Addendum Modification Coefficient

[georgejetson]

What is the difference between generating rack (profile shift) and addendum modification coefficient. does anyone know of any good books or publication on this subject?

Thanks

 

[israelkk]

Profile Shift in External Parallel-Axis Cylindrical involute Gears, Phillips D. Rockwell. GEAR TECHNOLOGY • NOVEMBER/DECEMBER 2001.

 

[dimjim]

The addendum shift and rack shift could be the same if
they are both specified as coefficients or if they are
both expressed in units of inches or millimeters.
Books dealing with long and short addendum gearing
or those with recess action gearing describe the reasons
for profile shifts if that helps.

 

[paulliu]

The following book is recommended:

"The geometry of involute gears" by John R. Colbourne, 1987,Springer-Verlag.

 

[JCJackson]

Nothing, but both should be expressed as undimensionable coeficients; i.e. refering to unit pitch (1 module or 1 DP) and in the same plane. An unqualified (transverse) add mod coef on a helical will always refer to the normal plane.

Maag Gear Book by Maag Gear-Wheel Company, Zurich Switz'
(paraphrases Swiss Std VSM 15525)
Gears by H E Merrit, pub' by Pitman
German standard DIN 3960 clause 2.5.4 and beyond.

Dudley (US) & Tuplin (UK) do not handle this subject well.

In my experience, US engineers I have worked with have been at best perplexed by the concept at worst frightened to death by it. There are limits as how far one can go defined by undercutting (-ve) & tip loading & pointing (+ve). Outside a fairly tight range in which slide roll ratios can be improved on non-unity ratios, capacity will be compromised. I've had to resort to case hardening where 250BHN sufficed on non-corrected gears. DIN 3960 fig no. 11 gives guidelines for practical limits. It does (& has) offer good solutions to many gear design problems.