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Most Reliable Way To Ignite Clustered BP Engines?

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TangoJuliet

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When I was building and flying model rockets 30+ years ago, I never tried to cluster anything because it appeared too difficult to get reliable ignition of all the motors. Though some of the more senior members of the club I belonged to at the time had spoken of flash bulbs and flash pans, that was all just a little over my head at the time.

Now, I'm wondering if advancements have been made in igniters to make clustered ignition more reliable, and what is the preferred way of going about it?
 

EXPjawa

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I use a clip whip and perform extensive continuity checks at every step of set up. I've also horded a bunch of the old black-tip Estes ignitors and use them exclusively for clustering. Most of my cluster rockets are three engined, though one has only two. To date, I've probably made 12-15 total cluster flights and have only had one motor not light.
 

TangoJuliet

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A clip whip? Photo?

Are the black tip Estes igniters not being made anymore?
 

jimzcatz

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Flashbulbs. Extend leads on bulbs with wire, I use telephone wire. Tape ring around motor, pour a small amount of BP into noozle, put bulb against BP and pinch tape closed. I have clustered 14 motors this way. Clip whip requires more current. You can light a dozen flashbulbs with a AA battery.
 

Charles_McG

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Any particular kind of flashbulb? And where do you find them?

I see a couple different styles on Amazon.
 

dave carver

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Thermalite (not Thermite) and heat shrink tubing. Thermalite is a explosives igniter that at one time was common and easy to find on the flightline. 1/8th in diameter and able to slide into the heatshrink. When the flame front hit the heatshrink it tubing shrunk and the flame that was going inches per seconds goes to yard per seconds. On a 3-in-a-row with a D in the center and 2 C's as strap-ons the Thremalite with heatshrink passed under the D. You ignite the D as usual and the flame from the D ignites the middle of the Thermalite that then ignited the outboards. After the "Lawsuit" loss by the ATF they got all butthurt and made it almost impossible to obtain Thermalite. I think you need at least a LEUP to obtain.
 

LW Bercini

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Flashbulbs. Extend leads on bulbs with wire, I use telephone wire. Tape ring around motor, pour a small amount of BP into noozle, put bulb against BP and pinch tape closed. I have clustered 14 motors this way. Clip whip requires more current. You can light a dozen flashbulbs with a AA battery.
Jim,

It's been many years since I did flashbulb ignition. But I seem to recall that, depending on the launch system, something as simple as a continuity check could fire the bulbs.
 

jimzcatz

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Lw, you are correct. Please verify flash bulb safe launch system. Get bulbs from ebay. Search flashcubes NOT magicubes! Magicubes will not work. You get 4 bulbs per cube. Just take the cube apart. Extend the leads with wire. I have a bag with over 1000 bulbs. Be glad to send you some, just cover shipping.
 

TangoJuliet

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I should have mentioned in the original post...

Please include photos whenever/wherever it may be helpful to explain something. I love photos!
 

EXPjawa

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A clip whip? Photo?


https://www.rocketarium.com/Launch-Equipment/Cluster?zenid=6mnstcm0f9vrrg9ltuft6d26o0

I use one of these, plus one I made myself (which I'll have to remake now that I have a better soldering iron). Basically, its a set of parallel wired ignition leads. They clip to all of the ignitors, eliminating the need to twist leads together, and get clipped onto the main leads from the LCO table/control box/etc. Once in place, I connect my continuity tester to the positive (input) lead, and check at all of the negative clips. Then move to the negative input and check across all of the positive clips. This does a good job of checking each ignitor coming and going, and eliminates false readings from the parallel circuits. Then an overall system check to make sure that the connection to Ground Control is OK. However, the one motor that I've had that did not light was still a continuity issue (the ignitor wasn't burned), so obviously it isn't fool proof. Either something moved between set up and launch or the other two lit so quick it pulled the connections. I'm guessing the former. The rocket still flew fine on 2 motors, just didn't reach the expected altitude.



(Upscaled Astron Cobra on two of three F15-8 motors)
 

jimzcatz

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Chances are if your launch system is electric match safe, it's flashbulb safe as well. But check in advance.
 

