22nd DANUBIA-ADRIA Symposium on Experimental Methods in Solid Mechanics September 28 - October 1, 2005 MONTICELLI TERME / PARMA - ITALY EXPERIMENTAL ASSESMENT OF BEVEL GEARBOXES Ass. Prof., Ing. Vojtěch Dynybyl, Ph.D., Ing. Pavel Mossóczy, Ing. Zdeněk Češpíro FME CTU in Prague, Technická 4, 166 07, Praha 6, Czech Republic Introduction Theoretical base An experimental evaluation of two bevel gearboxes has To compare a couple of similar gearboxes an exact been arranged to compare them. Two parameters methodology of measuring has been designed. efficiency and lost power have been determined to Conditions of experiments has been determined exactly discover damage of gears. Parameters of gearboxes are too. power – 2,5 kW, speed – 1200min-1 and ratio – 3. To compute lost power using SW, two values has been measured: input torque Mk1 (pos. 4) and speed n1 Arrangement of measuring station (pos. 6). The output torque transducer has been Fig. 1 shows block diagram of measuring station disassembled. Computing equation of lost power is: arrangement. M k10 .n1 PZ 0 = [kW] . (1.1) 9550 Oil temperature, surface temperature and ambient temperature have been measured to complete energy information of gearboxes. Since both gearboxes are arranged with tapered roller bearings preload of them was desirable. It causes high temperature and high lost power. This preload has to be realized to fix forces of bevel gears. Preload of mechanisms influenced the transfer of power. Efficiency of this transfer shows quality of both machining and assembling of gearboxes. It is an important parameter of all gearboxes. Supposing constant ratio i12, efficiency can be calculated using SW formula: M k2 η= , (5.3) M k1 .i12 where Mk2 is measured output torque. Data acquisition and data processing is done with Fig. 1 Block diagram of measuring station arrangement graphical programmable software LabVIEW. Basic measuring station consists of these Results of measurement equipments and devices: Table 1 shows result of measurement of two gearboxes 1. Measured gearbox, A and B left and right rotation. Gearbox B is two times 2. driving asynchronous electric motor, higher preload than A one. 3. braking asynchronous electric motor, 4. input torque transducer (HBM T20WN), Mk1 [Nm] Pzo[W] 5. output torque transducer (Vibrometer 100Nm) 6. angle encoder of driving motor, A-Pz-L 0,68 85 7. angle encoder of braking motor, A-Pz-R 0,71 89,5 8. sensor of oil temperature and surface B-Pz-L 1,26 167 temperature, B-Pz-R 1,36 170 9. ambient temperature sensor, Table 1 10. electrical device of out put torque transducer, Fig. 2 shows results of measurement of gearbox A 11. frequency inventor of braking motor, rotating left. Different preload of bearings corresponds 12. frequency inventor of driving motor, to higher difference of power lost. 13. PC Fig. 2 An example of lost power measuring Fig. 3 An example of efficiency measuring An example of measuring (gearbox A rotation left) is Comparing this value with difference of lost power we documented in fig. 3. Table 2 includes results of can see that the preload influence efficiency is less, if measured efficiency [%] of gearboxes A and B, load of gearbox is the highest. rotation left and right. Increasing load of gearbox the efficiency increases. Conclusions Load A_L A_R B_L B_R The goal of research was to determine cause of 50% 87,2 86,6 76,7 82 pitting of gear. Solution was surprising. However the efficiency of gearbox A was higher, the gear of that 60% 89 88,2 81,5 86 one was damaged earlier than gear B. It has been 70% 90,2 89,5 84,5 87,5 probably caused by lower quality of machining of gear 80% 91 90,4 86,3 88,7 and axial vibrations of input shaft. Preload of them did 90% 91,7 91,2 87,9 89,6 not exist and the clearance in tapered roller bearings 100% 92,6 92,8 89,3 91,5 has been detected. Table 2 References  Dynybyl, V. - Chysky - Mossóczy, P. – Novák, J. – Žák, P.: Experimental Analyses of Bevel Gearbox 25, kW. Research report. CTU in Prague, Prague 2004.  Dynybyl, V.: Evaluation of Machine Drives Using Simulation and Experiment. In: 19th Danubia-Adria Symposiumon Experimental Methods in Solid Mechanics-Abstracts. Warsaw : Warsaw University of Technology, 2002, p. 30-31.  Dynybyl, V. - Chyský, J.: Equipment for Testing Fig. 4 Summary of results and Measurement of Elektromechanical Rotary Drives. In: SEKEL 2002. Trenčín : FM TnUAD, 2002, p. 48- Summary of results is graphically realized in fig. 4. 50. ISBN 80-88914-73-6. (in Czech). Percentage difference of efficiency of both gearboxes This research has been supported by MSM grant is only 3,3, when load is 100%. No. J04/98:21200008.
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