- Project No 7 You Are Asked To Design A Three Stage Gear Box With Helical Gears Which Will Be Driven By An Electrical M 1 (42.98 KiB) Viewed 20 times
- Project No 7 You Are Asked To Design A Three Stage Gear Box With Helical Gears Which Will Be Driven By An Electrical M 2 (64.48 KiB) Viewed 20 times
d) Check bending factor of safety and wear (contact stress) factor of safety for the pinions and gears with the selected design parameters. You are free to select any material type for pinions and gears but you are encouraged to use material grade 17CrNiMo6 (EN 10084 in carburized and hardened condition with hardness of 430 HB) for pinions and 20MnCr5 (EN 10084 in carburized and hardened condition with hardness of 400 HB) for gears. (Values for Grade 1 should be considered, and factor of safeties greater than unity are acceptable. You are also free to select different material grades for each pinion shaft and gear.) e) Calculate magnitudes of forces and moments on each shaft and show their directions with sketches 1) Draw shear force and bending moment diagrams in both planes for each shaft. 9) Calculate the minimum diameters by Von-Mises and Modified Goodman criteria for each shaft and each critical point considering that pinions are integral with the shaft and output shaft material grade is also the same with the other shafts Safety factor for the shafts should be greater than or equal to 2.5. (Marin factors and stress concentration factors should be calculated according to your design) Compare the calculated shaft diameters, where the pinions are, with the selected pinion design parameters, and make necessary adjustments for the selected design parameters, if required. (Take Su values for 17CrNiMo6 and 20MnCr5 as 1700 MPa and 1500 MPa respectively.) h) Select shaft diameters by rounding the minimum calculated diameters to the next multiple of 5 mm size or to any suitable diameter considering good engineering, fabrication, installation, etc approaches. Then, calculate the required key lengths for ISO metric key sizes for gears by using material grade for keys with less strength than the gear and shaft material Consider that the calculated key lengths should be compatible with the gear of gear hub widths. (Use safety factor of 2 for key calculations and take K - 1.0 and S, SS, 1) Select appropriate anti-friction bearings for each shaft either by using "SKF Online Catalogue or by manual calculations. Show at least one bearing selection calculation manually. The minimum required bearing life is 20000 hours D Use KISSsoft software to check and verify your manual calculations. Compare the results and make discussion about the differences between the results, if there is any k) Prepare general layout drawing for the designed gear box in plan view as if its top cover is removed. Indicate all important dimensions (like overall dimensions of gear box, widths and pitch diameters pinions and gears, diameters and lengths at each part of the shafts, dimensions for key lengths and locations on shafts, etc.) and information (like number of teeth, module, helix angle and direction of gears, type of bearings, material grades for pinion/shafts, gears and keys, size of keys, etc) on this drawing. Take necessary sections, where required and partial details should also be given where required. Tolerance, shoulder diameter requirements for bearings, etc. should also be taken into account for preparation of this general layout drawing. 1) Prepare workshop drawings at least for one gear, one shaft with pinion one spacers, one cover, etc. and prepare hand sketch for casing of the gear box For preparation of workshop drawings all technical drawing rules should be taken into consideration and necessary dimensional, surface roughness, tolerance, filet radius, chamfer, etc. information should be indicated, where required, in order to give necessary and sufficient information to fabricate these parts with these drawings