Building a bed crane. Need advice

[Ironman03R]

I'm building a hitch mounted bed crane out of and old engine hoist and now that its almost done I have a problem. Once you load it, the pivot binds and wont turn unless someone hangs off the back and someone else pulls the boom. I've polished the tubes, greased it, and installed a large tapper bearing in the top of the pivot so all the weight rides on that bearing. I also tried to spread the weight out with a piece of 1/2 steel and 2 jack stands that helped but its still not what I want.
Anyone have sugestions on what could be done to help keep this from binding?

 

[obinella]

the last time i did something like this i used a spindle from a 3/4 ton chev. welded the stub in the vertical position- re install the hub without the brake drum. make a plate for the crane to mount to the lug nuts.

 

[tonkadoctor]

the last time i did something like this i used a spindle from a 3/4 ton chev. welded the stub in the vertical position- re install the hub without the brake drum. make a plate for the crane to mount to the lug nuts.

That's what I'm thinking. You need a bearing top and bottom like a car spindle has one inside and out.

 

[subway]

yup bearing top and bottom there is a whole lot of torsional force there. i am making a wild guess on the arm hook being about 5 ft away from the spindle. say you hang a 750lb weight off there, you are fighting 3,750ftlbs of torsional force. these numbers crank up fast to when you make the weight farther away and heavier.

 

[Ironman03R]

Thats kinda what I was thinking...Already have one bearing in there and theres another sitting on the bench.
The spindle idea is a good one, I might have one of those sittin around too.

I looked at those $100 harbor freight cranes and they use a setup similar to what I made, but they are about half the lenght on the boom.

 

[MUDKICKR]

find a frt hub bearing from a frt whl drive car. i bet that would work and hold up fine.

 

[BigRigTech]

I would get a kingpin and lower kingpin bearing for a big rig....Cheap and made for heavy rotating forces....You could make it greasable too from the bottom....Just an idea.

 

[93turbo_animal]

if you can't find anything in the junk its usually pretty easy to get trailer parts you could get a spindle and hub that way

 

[Diezel_Cowboy]

I would still put a jack under each end of your hitch apparatus. You could put a leg/foot with a few pin holes for adjustment but you may run into problems once the truck is loaded and squating down with the pinned legs being stuck. If you go lifting something heavy the length from hitch to crane will put a lot of torsional force on your trailer hitch. It may spin the square sligtly and mess up the fit or bind itself in there.

 

[RLDSL]

After you get the bearing situation straightened out you could Extend the boom arm out the other end and add some counter weights. that might help to keep it from wanting to rip the rear end of the truck off. Long threaded rod, make them adjustable

 

[obinella]

how about a trailer tongue screw jack

 

[subway]

how about a trailer tongue screw jack

that would be a good idea to take the torsional load off the reciever, depending on where the boom is swung that load i calculated quick and dirty would be almost double at the reciever.

 

[94f450sd]

could always use 2 trailer jacks like they were outriggers on a crane truck.if youre gonna do it,as we can see you are.you might as well make it safe as well.hate to hear you were squished by it

 

[Ironman03R]

Thats the plan, for the time being I have been using a jack stand. A trailer jack will end up there so I can swing it up out of the way when transporting it.
I thought about some kind of counterballast weight but this thing is already heavy enough!
I found some bearings and a piece of 1" shaft to run through the pivot so hopefully that takes care of the binding.

 

[Pipeliner_86]

Looks good Steve, I have had a crane in my last two trucks. Heres a couple of pics. My first one was home made by me out of misc. scrap laying around. I used two John Deere combine bearings on my first crane and it worked perfect, no binding. My second crane came with the truck, is a store bought, not sure if it came from harbor frieght? No bearings, but it does not bind. The rotational shaft is much taller then your's, that might be the key.