Design and Development of Torque Testing Rig for a Gearbox

Transcription

1 Design and Developmen of Torque Tesing Rig for a Gearbox Amrua Lomae 1, Suhas ohie, and Rahul Shinde 3 1 echanical Deparmen, Bharai Vidhyapeeh, College of Engineering, Pune, aharashra Amu384@yahoo.co.in echanical deparmen, Gov. College of Engineering, Karad, aharashra 3 Execuive direcor, Cyclo Transmission Ld. Saara, aharashra mohiess@yahoo.com, cyclobox@rediffmail.com Absrac - Gearbox is an indispensae elemen of power ransmission drives of mos mechanical sysems. Therefore, i is very essenial o assure he performance of gear drives before hey are pu o use o ensure he rouble free funcioning of sysems. While esing performance of he gearbox, i is imporance o check he orque carrying capaciy a raed speeds. This work presens he design and developmen of a orque esing rig for kn-m capaciy carried ou for a gearbox having muli-plae brake sysem. While calibraion of orque esing rig experimenally measured daa is compared wih he heoreical calculaions and a good agreemen beween experimenal and heoreical calculaions is observed. Index erms Gear box, design, orque, calibraion I. INTRODUCTION Gearbox is an indispensable elemen of power ransmission drives of mos mechanical sysems such as vehicles, machinery and cranes, ec. The main funcion of he indusrial gear drive is o reliably ransmi orque and roary moion beween prime mover and driven piece of equipmen, a accepable level of noise, vibraion and emperaure. When one or more of he preceding operaing characerisics exceeds allowable limis, i can lead o failure of he gearbox. anufacuring companies or cusomers have o bear big cos and ime for he failure of gear drive sysem during operaion. Therefore, i is very essenial for he manufacurer o assure he qualiy of gear drives before hey are pu o use o ensure rouble free funcioning of sysems. While esing he performance of gearbox, i is imporance o check he orque carrying capaciy a differen speeds. A presen, Cyclo ransmission ld. does no have any orque esing faciliy. So o measure he orque; company has o rely on heoreical calculaions according o ISO (Inernaional Organizaion for Sandardizaion) and AGA (American Gear anufacurers Associaion) sandards o specify orque raings. Therefore, i is very necessary for hem o have a es rig for gearboxes o assure qualiy of he gearbox. Torque esing rig is an essenial faciliy ha every gear manufacuring company mus have. To fulfil above needs of he orque esing rig, a lieraure survey was underaken wih he view o finalize is feaures and specificaion. Differen ypes of orque esing rig available in marke are sudied. From above lieraure i is found ou ha each mehod has some advanages and disadvanages. For orque esing back o back, digi-orque and muli-plae brake sysems are sudied Ref. [1-3] For back o back arrangemen wo similar gear boxes are required, which may no be available in some of he cases. In digi-orque mehod he flywheel was used o apply he orque, which is no suiable for high orque measuremen. Boh hese mehods are no suiable for his applicaion. uli-plae brake orque esing sysem (orque applying) is suiable because i can provide wide range of orque (from 500 N-m o 10 KN-m) a differen speeds. The brake plaes are parially weed o avoid wear and conrol he emperaure of brake plaes. For acuaing muli-plae brake sysem, acuaors are needed. While sudying differen brake acuaors [4]., i was found ha hydraulic acuaor is suiable for applying he pressure for muli plae brake sysem, because i provides fas response along wih smooh engagemen by conrolling he rae of pressure buil-up wih a pressure conrol valve. By referring o he lieraure in he poin of orque measuremen, i was found ou ha caniser ype load cell can provide high orque measuremen because his load cell is suiable for high orque or load range and also eliminaes he need of prior checking [5]. Finally i is decided o design and develop a hydraulically acuaed muliplae brake orque esing rig for differen gearbox, maximum orque of 10 knm a raed speed. II. ETHODOLOGY The proposed sysem has muli plae brake assembly as a main and core componen. The assembly is mouned in beween he bracke and fixed on and around he shaf. Figure 1 Ouline of he proposed gearbox es rig 1

