Anyone still use flash bulbs?

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icyclops

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This is probably a real stupid question but does anyone still use the old time flash bulbs to ignite an ejection charge. I know ematches are used today, but was just wondering if anyone still did it the old way.
 

SharkWhisperer

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This is probably a real stupid question but does anyone still use the old time flash bulbs to ignite an ejection charge. I know ematches are used today, but was just wondering if anyone still did it the old way.
Good question, actually. Sheesh, if you can find them way back in an old drawer. There's some on Ebay, but not worth the price for your purpose. Maybe you can still find them by film behind the counter at Walgreens etc., but doubt they're very common (or cheap). What works well, though, for cheap, are Xmas light bulbs that go on sale for pennies after the holidays, but are cheap anytime. There's plenty of tutorials available for making them, but it's probably cheaper, easier, and faster to make your own nichrome igniters. And the "reach" of either camera flash bulb or Xmas light filaments isn't too great. Probably going to run into difficulty getting them inside a commercial motor nozzle, and they're not very durable. Have potential uses, and I emphasize "potential", in fireworking, but that's a pretty ghetto approach with mediocre reliability... Nichrome is about $6 for a 100-foot roll in gauges 34-40, which is the balance point between adequate resistance and durability--smaller diameters are useful for bridgewires over chipboard pieces, but those, too end up too large for most nozzles (LPR/MPR). Larger diameters heat up fine and are often reusable (after cleaning off corrosive burn products and redipping) but require a hotter energy source (think motorcycle battery or LiPo with low internal resistance and good amp output) to heat up instantly, especially with clustered ignition. A good reference, with decent discussion of energy requirements vs resistance, is available here: https://jacobsrocketry.com/aer/ignition_and_igniters.htm and at Nakka's EX site: https://nakka-rocketry.net/igniter.html . I highly recommend you do not mention specific chems on this site. If your Ebay nichrome rusts, then you got ripped off--buy from a reputable vendor--there's plenty around. And remember, not all nichrome is identical--there's varying alloy ratios that affect resistance for a given gauge. Nichrome 60 and Nichrome 80 are probably the most common. There are easily located tables available that provide resistance per wire length so you can easily calculate igniter and total circuit resistance.

Oh, and here's a link to an NAR webpage that details construction of large igniters for rocketry, believe that??? Ooooh, bet the NAR is on the ITAR hitlist for that, no? Sheesh. Anyways, they'd suck for small motors but easily modded... https://www.nar.org/fai-spacemodeling/construction-techniques/igniters/

Last, if you're upgrading crappy Estes igniters, then do yourself a favor and carefully chip off the white crap they use in place of their old pyrogen--all it is is stankin' cornstarch and glue and it will impede your highly functional upgrade. 2.5 inches of cheap wire and a dab of cornstarch/glue for a buck? Bwaahhh hah ha ha ha!!!

Edited: Aha, I should have read more closely. Clicked on "Recent Posts" but didn't realize this thread was in the Recovery subforum. You're looking to ignite ejection charges, not motors. Same principles. Less worry about exact sizes. Simple to make a reliable igniter that'll fire off of a 9-volt battery. As always, test your igniters so you know well your all-fire current and power needs...

Attached is a PerfectFlite photo tutorial on making X-mas light ejection charge igniters. It's pretty straightforward...
 

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cerving

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What would be really cool would be if somebody came up with a way to just socket pre-loaded charges into the bulkplate, maybe with a bayonet or similar connection. Refreshing a charge would be as simple as just unscrewing the old one and screwing in a new one. Terminal blocks, wire wrapping, and posts are all a pain in the butt.
 

SharkWhisperer

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What would be really cool would be if somebody came up with a way to just socket pre-loaded charges into the bulkplate, maybe with a bayonet or similar connection. Refreshing a charge would be as simple as just unscrewing the old one and screwing in a new one. Terminal blocks, wire wrapping, and posts are all a pain in the butt.
That should be a cinch. Just epoxy a stock xmas bulb holder and drop in a new bulb/igniter each time. The bulb should afford reasonable blast protection for the socket or a better socket could easily be constructed. The bulbs pull right out easily. Simple mod to fill bulbs with pyrogen or BP and cover hole with epoxy or hot glue for long-term storage. The filaments are tougher than you'd think. No wire wrapping. No posts...
 

tsmith1315

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What would be really cool would be if somebody came up with a way to just socket pre-loaded charges into the bulkplate,
I'm pretty sure you just did. Screw mount sounds like what I've been looking for, too.

