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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've both got 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?
What a fantastic book. The preview has some great illustrations.
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My family owns some acreage down in Mississippi, in an extremely rural area where the gate-opening problem is widespread. The solution a lot of folks down there use is a "bump gate." The gate latch is connected to a bumper on both sides of the gate, so you drive your car forward slowly until it hits the gate, tripping the latch open and also swinging the gate aside. Then you drive through, and a counterweight or spring closes and latches the gate behind you.
There's a little bit of a trick to using a bump gate, in that you have to hit it hard enough to open all the way, but not so hard that it bounces back before you can pass through. Once it opens, you have to drive through quickly enough that it doesn't whack your side panels. It's pretty easy to master, though.
Google "bump gate," and the third or fourth hit is a YouTube video of someone going through one. The first hit is a vendor that sells them.
While the counterweighted sliding solution above is pretty darn clever, I've never seen it in use. My guess is that all those moving pulleys and wheels would be a bit finicky, and the gallows frame across the top could be a problem if you need high clearance.
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How about like the classic but campy batmobile gate/sign? As the batmobile rolled up it fell flat. A handle with a shackle for a lock could set it on either side. Speaking of locks don't you folks use them where you are?
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if you balanced this gate system juuuuuuuust right, you could get it so that when the hood of the car nudged the weight on the car's side up a little, the gate would go up of it's own accord, because your weights are balanced so perfectly. After it went up, you should have enough time to drive through, and then, due to your spectacular weight balancing job, the gate slowly falls back into place. might be tricky to get just right, but once you dialed it in, it should in theory, work flawlessly for many years...
hope that helps...
-M
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Seems like you'd have a tough time setting up a system that doesn't fall back down too quickly, especially if you're talking about a ranch truck that may or may not be towing a long, heavy load.
You could mitigate that by building in some kind of damping mechanism, either inertial or viscous.
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My dad solved the problem easily enough.. He had four kids far enough apart
that he didn't have to touch a gate for about 20 years. He just had to drive slow enough to give us time to close the gate back and get back in the truck.. Hah
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I see two problems with having to balance the gate perfectly. One is that if it rained, the wood in the gate would be a lot heavier, making it not work right. Two is that if you can just nudge the gate up then so can animals.
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There is also the book "Handy Farm Devices and How to Build Them" that is a maker's manual full of old tricks.
THIS is making! I don't need an Arduino to feed the hens.
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Use 2 sets of 4x4s and put them in a ditch. Nearer to the center make the ditch much deeper. The boards on their own will stay straight but when the truck rolls along the boards will bow. Attach a rope to one of the boards and run it under the other board. Run that rope along to a pulley and then attach it to a metal extrusion on the gate. The extrusion should be very close to the hinge.
http://img269.yfrog.com/img269/7269/automaticgate.png
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There are some gates around our ranch with sliding gates that are opened by driving the left front tire of your vehicle onto a ramp which transfers the weight and opens the gate. I'm heading there this weekend, I'll take a picture and post a link
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Here are a couple of pics
http://i230.photobucket.com/albums/ee73/mslubke/photo3-1.jpg
http://i230.photobucket.com/albums/ee73/mslubke/photo4.jpg
http://i230.photobucket.com/albums/ee73/mslubke/photo-1.jpg
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Found it on google patents... number 3163947. It includes some nice drawings
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Awesome! Thanks a lot, man. Gonna blog both these!
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