Bearing advice request

PHPaul

PHPaul

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I'm contemplating building a crane/hoist that will plug into the hitch receiver on my truck to assist me in loading heavy objects into the bed. Yeah, I know I can probably buy one cheaper than I can build it, but where's the fun in that? :D

hoist.jpg

One design question is what to use for a bearing between the rotating mast and the fixed base. My initial thought is some sort of "plastic" (used in it's generic sense) such as HDPE or one of it's cousins. Seeing as I know next to nothing about this sort of material I have three basic questions:

1. Is such a bearing practical given that I envision lifting loads up to say 500 pounds?
2. If so, what specific material should I use?
3. If not, what are some alternatives? I suspect a "lazy susan" or other roller bearing in that size would be prohibitively expensive.

Thanks for any input.
 
Many of the cheaper commercially made units that can lift up to a ton will often just have a steel on steel plate with some grease in there. You could be a bit more sophisticated and put a brass plate in between the steel. and put a grease nipple on top and underneath. There are a number of engineering plastics that would also work but just go with steel on steel. I'm guessing that this little hoist is not going to worked 24/7 After all 500lb is not a lot. Just keep it well greased if it's out in the weather a lot.
 
What kind of overhang are we talking about? Making a thrust bearing that can take 500 lb or more is easy, making a mounted shaft that can take 2000+ ft-lb of moment arm is a different story.
 
Well, that would certainly simplify things. Polish up the mating surfaces and add a grease zerk.

The plan is to build in in several pieces as a "take down" unit that will lay flat in the bed after use. Greasing the various moving parts would be simple to do.

Thanks!
 
Alexander McGilton said:
What kind of overhang are we talking about? Making a thrust bearing that can take 500 lb or more is easy, making a mounted shaft that can take 2000+ ft-lb of moment arm is a different story.
Click to expand...

Good point. This is just in the brainstorming phase so any and all input is welcome.

I need to figure out the requirements for lift and horizontal reach. 4' would be plenty for reach, but I also want to be able to lift an object 3 feet tall high enough so the bottom clears the tailgate and can be swung into the bed. Even better if I could lift it high enough to swing it over the sides.

I'm off to great-grandson's birthday party in a bit so probably won't see further replies until this afternoon.
 
I use one at work and it’s metal on metal. If one wanted it to spin really free I would use a tapered roller bearing off a trailer axle. Bearing on top part tapper down and the cup on the bottom part. Probably have to put limit stops cause it will pivot easily. The weight of the lift will keep Assy together.
 
Please show us this project as it goes. I am thinking about building one of these. Possibly aluminum.
Robert
 
Plate/grease/plate is simple and works well. It will get worse over time if contamination (water, dust, and grit) gets into it. Too good of bearings make the work swing when you don't want it to, due to the vehicle not often being perfectly level. As pointed out above, the length of the boom and the maximum weight lifted will determine the needed strength of the structure. The base needs enough strength to withstand that maximum load hanging at the end of the boom. A simple diagonal brace from riser to boom can help a lot to strengthen that joint.
 
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