Subject:
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Re: Why aren't the technic gear teeth primitives?
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Newsgroups:
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lugnet.cad.dat.parts.primitives
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Date:
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Fri, 29 Mar 2002 13:29:46 GMT
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Viewed:
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2015 times
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In lugnet.cad.dat.parts.primitives, Mark Kennedy writes:
> The teeth on the small 8 tooth gear are slightly different from the larger
> ones(Though in the file they are pretty much drawn as trapezoidal boxes).
If they were designed properly, the tooth profiles will be different between
the 8t, 24t, etc. gears.
The tooth profile of a gear follows an involute curve, which means the
profile is the involute of a base circle slightly smaller than the pitch
circle. Therefore the tooth profile is related to the gear diameter, and
will differ between different size gears.
The involute curve is more noticeable in smaller gears, which explains the
difference that's easily seen between the 8t gear and all other gears. If
you study the 16t gear closely, you'll notice a slight curve in the tooth
profile, and it will differ from the 24t gear.
For CAD purposes, it doesn't matter if the gear teeth are accurately
modelled with involute curves, or if they're made as trapezoidal boxes. We
know how Lego gears work and at what distances they mesh properly.
TJ
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