Model: Q06 Thumb-shaped Teeth, Rack and Pinion
Gear teeth profiles in the 19th century used both epicycloids and involute (evolute) curves as described in the abstracts of models Q3 and Q4. From Reuleaux we quote:

“By combining the evolute and epicycloid, using the two curves for opposite sides of the same tooth a profile of great strength is obtained. This form is of especial service for heavy driving when the motion is constantly in the same direction.*”

In model Q-6 the involute or evolute curves are on the side that contacts the straight line faces of the rock. The epicycloid curves are on the faces the contact the right hand sides of the rack teeth.

Francis Moon 2004-07-00

Reference :

  • Reuleaux : Constructor (4th Ed §212, Figure 595, 1893)