Advice on Building Powerful Toy Cannon

[Bill MaghenParticipant @billmaghen22367]

Hello everybody,

I am not an engineer, and if my question does not fall within the parameters of this forum I will of course understand.

My friends and I are creating a large, outdoor game for kids, part of which involves the participants building towers with hollow boxes while other kids fire large diameter plastic balls out of cannons in an attempt to demolish the upper part of their rivals' towers.

I am looking for suggestions on how to build a safe but powerful cannon, that shoots a ball really hard about 30 meters (the angle will always be higher than players' heads). Should I go the massive elastic band stretched through a pipe route? the Pneumatic route? Other ideas?

BTW, I would be happy to remunerate someone who would enjoy working on this with me (from a distance: I live in Israel, and with Corona and all it's going to be virtual).

Best,

Bill

[Bill MaghenParticipant @billmaghen22367]

[Paul LousickParticipant @paullousick59116]

"a safe but powerful cannon" these words are contradictory. Whatever you make could be dangerous for kids.

But a Balista or Medieval catapult is an idea. When I was a scout leader we made them to fire bags of flour. You could use soccer balls. Do a search on Google for examples.

Paul.

[Martin ConnellyParticipant @martinconnelly55370]

Google "garden trebuchet" for something safer than canons or catapults.

Martin C

[Martin KyteParticipant @martinkyte99762]

The 'danger' can be assessed by the stored energy of the projectile. A football travelling at say 10m/s thrown from a Trebuchet has the same energy as when ejected from a cannon.

My preferred option would be a pneumatic 'cannon' ejecting a low mass plastic (hollow) ball. In this way the muzzle velocity can be set and consistant and the device relatively simple to make. The constraint would be getting enough volume of compressed gas into the tube fast enough to create a decent pressure pulse to eject the ball. Smaller diameter balls would make this easier.

If you limit your device to balls commonly used in sports games and ensure the machine can throw no further than a person can throw or kick the ball I don't see why it should be considered any more hazardous than the usual range of sports.

regards Martin

[Sam Longley 1Participant @samlongley1]

Sounds to me like some sort of youth movement, training for artillery crews of the future

Would these "cannon" be spare 100mm field artillery pieces by any chance?– Crafty!!!

If so connect them up to an air compressor with a foam ball.( stick a piece of lead in the middle for weight perhaps) If it was rammed home hard it should come out fairly quick, then soon loose trajectory without hurting the home team.

Then in years to come all they need to do is stick a 100mm shell in it & Bob's your uncle.

[duncan webster 1Participant @duncanwebster1]

goggle 'potato cannon'

or if you want to go large try **LINK**

like Paul I was once a Sot Leader, we used to make trebuchet out of scout staves and bungee cord, great fun. We once made a ballista with a 5m bow, it would fire a steel tent pole over 50m, needed plenty adult supervision on that one!

[pgk pgkParticipant @pgkpgk17461]

A lot will depend on the parameters. how high these boxes get stacked, weight of the boxes, whether they are building while opposing team is firing, age of kids and so forth.
There are commercial machines for pitching tennis balls or baseballs already that might be adapted to avoid some legal potentials, perhaps or make the game really messy with the use of water-cannon…

Stored energy and projectiles and kids strikes me as a injury waiting to happen unless supervised to the point where the fun goes.

pgk

[Sam Longley 1Participant @samlongley1]

When I was very young a crowd of us kids cut some large "Y" shaped sections of trees & dug them into the ground. We built corrugated sheet barriers round them & bound on lorry inner tubes to them to form giant catapults. For ammo we went to the local rubbish dump, which was an old pit that was being filled in & forraged 3 inch reject stones.

Then we fired them at each other in massive battles. One side was in an orchard & one side was out in the pit. We were about 50-70 yards apart. The noise when the rejects hit the iron sheets was enormous and always raised a cheer from the attacking side. Surprising no one was injured .

Proper kids games in those days.

Edited By Sam Longley 1 on 20/04/2020 13:13:06

[Grindstone CowboyParticipant @grindstonecowboy]

They did something very similar on Scrapheap Challenge, there may be a video available. If I recall correctly, the winner was a tennis-ball launcher type of gadget with two contra-rotating rubber wheel – plenty of power and reliable, but aiming was the issue.

[Paul LousickParticipant @paullousick59116]

Duncan,

The HP safety police would not let us do the things that were done at scouts, years ago. The game of "Bulldog" was banned in the 1960's as was "Fire ball soccer" where a ball out of chicken wire was stuffed with cloth, soaked in kerocene (parrafin). Then set on fire and kicked around the field at night. All was good until a kid was hit with a hot ball and had the shape of the chicken wire branded on his face.

Paul

Edited By Paul Lousick on 20/04/2020 14:11:45

[Martin King 2Participant @martinking2]

During Sailing regattas in the BVI the main projectiles were water filled balloons (vegetable dye was BANNED!).

Normally thrown by hand, these took on a whole new dimension when fired by surgical tubing catapults held between the shrouds with a bra cup as the projectile holder.

Not only was the range vastly increased but the splatter effect on impact was massive.

Could hurt a bit if you stopped one at close range full in the kisser….

All good fun.

Martin

[Mick B1Participant @mickb1]

Some decades ago, someone in the rifle club I used to be in made a potato cannon out of some specific grade of drainpipe that could stand the pressure. It was powered by butane sprayed into the combustion chamber from a can and fired by piezo crystal.

It could easily throw a big baking potato into the butts from the 100-yard firing point. My guess would be the thing was at least marginally illegal in any context, and you certainly wouldn't wanna have kids playing with it.

[Neil WyattModerator @neilwyatt]

Well I would use a powerful spring and a pad to 'kick' a toy football. If the force is comparable to how far you can kick the ball then it should be safe?

I think the legality of potato guns is questionable…

Neil

[HopperParticipant @hopper]

Note, the OP is in Israel. So spud cannons may not be quite the same concern there, compared with some of the other ordnance about the place.

Edited By Hopper on 21/04/2020 11:41:57

[Steve FParticipant @stevef]

Hi

You need to watch this man. **LINK**

I will maybe help

I love his videos

regards

Steve

[Steve FParticipant @stevef]

An updated video here with increased power **LINK**

regards

Steve

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