The manager of a distribution warehouse called our locksmith company with a persistent problem. Inside the warehouse is a 13-foot tall chain link fence, separating the parts area from the shipping / receiving area. The fence has a double gate with a magnetic lock mounted at waist height.
This gate has one active side and one inactive side. The inactive side can be bolted into the floor, but the gate is so tall that there was a lot of play at the top. This led to misalignment, as people pushed on the gate, not realizing it was locked.
On chain link gates like this, the hinges and other components are only clamped to the steel tubing, so they can shift around even when the clamping is very tight. This can be corrected by zipping screws through the gate's hinge straps, into the steel tubing.
We offered to do that for this customer, but he told us he could do that himself. He just wanted us to eliminate the play at the top of the gate.
We suggested a standard barrel bolt, but the customer vetoed that; the inconvenience of having to get on a ladder to lock and unlock it was unacceptable. Another magnetic lock would have been too expensive.
We considered a very long barrel bolt that could be operated while standing on the ground. That seemed like the most promising solution, even if we had to fabricate such a bolt ourselves. That's exactly what we did, but with a slight twist. Instead of a surface mounted bolt, we decided to hide the bolt inside the tubing!
We welded a rectangular block to the bottom of a steel rod ¾-inch diameter by 7 feet long, thus forming an “L” shape (see photos 1 and 2). We drilled and tapped the end of the block to accept a small Allen-type bolt. That was for a small knurled knob we found, which would be attached later (see photo 3).
At the job site, we measured how much the rod would have to travel, and then we cut a slot in the steel tubing of the gate (see photos 4, 5, & 6). This slot was for the bottom of the rod to stick out, so we could attach the knob to it.
Once the slot was cut, we lowered the rod into the tubing (see photo 7) and attached the knob. The rod was heavy. It would be awkward to lock and unlock the gate without something to compensate for the weight.
We took the rod out and attached a spring to it, (see photo 8) so the ends of the rod and spring lined up. Note: this initial placement of the spring was experimental. We suspended the rod from the spring to measure how much the spring stretched. Then we moved the spring's attachment point on the rod down by that amount so that the spring would be holding the full weight of the rod (see photo 9). When we lowered the rod back into the tubing, we hooked the loose end of the spring onto the top of the tubing.
It took a little adjusting, but we got just the effect we wanted: the rod felt almost weightless when we moved it up and down inside the tubing.
To keep the rod in the “up” position, we drilled a pair of holes for a hitch pin (see photos 10 & 11), which we later hung from the gate with a small piece of chain.
Because of the difference in diameter between the rod and the tubing, the rod wanted to move around a lot. To put an end to this, we installed some carriage bolts behind the rod (through the tubing). This kept the rod near the front of the tubing (see photo 12).
Above the gates is a piece of horizontal tubing serving as a sort of header. We fashioned a keeper or strike plate for the rod out of angle-aluminum (see photos 13 & 14), and attached it to this piece of horizontal tubing. We rounded the top of the steel rod (see photo 15), so that it would find the hole in the strike plate more easily.
Operating the rod is simple – remove the hitch pin and let the rod down, or slide it up and put the hitch pin back in place. The operation is smooth and effortless. You barely even feel the rod entering the strike plate. Yet we've eliminated all play in the gate other than small tolerances we built into the strike plate, and the overall swaying of the whole fence. The customer was impressed and very pleased.
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