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[PyroDesu]

Alright, so most of us probably know the basic concept of an exoskeleton suit, right?

I want to make a device I can wear on my arm (Forearm and lower arm) that consists of 2 straight pieces of material (probably metal) and a tension spring at the elbow that makes the device want to contract like the elbow does, the basic thinking is that that will provide resistance to bending my elbow, meaning I can hold more weight with that arm.

If you've seen the Mythbuster James Bond Special Part 2, you may have an idea of what I'm talking about.

Any ideas if this is feasible? And more importantly, safe?

(Sorry if the description is vague, I think in pictures and it's really hard to describe it.)

[Eagleon]

Feasible, yes. Safe, no. You're basically introducing a new muscle, one that provides no warning pains when it's under too much strain, and your joints and back are still withstanding the full amount of strain you put on them. For the benefit you gain and the extra effort you use to bend your arm when you need to, you might as well just wear a harness.

[PyroDesu]

So using a harness that supports the back with the design is better from a safety standpoint? As well as something on the legs so that I can still remain upright? Perhaps a similar thing but with compression springs instead of tension springs?

I think I see what you're getting at, the spine still has to withstand the pressure from the weight as well, not just the arm.

[Funburns]

It's important to know what you're planning on using this for in order to design towards the goal. To explain why I think so, I'd like to expand on Eagleon's reply. Note: I am not a mechanical engineer.

A single muscle attached to a joint has only a single direction in which it can apply force. If you try to lift an object this way, the movement frame the muscle is acting in will need to be fixed so it doesn't move the wrong way or topple over (think of a car jack).

Most of the stuff we use our bodies for requires many muscles working at just the right power in different directions to keep everything supported the way we need it to be. Actually lifting and repositioning a weight requires variable muscle strength all over your arm to stabilize it, along with all over your chest, back and legs, since the weight needs to be supported and its motion controlled through all of those places before you can lift it off the ground.

If you try to make mechanical biceps, all the other muscles in your arm will be taxed harder than normal when the mechanical muscle's extra oomph is being used. Even if you arranged a body harness so this wouldn't be a problem, there's still the possibility that somehow losing stability while lifting a heavy object in such a device would pose the same risks as being caught next to a tipping car jack (!).

If all you want to do is find a better way to, say, lift boxes, it's almost always the case that the moving parts of the resultant machine shouldn't be right next to your body. Exoskeletons and other muscle-enhancing (or replacing) devices require either a high degree of refining or a restriction to a very narrow range of applications to be useful without being dangerous.

[Levi]

I have no idea if its possible/feasable, but I hope you try anyway because I love hearing about things like this.

[Lord Dullard]

OTOH, if you (or somebody) designed a metallic exoskeletal muscle-ehancing rig for your FINGERS, that would be awesome. It wouldn't depend on the existing strength of other major muscle groups (i.e. back, upper arms, etc.) and you'd be able to crush things with your fingers.

Come on, admit it... being able to crush a rock to pulp with your 'bare' hands would be pretty awesome.

[MetalSlimeHunt]

Unfortunately, the only materials both light and strong enough for exoskeletons cost way, way, way more money than you have if you aren't a major corporation or government.

[alfie275]

http://www.youtube.com/watch?v=SUeUzi-yRcY&feature=player_detailpage#t=362s

[counting]

There is a very practical reason why it's not commercialized - power issue. Power sources that are power enough are just too heavy and immobile. It may be good when exoskeleton is stationary, but when moving you will have to carry the extra weight of metal and batteries both. Unless there is more powerful lighter fuel-cell developed, it will met some same problems as in robotics. (Independence robots in human size have much less "muscle power"). But as for pure prototypes and scientific researches they have existed for decades.

[PyroDesu]

@counting: That's why it would be purely mechanical.

@Lord Dullard: I think a pair of gauntlets would be good for the lower arm attachment, not exactly strengthening your fingers, but cool and useful  nonetheless.

@Funburns (Nice username for commenting on this, BTW): For the leg attachments, I think having the calf attachment (Perhaps greaves along the same line of thinking for the gauntlets, reinforced, of course)  having a metal plate under where the foot would be would A: Stop the weight from crushing my ankles, and B: Spread the load and provide more stability. More area, more stability. As for the possibility of a spring snapping, make it so you can't put so much load on them without having them stop stretching.

Thinking about materials I would want to make this out of, I think Titanium Aluminide plates with Titanium reinforcement rods would be a good Idea, as both are strong yet relatively lightweight. Yeah, probably out of my price range now, but after a few years, maybe not. Who knows, I may even be able to interest some corperation![/probably not] It certainly wouldn't be as expensive or complicated as hydraulics, and as for safety, I think I want those plates at least a quarter inch thick, thicker around the springs, probably have some kind of housing for them so that is is IMPOSSIBLE to stretch them to breaking point (IE. It would hit the wall of the housing and stop.) And the leg components at least half an inch thick, plus the Titanium rebar. And a very high-grade helmet, obviously. The harness would have a bar running along the shoulders that had another spring attaching it to the arm, and the same for the legs.

Any other suggestions?

[Biag]

I second Lord Dullard's finger-strength idea. Rock climbing! Hell, brick-wall-climbing!

[counting]

It may be a low tech version of this

http://www.youtube.com/watch?v=ynL8BCXih8U

Robot Suit Hybrid Assistive Limb (HAL)

As the exoskeleton arm is just a platform under the arm to carry the weight. The servo just locked in the angle of the arm, and let the mechanical strength to carry the weight, hence the power use is just basically for the computer, not lifting. Using the waist to strap the exoskeleton, and than the weight is distributed to the leggings for walking purpose. Maybe you are looking for a similar design? minus the looks and using springs, and the arm angle will be pretty much fixed unless disengaged.

[PyroDesu]

Yeah, I've seen the HAL before and that's what I was thinking of when I came up with this.

[counting]

Yeah, I've seen the HAL before and that's what I was thinking of when I came up with this.

If using springs there will be 2 things I guess will be crucial.
1. There are 2 major kinds of springs extension and compression. You probably need a set of it in each arm, so the extension spring can dampen the weight and adapt different carry loads, the compression spring will storage energy.

2. The disengage mechanism will determine the safety. What energy stored within mechanical structure must go somewhere, especially springs. The force involved is not kidding, (there are safety protocols for industrial springs, and I guess you will need industrial level for the exoskeleton actually being functional). Simply you need to let one end of the spring detach when the heavy objects is put down. And since large amount of energy is stored within, the detached end will need to be attached with some short of shock absorption system, like something from breaks. (And the heat generated by it will need to be distributed somehow). Or the compression springs can be made with some sort of mechanical energy to heat exchange system. (Unfortunately the most convenient one, may be hydraulic system).

Just pointing some obvious design issues. And maybe easier for everyone to discuss.

[counting]

Some japan students using pure mechanical exoskeleton designs

It maybe what it would look like when you finished (plus the springs mechanism)