OT/ Jennie found me an interesting book...

[Shadow]

...at the library.

It's titled "Backyard Ballistics".

I'm in the process of gathering the stuff to make the Patato Cannon (commonly known as the spud gun) now.

[Lark]

Be afwaid, be wery, wery afwaid!

-Lark-

[mermdotcom]

... I'm not sure whether I should be amused or frightened!  

[Shadow]

... I'm not sure whether I should be amused or frightened!  

Want to know what the propellent is?

Aerosol hairspray!!!

Yep, on average about a two second burst of hairspray into the combustion chamber is enough to propel a large Idaho baker about 200 yards downrange.  Use the cheapest hair spray available since holding power and scent aren't the important factors here.

Didn't know the propellent in most aerosols is butane, did ya?

[Anonymous]

Didn't know the propellent in most aerosols is butane, did ya?

I did, but then again, I watch a lot of Scrapheap Challenge (they call it Junkyard Wars there). Wouldn't it be safer to use compressed air?

[Shadow]

Actually there are two plans for a patato cannon, one uses hairspray to fire as a combustion type propellent and the other uses compressed air.  We intend to use both.  According to what I've read the compressed air cannon is stronger and more accurate than the combustion type.

We also intend to make the carbide cannon.  It doesn't fire any type of projectile, big warnings about not trying to fire projectiles with this one.  It does however create a very satisfyingly loud BOOM and have a nice three to four foot flame that erupts fromt he muzzle of the gun.  In case anyone is wondering, yes you can buy a cast iron version of the carbide cannon on line.  In fact, for those of us who remember them from childhood they have been in continuous prduction since 1912, they just fell out of favor in the last couple of decades for whatever reason, probably has something to due with computer games.

However, buying these things is not the point.  The whole point is to get my son involved in making them so that he will learn the scientific principles involved.  In the process he will learn that he can have a lot of fun with science and still make things that go boom and be safe while doing it.

The cannons vary in legalitites.  The compressed air spud gun is legal but still dangerous in a residential neighborhood like ours, the cumbustion version is, at best, dancing on the line of illegal within city limits (which is why we will take it out to one of the local closed down marl pits, or up to our place in the country north of Gainesville).  The carbide cannon is completely legal but makes such a loud boom that firing it any time other than the fourth of July or New Years will most likely bring the local constabulary in a hurry. Again, we'll fire that one way out in the country.  I fugure that firing the carbide cannon about dusk (remember the three foot flame) after an afternoon of sacraficing about twenty five pounds of spuds in the name of science will give a nice display and make a great crescendo for the day.

[Anonymous]

Either way, it sounds like fun. I'd quite like to mount a potato canon to a truck and have a battle with other trucks.

[danae]

Oooooooo, a potato gun!  We made one in my high school physics class and then of course had to do all kinds of calculations before the teacher would let us play with it.  (No, I didn't go to a normal high school!   )  

Have some fun with building yours, and good luck on launching spuds all over town!

[Sebbi]

...at the library.

It's titled "Backyard Ballistics".

I'm in the process of gathering the stuff to make the Patato Cannon (commonly known as the spud gun) now.

That is so cool!

And it appears to be true that we say Potato and you say Patato!

[Fillionous]

This kind of thing is SO much good fun!

I had a very cool pysics teacher at school who specilised in making explosives and we blew large holes in the rugby pitch... much to the anoyance of the games master....    

but just as a word of warning for those the UK side of the pond... the laws here are definitly more fussy about 'fire arms' and explosives... indeed even an air gun over a certian pound per square inch incures issues... So check with your local laws before ending up with s.w.a.t. on your case!

Have fun with your science lessons!
 
Be bright, be bold
Fillionous

[mermdotcom]

However, buying these things is not the point.  The whole point is to get my son involved in making them so that he will learn the scientific principles involved.  In the process he will learn that he can have a lot of fun with science and still make things that go boom and be safe while doing it.

And of course, it has nothing to do with you wanting to launch a potato across your yard and making it go SPLAT!   :wink:

[Shadow]

Oh, I never said I wasn't going to enjoy this project.

For those who have to worry about the law, get your local high school or local clubs (like 4H, FFA, Boy Scouts, Junior Civil Air Patrol, etc...) involved.  They can usually find a convient place to do to actual pyrotechnics and if need be they can often get a variance that allows them to do the project.