GT and GM numbers not the same

[philbur]

Here's the gear profile generated by GT overlaid on the gear profile from another source. The root width meaures 0.800 so the profile looks to be correct but it seems that the tool diameter calc is not correct.



Phil :)

[ArtF]

Phil:

  No question, GM is more correct. GT tries to generalize so it can be used with all types..pulleys, sprockets..etc..

Doesnt work very well for Evolutes though, SO Ill probably swap it to GM's old code just for spur gears..

Art

[philbur]

Hir Art, here's a comparison of GM, GT and another source:

red = another source
green = GT
blue = GM

Contrary to what you say GT seems to me to be more correct than GM, the only significant difference being the root depth, so I'm a bit confused when you say GM is more correct.

[ArtF]

Phil:

GM is only more correct on max tool Diam stats, GT is the more correct program in
other ways. GT's profiles are those used by Yamaha for example, GM's were based
on various documents found on the net and were therefore simple approximations.
  GT uses formulas more complex and that take into account interactions between
the wheel/pinion sizing. GT, except in tool diam specs, is the more accurate program.
(This is specially so in helicals and such..)

Art

[ArtF]

Hi Phil:

  Ive updated GT's tool diameter code so that round gears are a special case in which
all factors that gm took into account are also taken into account. The accuracy
is much higher now in those gear types.  This release will be a little while as Im working on
other features as well..

Thx
Art