Hairspray cannon III

Well, after demonstrating a number of concussive firings I found that the cardboard
cylinder that a household abrasive cleaner is packaged in is just under the correct
bore, caliber 73mm or so. On my first launch out of my shorter "gun" I shot
the comet cylinder a good 4m and over a wall. It hit a palm. Very cool! Reminds me of the first beer-can shot with my first tube, surprisingly good results. Nice parabolic arc. Harmless fun.

I'm also experimenting with pure butane from an ITAWANI cartridge, which is a japanese thing. I like unusual (to me) food; I go to Mitsuwa, a japanese grocery in Costa Mesa, when I can. I always get fried squid, and either a bento or a sashimi & rice dish they have. Usually I take it back and eat at my desk. Anyway, cylinders of butane for small stoves are pretty cheap there.

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Actually, hairspray seems to be best. Its probably the isobutane propellant.

Hairspray canonn

Last trash day,
I was delighted to find that a neighbor was throwing out massive cardboard
tubes used as cores I think for tiling of some sort. Anyway I was needing
fodder for my hairspray cannon experiments. I'm not sure whether aspect ratio
matters or simply fuel:air mix. I have not yet been able to produce a concussion
with the new tubes. I could do this with a previous tube when I put
a potato-chip tube with a D-shaped metal part cut out of the end, leaving a D shaped
occluder. Without the partial occluder I got the same "whoomph" that I'm getting now. That difference (bang vs. whoomph) fascinated me; I've thought about reflection physics, thermo, detonation theory, etc.

The percussive setup would be great for 4th of july, very safe, legal, yet loud and boomy.

The new tubes are of sufficient diameter to hold a BBQ igniter module I had once bought, but which didn't fit earlier tubes. They are nearly 1/4" thick, I have to use a drill to make a hole in them. For either the igniter module or an exhausted
disposable BBQ lighter which still sparks. You can also ignite the tube with
a regular lighter, but since you're not blocking the touchhole, you get flame
from the touchhole (danger!) and limited compression.

I keep thinking that Blue Man Group needs to use pyro acoustics.

I've also never successfully launched & ignited Cremora powder, which is supposedly a nice optical fireball.

Campbell's soup plastic bowls are the proper size to block the breach. With friction. I've not yet found a nice-fitting projectile ---previous tube fit a large beer perfectly-- but am working on this. A good piston seems to enhance the efficiency greatly. We once cleared the house, which takes 30km/sec. This was with a small water balloon on top of a 24oz beercan inserted to its depth in the tube. Fired vertically.

Its both a tedious distracting pain and an interesting challenge to find proper-fitting accidental components. No art without constraint.

I need to find the right fuel:air for a full 6' tube and a piston. I might also
experiment with chokes, eg soda bottles that neck down the diameter of the tube.
Or expanders, eg trumpet flares, which are impedence converters, ie transformers, couplers.

Its fun to have a kid you're trying to interest in things, a smidgen of income and time, and some dangerous knowledge. Not even beginning to mention the trouble you can get into on eB*y or the innertubes in general.

This is Freeze-It hairspray, cardboard tubes, and a lighter. When I was a kid
I didn't know about this. Now, you can find Youtube tutorials...