Unpowered Mechanical Gate Opener

Energy & Sustainability
Unpowered Mechanical Gate Opener
self-opening gate.png

In an age of ubiquitous electronics and electromechanical systems, I think it’s easy to forget that we don’t necessarily need electricity for everything. I’m no Luddite, by any stretch of the imagination; I just think some problems are more sustainably and elegantly solved with purely mechanical devices.

Take the problem of opening a gate from a vehicle. Both my father and my brother live on gated properties, not because they’re rolling in so much dough, but because they live out in the sticks and keep livestock and pets that they can’t have wandering off. So they both have vehicle gates in their fences, and both gates are well removed from any source of municipal electricity.

Dad went to considerable expense to install an electric gate opener powered by a lead-acid battery kept up by a solar panel, which works just like a suburban garage door opener. Very convenient, in use, but expensive to install and with considerable maintenance troubles associated with the battery and the solar panel and the motor and the mechanics. My brother, on the other hand, opted for the minimal solution and has no opener at all. When he leaves in the morning and when he gets home at night, he has to stop at the gate, get out of the car, open the gate, drive through it, stop again, get out again, close the gate, and get back in the car before continuing on his way. A low-cost solution with basically zero maintenance, but he pays for it with inconvenience.

Personally, I’ve always thought an intermediate solution would suit them both better–something purely mechanical, that would be cheaper and hardier than the radioservomechanical rig my Dad installed, and yet considerably more convenient than the get-out-and-do-it-yourself approach my brother has taken. Then last weekend I was browsing a use bookstore and happened upon a copy of George A. Martin’s Fences, Gates, and Bridges and How to Build Them, first published in 1900. It included the diagram shown above, with the accompanying explanation:

Figure 204 shows a gate balanced in a similar manner, and arranged so it can be opened by a person desiring to drive through, without leaving the vehicle. It is suspended by ropes which pass over pulleys near the top of long posts, and counterpoised by weights upon the other ends of the ropes. Small wheels are placed in the ends of the gate to move along the inside of the posts, and thus reduce the friction. The gate is raised by means of ropes attached to the center of the upper side of the gate, from which they pass up to pulleys in the center of the archway, and then out along horizontal arms at right angles to the bars which connect the tops of the posts. By pulling on the rope, the gate, which is but a trifle heavier than the balancing weights, is raised, and after the vehicle has passed, the gate falls of itself. In passing in the opposite direction, another rope is pulled, when the gate is raised as before.

Googling around reveals, of course, that nobody is selling any such device, that I can find, so if one wanted one it would have to be a custom job. I wonder about the possibility of a system that uses the weight of the vehicle to trip the mechanism instead of a rope. Anybody seen a purely mechanical gate opener in real life?

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I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

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