14.2:1 Gearbox

Functional prototype gearbox with a 14.2:1 reduction ratio.

This project is a prototype gearbox for an electric 35 mm film rewinder. The goal was to design a new drive system with speed control and soft start, without modifying the original construction of the rewinder.

The gearbox is designed as a standalone 3D printed assembly. It consists of a main stand, front and rear side panels, a third gear holder, a cover, and a cover lid. The transmission uses a combination of gears and pulleys. The first and second transmission stages combine a gear with a V-belt pulley, while the third gear works as an additional reduction stage. The individual parts are secured with clamping screws and spacing washers.

The purpose of the gearbox is to reduce the high motor speed to a more suitable speed. In this prototype, the transmission reduces the speed from approximately 5500 rpm to 390 rpm at the film reel, which gives a reduction ratio of about 14.2:1. Further speed control is handled by an elect