how to draw involute curve?

[bahai705]

i want to draw a involute sprocket. but i don't know how to draw involute curve? help me!

 

[SRINIVASANIYER1]

search this forum for involute gear or search PTC's site for "Suggested Techniques for creating an Involute gear".

 

[brchapman]

You can generate an involute curve "from equation" using the following cartesian equations:


R=(PD/2)*COS(PA)


THETA = T*90


THETA_RAD=THETA*(PI/180)


X = R*COS(THETA)+R*THETA_RAD*SIN(THETA)


Y = R * SIN(THETA) - R*THETA_RAD*COS(THETA)


where:


PD = Pitch Dia.


PA = Pressure Angle in deg.


This will create the curve needed for one side of your tooth. You will need to create a datum rotated 1/2 the space width (for a cut) to mirror the curve about. Make sure you create the csys needed for the equations. This will allow you to position the curve where you need it. After the curve is mirrored, create the cut for the spaceusing the edges of the curves you just created. Complete the section by adding an arc for the Major dia. and an arc to create the root of the sprocket. The root can be a little tricky to create. I usually create a construction circle that represents the root dia. Then I create a circle tangent to three edges, the root circle and the involutes I just created. If the circle drops below the base dia., simply extend the involute curves below the B.C. using lines. Trim the section closed and complete the feature. The root will obviously not be a trachoidal fillet, but is good enough for most modeling purposes.


After the first cut is made, simply pattern it to complete the gear or sprocket.



Edited by: brchapman

 

[Shinto Mathew]

Second part of both equations need correction, I think we
need to subtract 90 degrees from 'theta'. I found following
link with similar equations,
Involute Curve In ProE

Edited by: Shinto Mathew