Addendum modif. coefficient vs Base Tangent Length

[[Wo...]]

Hi,

I'm trying to create geometry of an external spur gear with this table:

The problem is that I cannot get the addendum modif. coefficient to match with base tangent length:

How would I approach this to create a geometry matching the requirements?

Second question - the Gear Tooth quality requires DIN 3961 - but in the list of available specs I can see only 3962 - is this the one to use?

Third question: the "Two flank working deviation" - is there a way to measure it with Gear Pro Basic? I cannot find it anywhere to choose from in "tolerances/characteristics"

Any help is appreciated.

Thanks,
Wojciech

[[Ch...]]

Wojciech,

The gear data block looks like classic copy/paste, and I would say the Engineers are not real sure of themselves or just didn't do a great review, etc.

Example : spline data/pressure angle. The 20° pressure angle is correct for a gear, but the "spline data" does not pertain to this gear and probably shouldn't be on the line with pressure angle. Same for tooth 'trace' Fß. This is normally called 'helix' or 'lead'.

At any rate to help answer your questions :

1.) For addendum modification, perhaps they also did not calculate data well - I have seen this many times on drawings. What I would suggest is : base tangent is more of a function of pitch/module and pressure angle. The Adden. Mod. CoEf "x" is more important in my opinion for tooth shape and profile nominal calculation and the Ff profile tolerance. As long as this is correct in your Gear Pro geometry I think that is best way to go.

The base tangent length can be 'measured' and reported in pitch :
.


2.) DIN 3962 should be fine. You already have most of your tolerance in data block, so you may be able to use "user-defined".

3.) The "Fi" 2 flank working deviation is : the difference between the maximum and minimum values of the working center distance, which occurs during a double flank composite test. This is for roll testing with a master gear, not for Gear Pro any version.

Good luck let us know if you have more questions.

Thanks,

Chris

[[Wo...]]

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This was something that worried me - which one to follow to have the right geometry. I will go with that and probably have to contact the customer to confirm.

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Thanks for that. I knew I could modify the values somewhere without affecting the geometry itself

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This one I will definitely need to contact the customer as this is one of their "Key" dimensions.
I am not sure it even can be checked by rolling as this is a gear section with just 110 degrees of a circle.

Sorry if any questions seem silly - I'm completely new to gears as we do not machine them here - I was just tasked with checking stuff from the suppliers.

Thanks for the help Chris!

[[Ky...]]

Hello Wojciech,

Just to add to what Chris said, I did find a gear calculator online that can take the gear geometry you are given and give out what the span distance should be. Plugging in the values that you were given, it agrees with Calypso, at least up to the relevant number of significant figures. If you get some pushback on it, at least now its a 2 against 1 situation with Calypso agreeing with the 3rd party calculator.

https://evolventdesign.com/pages/gear-span-calculator

Hope that helps.

[[Wo...]]

Thank you Kyle! This is also super helpful - I was fighting with this discrepancy the whole day.

[[Ch...]]

You are welcome.

Wow sector gear as well huh ?

Yes sector gears can be roll tested - I think I have roll checked one many years ago - requires special fixturing obviously.
in theory it can be done

.Good luck.

Chris