TangoJuliet

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I bought a LightSword II controller and a Tri-Pad Max launch pad, but I haven't used them yet. I'm still building a fleet of rockets. Mostly LPR, but I'm almost done with an NCR Laserhawk and a Mega Der Red Max. I only asked this question looking ahead into the future for some scratch-building food for thought.
 

JStarStar

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Back in the 1970s I used to launch 3- and 4- motor clusters using only bare-wire nichrome igniters, with a 12V car-battery power source.

Over 90% ignition, maybe 95%; I'd have one flight out of every 10 or so go off with one unlit.

Ditch the penlite AA batteries and you'll be fine.
 
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TangoJuliet

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I've got a 12V Gel-cell battery that I used to use for my R/C starter. That should do it.
 

Cabernut

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I actually just finished my own 4-pad launch controller for this purpose. Separate continuity test on each up to 4. I'm not doing the cross-fingers method again.

So how exactly does a flashbulb ignite BP? Is it the intensity of light, or heat? It's been decades since I've seen anyone use a flashbulb for anything.
 

samb

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I think one of the preferred methods is to use low resistance igniters and enhance them with a pyrogen dip. The current Estes starters are not low resistance and create very little spark so many of us have started dipping them even for single motor use.

DSC01794 (1280x853).jpg
current style on the left / old style on the right

Rocketflite is one of the vendors who sell pyrogen dip kits: http://www.rocketflite.com/

Q2G2's used to be the preferred low resistance igniter but are now very difficult to find. AeroQuest has said they will return ... someday.

In addition to your standard controller, a relay box at the pad with a 12V battery connected will deliver the most amps in the shortest time due to shorter cable run. I don't know if anybody makes these commercially though.

You probably could get some insight from Boris Katan's webpage: http://www.bpasa.com/Rocketflite.htm That dude can light a cluster !
 
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dave carver

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I actually just finished my own 4-pad launch controller for this purpose. Separate continuity test on each up to 4. I'm not doing the cross-fingers method again.

So how exactly does a flashbulb ignite BP? Is it the intensity of light, or heat? It's been decades since I've seen anyone use a flashbulb for anything.
The heat. In my explanation of Thermalite I should have included the largest rocket launched on a single bulb and Thermalite is Ron Ussary's 8" diameter rocket in an early High Power Rocketry. Using G40's and G80's because that was the largest motor his sponsor sold.
 

cavecentral

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Thermalite is only leftovers. Made in Canada, can't sel to USA. I tried in 2009 or 2010. Leup would make no difference. My order was cancelled.
 

dave carver

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Thermalite is only leftovers. Made in Canada, can't sel to USA. I tried in 2009 or 2010. Leup would make no difference. My order was cancelled.
No wonder it's being hoarded. I've seen thick coils of the stuff in people's launch boxes...I'd bet that's something left at home now....
 

cavecentral

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No wonder it's being hoarded. I've seen thick coils of the stuff in people's launch boxes...I'd bet that's something left at home now....
Mostly. Old stuff can get brittle too. People buy them, make their own, use dip kits, dip ematches etc. Haven't clustered much recently.
 

jimzcatz

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Pratt Hobbies sells a relay box. Also his rechargeable controller is flashbulb safe.
 

TopRamen

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I've only done double D's myself, and only about 8 or 9 times, but never had a failure using two lengths of copper wire.

[video=youtube;QTItiJrt8U0]https://www.youtube.com/watch?v=QTItiJrt8U0[/video]

[video=youtube;VwLYp0sNXoM]https://www.youtube.com/watch?v=VwLYp0sNXoM[/video]

[video=youtube;SO6ylhJma9U]https://www.youtube.com/watch?v=SO6ylhJma9U[/video]
 

rstaff3

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This thread makes me sad about the state of the Q2G2's. A few months ago I lit 11 motors with 'em. Originals, of course.
 

rstaff3

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Quickmatch works great for BP motors too.
 

jeff_j_black

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From a safety perspective, my 3 and 4 way clusters are launched at mid-power distances from the controller. A relay system at the pad can really light them up.
 

apburner

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I love the flash pan. I had a lil wild thing. It had 7 A10T's and 1 C6-7. Never had a motor not light. And the puff of smoke that went up would get above the rocket and then the rocket would fly out of it. Great site indeed. But alas I think flash pan is no longer used much.
 
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