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Thinking about a pulley machine
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Author:  KenDowns [ Fri Feb 03, 2012 2:09 pm ]
Post subject:  Thinking about a pulley machine

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.

Author:  Oscar_Actuary [ Fri Feb 03, 2012 11:26 pm ]
Post subject:  Re: Thinking about a pulley machine

cable system is nice to increase your options.
You are no longer limited to the force vector being straight down

Author:  Jungledoc [ Sat Feb 04, 2012 7:47 am ]
Post subject:  Re: Thinking about a pulley machine

Ken--so you would have to have 2 stacks of balanced plates?

How about a floor flange attached to the floor, small-diameter pipe (?1/2"?). Second pipe, 2" or 2 1/4" or whatever is closest to the size of an oly bar, with a floor flange attached to the bottom end. Slide this over the small pipe. You'll need a link of some sort at the top. Slide your plates over this, and then attach your cable with a carabiner or some other kind of hook or clip. The small pipe would keep the big pipe from swinging around, and you could load any number, even an odd number of different sizes.

Author:  stuward [ Sat Feb 04, 2012 8:20 am ]
Post subject:  Re: Thinking about a pulley machine

I'm having a hard time visualizing what you're talking about but I would think that a pair of simple loading pins suspended from your pullies would be all you need. The hardest part would be to make the height adjuster for the pullies.

Author:  Jungledoc [ Sat Feb 04, 2012 4:37 pm ]
Post subject:  Re: Thinking about a pulley machine

The loading pins would swing around. My idea is basically a hollow loading pin with a fixed shaft for it to slide up and down on to keep it from swinging. He could have eye bolts attached at various levels to the wall, and simply attach a pulley with a caribiner or hook and move it to different hooks for different exercises.

Author:  KenDowns [ Sun Feb 05, 2012 4:57 pm ]
Post subject:  Re: Thinking about a pulley machine

Here are some pics of the basic starting point. The shaft is 3/4", which snugly fits "standard" non-Olympic weights. This does swing a bit, but it works. Cost: about $12.00, but I'd already mounted a pulley onto my power cage, so there is some extra expense.

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Author:  Jungledoc [ Sun Feb 05, 2012 9:39 pm ]
Post subject:  Re: Thinking about a pulley machine

How heavy can you load this?

Good job, by the way.

Author:  KenDowns [ Sun Feb 05, 2012 10:04 pm ]
Post subject:  Re: Thinking about a pulley machine

Doc, the limiting factor is that chain, with a working load of 90#, which rules out a Lat bar as long as I stick with that chain.

Author:  Jungledoc [ Mon Feb 06, 2012 3:56 pm ]
Post subject:  Re: Thinking about a pulley machine

Weld a ring or a loop at the top of the pipe that is no bigger than the pipe, then you can clip your cable directly to that.

Author:  KenDowns [ Tue Apr 24, 2012 1:54 pm ]
Post subject:  Re: Thinking about a pulley machine

UPDATE: Have used the pulley up to 85# since writing the OP, I guess 10 weeks or so.

PRO: simple and easy. Attach a garage door pulley to ceiling, make the bottom piece according to pictures above, use it. I think I can beat the 90# limit on the chain by going for a strap instead, but between you and me I'm likely to find out what the *real* limit is on that chain by just loading it up.

CON: Without stabilizing poles, the weight swings front-to-back wider and wider on each rep. Oscar the engineer may be able to tell us why. Anyway, imagine if you will 90+ pounds swinging in toward your jaw on the lat pulldown (no I haven't been clobbered thanks for asking), or the weight swinging forward to block your hands on the triceps pulldown (yes this happens a lot, very annoying).

Appendix: I'm picturing that if you lift the weight and it is not dead plumb, it will naturally swing towards center. But at the same time the cable is shortening, which means that since the period must be the same for any weight+length combination, a shortening cable means a shortening period, which would actually accelerate the weight? That's why it swings longer and longer. That's my its-been-25-years-since-college explanation.

Author:  stuward [ Tue Apr 24, 2012 2:11 pm ]
Post subject:  Re: Thinking about a pulley machine

Try a light bungy cord or latex tube tied to the bottom of the stack.

Author:  Jungledoc [ Tue Apr 24, 2012 4:13 pm ]
Post subject:  Re: Thinking about a pulley machine

I came across this a few weeks ago. I'm thinking about building a similar rack, but probably won't do the pulley.

http://www.home-gym-bodybuilding.com/homemade-power-rack-and-lat-tower.html

This is more like what I'm thinking about:
http://www.home-gym-bodybuilding.com/homemade-power-rack.html

Author:  KenDowns [ Wed Apr 25, 2012 12:46 pm ]
Post subject:  Re: Thinking about a pulley machine

Doc, those links show what are IMHO the top-of-the-line home built cages. They all feature doubled up 2x6's with drilled holes, for rigidity and strength.

If I were to ever do it again, which I don't see myself doing, I would go the same route. But for me now I have something that works, don't need to keep going.

Rather, I need to start thinking about building a leg press machine, which I don't want to build because I don't want to do them.

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