Flashbulb ignitors

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

jflis

Well-Known Member
TRF Supporter
Joined
Jan 17, 2009
Messages
15,470
Reaction score
239
Not really sure where would be the best place for this. I put it here as it relates to the thread: BP Clusters from electronics

many (most?) of us balding types will remember "Flash bulb ignition". That's where you tape a short length of jet-x fuse to a small flash bulb and then insert the fuse into the motor. a *very* small current will set off the flash bulb and that, in turn, will light the fues. You may remember "flashbulb safe continuity circuits" back in the '70's and '80's.

Well, with all of the technology growth allowing *model* rocketeers to loft some interesting payloads, it seems to me that finding a way to bring this *old* technology back may be of importance.

Flashbulb ignitors are great for clusters, would be *perfect* for multistage clusters, multistage where there is too much separation between stages and also for igniting an ejection charge for dual deployment.

the beauty of a flashbulb ignitor is that you can set it off with a single button cell (watch battery) or even a small charged capasitor. The entire circuit is very small, light weight and low tech. And they work every time.

What I would like to do is find a source for those old "flash cubes" that you used to see all the time. Those small bulbs were perfect. Something even smaller would be better, but you have to make due with what you can find...

I still have a few dozen bulbs and the jetx to go with it. It would be interesting to see if this technology could be reintroduced...

jim
 
I know of a surplus store that is selling off the old Magic-cubes, the type that didn't need any power source. I have heard that they have no use in rocketry? They also are selling off flip-flashes.
 
I went looking for some Ol'e blue dot's last summer Jim: covered all the photo shops in this area, did a little seraching on the net. only found a few in Penn camera. very old very dusty;) The system still works the same. I have a ton of old centuri sure shot igniters that use a similar material to the jet-X. If we could find an alternate material to these "fuses" and a better source for the bulbs maybe....
 
Yep, my experience too. I looked into having them made, but the minimum orders were too high (100K+). For personal use, I keep my eye open at flea markets and the like.

jim'
 
I bought 6 dozen two years ago from a place on the internet that sounded like 'Lightsource' or 'Lighthouse' and they were back east. Each pack of 12 cost $2 I believe. They were the AG-1B bulbs.

Edward
 
I look for them on ebay. I used either AG-1 or AG-1B, or else it was even cheaper (circa 1976) to disassemble Flashcubes. The Magicubes used some sort of small built in capacitor or static electricity device to work, so they were pretty useless for our purposes. I also have a stash of those Centuri Sure Shot sticks that is left over from the day, so I'm ready for some clusters next season.

Helpful note... have found in the past that these flash bulbs kick enough heat to reliably set off magician's flash paper which, in turn, was used then to set off black powder. From what I understand, black powder has been used for "flash pan" ignition to set off large numbers of black powder motors for "mosquito swarms" and the like. In lieu of SUre Shot Wicks, this may be an alternative way to go.

Al
 
FYI, there’s a far better replacement for Jetex wick as the means to ignite an engine when the bulb flashes. Well, for BP motors anyway.

Got this tip from Kevin Kuczek, who read it on RMR.

Place black powder engine nozzle-up and fill it with black powder. Set the flashbulb into the nozzle to trap the BP so it won’t spill out. I have added a collar of modeling clay to help prevent spillage once the engine is pointed nozzle down. Adequate amounts of Scotch Tape used to keep the flashbulb from being pulled out, which would let the BP spill. Masking tape normally would be good but it takes longer to burn through 100% to let the flashbulb fall free, Scotch tape melts fast (with the BP it pretty much vaporizes).

Unlike thermalite, or the older days Centuri Sure-Shot wick, where there would be a flash....then a sizzle, then engines staring to ignite, the ignition of the engines is almost instant.

Kevin used that method to ignite his twin engine F-14 plastic model conversion jet at NARAM-45. And I used the same to ignite two C6’s and one E9 in my F Dual Eggloft Glider at NARAM-45 (which then air-started another E9 two seconds after liftoff).

Of course all the above are for use with black powder engines. Don’t go filling up composite engines with black powder.....

Flashbulbs do not take much current, but you have to test to be sure that a really small battery can fire it. For example, the MN-23 12 volt (N sized) alkaline battery has eight 1.5 volt cells in it, each cell weighing about .8 to .9 gram each. One of those cells alone will not fire a flashbulb. But one of those cells will fire a NB-15 Daveyfire electric match. I don’t know how many of those cells it would take to get a flashbulb to fire, maybe not more than two, maybe several.

- George Gassaway
 
Back
Top