How to find backlash between two spur gears

  • Thread starter Shady99
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  • #1
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hello i have two spur gears. i would like to know the backlash that i would be getting. How can i calculate backlash?
 

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  • #2
billy_joule
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My guess; You'd need full engineering drawings, find the angular play the tolerance stack up on the meshing teeth will cause. You'll also need to know the axis to axis tolerance.
 
  • #3
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My guess; You'd need full engineering drawings, find the angular play the tolerance stack up on the meshing teeth will cause. You'll also need to know the axis to axis tolerance.
so i will need data from OEM
 
  • #4
billy_joule
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That or measure the gears you have.
Seeing as you have the gears, why not just do a test?
 
  • #5
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That or measure the gears you have.
Seeing as you have the gears, why not just do a test?
how can i measure the angular play?.....gears are small like one is 80mm pitch diameter and the other is 247mm pitch of 1 module and 20 deg pressure angle
 
  • #6
billy_joule
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I'd lock the small gear, set a dial gauge on the large gear, near the OD and rock it back and fourth.
Why do you need to know anyway?
 
  • #7
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I'd lock the small gear, set a dial gauge on the large gear, near the OD and rock it back and fourth.
Why do you need to know anyway?
i am designing a turntable. i want to know the backlash so i can mention it in its design specs i.e. the system has this much backlash ,so that the end user knows it
 
  • #8
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An audio turn table?
Gears can/will produce a lot of noise. Any reason you're going with gears over the proven belt drive?

Ignore me if it's not audio related.
 
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  • #9
CWatters
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You can design out backlash. One way is to have two large gears on the one shaft, one fixed to the shaft and one free to rotate. A spring is fitted to rotate one relative to the other. The spring is compressed slightly before both gears are meshed with the smaller gear on the other shaft.
 
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  • #10
Baluncore
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If the contact angle is 20°, then one tooth is really a 40° wedge.
Hold the gears against each other. Measure the axial separation, Sclose. Then mount the gears in the final environment and again measure the axial separation, Sfar. Compute dS = Sfar - Sclose.
The backlash is proportional to the difference in separation, dS.
The coefficient of proportionality is Tan( 40° ) = 0.839
Backlash = dS * Tan( 40° )
 
  • #11
CWatters
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Backlash increases with gear wear so is there a warranty issue if it increases beyond the specified value within the warranty period?
 

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