Like this old-school pre-made flashbulb charge container, but with a screw-in base and something better than a flashbulb. Disposable.
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icyclops

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Thanks for all the info.The reason I brought it up was twofold...just interested if anyone still used the old technique of mercury switch, capacitor, flash bulb for ejection charge (wick/fuse or BP can) and if these old bulbs last 40* - 50 years. I just found 4 full boxes of 12 bulbs ...old Westinghouse flash bulbs and was thinking of trying to see how it really works. Saw it in an old rocketry book and was wondering if anyone had tried it.
 

prfesser

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Way-back-when, I read that the cardboard tubes sometimes found as the horizontal part of an old wire coathanger are a near-perfect fit for flashbulbs removed from Flash Cubes. Slide flashbulb in one end of a piece of tubing, add hot-melt glue to hold it in place, dump BP onto the bulb and close the tube with tape.

But considering how old the flashbulbs are, I'd want to be as absolutely certain as possible that they will work. So I'd test half (yes, half) the bulbs with a battery. If they all work, it might be okay to use one in flight. Though I'd double up the bulb and charge JIC. The cost of a single failure in flight is enormously greater than the cost of a batch of e-matches.

Sell the bulbs on ebay and buy a batch of e-matches?

Best -- Terry
 

icyclops

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Way-back-when, I read that the cardboard tubes sometimes found as the horizontal part of an old wire coathanger are a near-perfect fit for flashbulbs removed from Flash Cubes. Slide flashbulb in one end of a piece of tubing, add hot-melt glue to hold it in place, dump BP onto the bulb and close the tube with tape.

But considering how old the flashbulbs are, I'd want to be as absolutely certain as possible that they will work. So I'd test half (yes, half) the bulbs with a battery. If they all work, it might be okay to use one in flight. Though I'd double up the bulb and charge JIC. The cost of a single failure in flight is enormously greater than the cost of a batch of e-matches.

Sell the bulbs on ebay and buy a batch of e-matches?

Best -- Terry
Ha, not a bad idea...but thought I would like to test it out and see how things work. It was a flash circuit i think pretty basic using D or C batteries if i remember correctly....not sure if it used capacitor but probably so...so it sounds like maybe 12v should fire it? Maybe.... come to think of it, the camera flash holder probably was just batteries....just not sure....will give it a try with 9v first or just charge up a cap with a switch. I think it called for a 1000 microfarad cap.

You know, on second thought i think you are right prfesser, sounds like a lot of trouble for nothing....
 

icyclops

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Hooked it up to 9v battery and it fired off fine...darn near blinded me...no wonder folks saw stars after using these in the old camera packs.

Thanks and take care,

Mark
 

jimzcatz

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A 9v will light a dozen or more bulbs. And don't be worried about the ages of these things. Hit the switch, they will flash. I have never had one not flash in 30 years of rocketry.
 

icyclops

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A 9v will light a dozen or more bulbs. And don't be worried about the ages of these things. Hit the switch, they will flash. I have never had one not flash in 30 years of rocketry.
Good to know, thanks
 

icyclops

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I pull my mercury switches out of old thermostats. I find them at those rebuild centers where they sell construction supplies people don’t use. Getting very hard to find anymore.
 

Nytrunner

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I pull my mercury switches out of old thermostats. I find them at those rebuild centers where they sell construction supplies people don’t use. Getting very hard to find anymore.
Best practice, ditch the merc switches. They rely on luck more than planning and have no safety features or inhibits.
 

icyclops

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Mercury switches don't work for apogee detection in atmospheric rockets. Air drag triggers them at booster burnout.
I’m talking LP here.....rocket tilts at apogee...mercury switch makes contact...not rocket science here HaHa....simple gravity. I wouldn’t use a Mswitch in HP at all....would agree not reliable....especially if the roc becomes unstable and wants to do a cruise missile effect. I had a LP Phoenix do that once....duck. Just wanted to know if folks ever use this technique with flash bulbs...
 

watheyak

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I’m talking LP here.....rocket tilts at apogee...mercury switch makes contact...not rocket science here HaHa....simple gravity. I wouldn’t use a Mswitch in HP at all....would agree not reliable....especially if the roc becomes unstable and wants to do a cruise missile effect. I had a LP Phoenix do that once....duck. Just wanted to know if folks ever use this technique with flash bulbs...
Actually, it is rocket science. And you're not thinking it all the way through.
 

