Compound Bow From PVC Pipe:

   This instructional video shows step by step how to make a compound bow from innexpensive, readily available materials. Anyone can do it if you have some patience and are willing to try. This is a good project for anyone who wants to get into archery with a compound bow but doesn't want to pay for such an expensive item. Or you could just make it to learn about how these types of bows work and gain experience working with this sort of thing.

   For those that don't already know a compound bow is a bow that uses a set of cables, pulleys, and eccentric wheels to create leverage and manipulate the force that it pulls with at different draw lengths. Normally you want this type of bow to pull with a lot of force during most of the draw, then "let off" to a lower weight once drawn all the way back. This way it is easier to shoot but still gives better performance than a more traditional type of bow.

Contests:

   I would like to enter this instructable in the UP! contest because it demonstrates that I do projects where I need unusually shaped custom parts made of plastic or other materials.

Step 1: Optional, Make a Sight

This step will show you how to make a sight for the bow. This isn't a traditional bow sight. It is more like an "iron sight." But it does work well on this bow.

The instructions are on the pictures.

To adjust this sight (assuming sight is mounted on left-side of bow):
-arrow shoots left of target = turn screw out.
-arrow shoots right of target = turn screw in.
-arrow shoots above target = tilt sight up.
-arrow shoots below target = tilt sight down.

Step 2: Scan of the Cams

I recieved a request for a template of the cams, so I scanned them. Yard stick included for scale check. The cam has several axel holes that I tested with. I am using the one that is lowest and furthest clockwise in the picture.

The second picture is an improved cam design, including the template and a tracing onto some light blue foam. I will cut it out of the foam and cast it in aluminum. The third picture is two finished cast aluminum cams.

Comments

[Alex739]

I've built a similar compound bow with a slight improvement on power.

Prior to bending the shape of the limbs I purchased a set of Fiberglass push poles that are used by those who do telephone or security system work.

they are 8' x 1/4" in diameter. Remove the threaded end by cutting them off (MAKE SURE YOU ARE WEARING A FACE MASK!!!! & EYE PROTECTION)

Measure the length you need below the notches for the two cams. Slide the lengths you want to install in to the shank of your bow. Once done you will find that ending will be a bit harder when heating. This is where you need to make a jig for the shape you want to make. Once heated place the bow in to the jig and clamp in place until it has cooled completely. When done correctly it increases the bow strength and draw from just 30lbs to more like 60lbs with a selectable cam design. It can be a 60 to 30 LB draw length, a 70/ 20 or a 60 / 40 depending on your cam choice. and YES it does work! just used caution that your draw does not break off your cam supports. that is your weakest point .

Other than that he did a Great Design on his bow.

[sde la maza]

Hi, by any chance do you have the templates for cutting the pulley? i have access to a waterjet cnc machine and i´m planning to build the pulley by layers of aluminium and then bolt them together, thanks.

[johndean30842]

Does it shoot?

[pacman23]

does it shoot

[Chrispcrunch]

So Cool!!

[That_second_guy]

The second picture cams do they create let off?

[Skwurlito]

I'd like a digital copy of your brain modified to act as an operating system to power my RasPi cluster.

[Tkerfien]

I think that what you have done is incredible and I am now planning my own. One tweak if you will. In your video, as you were flinging some arrows, you mentioned that the arrows weren't consistent. I think that it is due to the strings tracking different paths inside the cam and pulley with each fire; the laminated smaller disc is wider than the string is thick. The solution as I see it is as follows:

1. Cut out the smaller diameter discs and sand to the traced line so they are nice, round and smooth ~ as you did.

2. Find the center and drill your hole ~ as you did.

3. Set up a router table with a V notch bit. Build a jig/fence that (a) is an inch or so shorter than the diameter of the disc and (b) the laminated discs (smaller diameter ones) will bolt to. Set the disc on the table and snug to the fence and mark the hole onto the fence and drill it out.

4. Adjust the fence so that the center of the hole (from step 3.) is centered on the tip of the bit.

5. Adjust the fence so that the laminated disc is centered on the tip of the bit.

6. Adjust the height of the bit so that there is a small shoulder to each side of the V notch but not too narrow that would prevent the string from "seating well" inside the notch.

7. While holding the laminated disc against the fence and centered on the bit, start the router and slowly plunge the disc into the bit. Once the disc comes in contact with the table, slowly rotate the disc a little bit to clear a bigger channel and shut the router off and allow it to come to a complete stop.

8. Bolt the disc to the fence just tight / loose enough to prevent wobbling but allow it so spin smoothly ( a little dish soap would help reduce friction too). With the disc bolted in place and rotated into the plunge portion of the cut, turn on the router, allow it to come up to speed and start turning it slowly.

9. The complete your assembly to finish ~ as you did.

This notch creates a defined or fixed location for the string on the cam and pulley. By doing this, the string will produce the bow's part of the equation for consistent group of arrows; the other part of the equation is the shooter (that's where practice of follow through comes in). With the tighter and consistent group of arrows, keeping the same anchor point (hand to cheek at full draw), you can now start to adjust your sight wind-age and elevation making this a more accurate machine.

THANK YOU for the project idea and again, very impressive project. Well done.

[Jaycub]

That is a good idea and would probably make a better cam I agree. You might only need 3 layers of the PVC on the cam that way, which would be lighter so it can shoot faster. With the sight the bow actually was pretty consistent and could give tight arrow groupings even with the cams it had. It was just weird to shoot without a sight because of the way the arrow rest area was made.

[jaxy boy]

Yeah I'm 13 and I had ago with my dad after previous PVC bow attempts from my own designs I have it ago and it realy worked and we took it out and got some pretty good shots on some nice rabbits thanks man great build good to see people taking the time and effort for a serious project good job

[wesrurede]

I had been watching some science show from nova about how a bird's beak is comprised; a hollow shell of plastic for rigidity(the PVC in this case) and styrofoam to fill the void, is an equivalent to the extremely powerful bird beak of say a toucan. Do you suppose filling the inside with foam might give it more power?

[Jaycub]

Probably not much, of course you could try it if you want.

[Tech_Master]

You should put a D loop on the string and use a release it makes your shot waaaayyyy more accurate then when you use your fingers.

[Jaycub]

Yes, that is true. I was doing some experimenting with the cams but I will probably just go back to the original ones. Then when it gets it's final string (will be a "dacron" continuous loop string) I'll put on a d-loop and another sight (managed to break the first one) and get accurate with it. I have made another video which shows how to make a very simple release aid from a stainless steel latch, there is a liknk somewhere in the main video here I think.

[Fiddlehorn]

I don't get how you strung it

[Jaycub]

Look in the first fideo at minute 24:00. That is where the stringing begins, it is not too hard.

[darrenhall]

Great build - always nice to see a complicated project works so well.

[bethehammer]

you should use the same laminating technique you used for the CAM to build your release aid....
Not sure the power of the bow, but it sounds awesome. nice job.

[Jaycub]

I like that idea about lamination layers to make the release aid. That is actually what I originally pictured but I wasn't sure what I wanted I guess. I just wanted to try something quick when I made that one in the second video.

[bethehammer]

very nice. video was a bit hard to follow since you were filming and building in each hand. Having a full detailed instructable with pictures and instructions would be nice, to be able to print and follow. How powerful is this bow compared to others fps? if you did a kit what would it include and how much?