Sledgehammer Speeds
Bullet resistant glass is designed to stop high energy, tightly focused impacts: like, say, a bullet. However, a large amount of bullet resistant glass will break from a relatively soft blow from a sledge hammer—which is smaller energy, loosely focused. Some years ago, a British glass manufacturer developed a highly shatter-resistant glass, and wanted to ensure that it could also survive a simple sledgehammer hit.
They tested a wide range of individuals with various weights of sledgehammers and found, on average, a common sledgehammer swings at 22-33 miles per hour.
Fortunately, they were more interested the impact energy of the swing, more so than the speed. But interestingly enough, it’s quite easy for you to work out how fast you swing a sledgehammer, or indeed any weapon. All you need to know are two things: your weight, and the weight of the weapon.
The formula is:
If you want to try this, k equals 10 (to get a result in miles per hour). M is your weight in pounds, and m is the weapon’s weight in pounds.
If you use Microsoft Excel, you might find this version easier. Paste this into cell A3:
=10*(SQRT(A1/(A2+(A1/81))))
Then, in cell A1, put in your weight in pounds; in cell A2, put in the weapon’s weight in pounds.
Whichever approach you use, let’s see how this formula compares.
If a person weighs 170 pounds, and swings a 15-pound sledge, this formula spits out a velocity (v) of 31.5 miles per hour. That’s in agreement with the British findings.
What about a 200-pound person swinging a 12-pound sledge? That results in a 37-mph power shot: faster than their average.
Although this may be interesting to a few people in the sledgehammer trade, does this formula work for any type of swinging weapon? The answer is yes. If you know the weight of the weapon and the weight of the wielder, you can get a reasonable estimate.
Some FMA practitioners boasted to us they can swing a stick at 95 mph. Is this plausible? If you apply this formula, the student will never exceed 90 miles per hour, even if he weighed several thousand tons and used a stick that weighed only one ounce. As long as that stick is attached to a human arm, it’s highly unlikely (throwing an object can produce greater velocities, but that’s a different formula).
However, if you plug in typical values (a 180 pound student with an 8 ounce rattan stick), he can swing at 81 miles per hour. This is not only within reason, but pretty much matches up with high-speed filmed strikes.
What other values do we find? A four-pound sword swings at 54 miles per hour...which again matches video as well as general claims by sword experts.
A 30-ounce baseball bat swings at 66 miles per hour, which is within range for a major league hitter. And so on.
Have fun with this formula. Plug in your weight, and find the weight of your stick, hammer, shovel, or other weapon. With those two numbers, you can see what your probable swinging speed is.