decreased about 3.31 during the 250-hour run. This reduction, of course, would tend to weaken the belt. This is shown by the ultimte strength which was only 2223 pounds, or 3170 pounds per square inch of cross-section. This shows a decrease in ultimte strength of about 38.7%. 11 It will be noted further that at a load of 2000 pounds the used belt stretched 12.4%, while at the same load the new belt stretched 11.5%. This is probably due to the fact that the used belt was approaching the breaking point and was beginning to show signs of failure. There seemed to be considerable irregular- ity in the breaking loads of the samples of used leather belting. This could be due to the non-uniformity in quality of the various strips used to make up the belt. COLEABISON OF THE PERFORMANCES OF RUBBER AND IEATHER BELTS IN TENSIIE TEST. . The curves show that the elongation of the leather belt before and after use are respectively about the same as those of the rubber belt before and after use. The figures for the breaking stress show that for new belting leather is about 20.8% stronger than the rubber. For used belting the rubber is about 14% stronger than the leather. This last statement is not in all likelihood true in all cases, because of the variation in quality of the various strips that are used to build up a belt. BRIEF SUMMARY OF RESUIEI'S CIBTAINED THROUGHOUT THE TEST. Considering the performance of the belts during the horse-power slip ,tests and the results as shown by the curves the 12. leather belt delivers from 8 to 25% more horse-power at the higher speeds than does the rubber without slipping off the pulleys. Very likely this is due to the absence of marked deterioration of the surface of the leather belt. Of course, the driving properties of a belt depend to a.very large extent on the condition of the surface in contact with the pulleys. Increased diameter of the pulleys will, of course, increase the arc of contact. This will, in turn, decrease the slip and increase the horse-power transmission. (See articles by the Leather Belting Exchange Foundation, 3-13 by B. 1'. Jones.) After the use on the 250-hour run the leather belt showed no very noticeable signs of deterioration other than slight peeling at the Joints. However, on closer investigation the leather belt showed that some parts of it were narrower or thinner or both. These were parts which.were not of quite as good a quality as the othes parts, the belt being made up of strips cemented end to end. During common use when such.places occur and finally break they are out out and new pieces are cement- ed in place. It might be well at this point to suggest that a cement pliable as well as waterproof be used by belting manufactur- ers for Joining the parts of leather belting. This will eliminate cracking and peeling to a large extent and will add strength and life to the belting. 13. The rubber belting showed that the rubber on its surface had become spongy and sticky. This condition, of course, increases the slip considerably and cuts down the horse-power and transmitting qualities. This spongy surface on the belt rubbed off very easily exposing the cotton fabric. With the fabric exposed the belt would wear rapidly and would slip more. The fabric would also be subject to disintegration due to mildew or rot brought on by the moisture and the heat. If the oil gets into the rubber between the layers of the fabric the belt will soon become useless due to the loosenp ing of the layers with respect to each other. Some rubber belting manufacturers warn belt users not to allow oils to come in contact with rubber belts because the oil destroys the rubber used in making the belt. The leather belt showed.a little more stretch during the 250-hour run than did the rubber. This, however, is not a serious fault for belts can.be shortened or tightenede'used to take care of the increase in length. The tensile tests show that for loads up to many times the regular working loads both.kinds of belting show nearly the same amount of stretch. Going still further with the loading ‘until the breaking point of the belts was reached.we find that the leather belt showed a greater drOp in ultimate strength than did the rubber as shown by the figures previously given on 14. pageslo and 13-. During the horse-power slip tests the used leather belt was working under a stress of only 370 pounds per square inch as compared to a stress of 3170 pounds per square inch at rupture in the tensile test. This gives a factor of safety of nearly 9. It is very seldom in practice that belts are run at a tension of 370 pounds per square inch, so the factor of safety of 9 is very good. CONCLUSIONS. The so—called waterproof leather belting transmits 8% to 25% more power than the rubber under the same conditions after the 250-hour run. The surface of the rubber belting deteriorates such more rapidly than does the surface of the leather belt in the presence of oil, moisture, and high temperatures. The life of leather belting is evidently mich greater than that of rubber belting when operating under conditions as present during this test. While leather belting costs about 50% more than rubber belting it can easily be repaired in worn places and when no longer usable for power transmission it has a salvage value for other purposes. This salvage value mist be credited to the I leather belting. Considering the above statements, there seems to be 15. conclusive reason for recommending waterproof leather belting rather than rubber belting for use under conditions where the relative humidities and temperatures are high and oil vapors are present. 