How pick gears that will hold for given torque?

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    Gears Torque
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Discussion Overview

The discussion revolves around methods for selecting gears that can withstand a specified torque. Participants explore various approaches to gear selection, including considerations of gear specifications, ratios, and material properties. The conversation includes both practical advice and references to technical resources.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks a simple method for estimating gear selection for a given torque, expressing difficulty with complex methods.
  • Another suggests finding an off-the-shelf gear that meets the necessary specifications for the application.
  • A participant notes that the gear ratio and mesh configuration are critical factors, mentioning that torque distribution across teeth and gear dimensions affect performance.
  • One participant shares their experience of needing to select a gear with a larger modulus after realizing their initial choice was inadequate.
  • A technical question is raised regarding the interpretation of a formula for maximum tangential force on gears, specifically the meaning of the pitch factor K.
  • A later reply confirms the interpretation of K as DP raised to the power of 0.8.
  • Another participant provides a link to a comprehensive gear design guide, suggesting that issues with gear drawings may stem from CAD software quirks.
  • A participant expresses appreciation for the guide and shares a personal reaction to a related video advertisement.

Areas of Agreement / Disagreement

Participants express a range of views on gear selection methods, with some suggesting practical approaches while others delve into technical details. No consensus is reached on a single method or solution, and various perspectives on gear design and selection remain present.

Contextual Notes

Participants mention specific factors and formulas related to gear performance, but the discussion does not resolve the complexities of these calculations or the assumptions behind them. There are references to CAD software issues that may affect gear design accuracy.

Who May Find This Useful

Individuals interested in mechanical engineering, gear design, or those facing practical challenges in selecting gears for specific applications may find this discussion relevant.

Chevreuil
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Hello,

I was wondering if anybody could recommend a simple method to pick gears for a given task. I need to make a rough estimation to see if I'm off by more or less a factor of ten. The only method I have access to is very complex and hard to understand.

Cheers
 
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The easy method is to find an off-the-shelf gear that has sufficient specifications for the application you have.
 
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It will depend on the gear ratio and relative mesh configuration.
If the torque is countered by only one tooth then it comes down to the wheel radius and the size of the tooth as a short cantilever. Thicker gearwheels make a difference.
Give us some dimension and configuration specifications so we can be more specific.
 
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Thank you all, I ended up finding that my chosen gear was too weak, and I had to go for one with twice the modulus (i.e. with the cogs about twice as large).
 
http://www.hpcgears.com/pdf_c33/27.48-27.60.pdf

In this document, it is said that the maximum tangential force, in lbs of force, that a gear can take without succumbing to wear, is

(X_c * Z * S_c * F )/K

Where X_c, Z, S_c, F is a bunch of factors derived from the gears and their working conditions. K however, is described as "Pitch factor DP 0.8 power". What does that mean? Does this mean that K=DP^(0.8)? (exponentiation with the diametral pitch as the base and 0.8 as the exponent)
 
Yes it just means DP^0.8
 
This is a more comprehensive manufacturers guide to gear design :

http://khkgears.net/wp-content/uploads/2015/10/gear_guide.pdf

PS: I can't see anything wrong with the gear drawings that you Emailed . Your problem may originate in some quirk of the CAD program . Best thing to do is for you to draw your own gears to the supplied dimensions . Then you can be sure that you haven't got something silly like a scaling error from your CAD's interpretation of the downloads .
 
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Thank you very much! This guide looks great!

OT: Did you see their video ad? I'm getting really weird vibes from it, but it really gets the message delivered.
 

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