Cannons, fireworks, experiments, projects

[patrickg]

Old_Wanker, You might like rocketry on a small scale, relatively safe small scale. Take a paper match and lay a straight pin along the match stick with the point of the pin toward the match head and touching the match head a bit.

Wrap the match head and maybe 3/16 of an inch of the stick with aluminum foil. Press down around the pin to get a good impression then remove the pin. This has formed the exhaust nozzle. Prop the rocket up on a mangled paper clip. Lean the rocket over about 45 degrees. Light a second match and hold the flame under the head of the wrapped match. When the rocket's propellant (match head) cooks off (ignites) the rocket may go 0-15 feet depending on skill and luck.

To "hot rod" the design. Carefully trim away much of the width of the paper match stem (stick?), especially the part farthest from the head. Since the equation F=MA (force equals mass times aceleration) or for our use, solving for A (acceleration) we have A equals force divided by mass. Force is determined by propellant and nozzle and we are somewhat limited as we buy off the shelf rocket motors (paper matches) and the nozzle is "good enough" but can be subject to experiment however, the mass of the rocket's aerodynamic stabalizing fin (stem/stick) can be reduced by narrowing it. I don't recommend shortening it as aerodynamic instability ensues. You can hot rod the rocket motor a bit by including a bit of extra fuel say 1/4 of another match head (without any paper stem material of course. You can try to minimize the quantity of aluminum foil used but too little and the sidewall of the motor will blow out.

Caution, aluminum heated by a burning match can burn you. If a rocket lands on bare skin it can smart a bit or startle a napping tabby. Never started a fire this way but suppose it is possible so use caution around open pits of gasoline (petrol), caches of high explosives, and like that.

Dimensioned cad drawings available at modest cost.

Enjoy,

Patrick

 

[bgott]

I have always found acetylene bombs wired to brakelight circuits amusing, as long as I knew they were there. You can also build an impressive bomb just by pressurizing a sealed anti-freeze jug with 150 p.s.i. shop air. A car battery charged at a high rate is an effective hydrogen generator. I blew one battery up in my face, I remembered the warning signs, on the others I've had blow I've managed to turn and run. FYI, if you have a shorted battery and try to charge it, you'll hear a few little pops out of the battery just before it grenades. The first little pop will send me about two bays over before the second hits. To use the battery as a hydrogen generator we'd drill holes in the top of the caps and stretch balloons over them. Fuse the balloons and let them drift past second story apartment windows at night, coitus interruptus guaranteed!

 

[patrickg]

bgott, Outa sight duuuuuuuuuude.

Been lucky, only blown the filler caps off of a 100 amp hour 12 volt battery one time and no other similar action. Seems I was testing a prototypebattery operated arc welder on a consulting job to a startup company trying to get into the market with this man-portable battery operated arc welder (23 lbs less battery which in normal operation stayed in the vehicle). I was using it in stick welding mode, burning rod after rod with a 100 amp-hour truck battery as the power source. So this spark from my welding hits the hydrogen gas streaming out of the battery's vented caps and pop goes the caps. Kind of a whistle sound as the products of combustion rush out through the vent hole just before the caps are fired up into the air striking the ceiling of an open bay industrial rental with 20 ft ceilings. Banggety bang bang bang as they impact the metal roof then tink thunk tink tink thunk etc as they fall to the floor. Everyone looks at me as if I should be paying them to play there rather than them pay me to save their sorry little outfit from bankruptcy.

Been bunches of more careful since then.

Patrick

 

[Old_Wanker]

patrickg I like that device. I can see myself playing with that when Im at some of the usual summer picnics with the wifes family.

Heres a tip for a handy ignition device for fireworks. Take a flashlight bulb and with a dremel carefully cut off the glass. Crumble some of the heads of some matches into a fine powder. Spray glue on the filament and filament supports of the bulb and sprinkle the phosphor on. Repeat a few times. Now apply a voltage to the bulb.

 

[TWINKLE_TOES]

Old_Wanker,

Flash bulbs work very well. The glass is laced with plastic and easy to drill and stay intack.
Al

 

[Old_Wanker]

I tell you - put a radio control unit on one of these with the innards from a nice big firework and you can have lots of fun.

 

[TWINKLE_TOES]

Old_Wanker,

How did you get the handle "Old....." thinking that way /w3tcompact/icons/wink.gif Might work great until the first trucker rolling thru with a 1000 watt linear. Yikes
Al

 

[patrickg]

Old_Wanker Yeah, neat DIY igniter. Saw something like that in a prison movie with, I think, Sean Penn. Small hole in the base of a light bulb and fill partially with gasoline (petrol). Put in overhead light fixture and wait for victim to turn on the light.

Estes engineering sells rocket kits, motors, A N D igniters. piece of resistance wire with a plastic coating. When wired up and energized with a battery it gets hot and lights their rocket fuel. Shouldn't be as hard to duplicate skill and tools wise as your igniter but if you have the stuff for yours and not theirs it would still get the job done. I have set off a lot of remote pyrotecnics by clipping a couple small alligator clips to the fuse or sticking pins in it. Connect up 120VAC (less would probably be fine, but never tested lower limits) and we have I G N I T I O N. Needles driven into a cherry bomb or M-80 type firecracker itself, not the fuse gives virtually instant response should delay be a problem.

Try the match rocket. We used to have contests at lunch time trying for greatest range or accuracy (waste of time,not accurate) when there weren't any engineering majors for us physics majors to pick on or have match rocket duels with.

You could use match rockets to celebrate... D A R E I S A Y I T, the 4th of July. I gotta go...

Patrick

 

[DocHeb]

For your consideration. Sorry, a bit difficult to read.

 

[bgott]

I was about thirteen and working in a junkyard when I blew the battery up in my face. We had an old wrecker there that needed jumped because we never had a good battery in it. I was jacking with the cables when one of the posts broke loose in the battery. Pop, pop, pop, POW! The other ones I've blown just started popping with the charger on high. I guess they had a connection melt from the heat and short out.