Anyone still use flash bulbs?

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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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Ok, got it....thanks.
 
At best, a mercury switch will detect motor burnout, nothing else.
False triggering at power on is a big problem.

To use it for deployment, you will need at the very least a timer from burnout to estimated apogee time using the mercury switch as the trigger.
There are easier ways to achieve this.

AFAIK mercury switches are not allowed by TRA or NAR
 
At best, a mercury switch will detect motor burnout, nothing else.
False triggering at power on is a big problem.

To use it for deployment, you will need at the very least a timer from burnout to estimated apogee time using the mercury switch as the trigger.
There are easier ways to achieve this.

AFAIK mercury switches are not allowed by TRA or NAR
I went to the NAR website...read both LP and HP safety codes....no mention about Mercury switches not being allowed that I could find....
Maybe that info is located in another document....I could not find.
 
I went to the NAR website...read both LP and HP safety codes....no mention about Mercury switches not being allowed that I could find....
Maybe that info is located in another document....I could not find.

I found the reference to mercury switches I thought completely banned them, but it only prohibits motor ignition.

Tripoli High Power Safety Code, page 6, Appendix A, reference A-5:
A-5 A rocket motor shall not be ignited by using:
a. A switch that uses mercury.
b. “Pressure roller” switches

I personally would stay away from them for triggering ejection charges also. I've seen too many motors chuff and cause the rocket to jump up a bit before coming to full pressure, or not ignite the motor at all.
I doesn't take much bounce to activate a mercury switch.
 


If you go back even further, you can see where John got the pairing of AG-1 and SureShot wick -- from page 6 of March 70 Model Rocketry Magazine:
https://www.ninfinger.org/rockets/ModelRocketry/Model_Rocketry_v02n06_03-70.pdf
And of course, you can see the NARAM 13 demonstration and R&D official flights on my Rocket Film ( ). Starting at 11:40 and culminating from 33:00-35:20 with the official flight. Then at 39:30 with the first flight mentioned in the article above.
 
What does this movie have to do with flashbulbs and mercury switches....kinda hard to follow
 
Oh, i see the article now about engine ignition with a mercury switch and bulb....
 
I don't find terminal blocks a pain to use , hiding under the tape to protect it from the debris View attachment 452273
Sure, but wouldn't it be cool to literally just plug in a new charge, swapping them out in seconds? Maybe like a pre-filled charge well with some kind of contacts, you just twist it in 1/4 turn like a bayonet bulb? (No, I'm not working on it... I just think it would be a cool idea.)
 
What does this movie have to do with flashbulbs and mercury switches....kinda hard to follow
Partly it is a response to Dave F about the history of the use of flash bulbs in rocketry, but the article "Building the Super Titan" in the PDF that is linked briefly discusses using a mercury switch (though the author chooses a mechanical method instead) . It also mentions the pairing of AG-1 flashbulbs and Centuri Sureshot igniter wicks for igniting motors, which John Langford used in Flashbulb Cluster Ignition, which is arguably the point from which all use of flashbulbs in rocketry has come. Again, most of that is for Dave, not you, but the film refers to John's article, which Dave linked to and to which I referred.

I *thought* I was going to link to another article actually about mercury switches, but I now think that article was in The Model Rocketeer, not Model Rocketry Magazine., and I don't currently have access to those issues.
 
Yes, I saw that after I wrote the first message, sorry. I wish I could find that article in the old roc book I had about how they used it for recovery and not wick or motor ignition....but of course I can’t find it now....
 
I found the reference to mercury switches I thought completely banned them, but it only prohibits motor ignition.

Tripoli High Power Safety Code, page 6, Appendix A, reference A-5:
A-5 A rocket motor shall not be ignited by using:
a. A switch that uses mercury.
b. “Pressure roller” switches

I personally would stay away from them for triggering ejection charges also. I've seen too many motors chuff and cause the rocket to jump up a bit before coming to full pressure, or not ignite the motor at all.
I doesn't take much bounce to activate a mercury switch.


NOTE : This mechanism uses NO MERCURY, yet functions in the same manner . . .

Dave F.

I - CROP.jpg

H.JPG


I.JPG
 
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Yes, I read that diagram and info from the link earlier. I don’t think I would ever use a Mswitch in HP anyway. Very interesting constructed technique/device. Thanks for this information.
 
