I was idly wondering how to make a general purpose pulley machine, suitable for the whole family of exercises needing a horizontal pull, like cable rows and face pulls, as well the verticals like assisted pull-ups and lat bar stuff.
The basic question I was pondering was how to make a system that I can load plates onto that will not swing around freely, and of course can be built by somebody with little more than a saw and drill out of parts from the hardware store.
Seems to me you can do it something like this. It will be wider than the commercial stack-plate systems, but let's you use your own plates.
Take a 2x4, probably kind of long, like 3'. Laying it flat, attach two floor flanges out near the ends, and screw in a two foot length of 1/2" diameter pipe into each. This gives you two poles sticking up into the air. Assume this will be mounted on the larger structure so that it can't go anywhere.
Take a 2nd 2x4, same length, and drill two holes into it so it will drop onto the first one. Then mount a hook dead center. The cable will attach to the hook. If we can add weight to this in a simple way, we've got our stable system. So, attach two floor flanges at equal distances left and right of center, and screw two shorter lengths of pipe onto those. Toss plates onto these. Make them wide enough to allow your largest plates (figure 25's maybe) onto there w/o bumping into the center cable or the outer stabilizing columns. This gives you a nice stable system with the cheapest parts.
This requires you to evenly load the plates, but it is far simpler than anything else I could think of.
Not building this at the moment, just filling idle moments thinking about it.
The Angels have the phone box.