gin poles with a twist

[rjmack]

somewhere back in june i decided to build a set of jin poles for the myriad of lifting chores that seem to crop on my property.

i had an old truck (superdodge) named in honour of super dave osborne. it already had a steel deck that i figured would be heavy enough for the task, and i had lots of scrap pieces left over from various projects, so i bought some square tubing, snatch blocks, an 8000lbs winch, and went for it.

the hinges are discarded deck chain from a dumpster behind a sawmill, the hss drop is a piece left over from a front bumper build, and the 1/2x6 flatbar is going to be the base for the winch. the main body of the boom is 2x2x.125 hss.

 

[rjmack]

okay, so the next step, after measuring the rough length of the poles was to fab the head of the boom. i wanted it strong, simple, and versatile. i cut a hole for a shackle at the top and reliefs on the side big enough to easily slide chains through with a lock slot. the stock was a piece of 6x10x.375 hss

 

[rjmack]

so the next thing was to put the hinges on. part of the initial layout positioned the base of the boom legs over structural members in the deck so that there would be more than just the checkerplate holding the weight of the assembly/load. the yard gantry is really handing doing stuff like this, it will pick a lot of weight and it never weaps... once you set the load, it stays. the boom assembly was placed on the deck and removed a few times during the build. there are just too many variables for a brain like mine to keep track of doing something like this. sometimes its best just to put the thing up there and see what it looks like.

with the boom on the truck, i noticed that the head needed some more reinforcement, also the chain grabs that i had put on were going to be okay down low but didn't look all that handy for loads up high, so i put in a couple more.

 

[rjmack]

so the next thing was beef the boom up as best i could adding as little weight as possible. the strongbacks are 3/8x3 flatbar. the upper crossbrace/snatch block mount is 1/2x6 flatbar.

this is where the head scratching really got going. i had to guestimate where the snatchblocks would mount to the boom and how the relationship between the snatchblocks on the boom and the snatchblocks at the winch would work.

i tacked the strongbacks on first, then realized that the boom needed more. i was low on flatbar so i decided to use some cross bracing to strengthen it as i had extra hss. i think this was one of those times where fate intervenes and helps you out. i think using the hss for bracing resulted in a stronger boom than i would have had if i had bought 'enough' 3/8x3 to begin with.

i ran the 3/8x3 from side to side rather than down the center of the boom rails in order to pick up the vertical section of the hss at each end.

 

[rjmack]

next thing was to tack the boom in place and then work on mounting the winch and fabbing the snatchblock mounts on the winch bar. if you notice the winch is mounted on 1 1/2 sch40 pipe at each end with the snatchblock mounts tying the winch base to the 1 1/2 pie the spare tire is mounted on. i thought about tying the winch bar to the deck with risers but opted not too... a mistake.

also, you can see in the last picture where i originally planned to mount the boom snatchblocks mid-point in the upper strongbacks. once i got the boom back up on the truck it became obvious that the geometry for that wasn't going to work. that moved the mounting point down the boom, and that screwed up my idea of using the strength of the flatbar to offset boom deflection... oh well.

 

[rjmack]

so the next thing was to use it. as you can see, the bars that the winch was mounted to really aren't up to the task. it actually did a lot more work than you can see in these pictures, but with constant abuse (as per the instructions that came with the truck) it got to the point where welds on the boogie bars were breaking. so it was back to the drawing board.

 

[rjmack]

so i cut out and replaced the bent bars, then used 3' channel iron and tied the winch bar to the deck where the boom hinges mounted. i figured that would be plenty strong.

 

[rjmack]

so anyways... long story short... it turned out the mods were plenty strong, and everything was good...

then, one day i decided to use the gin poles to pull some old fence posts that had been in the ground for quite a while... they were really in there good too. i think i got about half a dozen of them out and then ran into one that wouldn't budge, so i just kept reefing on it.

there was a resounding crash, the chain went flying in the air, and i though maybe i got a flat tire or something...

the frame rails are both bent, under the cab on the passenger side and just ahead of the spring perch on the drivers side. i still use it around the yard, that lawn tractor in the picture is very heavy, enough that my gc2410 wouldn't lift it.

i'm not sour on jin poles by any means, but clearly you need a pretty heavy frame. i'm wondering if i beef the frame, what would go next, the springs?

you might notice there is a winch mounted in the back bumper area. part of this project (a long time ago) was a set of outriggers to pin the truck to the ground while using the winch to skid logs. unfortunately i left the outriggers behind in a move, and they were a ton of work to fab up, but that would probably take care of the spring problem. maybe i can build a hydraulic set...

 

[jimmer2880]

Quite a project. Looks like a neat project. I bet you have a lot of fun with it.

 

[20 20]

good job, it's great when junk turns into treasure.