Slingshot Cannon

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About: I am a curious soul with the means and ability to take over the world....but I would like to avoid any such headaches so I create to give kids with disabilities something to remember.

I made these cannons for a pirate themed Camp Cranium at Camp Victory.  Arrrrrrgggg!!

Step 1: Materials

I have 7 of these cannons to make so you may see pictures with more supplies then needed.

MATERIALS

1-> 2' piece of 6" PVC
1-> 6" PVC cap (thick PVC)
2-> 18" pieces of 3/8" Latex Tubing (Surgical Tubing)
1-> 12" piece of 1/2" nylon rope
1-> 5' piece of 1/4" nylon rope
1-> 3/16" x 1-1/2" Eye-bolt
1-> 3/16" Lock-nut

TOOLS    

Drill
Saw (PVC)
PVC Glue
Epoxy
5/32" Drill bit
1/4" Drill bit
3/8" Drill bit

Step 2: Firing Assembly

Cut the 6" PVC cap in half, and cut a notch in the center about 5/8" wide and 3/4" into the cap.  About 3/4" from the notch drill a 1/4" hole on the other side about 1 1/2" from the notch drill a 5/32" hole.

Step 3: Firing Assembly Continued

Thread the eye bolt into the 5/32" hole and attach the nut to lock it in place.

Step 4: Attach Firing Assembly

Simply glue the half cap onto the 2' PVC pipe

Step 5: Holes for Latex Tubing

Drill four 3/8" holes at the end without the cap on it.  It is best to drill them at 90* angles about 1/2" from the rim.  First level the entire barrel using a larger level (you can just make it out in the first picture across the half a cap).  I used a combo square with a level in it to mark at 90*.  Mark two points that the level touch in one position then move it around so one of the points is still in contact with the square.  Once they are drilled by sure to smooth the edges they will cut through the latex tubing if not rounded off.  I used a x-acto knife and sand paper.

Step 6: Attach Latex Tubing

Insert Latex through 3/8" hole and tie.  Be sure the knot is big enough to keep the tube from slipping through.

Step 7: Setup Loading Rope

Take the 1/2" rope and tie it onto the Latex tubing.  Use the Epoxy to secure the knot be careful not to get any epoxy on the latex.  Next tie two knots one in the center of the rope and one at the end.

Step 8: Launching Cord

Attach the 1/4" cord to the firing assembly.  Insert the line into the 1/4" hole and tie off.  Thread the line through the eye bolt.

Step 9: Loading Cannon

Pull rope back and set middle knot in notch.  Insert cannon ball (tennis ball) from back of cannon. DO NOT GO TO THE FRONT OF THE CANNON AFTER IT IS COCKED!

P.S I am still finishing up the rest of this ible.  From this point on at the moment the instructions are a bit cryptic and dont cover the entire build.  I will get it to make sense ASAP.

Step 10: Materials for Cradle and Pivot Points

Materials
2" x 12" at 16" long -  Cradle Base
2" x 12" at 15" long -  Cradle Sides (45* trajectory)
               or
2" x 10" at 15" Long- Cradle Sides (Flatter trajectory)
12" of 1/2" Dowel rod - Wheel Axles
4 - Finishing nails - Axle pins
4 - wooden wheels (mine are 5" diameter)
4 - 1/4"x2-1/2" Lag Bolts
2 - 1 1/2" PVC Tubes (Pivot Mounts) at 3" long


Tools
Drill
Saw
1/2" Drill Bit
3/4" Drill Bit
6/32" Drill Bitt
1-1/4" Drill Bit
5" hole saw (optional)
1/2" Socket
Measuring Devices
Epoxy or PVC cement

Step 11: Pivot Points

Installing the pivots is very similar to the method used for drilling the holes for the latex tubing.  It is best to drill them at 180* angles about 12" from the rim.  First level the entire barrel using a larger level, then use a combo square with a level in it to mark at top dead center.  Mark the two points that the level touches in one position then move it around so that another point is 180* from the point on the side of the barrel.  After they are marked drill a 1-1/4" hole on each side (I tried a 1-1/2" bit the first time to fit the PVC but there was to much play in the pivot mount for me.)  You may need to shave the sides of the hole to allow the PVC pivot tube in.  After the tube fits use Epoxy to attach the pivot tubes to the barrel.  You will want to leave as much PVC sticking out of the barrel to make it easier to mount to the cradle.

Step 12: Cannon Cradle Base

For the base of the cradle I cut a 2x12 at 16".  Then drilled four 1/2" holes at 1" from the end and 3/4" from the face at 1" deep or just drill until you get to the angle on a paddle drill bit.

Step 13: Axles

Sorry for the blur.  It is a 3" piece of 1/2" dowel rod, this will be used as the axles for the wheels.  I drilled a hole large enough to put a finishing nail through to hold the wheel on.

Step 14: Wheel Making

This is a finished wheel I made it a 5" diameter.  I wanted a bumpy shape so I traced a 5" circle and used a hand jig saw to cut them out.  I would now suggest just using a 5" hole saw.  The hole in the center of the wheel is 5/8".

Step 15: Cradle Sides

Ok so here is where things are up to you If you want the cannon to go to 45 degrees for the furthest firing use a 2x12 that is 15" long and cut steps into it at 3-3/4" x 3-3/4".  If you want a flatter trajectory use a 2x10 at 15" long and cut two steps at 3-3/4" x 3-3/4" and the last step at 3-3/4" x 1-3/4".

Step 16: Cannon Mounting Points

With the sides cut, clamp them together and drill a 1-1/4" hole at 1-7/8" in from the sides.

