How do sliding doors on vans work? --- Zach, Covington, Wash.
Marshall Brain Answers:
The invention of the motorized sliding van door is perhaps not as significant as the invention of the artificial heart, but if you are a parent with small kids, it certainly ranks up there as an important invention. It is something that gets used every day.
So how do they work? This little video is surprisingly revealing:
Watching that video you can see that there is a toothed track bolted to the car's frame, and a big plastic gear that engages the toothed track. Underneath the gear is a little gear box, and attached to it is a flexible black casing that contains a flexible spinning rod. This spinning-rod-in-a-protective-casing technology is fairly standard. Mechanical speedometers used it, and most modern weed whackers (with the engine at one end of a shaft and the whacker at the other end) do too. So there is an electric motor in the door that spins the spinning-rod-in-a-protective-casing, which then spins the gear. That is how the door slides open and closed automatically. The wires that he is fixing provide power and control signals to the motor and any accessories in the door (e.g. a power lock/latch, a power window, etc.)