0n the following few pages in the form of an appendix is a composite summary of results and conclusions taken from the report of Dr. E. D. Wilson, B. Sc., Ph.D., of Mellon Institute of Industrial Research of the University of Pittsburgh to the leather Belting Exchange, and from the foregoing work of the writer. This smmnary, the writer believes, should be an aid in selecting belts for packing houses or similar use. A.COMPOSITE SUMMARY OF.RESULTS AND CONCLUSIONS OBTAINED EEC“ TESTS ON IEATHEE AND RUBBER BELTING TO DETERMINE WHICH IS THE BETTER FOR POWER.TRANSMISSION UNDER CONDITIONS SUCH AS ARE FOUND IN THE PACKING INDUSTH . PREFACE. Statements in this summary are taken from the report of Dr. E. D. Wilson, B.Sc., Ph.D., of Mellon Insti- tute of Industrial Research of the University of Pittsburgh and from.the results of the tests by the writer made on waterproof leather belting and rubber belting as recorded in the foregoing pages. The object of this summary is to combine in a few paragraphs the important facts and results, obtained from the reports and tests above-mentioned which will aid in choosing between leather belting and rubber belting for use in the packing industry or similar use. In this summary substitutes for leather other than rubber are not considered. The writer claims no credit, whatever, for any- thing in this summary which has been taken from Dr. Wilson's report. Dr. Wilson has made many tests with excellent facili- ties and his results and conclusions are such as can be depended upon and should bear considerable weight when making decisions regarding the choice of belting for the purpose of transmitting power. He found that rubber belting as well as other substi- tutes for leather belting could not transmit power when slipping more than.0.5%. He brings out the important point that there is a definite limit to the ability of substitute belts to transmit power and that this limit is far below the safe carrying capacity of leather belting. He says, ”The only place where a gum, rubber, or canvas belt could possibly be successful is where the power to be transmitted is not more than 60% of the rated capacity of a leather belt of the same size." . It is also brought out in Dr. Wilson's tests that the rubber on the pulley side of the rubber belts wore off very quickly exposing the fabric and destroying the waterproof qualities of the belting. The writer, also, found that the exposure of the rubber belting while in use to oil vapor and moisture at high room temperatures caused a very marked deteriorating effect. The rubber on the surface of the belting became spongy and very plastic. In the horse-power slip tests made it was observed that this condi- tion of the surface of the belting increased the slip. This Cur- face soon began to wear off, thus exposing the fabric to the pulleys. 2. The leather belting running under the same conditions showed no marked signs of deterioration on the surface. It is the condition of the surface of the belt that is an important factor in power transmission for slip is due largely to surface conditions. If a belt slips, the effective pull per inch is de- creased. Dr. Wilson says, ”The real ability of a belt to trans- ndt power can be measured by the number of pounds of effective pull per inch of width, which it is capable of developing.I From.his tests be worked out the following figures for pounds of effective pull per inch of width with an initial tension of 60 pounds per inch, leather belting 87.5 and rubber belting 28.5. These figures show at a glance which belt has the better power transmdtting capacity. To the writer, very interesting and convincing state- ments of Dr. Wilson regarding the above findings are brought out in the following paragraphs quoted from his report. "Since,'in actual practice, a belt is compelled to work 'under varying loadpconditions, it is desirable to use a belt which has the greatest power of adapting itself to rapid and wide fluctua- tions in load. That leather belting possesses this ability, to indeed a remarkable degree, was clearly showh in the tests described by measurement of the arc of contact. When the load became heavy, the leather belts, by reason of their elasticity, hugged the pulleys, OJ and the top strand sagged down, thus giving a greater are of contact. "In the case of leather belting, the arc of contact increased from.180 degrees at no load to as high as 200 degrees at full load. The substitute belts including rubber were all deficient in elasticity; they were, in fact, unable to prOper- ly hug the pulleys. The are of contact on the case of substi- tutes never exceeded 185 degrees. ”Any comparison between two belts as to price should take into account their relative abilities to transmit power, as well as to consider probable life, etc. To illustrate: In comparing the price of leather and substitute beltings the price per foot is not a fair basis but rather the price per foot per horse-power.