Thanks for the PM and the data too. Will keep it in my files for good info.
 
I have 2 or three boxes of flashbulbs, one of the old CPR systems used them.
I believe Badass Rocketry is working on a Plugin type ejection for one of his future products.
 
Flashbulbs would work OK for ejection ignitors, but they are bulkier than e-matches.

There is one other safety issue: flashbulbs have a *very* low no-fire current, 20-30 mA if I remember right. Continuity circuits can fire them unless carefully designed. Back when flashbulb ignition was popular, you had to be very careful that the club launch system would not pop the bulb upon a continuity check.

Modern altimeters have really low continuity current and should be OK, but you definitely want to verify and test before flight, keeping in mind that everything now is designed with e-matches in mind, where the no-fire current is more like 200 mA.
 
There is one other safety issue: flashbulbs have a *very* low no-fire current, 20-30 mA if I remember right. Continuity circuits can fire them unless carefully designed. Back when flashbulb ignition was popular, you had to be very careful that the club launch system would not pop the bulb upon a continuity check.

"Back in the day" ( mid-1970's ), our club, BCMRA ( Broward County Model Rocketry Association - Section # 217 ) used to do a separate "Countdown to Continuity Check", in case it fired the flashbulbs. A couple of years later the system was upgraded with a separate Continuity Circuit, specifically for Flashbulb Ignition.

Dave F.
 
I’m a little confused. The continuity check from the pad controller usually checks the motor ignitor. The flash bulb is on a different system??? A bulb connected to a mercury switch or g switch then to a capacitor...how does the pad cont check even access that. Maybe you mean using a altimeter....does the cont check connect to that? I have never used one but how can a cont check jump from motor ignition to recovery ejection system....their is no electrical connection. Please clarify.
 
A continuity check sends current through the system. That miniscule amount of current can set off dozens of flashbulbs. Always check in advance. I never used flashbulbs for anything but BP clusters. One bulb per motor. Same issue if hooking to an ejection charge, the POST can set them off. I have never has a problem but I did try an estes controller just as a test, bulb flashed when key was inserted.
 
I’m a little confused. The continuity check from the pad controller usually checks the motor ignitor. The flash bulb is on a different system??? A bulb connected to a mercury switch or g switch then to a capacitor...how does the pad cont check even access that. Maybe you mean using a altimeter....does the cont check connect to that? I have never used one but how can a cont check jump from motor ignition to recovery ejection system....their is no electrical connection. Please clarify.
Many flight computers do their own continuity checks.
 
I’m a little confused. The continuity check from the pad controller usually checks the motor ignitor. The flash bulb is on a different system??? A bulb connected to a mercury switch or g switch then to a capacitor...how does the pad cont check even access that. Maybe you mean using a altimeter....does the cont check connect to that? I have never used one but how can a cont check jump from motor ignition to recovery ejection system....their is no electrical connection. Please clarify.

The issue of low current firing flashbulbs was already addressed by Jim Scarpine.

Now, as for the onboard system, there is no continuity check circuit. The rocket is "hot" and if anything closes the circuit, the flashbulb ( or electric match ) WILL fire !

A Mercury Switch functions by aerodynamic drag slowing down a rocket, allowing the Mercury to travel upwards to complete the circuit.

A "G-Switch" functions to arm electronics ( such as a timer ), AFTER a rocket has lifted off. But, it does not fire the igniter itself.

A capacitor is used to reduce the weight and is charged through a "plug", AFTER the rocket is on the pad. "Back in the day", rocketeers commonly used HEAVY 9-volt "Transistor Radio Batteries" in their onboard systems.

Dave F.
 
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...
Slightly off topic question: I did not know about the nichrome 60 (60 percent nickel ) versus nichrome 80 (80 percent nickel) wire. Is one better than the other at being a black powder rocket engine igniter?
 
If you go back even further, you can see where John got the pairing of AG-1 and SureShot wick -- from page 6 of March 70 Model Rocketry Magazine:
https://www.ninfinger.org/rockets/ModelRocketry/Model_Rocketry_v02n06_03-70.pdf
And of course, you can see the NARAM 13 demonstration and R&D official flights on my Rocket Film ( ). Starting at 11:40 and culminating from 33:00-35:20 with the official flight. Then at 39:30 with the first flight mentioned in the article above.

Travel back in time!
 
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