Definition
This model shows a fanciful gear that reduces the rotation speed by half and uses an off-center drive. The small black triangle drives the larger white wheel, but it can also work in reverse. It can be made with 3 or 5 pins. The design is quite old, with variations seen in the 1600’s, but is not widely used today. While not a practical gear, it bears a similarity to the Trammel of Archimedes, an ancient tool used in mathematics to draw a perfect ellipse. It is also similar to the powerful cycloidal drive, which is used widely in robotics.
Gear teeth made of pins have a long history dating back before the Renaissance and perhaps to the late Roman engineering era. Reuleaux references the machine book of Zonca (1621) Teatro di Machine who called such teeth 'Scudi Dentati'.
View in 3D
Display
This model demonstrates a multiple gearing mechanism. A very small gear motor drives the black triangle, which rotates the larger white disc at half speed. This model illustrates a method for reducing speed and obtaining an out of line or off center drive.
Images
3D Printing
Reconstructing the Library Display
The library display is composed of
- (1) Custom cut 1/2" plywood panel (400mm x 400mm)
- (1) Custom laser cut 1/4" acrylic slotted wheel (2 layers, clear and white), 4mm clear rod to pin layers while gluing
- (1) Custom laser cut 1/4" acrylic driving triangle
- (1) Aluminum U channel, cut to 400mm length
- (1) G12-N20 5vDC Mini Metal Gear Motor 30RPM
- (1) Custom 3D printed support G12-N20 motor
- (2) Custom 3D printed support bar stands
- (1) Flanged Ball Bearing (6mm)
- (3) 6mm ID Non-Flanged Ball Bearing
- (1) 1120 Series U-Channel (1 Hole, 48mm Length)
- (1) 20mm aluminum bushing 6m OD x 4mm ID
- Various M4 screws, round headed