Have you ever wanted to make your own compound bow for fun or even fishing? [New creative DIY] shows us how in their YouTube video. Compound bows are very powerful in comparison to their longbow grandparents, relying on the lever principle or pulleys. meaning less power exertion for the same output.
Compound bows can be really sophisticated in design using pulleys and some exotic materials, but you can make your own with a few nuts and bolts, PVC pipe, string and a tyre inner tube. The PVC pipe can be melted into shape using a heat source such as a portable stove or even a blow torch, and once you have shaped your bow you will want to put a small piece of pipe at both ends with a nut and bolt. Then you can use rubber to give the flexibility your bow needs to shoot arrows, using the tyre inner tube cut to the right size. A piece of string for the ends of your arrows to rest on is then all you need, attach this to either end of your pipe and you should have a DIY PVC compound bow ready for shooting arrows. Alternatively you could always make a recurve bow out of skis.
–Update [Leithoa] in the comments has pointed out this is neither a bow nor a compound and that they are often confused. This is actually a slingshot, of sorts.–
Queue the PVC pipe hate, and go!
I was considering commenting “Is this safe?” but on reflection it was a silly question, this is a weapon, of course it isn’t. Still, how would PVC hold up under these kinds of load?
Surprised someone isn’t 3D printing the thing.
>Still, how would PVC hold up under these kinds of load?
Badly. I had a crossbow made in a similiar way when I was 7. The plastic would turn white at the stress points near the body and either crack or buckle.
There’s a weak spot in the design where the squeezes the pipe flat and then bends it. The pipe goes flat in the wrong direction and forms a sort of flex hinge that has almost no resistance to bending, so it will snap off there.
This is neither compound nor a bow.
This is a slingshot in the shape of a bow.
>>Compound bows are very powerful in comparison to their longbow grandparents, relying on the lever principle or pulleys. meaning less power exertion for the same output.
This is a common misunderstanding.
Compound bows do not take less effort for the same draw weight. A #150lb compound bow is going to take the same strength to draw as a #150lb long or recurve bow. You can change the ‘hardness’ (ie, the draw weight profile over the draw length) of the draw but it’s still the same weight. The compound bow will however take less effort to hold at full draw since the cams direct the tension across a cable. As for ‘more powerful’ that’s technically true, but IMO talking in terms of efficiency is less confusing. That is comparing two bows of equal draw weight, the compound bow will shoot faster (if the cams are adjusted correctly) than a traditional design but require the same strength to draw.
> That is comparing two bows of equal draw weight, the compound bow will shoot faster (if the cams are adjusted correctly) than a traditional design but require the same strength to draw.
So, for the same draw, it will shoot faster, which means it’s output is higher? So for the same output you need less power exertion?
It’s not less power exertion I think. It’s comparing longbows where (for example) the first 50% of the draw is easy and the last 50% of the draw is super hard, to a compound bow where 100% of the draw is of medium difficulty. The same energy is required for both but the compound is easier to draw because it’s uniform.
Aren’t compound bows also more compact compared to a longbow? I thought that was one of the advantages, because it allows a higher amount of power to the arrow in a smaller form factor. It still requires the same amount of effort to draw it, but you can do so without requiring all the space of a straight corded bow.
There’s a comfort thing too, I shoot a 66lb recurve instinctively with bare fingers and no release, but I can’t get on with the compounds Ive tried because the shorter limbs mean the string angles are tighter, if I went to a compound I have to use a release to stop my fingers getting crowded round the arrow and that sort of spoils it for me.
The longer recurve, while not as long as a longbow does suit me physically much better, but has the trade off against a compound that at release its harder to keep drawn, so aim, draw, release has to be a fluid movement or muscles get fatigued and you start to wander. I’d like to work up to a 100lb+ longbow eventually because then it becomes more of a raw skill of the archer than a assisted by equipment kind of thing and thats part of the attraction of archery to me.