Ez2cDave

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Thanks for all the info.The reason I brought it up was twofold...just interested if anyone still used the old technique of mercury switch, capacitor, flash bulb for ejection charge (wick/fuse or BP can) and if these old bulbs last 40* - 50 years. I just found 4 full boxes of 12 bulbs ...old Westinghouse flash bulbs and was thinking of trying to see how it really works. Saw it in an old rocketry book and was wondering if anyone had tried it.
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Dave F.
 

Ez2cDave

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From SNOAR News - August, 1990 . . .

Dave F.

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OverTheTop

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Mercury switches for staging is different than for apogee detection. The switch will trigger when the booster ceases to boost, triggering the sustainer immediately. In that case it works if you want the sustainer to light without delay after booster burnout.
 

icyclops

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Ok, so i can see that. But also have seen information long ago on using it for ejection charges which is what i originally asked. Time before digital altimeters and electronics using chips....which were expensive at the time for kids to acquire.

As there are many types of mercury switch bulbs. Some are longer than others and i would assume those are the type you want to use for this...as it allows for much more space between the mercury and the conductor wires. I have 4 and they are all different lengths...the longest measuring 1 1/2”. Shortest was 3/4” which I would agree may contact on air drag when the motor stops thrust...in LP I don’t think the longer Mswitch would be as effected to that and would contact at the tilt, apogee.

If it didn’t work at all, why so much info saying it works and was commonly used along with Flash bulbs to ignite an ejection charge....longtime ago.

Just interested if anyone used this technique before and how it worked for them.
 

cerving

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Mercury switches were banned long ago, too many problems with false triggering on or near the ground. There were also "G switches" that used a similar non-mercury trigger, they're no better. Unless they have some kind of intelligence, at least the ability to detect the difference in acceleration for a period of time, those types of switches have no business in modern hobby rocketry. There are just way too many better, and safer, alternatives.
 

jimzcatz

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Mercury switches were banned long ago, too many problems with false triggering on or near the ground. There were also "G switches" that used a similar non-mercury trigger, they're no better. Unless they have some kind of intelligence, at least the ability to detect the difference in acceleration for a period of time, those types of switches have no business in modern hobby rocketry. There are just way too many better, and safer, alternatives.
Thank gawd!!!!
 

jbr

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What would be really cool would be if somebody came up with a way to just socket pre-loaded charges into the bulkplate, maybe with a bayonet or similar connection. Refreshing a charge would be as simple as just unscrewing the old one and screwing in a new one. Terminal blocks, wire wrapping, and posts are all a pain in the butt.
I don't find terminal blocks a pain to use , hiding under the tape to protect it from the debris
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JoePfeiffer

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Ok, so i can see that. But also have seen information long ago on using it for ejection charges which is what i originally asked. Time before digital altimeters and electronics using chips....which were expensive at the time for kids to acquire.

As there are many types of mercury switch bulbs. Some are longer than others and i would assume those are the type you want to use for this...as it allows for much more space between the mercury and the conductor wires. I have 4 and they are all different lengths...the longest measuring 1 1/2”. Shortest was 3/4” which I would agree may contact on air drag when the motor stops thrust...in LP I don’t think the longer Mswitch would be as effected to that and would contact at the tilt, apogee.

If it didn’t work at all, why so much info saying it works and was commonly used along with Flash bulbs to ignite an ejection charge....longtime ago.

Just interested if anyone used this technique before and how it worked for them.
The only information I can remember coming across on using them for recovery systems didn't use them directly, they used them to detect burnout and start some sort of timer or fuse that fired the ejection charge. Where have you found someone who claims to have used it directly?

At motor burnout your rocket's deceleration will be much greater from drag than from gravity. Your mercury will, as others have said, go to the front end of the capsule and trigger your recovery system. The length of the switch will make no significant difference in how long this takes.
 
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