Search found 113 matches

by GalFisk
Wed Jan 09, 2008 2:14 am
Forum: General How-To & Discussion
Topic: 101 Ways (Not Really) To Use a Camera Flash...
Replies: 21
Views: 4652

The output frequency of the inverter is in the >10 kHz range (it's the frequency of the whine you hear when the circuit is charging, and it's higher the less load you put on the circuit). The trigger cap is a normal type of small high voltage cap, possibly with polyester or polypropylene dielectric....
by GalFisk
Sun Dec 09, 2007 11:49 am
Forum: Hybrid Cannons
Topic: valve hybrid design
Replies: 16
Views: 1546

You can build a variation of the DFTV (http://antennalaunchers.com/dftv19/) that opens when the chamber pressure rises. My copper hybrid uses this, it has been dry-fired successfully a few times but I haven't had time to finish it completely (it cn also be used as a pneumatic and there the valve per...
by GalFisk
Thu Aug 02, 2007 4:28 am
Forum: Hybrid Cannons
Topic: Camera flash on metal hybrid
Replies: 18
Views: 1673

2 mA is harmless. A flyback is well suited for hybrid ignition. With a metal cannon, something to note is that you will have high voltage between the cannon body and most parts of the circuit (including the low voltage parts). This is if one end of the circuit is grounded to the metal, you can elimi...
by GalFisk
Sat Jun 09, 2007 7:28 am
Forum: Off-Topic Hobbies
Topic: Space shuttle launch!
Replies: 7
Views: 494

jrrdw: thanks, I've been looking for that link forever. I saw the launch on NASA TV, made me want to be along for the ride. A space rocket launch (shuttle or otherwise) is one of the things I want to witness in real life before I die (the others are a total solar eclipse, a volcano eruption and (if ...
by GalFisk
Thu Jun 07, 2007 4:01 am
Forum: Off-Topic Hobbies
Topic: Making sodium?
Replies: 11
Views: 567

Details and success reports about electrolysing melted NaOH here: http://www.sciencemadness.org/talk/view ... p?tid=2103

Beware that hot melted lye is very corrosive and will eat your skin and blind you. Take appropriate safety precautions.
by GalFisk
Wed May 23, 2007 1:15 pm
Forum: Off-Topic Hobbies
Topic: Fireworks Launching Platform
Replies: 16
Views: 1339

0.25W 10 ohm carbon film resistors glow red hot at 9-12 volts, and usually survive multiple firings. They're also dirt cheap. The paper clip method sould also work nicely, but you need thick leads (jumper cabler or similar) or they will heat up as well. Nichrome ignition works as well, is probably m...
by GalFisk
Mon May 14, 2007 3:48 am
Forum: Off-Topic Hobbies
Topic: Rapid Desoldering?
Replies: 15
Views: 952

If you can melt a lot of solder points at once (by whatever method), you can just hit the PCB agains something solid and the liquid solder will fall off. Beware of splatter.
by GalFisk
Sun May 13, 2007 9:35 am
Forum: Off-Topic Hobbies
Topic: Rapid Desoldering?
Replies: 15
Views: 952

And high voltage caps and diodes, high wattage resistors, power transistors, and other assorted stuff.
by GalFisk
Sun May 13, 2007 4:11 am
Forum: Off-Topic Hobbies
Topic: Rapid Desoldering?
Replies: 15
Views: 952

And from what I've heard, it kinda sucks.
Soldering iron with a clean tip, desoldering pump, flathead screwdriver and pliers work well, as others have commented. There are specialty desoldering tools to remove ICs and desoldering irons with built-in tin pumps, but those are really expensive.
by GalFisk
Fri May 11, 2007 6:13 am
Forum: Off-Topic Hobbies
Topic: the BEST way to make sugar/kno3
Replies: 49
Views: 2926

Depends on where you're living, I live in Sweden and can get KNO3 fertilizer under the brand name Krista K-plus (25 kg for about 200 SEK). The chemical name is often not obvious on fertilizer bags, look for 13-0-46 fertilizer. If farming supply stores don't carry it, you may be able to get it from a...
by GalFisk
Thu May 10, 2007 9:52 pm
Forum: Off-Topic Hobbies
Topic: the BEST way to make sugar/kno3
Replies: 49
Views: 2926

Ammonium nitrate can detonate if properly sensitized and initiated, but as an oxidizer it's not that much different from KNO3. IIRC it's less used because it's hygroscopic. If you want cheap and pure KNO3, buy it as fertilizer, not stump remover. The latter is both more expensive and has more crap i...
by GalFisk
Thu May 10, 2007 9:40 pm
Forum: Off-Topic Hobbies
Topic: making a smoke grenade inside a good pot help..
Replies: 7
Views: 626

If you're using sugar/saltpeter, that burns hot enough to melt aluminium.
I've burned it inside homemade cardboard tubes, made by covering thin cardboard with wood glue and rolling it around a wooden dowel, then hammering an end plug of bentonite (kitty litter).
by GalFisk
Wed May 09, 2007 6:38 am
Forum: Pneumatic Cannons
Topic: GB Semi
Replies: 118
Views: 74236

Interesting valve, I think it could be streamlined to fit inside a tee. It seems like the opening time will be much slower than traditional valves though, owing to the much smaller imbalance between the forces acting on the piston. If you're willing to sacrifice the air in the pilot, that could be f...
by GalFisk
Wed May 09, 2007 6:06 am
Forum: General How-To & Discussion
Topic: Bicycle Propulsion
Replies: 30
Views: 2108

Too bad, a pulse jet would be totally awesome for propelling a bike (though it'd probably break some kind of vehicle noise regulations).
If you want to use gas pressure, you're better off using a piston arrangement driving the wheel if you want any kind of efficiency/sustained power.
by GalFisk
Wed May 09, 2007 6:02 am
Forum: General How-To & Discussion
Topic: rapid fire "shell" idea.
Replies: 20
Views: 1266

Re: rapid fire "shell" idea.

hi wrote:ps- what is a good program for drawing 3D images?
Rhino3D.