The Weight of the Fist of Hydra: Bucky Barnes’ Arm

stele3:

WARNING: there is a shitton of math in this post.

So this response to the post I did on the physical issues that Bucky Barnes probably has as a result from his time with HYDRA (strictly from a massage therapist’s POV) got me wondering: how much WOULD the metal arm weigh?

If we take his height and weight from the comic books, he’s 5’9" and 260lbs…which is a lot for a 5’9" dude to weigh! The logical answer is that a lot of the weight comes from his arm. Much as Wolverine is listed as being 300lbs with the adamantium skeleton and 200lbs without, I think we can safely say that from the POV of comic book canon, the metal arm must weigh about 50lbs, and that’s assuming Bucky weighs a super-jacked 210lbs. (Though the ideal weight for a man of 5’9" stature tops out at 174lbs.)

But that’s comic books. What about in the movie perspective? Well, let’s look at it.

• In CA: TWS, the arm is shown to deflect bullets from a handgun fired at close range with no apparent damage and when Bucky punches Steve’s shield neither is damaged. From this I think it’s safe to say that at least the outer surface of Bucky’s arm is made of vibranium.
• From that we can also extrapolate that the outer vibranium plates, which were shown shifting around a lot in TWS, must be about the same thickness as Steve’s shield.
• I can’t find any resources as to how thick Steve’s shield is, but it’s 12lbs and 2.5’ (or 30") in diameter.
• There aren’t any measurements or calculators for the weight of imaginary vibranium, but in CA: TFA, Howard Stark mentions that vibranium is one-third the weight of steel. That means that, if the shield were made out of carbon steel, it’d be 36lbs (12 x 3 = 36).
• Fortunately there ARE calculators for the weight of steel!
• A circle of steel that’s 30" across and 36lbs would be about .18" in thickness.
• Thus, Steve’s shield is .18" in thickness.
• And so are the outer vibranium plates of Bucky’s arm.
• That steel weight calculator doesn’t have a cylindrical option, but this one does.
• Circumference of a human arm is a little difficult to figure–obviously personal fitness causes the size of one’s arm muscles to vary quite a bit. Various sites that I’ve looked at indicate that a highly-fit man could expect his biceps to be 17" in circumference at their widest and his forearms to be about 13" at their widest. (For reference, I’m a not-fit woman and my biceps are 13.5" and my forearms are 11".) Obviously that’s at their widest points, so I’m going to knock 2" off both of these measurements to make it more equal across the length of the limb.
• Various sites helped me figure out that for a 5’11" man, a normal forearm length would be about 10" and upper-arm length would be about 15". (My forearm is 9" and my upper arm is 12".)
• Thus: assuming that Bucky’s forearm is 11" around (which is a conservative estimate) and 10" long, the metal plating covering that area, at a .18" thickness, would weigh in steel about 9lbs. Divide by 3 and in vibranium that’d be 3lbs.
• Assuming that Bucky’s upper arm is 15" around (again, conservative) and 15" long, the metal plating covering that area, at a .18" thickness, would weigh in steel about 18lbs. Divide by 3 and in vibranium that’d be 6 lbs.
• 6 + 3 = 9lbs. The outer vibranium plating on Bucky’s forearm and upper arm weighs about 9lbs. (Based on conservative estimates of arm circumference.)
• That’s just the outer plating on his forearm and upper arm. That doesn’t count his hand.
• Looking at body segment percentage weights, we see that in terms of typical body percentages, a hand usually weighs .65% of the total body weight compared to 1.87% for the forearm. Thus, the hand usually weighs about 1/3rd of the forearm.
• Assuming that holds true for the metal hand, then the vibranium plating on the hand would be about 1lb.
• 6 + 3 + 1 = 10lbs. The outer vibranium plating on Bucky’s whole arm weighs 10lbs.
• If we bump Bucky’s height up to 5’11" (actor Sebastian Stan’s height), the ideal body weight for a 5’11" man with a large build tops out at 184lbs. Looking at the body percentage index again, we see that typically, a whole human arm is about 5.7% of a person’s bodyweight. So for a 5’11" guy with a large build at 184lbs, that’s about 10.5lbs.
• The outer plating on Bucky’s whole arm already weighs about as much as his regular flesh-and-bone arm, assuming that a) it’s made of vibranium, a very light metal, b) the plating is the narrowest possible width that can deflect bullets, and c) the circumference of the arm isn’t very big. All of which would make the plating a lot heavier than what I’ve calculated.
• That is just the outer plating.

tl;dr Bucky Barnes’ arm is heavy.