On Wed, 07 Jun 2000 22:59:50 -0700, Loial Raven <Loi### [at] telusnet> wrote:
Hi Loial,

>this is very strange... um... it could be because of number of points, oh wait, i
>know why...
>The outside of my teeth are clipped by a cylinder to make them round, this uses a
>difference, making it slower.
>I bet i could make it faster by moving the clip to when i create the tooth, instead
>of clipping all the teeth at once.
>
Yes it's your intersection with a cylinder to make them truly cylindrical on the
outside that does it.  I tried differencing the teeth with a cylinder in my
macro and the time taken goes up dramatically -. 6m.24s. as against 17s. !
Probably the fastest way would to do this would to add some more points to the
tooth prism.
>
>i don't use diametrical pitch because it's an imperial base messurement, i use
>metric when ever i can... i'll add it to the next version.  mdl = 1/PD   (= mm of
>pitch diameter per tooth)   :)
>
yes, as you say, continental europe always use module because it relates to the
metric system and probably many British firms do so nowadays.  I don't know
about the USA, they have been pretty reluctant to change to the metric system,
but it's many years since I was involved directly in mechanical engineering.
>
>I added the center_point and rotangle because i didn't think you could use
>gear(...) directly in an object... i thought you had to #declare it first... oops.
>
You will notice I made my gear macro with the centre of one of the teeth lining
up with the y-axis and also make available the angular pitch outside the macro
so that it is easy for a user to arrange for them to be correctly meshed. 

>hmm... things that i notice your code lacking, but realy is just superfluous in
>mine... solid gears(uses merge instead of union), adjustable quality, a problem
>with realy large gears(see below), rounded outside, meshing code, adjustable
>pressure angle.
>
>the problem with realy large gears won't be noticed in your stuff... but i've added
>the ability to leave the center out, speeding up spoked centers. If you have a very
>large gear(many teeth) the base of the involute dips below the root circle, if you
>have a thin ring holding the teeth, this will cause a spike into the center of the
>ring... um... kinda not importaint most of the time... but i disliked that when i
>did some tests.
>
As you say there are a lot of bells and whistles that can be added, I tried to
keep it as simple as possible for non-engineers who just want to model some
gears that are realistic.  Things like the pressure angle and accuracy are very
easy to alter in the macro.  If you want to go for extreme realism, then perhaps
you should  consider adding radii to the root of the involute, tip relief to the
top of the tooth - and even the positive correction of both gears (this is how
engineers avoid the working surface of the tooth going below the root circle).
>
>This one is called polar_gear 'cause it is my middle step before making the bevel
>gear one. polar coordinates are easier to convert into bevel gears...
>
All the best with your efforts.  I look forward to seeing your results.
David
dav### [at] hamiltonitecom
http://www.hamiltonite.com/

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