Misc - Help Items

The cheater pipe is what got you I think, it allowed you the leverage to pull the come along tighter than it was meant to. The fact that it won't disenage now is a good indicator that you have more than its 2000 lb spec'd tension load on it. Why do you think it only has 1200 lbs tension on it? 

I probably didn't explain my point very well. What you are doing when you pull down the 2 feet is adding tension, not pulling slack. Cables can only support load along their length, they're wet noodles. So its impossible for a horizontal cable to support any vertical load at all. If you pull down on it it will sag, it has to. It will sag until either it can support the load or something fails.

 

The amount of vertical load the cable can support is in direct ratio of the vertical sag divided by the horizontal distance. So, say you weigh 200 lbs and pull down with your full weight in the center of a cable which is wrapped around two trees 40 feet apart (20 ft from either end).  The tension on the cable (neglecting the weight of the cable itself) is going to be 200*20/2=2000 lbs. If you start with a less tight cable that allowed a 4 foot sag then the tension would only be 200*20/4=1000 lbs. So if you make the cable too tight to start with trying to get the sag out when you load it you'll end up breaking the cable. That's what I meant by leaving some slack in initially.

Back to your current predicament. The good news is that while you don't know how much tension is on the cable and come along just stretched out between the trees the fact that you know how far apart the trees are and can pull down a known distance (2 ft) with a known weight (yours) at a known point (the middle) means that you can know that the cable and come along can hold at least that much tension without breaking. So, do the calculation above for the actual distance between the two trees and the actual weight and sag you had and see if that number is below or above the rating of your come along. 

Say the number you get is 2000 lbs as in my example, and that is the rating of your cable or come along. Then you also know that the tension without pulling down on it is less than 2000. You don't know how much less because you don't know how elastic the trees and cable actually are but it is for sure less. So you should be able to do what has been suggested and get a little more tension on the come along so you can release it.

If however your number comes out at 3000 lbs on a 2000 lb come along then you have a definite safety problem and should either try your buddy's approach or go back to the orange or blue big box of your choice and get a heavier come along.  Then, use it to relieve the tension on the 2000 lb one. The smaller one will have been over stressed so shouldn't be used again, at least not anywhere near its rating. If it was me I'd toss it. 

Keep the big one for future adventurous projects. For this project if you still want to proceed figure out how much load you want to be able to carry, triple it (to account for typical forces of about 2 gees from swinging plus a good safety factor ). That is your design load.  Decide how much sag you can live with, the more the better. Then, do the calculation above and get a cable  that can handle that tension. Install it but leave it loose to start with. Hang the design load (the triple load) and measure the sag.  If too much, remove the load and use the come along to tension the cable a bit. Remove the come along, add the load back, and measure the sag again. Repeat this process till you get the sag down to what you designed for, but no less. Done, and you've never over stressed anything, and you don't need the come along to be able to handle the full load. And you've proof tested it too!