describing diameter of circle by tooth pitch 2

[G1DESIGN]

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

 

[drawoh]

G1DESIGN,

I have done something very similar with gears. The best solution is to use a design table. You can place the design table on your drawing, and use it to display undimensional values such as diametral pitch.

To add non-dimensional data to a design table, type in headings such as $PRP@DP and $PRP@TEETH. Plug your diametral pitch value and number of teeth underneath these and use the values to calculate your pitch diameter. All of this is easily displayed on your drawing.

Obviously, I am thinking English spur gears here, but you can easily plug in the appropriate values for chain sprockets.

JHG

 

[Arlin]

If I understand correctly, this formula should do:

diameter = pitch * (# of teeth / 4 - 0.5)

 

[G1DESIGN]

forgive me for being stupid

can you explain arlin just so i understand properly

/4-0.5 what do these values represent

 

[Arlin]

DARN, never mind that last equation (stupid mistake). This should be the real thing:

dia = 2*pitch*sin((90-180/#_of_teeth)*pi/180)/sin(360/#_of_teeth*pi/180)

 

[G1DESIGN]

now you,ve got me

 

[Arlin]

Here, if you still do not understand it, do this:

Copy the follwoing into the SWX equation editor (Tools/Equations/Add).
diameter=2*pitch*SIN((90-180/#_of_teeth)*ATN(1)/45)/SIN(360/#_of_teeth*ATN(1)/45)

Now replace diameter in the equation with your diameter dimension name.

Replace pitch with your pitch dimension name.

Replace #_of_teeth with your pattern number dimension name.

Now it should work!

 

[G1DESIGN]

arlin your the man


thanks mike

 

[TheTick]

Since this is a chain, and not a belt, the pitch can be determined by a circle circumscribed about a polygon of n equal sides with pitch p.

diameter = p/sin(180°/n)

"When everyone is thinking alike, no one is thinking very much." --Eckhard Schwarz (1930--2004)

http://www.EsoxRepublic.com

 

[Arlin]

Cool, thanks Tick, My equation is the same thing, but I needed to lookup a few trig identites to get it into the simple form you presented.

Also, I included the conversion from deg to rad in my equation, which is required in SWX.

So, the final equation for SWX becomes:
diameter = p/sin(4*atn(1)/n)
where p is pitch and is number of teeth

MUCH SIMPLER!!!!

 

[TheTick]

Actually, SW equations supports pi as a function. Since pi radians = 180°, the equation can be written as follows:

diameter = p/sin(pi/n)

"When everyone is thinking alike, no one is thinking very much." --Eckhard Schwarz (1930--2004)

http://www.EsoxRepublic.com

 

[Arlin]

Hey, thanks Tick. Learn something new every day.