cluster ignition without fuse?

I was just wondering what the current method of igniting clusters are? From what I've read, isn't thermalite wick a no-no nowdays and if so what has replaced it in flashbulb ignition, and is flashbulb ignition even used anymore? Just wondering what the possibilities are for igniting clusters beyond Estes Solar Ignitors... Thanks for any information! OL JR :)

What type of motors are you wanting to use?
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Mostly D or E BP but I might try similar impulse composites too at some point. Thanks!

Betty S. Roberts wrote:
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Use the flash pan method.

for BP motors consider flash pan, or a spider or perhaps quickmatch if you can get it.... skylighter sells it but you have to pickup..
terry dean nar 16158

shockwaveriderz wrote:
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Spider?
Ted Novak TRA#5512 IEAS#75

does it involve setting a large spider like a tarantula on fire so they can run around lighting motors?

a variation on the theme of a flashpan....might be considered a directed flashpan:
http://www.meatballrocketry.com/spider.htm
terry dean nar 16158

shockwaveriderz wrote:
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Would this be along the lines of a pan with a cover that has individual pipes/tubes that go directly into the nozzles? I saw something like this at our August launch and it worked great on a 5 E9 cluster.
Ted Novak TRA#5512 IEAS#75

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Yes. The spider was written up in a recent SR issue. There are some pics there.
FWIW, and I know I'm swimming upstream and therefore contradicting every other post in this thread, I've had great results clustering with plain old Solar Igniters. I inspect them, looking for goodly portions of pyrogen as well as making sure they appear to be intact and not bent or bruised. Then I ohm them out to make sure the cluster set is all within a reasonable tolerance of each other, perhaps within 1/10 of an ohm.
Next, I wire them in pairs and recheck with the ohmmeter to be sure I didn't short or open something. In the past, I've connected clip whips. But in the future, I'll be instead using throwaway clip-whips - IOW, I'll be attached flying leads to the igniters which can be twisted together. This allows me to insulate the connections at the ignitors, and these connections are more reliable than the alligators of the clip-whips, and they won't touch and short each other out like alligator clips can, nor will they fall off which clips sometimes do.
Anyway, I use a relayer - ie, high power pad - to fire them. I've flown my Super Better Bertha twice now this way lighting all nine motors each time.
While inspecting, ohming and extending the leads on the igniters sounds like lots of work, building a spider and setting it up ain't no piece of cake either. Plus, getting all the spider flues lined up perfect with the nozzles might turn into a major PITA. Anyway, the direct approach works fine for me.
Doug

Thanks for the explanation. What is a PITA though?? :) I have a hunch it's a humorous anagram.
So flashbulb material is hard/impossible to come by then and regulated?
I have thought much the same thing vis-a-vis the Solar Ignitors. I know from what I've read that most writers seem to think that clustering with Solar Ignitors is a disaster waiting to happen and suggest other methods. But it would seem to me that if you had good ignitors, ohm-metered them to make sure that they were electrically sound, insured the pyrogen was intact and not cracked or chipped, and then soldered either small leads or a small 'harness' to them so you KNOW that there was a good electrical connection between the leads and the ignitor itself (thereby doing away with clip whips and the notoriously bad connections clips can have with ignitor wires) and pumping plenty of power to them when you hit the switch they should be about as reliable as anything else.
Didn't really WANT to do flashpan because I've heard it tends to roast the rear end of the rocket. The spider sounds a lot more 'elegant' as far as the flash pan method goes.
BUT how about composites or composite upper stages?? How are those ignited?
Thanks! OL JR :)

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Pain In The A$$
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Ground starting composite clusters requires special igniters. Air starting composites requires even more specialized igniters.
In a composite cluster, you want the igniter to come up very quick, then burn big AND hot to ensure the motors light together.
In airstarts, you typically have a limited battery. It won't be a 12V car battery, so you won't have the voltage and low output resistance (ie, current capability) of a lead acid battery. Small NiCads are probably about the best bet.
Similarly, your electronics typically don't have the current switching capability of a relay. They tend to use FETs which can have much higher on resistance thus limiting current. Usually, with a FET, the harder you drive the gate, the lower the channel resistance, but you need to drive the gate above 5V for that. Most microcontrollers are limited to 5V outputs. To go higher then would require specialized circuits such as charge pumps thus adding cost and complexity and reducing reliability.
If you get what's called a "logic level" FET and use a 5V micro, you can get a reasonably low impedance switch. I have a PerfectFlite timer which, when powered by an 8V NiCad, can light a Solar igniter. But these situations have a fairly narrow range of operation. Small changes in voltage or resistance can render it in-operable. IOW, it's marginal.
So, for airstarts, you want an igniter built around a low-current e-match which can be lit without need for big batteries and ultra low resistance FETs.
www.quickburst.net has made several products which will work well for these applications. As soon as he has his licensing issues resolved, he will be a good place to look if you're doing a composite cluster or airstart.
Doug