I think a lot depends on your physique, I’m 6’3 and built like a brick outhouse.
Sort of.
If you have a #100 bow, there’s no way around it, you have to draw #100. Once you get past the let-off is where the advantage comes in, you’ll still be holding a significant portion of that draw weight (80-50% for most designs) but traditional designs would have you holding the entirety.
They’re within 15% of each other in terms of performance and you can take most game with #60 so the efficiency difference is immaterial for hunting. Most of the benefit is in the attachments & let-off with compound bows.
Work (energy) is force times distance. Even though the draw force is the same, the compound bow may indeed store different amount of energy and impart more speed on the arrow.
If your force is directly proportional to the draw distance, then the energy stored is 1/2 * draw * force. If the compound bow modifies that, for example by making the force constant over the draw, then the pull force may be halved and the bow still stores the same energy.
To know what is going on, you must know the draw force profile and integrate over that.
Hunting, bah.
But the AI killer robots are on the way, so we better start on perfecting some defense, and bows are silent so it can’t use its microphone array to quickly locate the attack.
Now we just need a bow that charges a capacitor on the arrow that discharges into the target like a taser to fry the evil robot’s circuitry.
They have these charging caps at the home improvement stores that look like 22 cartridges. I bet they’d make a great little hole in a bot. The combined weapon could be called a ” bot hole killer” 😂
Sort of.
A #60 bow requires #60 to draw no matter the design. Not all #60 bows are equal though.
You can gain 15% performance between designs. So a well designed/tuned compound bow at #51 would offer similar performance to a traditional #60 design.
You can hunt most game with a #60 bow, it may even be ‘too much bow’ for smaller game so all this talk of more power (KE more specifically) is mostly academic.
This is not true. Draw weight is a crude way of assessing a bow and only makes sense if you compare identically constructed bows.
What you want is a force-displacement curve for loading and unloading to find the hysteresis.
You want to compare peak force, force at draw length, and the work-done (area under the curve) on discarging.
It’s possible to make a compound bow which draws at 100lb over 28 inches but with a hold weight of 10lb and a wall of 300lb. This will be an incredibly easy to draw and fire bow compared to a 100lb recurve for most shooters (using my Kassai bear at 105lb/28inches is a bitch compared to my 100lb compound).
True, but at the end of the day you’re still drawing #100.
The perceived ease of draw is probably related to the muscles you’re using and when multiple groups engage. The scales don’t lie.
http://www.buildyourownbow.com/wp-content/uploads/2011/11/FDC_compound_bow_3.jpg
It is the efficiency of the bow to tranfer energy to the arrow that is the big difference between longbows, recurves and compbounds. Draw weight is, as Alex pointed out a crude way to ballpark the power of a bow. It is mainly used to match a bow to the strength of the person shooting it.
Hey thanks for you comment, I’m not a bow/slingshot expert I just thought it was a neat hack so my terminology was a bit wrong. I’ll credit you in the article thanks for pointing this out.
No need for the credit, but thanks!
There is some argument for it being a bow, IMHO most if not all of the power comes from the inner tubes, but that’s just from what I see in the video. I could be wrong.
I didn’t solely rely on your comment I did some digging and while strikingly similar to a bow the rubber does the work just like a catapult. Sometimes this happens on HackaDay you get some details wrong and when you do it’s good to credit people. I’d rather be wrong and know about it so thanks for the comment.
If you’re drawing a 150lb bow of any kind, I don’t want to be anywhere within 2 miles of you :-)
Look for backyard bowyer on youtube. He’s been doing this for years. Tons of bow designs and he shows how to make them. He even wrote a book about it.
My father in law ran a bow shop for a number of years. Despite this I know nothing about bows except that this video is a lot easier to watch at 1.5x!
I always watch video’s like this at 1.5x speed. the only time I watch at normal speed is if I can’t understand what is being said anymore more but that is rare unless you have a fast talker in the video but video’s with no speech 1.5x is great.