How to find backlash between two spur gears

[Shady99]

hello i have two spur gears. i would like to know the backlash that i would be getting. How can i calculate backlash?

 

[billy_joule]

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.

 

[Shady99]

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

 

[billy_joule]

That or measure the gears you have.
Seeing as you have the gears, why not just do a test?

 

[Shady99]

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

 

[billy_joule]

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?

 

[Shady99]

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

 

[RNickl]

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.

 

[CWatters]

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.

 

[Baluncore]

If the contact angle is 20°, then one tooth is really a 40° wedge.
Hold the gears against each other. Measure the axial separation, S_close. Then mount the gears in the final environment and again measure the axial separation, S_far. Compute dS = S_far - S_close.
The backlash is proportional to the difference in separation, dS.
The coefficient of proportionality is Tan( 40° ) = 0.839
Backlash = dS * Tan( 40° )

 

[CWatters]

Backlash increases with gear wear so is there a warranty issue if it increases beyond the specified value within the warranty period?