So I seen a similar question to this, I tried to find if it was already posted or not so please forgive me if it was already asked.
So a more complete version of the question would be, can you remove someone’s limb by exploiting the human body’s weak points, such as joints, vulnerable areas, etc. I heard that the inner area of the elbow and knee are the weakest areas, and since I am currently writing a story with a character who exploits such weaknesses, I just wanted to know if this would be realistic.
Cory Doctorow says that the breaking strength of tendons is 50-150 MPa. As he notes, it’s rather complicated to extrapolate from that to the total strength of an arm. But even if we take the lower limit of 50 MPa, and use a rather spindly 4 inch diameter arm, it would require 91,000 pounds of force to tear the arm in half. This assumes the arm is composed of pure tendon, so adjustments for reality probably need to be made.
I think that, unless you were an insanely muscled bodybuilder, to have any chance of removing someone’s arm by hand you’d have to twist it around until the connective tissue broke. Probably bending the elbow and using the forearm and hand as a kind of crank handle.
Of a living person or a corpse? If it’s a corpse, and it’s even a couple of days dead, it might be decayed enough that it will come off more easily, and of course, won’t offer any resistance. A living person will be way, way, way harder, but twisting an arm of a corpse just might be possible.
The difficulty you run up against with a corpse or a living person is that it’s going to come apart as you twist. An arm isn’t a steel bar or a log. It’s a collection of a lot of different tissues that require different amounts of pull of torque to separate. And once you pull the skin apart, you don’t have anything to grip, and blood is making everything all slippery.
Even if it could be done it’s not going to sound realistic, so you’re better off just having your character dislocate the other guy’s shoulder or something equally incapacitating. Tearing off somebody’s arm should be left to explicitly superhuman characters.
You could probably dislocate a shoulder by hand, but tearing off the limb is another story. Arms are basically meat on a bone. Next time you buy a steak, before you cook it try to tear it in half. Or even try to tear a raw chicken wing in half.
This. If the victim were somehow prevented from fighting back, I would think the forearm is a pretty good crank handle for twisting the shoulder joint until each individual tendon and ligament is stressed to failure.
You’re assuming the shoulder is weaker than the elbow. For the first 90ish degrees you’re right that the forearm makes a good crank. Once the shoulder reaches the limit of its normal twisting range then all the torque you apply is trying to do three things simultaneously:
Tear shoulder “meat” (muscle, tendon, cartilage, etc) via rotary tension.
Spiral fracture the humerus bone via axial torque.
Rotate the elbow joint in the plane it normally doesn’t turn, tearing the “meat” there.
Of the three, my bet is the last one will fail first.
If one could actually break the bone, not just dislocate the joint, the broken end of the bone might assist in tearing the muscle so that the limb would actually come off. It would take some time, probably closer to hours than minutes, but working it back and forth and back and forth might work eventually.
It would have to be a twist and not a pull. If four horses can’t pull a man apart, one man isn’t going to be able to bring it off.
Holmes’ number is obviously way off. If it only took 495 pounds of force (not pressure) to tear off a hand, weight lifters would be losing hands all the time.
The point everyone is missing is: people are all different.
A 390 lb powerlifter might have 19” diameter upper arms, compared to a 150 lb desk jockey, with 12” diameter biceps. That’s a almost a 3x difference in volume. I’m pretty sure that the big guy’s arms are going to be hard to detach than the little guy’s.
It would be incredibly hard to pull someones finger off even, the things will happily hold your entire body weight (well healthy body weight of course)
You mean circumference, not diameter, right? This particular desk jockey’s biceps are nowhere near 12" in diameter, although probably close to 12" circumference. The force required to tear an arm apart (as Galileo noted in another context) is proportional to cross-sectional area, not volume. The ratio of cross-sectional area between a 19" cylinder and a 12" cylinder is about 2.5x.
Certainly true. That’s why in my calculation earlier in the thread I deliberately used a “spindly” arm of 4" diameter.