OL JR wrote:
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I agree with Doug that clustering with standard Estes igniters works fine. I follow the same procedure with a digital ohmmeter, but take it a step further: I write down each igniter's resistance, then calculate the combined resistance of the cluster and then verify it once the igniters are connected together. Works OK for up to four igniters or so (larger clusters drop the combined resistance below the limit of my ohmmeter.) When I get around to doing larger clusters I will use a combination of series and parallel wiring to overcome this limitation and to keep the amperage requirements under control.
You don't need to solder leads, in fact you will find it difficult to solder to the nichrome legs of the Estes igniters. Use a wire wrap tool and 30ga wire wrap wire. I wrap a red wire to one leg and a blue wire to another so that when I twist the leads together I don't get confused.

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I was sorta doing that. When I twist the igniters in pairs, I re-ohm and make sure they're ~1/2 of what I was previously reading.
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I don't know. Doing the combo will make measuring easier, but you run the same risks as any series ingiter scheme. I'm thinking a new ohm-meter might be a better idea :)
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Steve, I think the legs are steel and only the bridge is nicrhome.
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Actually, I made up 20 or so igniters with extended leads doing this. The problem I ran into was that the wire wrap doesn't bite the round igniter lead nearly as well as it does a square wire wrap post. They can slide off. So I then hit the wraps with a dab of solder. Worked great.
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That's paramount. Just imagine standing at the pad with 9 white wires inone hand and 9 more white wires in the other, trying to figure out if more than one wire in either hand goes to the same igniter :)
Doug

Doug Sams wrote:
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Yeah, you ever price one of the good ones? :-)
I think series wiring will work with Estes igniters, but I must add that I haven't tried it except in bench testing. That paper on the current requirements of various igniters--darned if I can find it now but it was mentioned here recently--showed that burning igniters continue to conduct through the plasma ball. The early bare-nichrome igniters would break when they got hot enough to light the motor, thus breaking the chain in a series wiring, so early cluster experimenters quickly gave up on series wiring. But blasters use series wiring, though not with Estes igniters. :-)
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After wrapping the wire--down near the paper strip--bend the free end of the Estes igniter leg back up over the wrap to keep the extension lead from sliding off.

Steve Humphrey wrote:
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Hi, Steve,
Yeah, I was afraid of that. I have an old one that was pretty good in its day, but needs replacing, and I haven't done any of the legwork yet to know whether it's gonna cost me 40 bucks or two hundred.
Doug

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Stay away from Radio Shack digital multimeters - even the high-end ones.
The latest Chinese-made models they have been selling look, and operate, just great (at first), but have an Achille's heel in that their test lead sockets contain flimsy, brittle plastic pieces that break off after a few insert/extract cycles, rendering them useless.

Why stay away?
Why not take delight in buying one and returning it after it breaks for a new one over and over again for months until they correct the problem?

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Because Radio Shack's DMM warrantee is only 90 days. My own DMM broke after about 6 months, after only a few dozen remove/insert cycles, which is probably typical usage, IMO.
I have it jury rigged now- it works o.k., but if I accidentally remove the negative lead from its socket, getting it back in takes a minor surgical procedure.
The weak point is a plastic sleeve that contains the female prongs inside the socket; it is made of thin, brittle plastic. Once this breaks, the prongs are succeptible to bending or breaking when trying to insert the male end of the test lead, and must be precisely straightened into just the right position before attempting to insert the test lead.
The other thing that miffs me about this meter- the fuses are internally mounted on the PC board, and can't be reached without opening the case, which involves removing the screws and separating the case halves, meaning the 9V battery has to be taken out, and putting strain on the cable that connects the PC board to the display....

Steve Humphrey wrote:
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A good four wire ohm meter is a bit expensive. A purpose built igniter tester is even more so. That is why I designed and built my own. 0.000 to 1.999 Ohms range. Very handy. Plans on my web site of course. :-)
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http://www.privatedata.com/byb/rocketry/Ignitor/igniters.pdf http://www.gwiz-partners.com/igniters.pdf
I am sure there are copies elsewhere too.
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I cut the leads on the igniter side of the paper strip, wrap one blue and one red wire wrap wire, and then solder. With a heat sink protecting the bridgewire and pyrogen.