Help decoding old term "Involute tooth thickness scaling factor" Ct

[mhc190]

I've been working on an involute sprocket (hobbed like a gear, but used with rocker joint inverted tooth silent chain) and gotten horribly stuck on the terminology in a journal article that I've been using to help guide the design process.

Specifically it declares the variable: Ct(j)
where (j) refers to the sprocket in question and t is subscript
and Ct is described as "involute-tooth thickness scaling factor" in the variable declarations and in the text as "The parameter, Ct(j), is a scale factor for the sprocket tooth thickness at the pitch circe with Ct(j)=0.5 corresponding to the AGMA gear standard."

I've dug through AGMA 913- A98 and ANSI/AGMA 1012-G05 but can't find any reference to the term.

The references for the article omit the name and/or number of the AGMA standard listed in the text quoted above. It does cite the primary author's doctoral dissertation, from which the article was adapted, but I don't have access to it (anyone at Columbia?).

The article reference is:

Kinematic and static force analysis of rocker-pin jointed silent chains with involute sprockets
BUCKNOR, N. K. and FREUDENSTEIN, F.
Journal of Mechanical Design, Transactions of the ASME
Vol 116, September 1994 p842-8

I sincerely appreciate any help or advice!

Thanks, mike

 

[michellepace]

Hi Mike,

Although I can not guarantee if my answer is correct, it sounds to me as though they are talking about an "addendum correction factor".

An addendum correction is also known as "profile shifting", perhaps that is more familiar to you.

When manufacturing a gear, the gear cutter may be fed in or out to make a size change. This shift will make a correction to the addendum of the gear being cut. What this actually does is make the teeth thicker or thinner, at the standard pitch circle (i.e. the gear reference circle).

I've attached a screen shot of a 'collage' picture I made when trying to understand addendum corrections for myself. Perhaps it may be of help to you.

http://michellepace.com/temp/addendum-correction.png

Cheers, Michelle