Can a potato cannon work at 9000 ft above sea level? Do you need canned oxygen because the air is too thin?

I live in Lake City Colorado and my potato cannon won't work is it because the air is too thin? If so can i correct the problem with a can of oxygen?
And where can i buy a can of oxygen? Online or if you know of a store where you can buy it, please post a link in comments.

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ASL10143 years ago

You can modify the potato cannon to were you can you an air compressor to make pressure in a pressure tank which should make it work. It will take a little longer to fill the pressure tank in higher altitudes.

There are other oxygen requiring processes which do work at that altitude. For example, you've probably seen cars running at 9000ft, without supplemental oxygen. There are probably people walking around too without difficulty breathing. However the car engine is the more interesting example, because that's almost the exact same process as firing a potato gun.  You know:  a mixture of flammable gasses and air, ignited by a spark.

By way of annectdotal evidence, I have seen potato guns fire sucessfully at an elevation as high as 6000 ft.  I've also seen them fire at sea level.

If you're how much wondering how much oxygen your mountain air actually has in it, the formula for atmospheric pressure is roughly a decaying exponential, P=P0*exp(-h/hs).  In this formula, h/hs is the ratio of your elevation h, above sea level, to the so-called scale height, which for the Earth's atmosphere is about hs=7400 meters.  The calculation for your elevation, 9000 feet, is shown below:

octave.exe:12> 7400*3.048
ans = 2.2555e+004
octave.exe:13> hs=22555;P0=1;h=9000;P=P0*exp(-h/hs)
P = 0.67097
And the answer is that  atmospheric pressure where you are is about 2/3 what it is at sea level.  So, supposing every liter of air at sea level has:
9 mmol O2 + 36 mmol N2 [ h= 0, sea level]

Every liter of air where you live has:
6 mmol O2 + 24 mmol N2 [ h= 9000 feet above sea level]

I'm just saying, I think you've got plenty of O2 to work with, in your air.  Somehow the automotive engineers are making it work.  You might want to check the other factors, like fuel, and spark.

If you really want bottled oxygen, I have seen small bottles of oxygen it sold in hardware stores, for use with a oxy-mapp torch.  The brand I'm thinking of was sold by Bernzomatic(r). If I remember correctly, it was sold in bottles similar to those used for propane or mapp gas, except the bottle was red, and the connector had a funny backwards thread, to make sure you did not hook it up to the wrong place.
http://www.bernzomatic.com/products/torches/professional-torches.aspx

The drawbacks to bottled oxygen is that it is a dangerous material, (It makes things burn expode more easilly.)  and also you'd have to figure out some way to do the plumbing, and connectors and stuff.
I've had a potato gun work fine at sea level and not at all at 5000 ft elevation. I tried everything.... leaner mixture, different fuels (hair spray, propane, gasoline), nothing would work at 5000 ft. I would get a dull thud as the fuel ignites, but nothing strong enough to send the potato out of the barrel.

Your "automobile engine" analogy is slightly flawed, by the way. The difference being that the fuel air mixture in an automobile engine is compressed about 8:1 before the spark is applied. In the potato gun it all has to happen at atmospheric pressure.

Yeah.  That's true.  It's not the same thing, because the IC engine compresses the fuel-air mixture before sparking it. 

However I have seen potatoes, or pieces of them, thrown great distances, from a potato cannon, at an elevation approximately 6000 feet above sea level.

It may be the case that  potato guns, I mean the fuel-air mixtures therein,  are harder to ignite at higher elevations. 

It seems like when we were doing this, a few times the ignitor would just buzz and buzz, without doing anything, or buzz for several seconds, and then go boom.  It did not always ignite easily.
+1
nurdee15 years ago
How warm is it where you are? Sometimes things like this won't work if it is to cold.
GusN (author) 6 years ago
Thanks so if its not the oxygen mixture, or the fuel because I've tried multiple types, then it might be is the ignitor.

I use a disposable camera capacitor charged with a Kodak disposable camera. It makes a very big spark but it is very fast.

Does this type of ignitor work?
caarntedd6 years ago
It's probably just the fuel/air mix. You could be too rich at higher altitude. Try less fuel, or a different type of fuel. Has the canon worked at lower altitude? If so, are you sure you are getting good spark?
Jayefuu6 years ago
Can you breathe? Can you light a match?