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Cheapest cannon possible

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Cheapest cannon possible

Unread postAuthor: Duct Tape » Sun Apr 18, 2010 6:39 am

Can anyone beat my cheapness?

It launches a football over 200 feet, cost $5 for the duct tape. The cans were free. I already had the propane blow torch...

Enjoy!

[youtube]http://www.youtube.com/watch?v=t4gZUyennBc[/youtube]
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Unread postAuthor: tghhs » Sun Apr 18, 2010 7:10 am

Hahah dude, impressive but comon, just get some dwv at least
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Re: Cheapest cannon possible

Unread postAuthor: jackssmirkingrevenge » Sun Apr 18, 2010 7:21 am

Duct Tape wrote:Can anyone beat my cheapness?


Actually... :roll:

Welcome to spudfiles :D
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Unread postAuthor: Duct Tape » Sun Apr 18, 2010 8:16 am

DWV? Does it come in a diameter that will accommodate a football?

The cans were free, why would I buy plastic pipe?

Plus if it fails it tends to fail safely at the duct tape seams, and you can always experiment with combustion chamber and barrel length. It's easy to replace dented sections too.
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Unread postAuthor: Duct Tape » Sun Apr 18, 2010 8:17 am

... oh and it takes 15 mins to make, if you're quick, but earplugs would have been a good idea.
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Unread postAuthor: Crna Legija » Sun Apr 18, 2010 8:54 am

lol 45 seconds of gas sounds like way to much
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Unread postAuthor: POLAND_SPUD » Sun Apr 18, 2010 9:22 am

The cans were free. I already had the propane blow torch
well yeah but these things do cost...

If you really want to save a lot switch to threaded metal fittings & pipes...

They are wayyyy stronger than PVC and can be reused... not to mention that it only takes a couple of minutes to assemble a complete gun from parts
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Unread postAuthor: Duct Tape » Sun Apr 18, 2010 10:19 am

45 seconds may sound like too much gas, but it isn't.

We tested it from 10 seconds through to 80 seconds.

60 was the most powerful, but it kept popping seems and blowing the back out, which meant replacing the bottom can. 45 was still powerful, but didn't wreck the cannon, plus we could still hear afterwards!
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Unread postAuthor: MRR » Sun Apr 18, 2010 11:43 am

This might be in the same price region, without the fancy stuff (pistol grip).

Cardboard combustion http://www.spudfiles.com/forums/cardboard-cannon-d-t11552.html
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Unread postAuthor: jimmy101 » Sun Apr 18, 2010 12:13 pm

Any low-ball quote of a cost is pretty silly. I've got guns that were "free" since all the parts were left over from other things or just scrounged from the garage. For example;
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And I'm a bit suspicious of the 200 feet claim. For an unstabilized football?
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 18, 2010 12:16 pm

jimmy101 wrote:Any low-ball quote of a cost is pretty silly. I've got guns that were "free" since all the parts were left over from other things or just scrounged from the garage.


Yup, how expensive is a schrader valve? :D
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Unread postAuthor: Duct Tape » Sun Apr 18, 2010 3:00 pm

200ft is an estimate, but we didn't measure it.

I'm pretty sure that it's not an over estimate. Here are some figures...

We fired our best vertical shot with a flight time of 6.5 seconds (This almost blew the base plate right out of the bottom can). Ignoring air resistance (I know :roll:) this would give an exit speed of around 32 m/s, and a maximum height of 52 m. At 45 degrees this would give a range of 104 m or 341 feet, so a claim of 200 feet is actually quite reasonable. I would guess that air resistance reduces the range somewhat.

Even if you just take the shots we filmed for YouTube you'll see we have 5 seconds of flight time at about 75 degrees, equating to an exit speed of about 26 m/s. This would give a range of 69 m or 226 feet at 45 degrees.

You can use the equations of motion to verify my figures or just use this projectile motion simulator.

http://www.walter-fendt.de/ph14e/projectile.htm
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Unread postAuthor: jimmy101 » Sun Apr 18, 2010 3:48 pm

Figure drag cuts the range by ~30%. For something with a sectional density as small as a football it might be 50%.

The linked ballistic calculator appears to be way off. I get range estimates that are 5X to 10X what actually happens with say a 100g spud at 100m/s.
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Unread postAuthor: Duct Tape » Sun Apr 18, 2010 4:04 pm

Ok, I'll take your word for it, but whatever the calculations, we got a max flight time of 6.5 seconds. I'm very pleased with that.

I still think 200ft was a reasonable estimate. Next time I will try for a max range and actually measure it (pace it).
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Unread postAuthor: Moonbogg » Sun Apr 18, 2010 4:17 pm

Nice cannon, and you can't beat the cost of materials there. It looks like fun because of how huge it is.
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