I want to build an arm

Well, to be more specific, I'd like to build 6 or 8 of them. I'd like them to be able to support themselves plus 50-100lbs. I'd really like them to be able to collapse into themselves as well. 

Confused yet? Maybe this drawing will help.

I want to use 2 foot sections, 3 or 4 of them, with holes drilled every inch to make extended length as adjustable as possible. On the end, where the "hand" would be, something like a vise or adjustable clamp. 

Giving the hand the ability to rotate would be a pleasant bonus, but I'm really only specifically concerned with making the base rotate and lock into place. 

To get the extending arms to lock into place, I'm thinking studs with a spring behind them, so you can pull out to the length you need and set the pins in the holes. 

Carbon fiber is too brittle, I think, to be of much use. Titanium is too expensive, aluminum to soft, and steel could be too heavy. Maybe DOM tubing?

I feel like all the parts I need to make this come together already exist, they've just not been put together in this setup before. 

In a fantasy scenario, this would be hydraulic or air powered, but unless I could get a grant to develop it, that hasn't going to happen. The connections between each arm would also allow for rotation and position locking. 

Now I want to build 6 or 8 to attach them all to a central base, like say a 55 gallon drum, or even a table, pallet, or truck bed. That would leave 3-4 points for stabilization on the ground, and 3-4 points to be used in service. 

Does this seem like an overkill solution to not being able to get extra hands to help around the house or shop? Maybe. But who couldn't use an extra set of hands that doesn't talk or complain about being stuck holding things for long periods of time?

Thoughts? Criticisms? Links to lockable elbows or industrial versions of those phone tripod things?

Looking for a positioning arm?

https://www.mcmaster.com/#positioning-arms/=1e9akpi

In reply to java230 :

Yes, basically. But twice as long and not $350. 

I'd been digging around on McMaster for a locking elbow style joint, I guess they really do have everything. 

Maybe try finding pipe/conduit that isn't too heavy, PVC, EMT, maybe square stock comes in sizes that would fit inside each other or something similar . Aluminum electrical conduit is pretty beefy as far as strength goes. You might have to make some sort of bushing at the moving end as the different sizes may not fit perfectly inside the next diameter size pipe. With two foot sections I think you could keep it fairly sturdy if you started with a big size of the bottom/first section, like 1.5' or maybe even 2". If they don't need to be super portable the larger size pipe shouldn't be an issue. Seems like an interesting idea. Will be following this to see what you end up with. Good luck

What about a foundation jack? Its most of the way there 

What got me started on this train of thought was actually an office chair, the way the "suspension" can raise and lower the seat, and hold a bunch of weight. The other part of the birth of the idea was trying to hold 2x4s above my head and connect them at the same time. 

For proof of concept I was thinking conduit or sprinkler pipe because I can get as much of them as I need, in concentric sizes for very little money(gas to a former employers scrap pile). If I find that conduit can hold the weight, I might just go that route.

I hadn't thought of the foundation jacks, they do fit the bill nicely and come up cheap on craigslist occasionally. There's even been some thought of modifying an engine hoist, since it already has a stable base, a lifting capability, and can be cut and welded into shape. 

I even have something left over from my construction days, it's basically a paint roller on a tripod, to hold sheets while your cutting. I just don't think it could hold much weight at full height, or that putting a roller on a regular tripod would work very well. Although, my idea for the "hand" is a 18" ratcheting bar clamp instead of a roller that might be worth trying. 

I'm sorry if this is more scattered than even my usual idea posts, but I've been thinking about it for a while, and I'm trying to organize my thoughts as I type them, I'm also still very much in the brainstorming portion. Right now, the final idea is somewhere between Bender from Futurama and doctor octopus.

Keith's car selfie stick was also a bit of inspiration due to its modularity.