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Refer to your solution to Probs. 15-1 and 15-2. If the pinion core hardness is 300 Brinell, use the relations from Prob. 15-7 to determine the required hardness of the gear core and the case hardnesses of both gears to ensure equal power ratings.
15-1 An uncrowned straight-bevel pinion has 20 teeth, a diametral pitch of 6 teeth/in, and a transmission accuracy number of 6. Both the pinion and gear are made of through-hardened steel with a Brinell hardness of 300. The driven gear has 60 teeth. The gearset has a life goal of 109 revolutions of the pinion with a reliability of 0.999. The shaft angle is 90°, and the pinion speed is 900 rev/min. The face width is 1.25 in, and the normal pressure angle is 20°. The pinion is mounted outboard of its bearings, and the gear is straddle-mounted. Based on the AGMA bending strength, what is the power rating of the gearset? Use K0 = 1 and SF = SH = 1.
15-2 For the gearset and conditions of Prob. 15-1, find the power rating based on the AGMA surface durability.
15-7 In straight-bevel gearing, there are some analogs to Eqs. (14-44) and (14-45) pp. 766 and 767, respectively. If we have a pinion core with a hardness of (HB)11 and we try equal power ratings, the transmitted load Wt can be made equal in all four cases. It is possible to find these relations:
| Core | Case | |
| Pinion | (HB)11 | (HB)12 |
| Gear | (HB)21 | (HB)22 |
- (a) For carburized case-hardened gear steel with core AGMA bending strength (sat)G and pinion core strength (sat)P, show that the relationship is
This allows (HB)21 to be related to (HB)11.
- (b) Show that the AGMA contact strength of the gear case (sac)G can be related to the AGMA core bending strength of the pinion core (sat)P by
If factors of safety are applied to the transmitted load Wt, then SH =
- (c) Show that the AGMA contact strength of the gear (sac)G is related to the contact strength of the pinion (sac)P by
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Chapter 15 Solutions
Shigley's Mechanical Engineering Design (McGraw-Hill Series in Mechanical Engineering)
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