Automatic Transmission Model

thingiverse

Learn how an automatic transmission works by assembling this desktop model featuring six forward speeds and one reverse gear. This educational tool mimics an actual automatic transmission system through manually controlled brakes and clutches. The designer of the model aimed for gear ratios similar to those in real cars, with input being the crank and output the annulus. Gear ratios are as follows: 1st gear - 1 : 4.29; 2nd gear - 1 : 2.5 (71% increase); 3rd gear - 1 : 1.67 (50% increase); 4th gear - 1 : 1.3 (28% increase); 5th gear - 1 : 1 (30% increase); 6th gear - 1 : 0.8 (25% increase); and reverse - 1 : -3.93. The OpenSCAD file is included, allowing for customization of gear ratios. Printed in PLA at 120 mm/s on a Replicator 1 with Sailfish firmware, this model showcases snap-fits instead of requiring glue. Assembled pieces include stand, gears, carrier, shaft, crank, handle, and planets along with pins. The stand features brake elements that rotate freely for seamless movement. Gears are herringbone-shaped to run smoothly without thrust bearings. Assembly steps are illustrated in photos provided by the designer. To loosen up tight parts, consider greasing pins and spinning the model for a while. Updates to the design include front_loose.stl and back_loose.stl files for easier brake disengagement.