Gear Train horsepower calculation

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Discussion Overview

The discussion revolves around the calculation of horsepower and torque in a gear train setup for a basic mechanisms class. Participants explore the relationships between input horsepower, gear ratios, and resulting torque across multiple shafts in the system.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant states the input horsepower is 10 and rpm is 1750, and questions whether horsepower remains constant throughout the gear train.
  • Another participant explains that torque will change based on the gear ratios, noting that power in should be approximately equal to power out, with minor losses due to friction.
  • A participant seeks clarification on whether the calculated torque of 1028.6 in-lb applies to the entire second shaft or just the 40t gear.
  • One participant asserts that if the shaft connecting the 40t gear and the 22t gear is regular, the torque remains the same along the shaft, barring minor frictional losses.

Areas of Agreement / Disagreement

Participants generally agree that torque varies with gear ratios and that power is conserved with minor losses, but there is uncertainty regarding the specific application of torque values to the entire shaft versus individual gears.

Contextual Notes

Participants have not fully resolved the implications of torque distribution across the shafts and the impact of frictional losses on their calculations.

srkirkpatrick
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I am designing a gear train for my basic mechanisms class that consists of three shafts. The input horsepower is 10 and rpm is 1750. I calculated the torque of the first shaft to be 360 but I am not sure if the horsepower stays the same throughout the whole train or not. The first shaft has a 14t gear meshing witha 40t gear on shaft two. Shaft two then has a 22t gear meshing with a 48t gear on shaft three for an output rpm of 281. In order to calculate the torque and force per tooth of each gear do I just use the input horsepower? Thanks in advance for any help.
 
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The torque will be multiplied (or reduced) depending on the ratio of gears between the input and output. Except for minor frictional losses in the geartrain, power in should be approx. the same as power out. (Well-designed gear boxes usually have 2-3% loss).

For example, the first gear ratio is 40:14 or a ratio of 2.857 : 1. The input speed of 1750 rpm is slowed to 1750/2.857 = 612.5 RPM, and the input torque is multiplied to become 360*2.857 = 1028.6 in-lb.
 
So is the 1028.6 in-lb the torque for the entire second shaft (the 40t and 22t gears) or the torque for the 40t gear alone? Thank you!
 
Assuming that the shaft connecting the 40t gear and the 22t gear is a regular shaft, the torque will be the same along the length. Look at it this way, if the 40t gear makes one revolution, the 22t gear will also make one revolution. There is nothing between the two gears which will cause the torque to decrease, except for minor frictional losses in the shaft bearings.
 

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