2 uli-plae brake sysem is used o apply he orque on he gearbox. For acuaion of he brake, hydraulic acuaor was used. Brake sysem is direcly coupled wih he gearbox wih he help of coupling or gear pair. As he shaf is coupled wih gearbox shaf, brake force is ransmied o he gearbox and a he same ime orque arm (orque arm is fixed wih brake assembly). Torque arm in urn exer he same amoun of force on load cell. To mainain normal emperaure of he brake plae, proper cooling sysem is designed. The oal sysem is divided ino following sub sysems, viz., A. Brake assembly B. Acuaion sysem C. Cooling sysem D. Torque measuremen and display uni III. DESIGN AND ANUFACTURING To design a orque esing rig for a gearbox is an innovaive idea. On he basis of he concepual design, he main sysem is divided in o a number of subsysems carrying ou specific funcions as follows. A. Brake assembly B. Acuaion sysem C. Cooling sysem D. Torque measuremen and display uni The overview of he es rig depicing differen sub sysems is as shown in Fig.. Where, is maximum orque, F is working force, Z is number of maching surfaces, µ is coefficien of fricion, D 10 is inner diameer of ouer brake plae and d i is ouer diameer of inner brake plae. Toal number of brake plae is 7. Shaf is basically designed for crushing, shear, orsional and bending ype of loading. aximum shear sress heory is used for deermining diameer of shaf because maerial of he shaf is ducile 16 τ = ( k ) ( ) 3 b b + k () π d Where, τ is maximum shear sress, d is diameer of shaf, k b and k are shocks and faigue facors respecively and b is bending momen. The minimum diameer of he shaf is 10mm. Acuaion Sysem The hand operaed hydraulic acuaor has capaciy of 0 bars is used. C. Thermal Calculaions and Design of Cooling Sysem In case of muli plae brake, hea dissipaion is he main problem. As he emperaure of oil increased above 90 0 C, oil does no obeyed is properies, because ha wear of he brake plaes will be akes place so o avoid such problem waer cooling jacke is provided. Torque easuremen and Display Uni For orque ransfer from brake assembly o he load cell, orque arm of 1000 mm was used. For orque measuremen caniser ype load cell of capaciy 000 kg is used wih digial display. Resoluion of ±0.1 kg-m in 100 kg-m is used. Afer design manufacuring and assembly is done as per drawings. The acual view of es rig is as shown in Fig. 3 Figure Overview of he designed orque esing rig A. Brake Assembly Brake assembly is he main par of es rig. During design of brake assembly, following procedure was followed. Selecion of maerials Ref. [6, 7], design and analysis of various componens like shaf, brake plae, pison, cylinder, orque arm, selecion of bearings, oil seals, and pison rings ec were done. Some of he imporan calculaions are shown below. For finding number of brake plaes required we used uniform wear crieria for brake plae design. Ref. [8, 9] 13 FZ ( D1 O + d i ) = µ (1) 4 Figure 3 Torque esing rig IV. EXPERIENTAL WORK In he experimenal work he se-up he es rig as shown in Fig.4 and by using he few gearboxes calibraion of es rig have been done in following way. The analyically deermined orques values were compared wih he measured orque values for differen models of he gear

3 box. The analyical and he experimenal readings are compared. Figure 5 Comparison of analyical and experimenal orque values Table I. Comparison of analyical and experimenal orque values 14 Figure 4 Schemaic arrangemen of he es rig for calibraion These resuls are given for differen pressure values ranging from bars o 0 bars. The calibraed measuremen unis (load cell, digial display and pressure gauge) are used. For finding heoreical value following equaion is referred. µ π Z ( D d ) ( D1 + d ) O i = 16 (3) Where, P h is hydraulic pressure, D is ouer diameer of pison and d is inner diameer of pison. The es rig can also be esed for duy cycle es of some of he gear boxes. V. RESULTS AND DISCUSSION The esing has been done on differen ypes of gearboxes, differen ypes of esing is done he resuls are discussed below. Calibraion of he es rig carried ou by comparing experimenal resul wih heoreical values. The es resuls of a few models are done, one is discussed below. 1. Gear box odel number ,[11]. Specificaions: Inpu power- 10H.P., Oupu speed r.p.m, Oupu orque Nm. Tesing was carried ou for 10 minues a differen consan pressure values and readings were observed afer every minues o allow for he sysem o ge sabilized. Torque, Nm Pressure, Bar Experimenal Torque, Nm Analyical Torque, Nm P h Sr. No. Pressure Experimena l Torque Analyical Torque Absolue error % Error I is observed ha he experimenal readings for orque are higher han analyical values by an absolue margin of Nm for he enire orque range. In erms of he percenage his accouns for approximaely 5 o 0.5%. Furher, higher error (5%) is observed a lower orque (and lower pressure) whereas, lower error (0.5%) is observed a higher orque values. The reasons for his error could be aribued o various causes ha are no considered in heoreical calculaions. The possible causes are menioned below. a) In analyical calculaion, fricion in he bearings, oil seals and oher moving pars is no considered. b) The esed gear boxes have a lower operaing speed (5-10 rpm) a such speeds he sick-slip phenomenon in beween he brake plaes is more significan, his could be one of he sources of he error. c) Ineria of he sysem. d) When he hydraulic pressure increases he fricion in he various pars increases. e) Errors in load cell readings. f) Errors in display uni. g) The error in he pressure gauge also he pressure indicaor is analogue display so he manual misake may be occurred. The obained resuls were compared o he heoreically calculaed and a good agreemen beween he experimenally obained and heoreically calculaed resuls were seen. The analyical and experimenal values are closely mached. A. Comparison of errors in experimenal values wih respec o orque

