Sync Digital Sound to Your 16mm Film Projector

Step 3 The Worm Gear

Most projectors have a worm-gear that interlocks the shutter/ claw to the 2 sprocketed rollers that pull the film through the machine. The 16-CL has a brass worm-gear on the main drive shaft that performs this function. This is convenient because we know that once the projector gets rolling, the spinning of this gear has an unbreakable 1:1 relationship to the spinning of the shutter and the advancement of the film (until your splice breaks, of course).

So, get out your little magnets and epoxy them to the gear:
You want them to be directly opposite each-other...
AND opposite polarity (one should be "north-up", one should be "north-down")

(Use epoxy for this because Super glue is brittle and this part vibrates a lot. Clean the parts with alcohol first to get rid of grease and oil.)

I chose this method for measuring speed because it was easy. It would be more accurate to introduce an extra sprocketed roller to the film path. That way, as the film moves through the projector you would know exactly what was going on. (With my method, the sound keeps playing if the film breaks, and sync is lost during stopping/starting as the clutch engages the transport.) For all of its benefits, a sprocketed roller introduces issues of complexity, reliability, and possible film-scratching. Feel free to come up with your own solutions and modify the software accordingly.