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I was working on designing some robotic grippers and I find I have to make a pretty large device to have anywhere near the same power as the human hand.

Is this other engineer's experience? Is the human hand, cubic centimeter for cubic centimeter just really strong compared to a machine?

I guess this translates down to how ants can pick up "boulders".

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  • $\begingroup$ Keep in mind that the grip strength in your hand isn't generated in your hand, the mussels for gripping are in your arm. $\endgroup$ – Andrew Oct 4 '16 at 10:27
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I find I have to make a pretty large device to have anywhere near the same power as the human hand.

Is the human hand, cubic centimeter for cubic centimeter just really strong compared to a machine?

Keep in mind that power and strength (force) are very much separate things.

It is easy to make a very strong and small gripper, by using worm gearing to magnify the force of a small motor. The limit is the strength of the materials used. Human bones and tendons are pretty strong, but there are engineered materials that are even stronger for the same size.

As for power (work done per unit of time), one cannot look at the hand in isolation. Like Andrew mentioned in a comment, the muscles are actually in your arm. And the cooling and energy supply are all over your body. To compare, a hydraulic gripper can deliver very high power in a small space because it offloads part of the work to the hydraulic pump supplying it.

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Human hand is certainly a very efficient and compact machine. It is so versatile. It can pick up a miniature gem of a diamond barely visible and place it in an expensive watch; same hand when fisted can break a slab of concrete or kill a cow.
Hand doctors have tables of range of motion and power from each joint and finger or combination of them. At our gym many regular looking guys can exert 120 lbs. to the grip machine.
The miracle of power and flexibility of hand is its complex set of tendons and ligaments which allow for great range of tasks, from fine work of a brain surgeon to blacksmith workers or marshal art athletes.
There are definitely specialized tools, levers and machines that are designed to extend the strength of and spectrum of its capability hand and they are getting more efficient and take advantage of modern light weight material. But non are as compact and multifaceted as our hand. Hand has this extreme range of dexterity because its muscles can turn from holding to stabilizing to active to passive, or even sometimes just add bulk under the active muscle so its arc of flexion is optimized, for wider lever arm advantage.

And all this time we have not even scratched the surface of subject of our nerve network in hands and how they read the input as far as touch, pressure, heat, etc.

our hand is a respectable example of nature's perfection.

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