Step 17: Wheel Attachment

Take the 3" pieces of 1/2" dowel with the finishing nails 1/4" from the end and insert it through the wheels 5/8" hole.  Insert the dowel into the 1/2" holes with glue in the hole and around the end.  You may need a persuader (hammer in civilized shops).

Step 18: Measuring for Cradle Sides Anchor

Decide which end you want to be the front then measure the 1st mark 2" from front of cradle @1-3/8" in from side.  2nd Mark 8" from front of cradle @1-3/8" in from side.  Mark the opposite side of cradle on the same face with two more marks at the same measurements.

Step 19: Lag Bolt Set Holes

At each mark drill a 3/4" set hole at 1/2".  This will keep the lag bolts hidden within the wood and allow the socket wrench to be used to screw the lags in.

Step 20: Cradle Sides Alignment

On the top of the cradle place a line at 2-1/8" in from the side that runs from the front of the cradle toward the back.  This is the line you will use to space the sides the correct distance apart to allow the barrel between the sides. (This is where problems will arise if you have different PVC then what I used.  You may want to do the calculations yourself.)  After the line is drawn you will want to glue the sides in place.  The sides inner edge is what you will place on the line. (You may want to try clamping it in place before glue and set the barrel in to check proper positioning.)  After you have glued the sides and clamped them in flip the cradle over so you can get to the 3/4" set holes you drilled for the lag bolts.

Step 21: Cradle Sides Attachment

Drill a guide hole with a 6/32" drill bit in each of the set holes for the lag bolts.  Screw the Lag bolt in with a driver or socket wrench.  The lag does not need to be super tight just snug to hold the side in place.

Step 22: Barrel Mounting to Cradle

Take barrel and place in cradle.  Now this is where it is up to you haw the mount the barrel to the cradle.  I simply put 3 drywall screws through it and that held very well.  I placed 1 in each of the pivot points and 1 in the base of the barrel.

Step 23: Activate Your Cannon Ball Retrieval System

Call dog.  BEGIN THE BOMBARDMENT!!!!! ARRGGG!!!!! fire, repeat, enjoy.

Later!

Step 24: After Thought!

It might be hard to see but I trimmed about 3/4" off of the back of the barrel above the PVC cap part.  Trust me it is worth removing that material before it removes skin on every load.  (Yes I learned it the hard way, but only once twice tops.)

Step 25: Video Stuff

Hopefully these two videos will work one is the how to load and fire the cannon the other is a fun video of what its like to be a cannon ball.

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    38 Discussions

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    codongolev

    7 years ago on Introduction

    this, unfortunately, reminds me of a recent project one of my friends made in an engineering class. the objective was to play cornhole from a series of distances using a machine we build in class. his team's original design was to use varying amounts of weight and a system of pulleys to accelerate a cornhole bag forward. however, as the build time in class progressed, they spent more time than anticipated building the frame. with only a few days of building left, they ended up strapping a barrel from one of last years' projects to the frame and took some scrap surgical tubing and exercise bands and basically made this design. it... didn't go to well. this design isn't made for accuracy (they basically guessed on all the calibration.) they came in last place. (we, on the other hand, built a catapult as precisely as possible, and ended up coming in second place.)

    3 replies
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    Wise Ravencodongolev

    Reply 7 years ago on Introduction

    Once it is dialed in I can put tennis balls in a 50 gallon drum at 35 yards consistently. As long as the bands don't get twisted during loading it stays very accurate.

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    PhoghatWise Raven

    Reply 2 years ago

    If you only used 2 bands, and used looped bands, making it more a less a regular slingshot inside the tube, accuracy and power would be better

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    codongolevWise Raven

    Reply 7 years ago on Introduction

    the problem with theirs was that they tried to jam too much rubber into a tube that was too small. the rubber actually caught on the edges of the barrel, and cause innacuracies. (also, dialing it in was impossible, because they had no way to do that. like I said, they were just guessing.)

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    WilliamH158

    2 years ago

    are there any videos showing how to launch this? Also, what does the launching cord on step 8 do? also, would it work in a smaller sized pipe?

    1 reply
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    Wise RavenWilliamH158

    Reply 2 years ago

    The launch cord is used to dislodge the knot from that slot you cut in the back of the cannon. As for a smaller barrel I think it would depend on what you wanted to shoot from it. There is not alot of space inside the barrel and things sometimes get snagged, but there is one way to find out. Good Luck!

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    prashob kp

    4 years ago on Introduction

    what is the speed of this thing and can it be used as a bowling machine, btw where are the videos

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    Wise RavenSARAGOGH

    Reply 6 years ago on Introduction

    Not really as long as you only use tennis balls but if you lengthen the rubber tubing it will reduce the velocity.

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    Wise Ravenverbstyler

    Reply 6 years ago on Introduction

    Its accurate to about 35yds. You can crank it up a little more but be careful when the bands snap it hurts.

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    codongolevtwighahn

    Reply 7 years ago on Introduction

    one wonders if you could make one large enough to do the entire paper route from your backyard.

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    Wise Raventwighahn

    Reply 7 years ago on Introduction

    Yes!!! I love it! When you can get it from the road to the kitchen table in one shot. Just add 1 or 2 more bands and you can get the Sunday paper moving

    I'm totally going to use this design and make a more modern-type cannon and use it for airsoft >:D
    Thank you very much!

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    ilpug

    7 years ago on Introduction

    great. must make this on a smaller scale...

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    Wise Ravenbonnie13

    Reply 7 years ago on Introduction

    Thank you, they are a lot of fun. Especially when firing at an inflatable pirate ship in a pond!