Why do compound bows have wheels on the outside?

Reduces friction, making it easier to draw the string, at least, that’s what I’d assume.

edit: well, not so much friction, but just makes it easier to draw the string, so you can probably use a much stronger one that you would be able to use without the wheels. (technically pulleys)

The power is from the pulling the string back. Two bows curved and compound with the same drawing weight (effort to pull) will have the same power. The wheels (cams and pulleys) are used instead of the curved bow to transfer the energy from the much stiffer limbs to the arrow.

The wheels are actually pulleys, which enable the archer to put more power behind the arrow than can be done with a simple bow.

The wheels are a cam and an idler wheel, they provide “let off” which makes the pull much easier once the they engage. It’s a little help from physics to give you a much stiffer effective pull. Many have like a 75% let off meaning if the pull is 100lbs you only have to hold back 25.

@all I prefer a normal bow that requires strength. I hate the pulleys. The pulleys bow doesn’t have the oomph that a normal bow has.

@RedDeerGuy1 It’s got more oomph

@ARE_you_kidding_me Maybe the user put too much slack so junior high school students can use it. I used the normal bow and arrows in gym and they could pierce Styrofoam.

Piercing styrofoam isn’t exactly setting the bar high though.

@Darth_Algar Yet the compound bows I have used couldn’t even do that.

A 25 pound compound bow will be weaker than a 85 pound curved bow. What was the “pound draw” on the two bows? ?

@Tropical_Willie I don’t know. It’s was for gym in junior high.

Most compound bows have adjustable draw force and let off. It is possible that the bows you were using indoors were intentionally set light so students would not accidentally do damage or hurt one another.
My compound Bowtech Diamond is adjustable from 40 pounds to 70 pounds and has an 80% let-off cam. It is powerful enough to send an arrow completely through a deer. (I’ve been told.)

The only compound bow I’ve used was my stepfather’s; a little 30” one that had a 70-pound draw. Nasty little brute! As I was only about 12 at the time, I had a hard time drawing it back to the let-off point. I’m not sure what that particular bow would do to a deer, but it put a nice hole in the fender of a ‘72 Ford from about 15–20 feet. Didn’t send it completely through (only up to the fletching) but still…

I’m thinking you used a de-tuned bow. I know that if I handed a compound bow to a bunch of unskilled half-grown people of questionable discipline for use indoors, I’d set the thing pretty damn low. Think what a full-power compound bow that could put an arrow through 1/8” steel could do if the wielder was totally inept, or worse, engaged in any sort of horseplay. Think of what a bow designed to put an arrow deep into a deer at 250 feet would do to a person at 25 feet. Then again, a cheap “sportsman grade” compound bow runs $300-ish, so odds are you used something like this instead of a real compound bow

Oh, and if you dry-fire a real compound bow, you may crack the limbs in ways that you won’t notice until the bow explodes in your face. ALWAYS release tension slowly unless you have an arrow nocked or else all the energy that would normally go into the arrow instead goes towards breaking the bow… and possibly whoever is holding it too. Since that is a danger of compound bows, that is yet another reason why they would use a low-powered $20 bow instead of actual $300–1,100 bows that have enough power to kill a person; a beginning archer may dry-fire, hopefully by accident but possibly out of ignorance, and it’s best for all concerned if there is zero risk of serious injury (including possibly losing an eye or two) unless/until the archer knows damn well not to make that mistake.

FYI, that “let-off” point really is the big advantage of compound bows. Take a regular bow with a 70-pound draw and see how long you can hold it back while you aim without shaking. You may think you’re strong, but I guarantee that by the time you hit the two-minute mark your fingers will hurt and your arm will start shaking. Meanwhile, that bow my stepdad had had a “hold weight” around 20 poundd… which is probably still more than the draw of the “compound bow” you tried.

Also note that pulling the string back the normal distance doesn’t move the bow limbs as much as it would a regular bow. Well, when you let go that reverses; the bow limbs only have to move a little to move the string (and thus the arrow) a lot. If you paid attention in physics, you’d know how that E=½mv^2 and from there be able to figure out how increasing v would make the arrow fly farther and/or hit harder. You would also have a rough idea how much energy is stored in the bow limbs and realize that it’s considerable more than “regular” bows.

In any event, try a REAL compound bow and see if it’s even anything like the alleged “compound bow” you tried as a kid. I’d wager you’ll be surprised how different it is from the toy you used.