“ ‘ Using the above method of comparing prices of the two kinds of belting considered in this report Dr. Wilson found that on the basis of 1917 retail prices the rubber impregnated belt- ing cost 2.21 times leather belting. There can be added to this statement the fact that leather belting when no longer usable for power transmission has a salvage value, while rubber belting has practically no value when it has become worn out. This salvage value, of course, must be credited to leather belting, thus decreasing the ultimate cost of leather belting. Tehsile tests by the writer on rubber fabric and water- 4. proof leather belting showed that the percent of elongation per increment of load of the two belts were not at so great a variance. Testing for ultimate strength or breaking strength it was found that new rubber belting is about 83%.as strong as leather. The writer found, too, that while running the rubber belt exposed to oil and moisture at high room.temperatures there was an increase in thickness due to the fibres soaking up moisture and the rubber becoming spong fro. oil. One function of the rubber surface on rubber belting is to make the belt waterproof. The above statement of the con- dition of the fabric shows that the waterproof quality of the belting hai disappeared. It is probable that shortly rotting of the fabric would occur. 5. CONCLUSIONS. From Dr. Wilson's tests we have conclusive proof that rubber belting can not replace leather belting for power transmission under normal conditions where efficiency, life and cost are considered. From.his summary we have, concern- ing leather and rubber belting, the following. "Leather belting will stand a very heavy overload while rubber will not. The effective pull per inch of width for leather belting is more than three times that of rubber belting. Leather belts require less tension than do rubber belts to transmit the same power. On the basis of four-inch belts the horse-power per foot cost of rubber belting is nearly two and one—quarter times that of leather. Leather has a high degree of desirable elasti- city and hence is able to enlarge its arc of contact upon sudden increase of load. Rubber belting is deficient in this respect." The writer finds that leather belting under conditions of eXposure to oil vapors and high temperatures and humidities shows a greater horse-power transmission than does rubber belt- ing. He also finds that there is much.more surface and interior deterioration on the part of the rubber belting when used under the above conditions. Considering all the statements by Dr. Wilson and the findings of the writer as stated in the foregoing pages, there seems to be no doubt but what leather belting is better than rubber belting for power transmission in al— most any place, including the meat packing industries. 6. .0.’ -_sl—Vm-.‘:-~ -...xA—Q? BIBLIOGRAPHY. "Study of the Various Types of Belting", by E. D. Wilson, Leather Belting Exchange, June 14, 1919. "Report of the Proceedings of the Educational Sessions“, Nov. 1922, Leather Belting Exchange. "Power Transmission by Belts", by H. W. Swift, "Engineering" (London, England), Vol. 146, No. 3802, Nov. 1923. "Finding Best Belt for Severe Driving Conditions", by W. Staniar, Industrial Engineering, Vol. 86, Nov. 1928. “Belts and Belting—Slipping", by T. Nishikara, Society of Mechanical Engineers, (Tokyo) Vol. 81, No. 138, Oct. 1928. "Leather Belts and.Belting, 'Testing' The EaughtOQMeter, "Black and Whitefl (Textile Ed.) Vol. 2, No. 1, Dec. 1928. "Power Transmission by Belts“, by C. A, Norman and G. N. Moffat, "Engineering" (London), Vol. 126, No. 3285, Dec. 28, 1928. "Power Transmitted.by Leather Belts", by W. W. Nichols, Ameri- can MaChinist, 68: 347, Feb. 28, 1928. I'Power Transmission by Belts", by H. .. Swift, Engineering (London), Vol. 126, No. 3280, Nov. 23, 1928. "Power Transmission by Belts", by H. W. Swift, Machinery Market (London), Nos. 1466, 1467, 1468, Dec. 7, 14, 21, 1928. ”Power Transmission by Belts", by B. W. Swift, Mechanical World (Manchester, England), Vol. 84, Nos. 2189, 2190, Dec. 14, 21, 1928. "Power Transmission by Leather Belting", W. Stainar, Industrial Engineering, Vol. 87, No. 2, Feb. 1929. "How Temperature and Humidity Affect Leather Belting", Power Transmission, Vol. 34, No. 3, Mar. 1929. ‘ ”fa-1* ' .4 r.“ ROOM on: may 35m”- . ti. - i- ... 1.2.2.3 ..d-uvuv. . n ...W S m R A MIG U.|I- 6 YHB H" 8'17 R E 5 V 0 MIA...» Ulllllo ml3 A 9 le Sllal ~l A 3 m H m M . fie. v... .‘tti «38$ -.. ..br f.?‘ .8..|‘ .038.“ . ...a mum... .- .....v..W...,. \ I'M. . c-4PeM