Thursday, May 11, 2006


More on Involute Gears...

This afternoon I decided that I was being silly. I was eventually going to manage to write a script to do involute gears. What was the point, though? It's already been done many times. With that thought in mind I started web surfing.

Finally found a description of how to do it that was orderly enough for my retarded mind and complete enough to give us some good results at the University of LuleƄ engineering department website.

It was written in something that's about half-way between BASIC and FORTRAN that look like some antediluvian scripting language. Lord only knows what it is. Anyhow, the formulae are clear enough except that their trig functions actually take in angles in degrees instead of radians. :-0

I've got it all in a VB.NET module and am in the process of debugging it using their rather good drawings as a reference. It creates a half-tooth section. You put as twice as many of them together as there are teeth and you have your profile. It's going to make a tight little script in Java, I think.

Hah! The numbers just clicked! They look like the drawing and all the corners hook up save one. Looking good! :-D

Sounds like you're getting somewhere.Soon I might actually be able to print the thing, so a Wiki entry would be nice :)

Vik :v)

Sure thing. I found it in one of their student CAD workbooks. Here you go.

Makes me nostalgic for the time I was a research professor at Lund's University. :-)


I'm going to get all the bugs worked out in VB.NET and address the problem of designing meshed gears, then write an AoI plug-in using your cog plug-in as a starting point. I figure I should have it done this weekend at the latest unless something really untoward happens.
Oh yeah, I got the last bug out of the original code sorted out last night. There was one little factor in one of the equations with units in degrees that I'd missed seeing when converting degrees to radians before plugging it into a VB.NET trig function. That closed the last open end on the tooth segment.

About the only thing that they don't do that I've seen in other methods is do a fillet for the corners at the bottom of the tooth. Is that important, do you think?
I think the fillet at the bottom of the gear tooth is for stress relief, because sharp corners crack first. Must also help with machining and casting gears in assorted materials. I don't know if this would matter much at this point in this project...

Looks pretty good so far!
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