Cycloidal Gear Design

Last crawled date: 1 year, 11 months ago

How to draw cycloidal gears after B.S. 978

Choose values for size and number of teeth:
Module, m (size parameter in mm)
Teeth count on wheel, n(w)
Teeth count on pinion, n(p)

Punch these into online Gear Builder calculator to obtain values for drawing the gears.
http://www.csparks.com/watchmaking/CycloidalGears/CycloidCalculator.html

Use the result to draw the gears:
1) Draw the pitch circle for the wheel with diameter n(w)*m
2) Draw the pitch circle for the pinion with diameter n(p)*m so the it is tangent to the wheel pitch circle. [The distance between the centres is (n(w)*m+n(p)*m)/2]
3) Draw the addendum circle for the wheel by adding the value from the table to the wheel pitch circle.
4) Draw the dedendum circle by subtracting the dedendum value from the wheel pitch circle.
5) Draw the linear dedendum of one side of the tooth from the centre at an angle of 360/n(w)/4
6) Draw an arc from the centrepoint on the addendum circle to the linear side with radius from the table.
7) Mirror the tooth about the centreline.
The process for drawing the pinion is different and changes according to the number of teeth.
For 10 or more teeth:
8) Draw the dedendum circle for the pinion at a distance from 0.4*m from the wheel addendum circle. This to avoid interference between the gears.
9) Draw the centerline for a tooth at an angle where it doesn't intersect the gear wheel.
10) Draw one tooth side from the pinion centre to pinion pitch circle with a tooth width of 1.25*m at the pitch circle.
11) Complete the outline with a tangent circle arc and mirror the profile to complete the tooth.
12) Pinions with fewer teeth than 10 typically have a pointed end. Instructions/values can be found at this link:
http://www.csparks.com/watchmaking/CycloidalGears/index.jxl

You can verify your design by using this link:
http://hessmer.org/gears/CycloidalGearBuilder.html