How Compound Bows Work

The fastest, most powerful, most accurate bows ever made are modern compound designs. What advantages do they have over traditional bows of yore and how do you shoot one?

The Difference Between Compound And Traditional Bows

All bows use the mechanical advantage of leverage to store energy in flexed limbs as you draw them. This is how they shoot an arrow faster than you could throw one.

Traditional bows — longbow, recurve, whatever — store this energy directly. The further you draw them, the harder they get to pull and the more energy is transferred into the arrow when you release. The more effort it takes to draw a traditional bow, the faster it will shoot an arrow. When you’ve drawn a traditional bow all the way to your ear, you’re left holding the entirety of its draw weight. So if your bow draws 70lbs, you’re holding 70lbs between your hands. Which is hard.

The big wheels on the ends of a compound bow are cams and their profile is designed to create a “let off” at the end of the draw. Typically this is between 60 and 80 percent of the draw weight. So with my bow — a PSE Full Throttle— I have a 70 percent let off, meaning that with its 70lbs draw weight, I only have to hold 21lbs. That allows me to hold it at full draw for longer, using that time to take more careful aim on the range or to wait for the animal to move into a perfect shot while hunting. Less effort also means I’m able to hold the bow steadier, further increasing accuracy.

Through the profile of those cams, bow designers are also able to determine how much of the bow’s power is applied to the arrow at what point in the string’s travel. The Full Throttle is so fast because it’s able to get full power to the arrow very early in its travel, then hold it there until it leaves the string.

You may wish to join an archery club. Here are a couple of clubs to join:

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