descibing a circle diameter help needed

Hi all

I need some help if i might ask

I need to Model a chainwheel and drive its diameter by the pitch of
each tooth.

the pitch is 12.5 mm or 0.492" for our american buddies

what i need to do is describe diameter as a result of the tooth pitch
x the number of teeth

im puzzled this is probably really easy to some of you guys i can only
describe the diameter of the circle using dimensions and not the
circumference

any help

 

diameter = (number of teeth) x pitch / pi

 

That equation can come close, especially for large sprockets with a lot
of teeth, here is a more accurate forumala:
diameter=2*pitch*SIN((90-180/#_of_teeth)*ATN(1)/45)/SIN(360/
#_of_teeth*ATN(1)/45)

This equation includes the conversion to radians as solidworks requires
(all SWX trig functions input/output radians)

 

I just answered a similar post on eng-tips.com. Is this the same
poster???

Anyhoo, for a chain, look at the problem as a circle circumscribed
about a polygon with "n" equal sides and length equal to pitch "p".
Draw a line from the endpoints of one segment to the center, and
calculate the radius by bisecting the resulting isoceles triangle.

The result:
diameter = pitch / sin(180°/n)