Crane Help

thanks to everyone how helped me with my last crane design, due to time reasons I just bought a cheapo from harbor freight and modified it. Now Im setting up a truck with a flatbed and I want to make a better one. Heres my rough idea.

The top of the post you see will be about 4 feet higher than the top of the flatbed. Not sure what the angle is but at 4 feet it will stick by the back of the truck about 12 inches. The angle of the post would be fixed, centered on the faltbed side to side and if possible will swivel. Winch would be mounted on the plate that swivels and tere would be a roller on the end of the tube for the cable. As its shown it would be used for ripping out old basketball goals after I dig around them a little and break them free by tugging on it with a tow strap. The average one will be a couple hundred pounds of concrete but as much as 1000 pounds. So I figure it should be rated for about 3000 pounds. So heres my questions
What size square tube should I use?
In the past people have recomended using a truck spindle and hub for the crane to swivel on...would that still work for a heavy weight rating?
Its other use would be putting up large basketball backboards and there would be another piece of tube that would fit into sleeves mounted to the lower piece of tube making the overall height above the deck 8 feet. The biggest backboard weights around 200 pounds so that piece of tube would be smaller....i was thinking 1.5x1.5x3/16 is that enough?

This is just an early brainstorm so Im open to any ideas.

thanks

oh ya I forgot to mention that I was going to make some outriggers in the rear to keep the front wheels on the ground.

[Evan Whytsell]

The truck hub is a cool idea for a swivel. It could work pretty well if you used a 14bolt or Dana 60 rear from a 1 ton chevy, ford or dodge truck. They are rated for alot of weight anyway, but if you really needed it you could go to a D70 or 80 hub.

Evan

[zapster]

its too late to go over this for me..

maybe tomorrow..

..zap!

I was working on a drawing of the crane itself with more detail but Im at a standstill.....if the crane itself were mounted to a 1/2 plate and the plate is what would rotate how should the square tube be braced to the plate?

[backuproller]

someone is probally going to disagree but, weld the pipe directly to the plate, the put some 1/2" plates on all four side to help with flexing. say 3" triangles with the top notched off to go over the weld and then turn and burn. on a scraper arm i use on my crusher, i cut the plate to accept the 2" tube and welded it to both sides and then used the angular plates on both sides. we kept breaking them everytime we got a new operator to run the bobcat, and they started pushing/pulling rocks and asphalt all day on the back 2 tires. now i only have to build about 1 a year instead of every 1 months.

what may i ask are you going to use to swivel the crane around?

Originally Posted by backuproller

what may i ask are you going to use to swivel the crane around?

It wont need to swilvel when Im ripping out old basketball goals I will do that with the crane pointing straight off the truck. The only reason it needs to swivel is when I have the extension on it and Im putting up the backboard. So 2x2 would have enought strength? What gauge should it be?

[lotechman]

In a previous life I made numerous end trucks for overhead cranes as well as a variety of job cranes.
I will try to attach a sketch. An extremely reliable version is to put a taper roller bearing at the top of a post then over that slip a larger pipe with the roller race at the top end.
At the bottom end you make cutouts on the wall and install rollers that run on the outside wall of the inner post.
The big thing to making a rigid crane is to gusset the base and reinforce under the deck with heavy angles bolted through. Go as large as you can in the diameter of the pipes.
Your biggest problem with free standing jibs is that they flex like crazy long before failure.
I attached this sketch after reducing it over and over and over :'))