4 Inernaional Journal of Compuer Communicaion and Informaion Sysem ( IJCCIS) Torque, Nm % Error Afer calibraion of he es rig, i was found ha in he sysem here are hree ypes of error, error in load cell, error in brake assembly and error in digial display. Afer calibraion of es rig, oal error was deermined for each orque value, which is abulaed in he Fig Load, Kg % Error in load cell % Experimenal error Figure 6 Error analysis of orque esing rig While acual esing of he gearboxes, corresponding error facor should be added in he experimenal readings. Gear box was esed for 10 minues. Reading was observed for every wo minues and average orque reading was aken, which is shown in below Table. Table Tess conduced on he differen models (oupu orque) Sr. No odel No Acual orque Experimenal values Oupu speed oupu orque 940 Nm. Figure 7 Comparison of analyical and experimenal orque readings wih ime Ti me,mi nu e From above graph i was observed ha he orque value is flucuaing in-beween 936 o 941Nm wih respec o ime. Tha variaion is negligible (approx. 0.5%). C. Relaion beween power and oule emperaure Temperaure is an imporan parameer while calibraing he es rig, because if he oil emperaure is increased beyond 90 0 C, he lubricaing oil will lose is properies and rig will no work efficienly. Cooling jacke is used for hea dissipaion purpose. Waer is used as a coolan. The mass flow rae of he waer was aken as 9.5 li/minues. 0 C Tempraure, Inle Temperaure Oule Temperaure Inpu pow er (HP From he above able, i was observed ha all he gear boxes are successfully running for oupu orque a given speed. B. Duy cycle es For he gearbox, i is necessary o carry ou he duy cycle es. One such resul of he duy cycle ess conduced on gearbox is presened in Fig.7. The gear box model wih an oupu speed 5.4 rpm and Figure 8 Comparison of emperaure and inpu power a differen models I is observed in Fig. 8 ha as he inpu power increases he emperaure values also increase seadily. XI. CONCLUSION Design and developmen of hydraulically acuaed muli-plae brake sysem is carried ou for measuring orque on he gearbox. Sysem is designed for measuring orque from 0.5 knm o 10 knm a raed speed. The es rig is calibraed wih heoreical values. During calibraing of he sysems, i is found ou ha he maximum error in he measured orque using he es rig is abou 50 Nm (carried ou on few gear boxes using he es rig and he resuls are in good agreemen wih he heoreical values. The es rig can also be used for peak load es and duy cycle es of some of he gear boxes. Temperaure of cooling waer is measured and i is found o be well wihin he acceped limis. The overall performance of he es rig is found o be rouble free. XII. ACKNOWLEDGENTS 15

5 The auhors wish o hank Cyclo ransmission Ld., Saara for providing no only an opporuniy o work on his projec bu also providing all he echnical knowhow and pracical experience in he facory as well as in he design office. XIII. REFERENCES [1] Waler usial, Dynamomeer es bed, Naional renewable energy laboraory wind echnology cener, 001, pp. 1-3 [] Auomaion Technology -oor Tesing Sysem brochure (TS 3800), Theory of Digiorque Opraion,Dayon,Ohio 00, pp. 1- [3] Paul G. aring And Nick J. Colarelli, Low Speed Plae Brake Teser, SAE echnical paper series , 007, pp. 5-8 [4] Power ransmission producs fundamenals Power ransmission design magazine 1997, pp. A136-A141 [5] Transacion in measuremen and conrol, a echnical reference series brough by Omega vol-3 Puman Publishing Company and OEGA Press LLC.1998,pp [6] Bauccio. AS eals Reference Book 3 rd ediion, AS Inernaional, aerials Park, OH, [7] Harvey P. D. Engineer Properies of Seel, American Sociey for eals, eal Park, OH, [8] V. B. Bhandari, Design of machine elemens Taa cgraw Hill, Second ediion-008, pp. 8-90,33-385, [9] Harvey P. D. Engineer Properies of Seel, American Sociey for eals, eal Park, OH, [10] Joseph E. Shigley, echanical engineering design, Taa cgraw Hill, Sixh ediion, 006, pp , [11] Cyclo planeary and cycloidal drives anuals, Cyclo Transmission Ld. ediion 006 pp