Why Not Cluster AT FirstFire's?

The last I read we are told not to cluster FirstFire igniters. Why is that? I was thinking of using Triple 7 .50 cal pellets & FirstFire's in each
motor of a three-motor cluster. What do you think? Larry Lobdell Jr.
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"Larry Lobdell Jr." wrote:

I think you should test the idea outside of motors a few times. Will the FirstFires ignite at the same time every time? Testing the concept with motors in a rocket is not the best idea.
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Larry,
If you're going to use 50 caliber Pyrodex pellets at the top of your motors, all you need for ignition is a single e-match. The Pyrodex will not only ignite the propellant, but will pressurize the motor, and lift off will be quick. Works well.
James

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That should read a "single e-match for each motor."
J

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Larry Lobdell Jr. wrote:

The problem with FirstFires is that they require a lot of juice to get them to fire, compared to a regular e-match. That's also why they can't be used for airstarts -- most electronics don't put out enough power to fire them quickly and reliably.
You could probably cluster them for ignition on the pad IF you will be using a powerful launch system. The only way to be sure it will work, and work reliably, is by testing them with the system you'll be using. Use as many igniters as you intend to use in the rocket. No motors, just the igniters. If they all light, at the same time, you should be ok.
·
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snipped-for-privacy@aol.com wrote:

I would use them to launch off the pad. I don't remember seeing any numbers but do they draw significantly more current than other igniters such as Firestar, Magnalight, etc? I have clustered 3 of those and they all lit OK in the past. I have had a few not light the motor and that's not good :( in a cluster. That's why I thought about using a Triple7 pellet with them.
Of course I would use an e-match if possible but the ATFE.... Since FF's are still included with 38 mm AT reloads I am looking for a way to use them. I didn't renew my LEUP when it expired a while ago because I had no permanent job or residence, but it looks like we'll be in Phoenix for a time so I'll do the paperwork and try to get one again (in the meantime I'll sure miss 54 mm motors). Larry Lobdell Jr.
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Zero, nada, zip chance of getting storage within the city of Phoenix. The local fire marshal won't allow it. I know of one approved storage in the area, and it's on "county land", and not part of any town or city. Talk to the "Hillbillies".
Also, ask BBBBBBBB about clustering "first Fires" in the BDR! (what an interesting flight it was!)
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You mean what a mess to clean up! Still have the nose cone frome that day! 7.5" Loc under my house as a reminder to not let the money guy install the igniters. He is only allowed to push the button!
Clustering First fires BAD IDEA!!!! Easy to do but a BAD IDEA!!!! Even with MASSIVE current they will fail! But it's your rocket and I like to see see other people crash rockets! Just NOT ME!
BBBBBBB

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Robert Iannucci wrote:

Now I'm really curious. No flame wars - just curious. I don't like to see anyone's rockets crash. Why do they fail? Are they just bad igniters? Then why do they work as singles for me +80% of the time? Maybe the bridgewire is like a #10 nichrome or something so it takes a huge car battery just to heat one up? Looking for answers. Larry
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Larry Lobdell Jr. wrote:

Judging from the MSDS on the Aerotech web site, the First Fire igniters use the same conductive pyrogen as Copperheads. So it would appear that the First Fire is also a conductive pyrogen type igniter. This will result in a lot of unit to unit variance which is always bad news for clusters.
I was going to sacrifice a First Fire to check on its construction, but they seem to have all scurried for cover.
--
David W. Schultz
http://home.earthlink.net/~david.schultz /
  Click to see the full signature.
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snipped-for-privacy@afo.net says...

No flames intended here, but you just answered your own question.
They are simply not reliable and/or efficient enough for clustering.
--
Tweak

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Robert Iannucci wrote:

Now I'm really curious. No flame wars - just curious. I don't like to see anyone's rockets crash. Why do they fail? Are they just bad igniters? Then why do they work as singles for me +80% of the time? Maybe the bridgewire is like a #10 nichrome or something so it takes a huge car battery just to heat one up? Looking for answers. Larry
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Robert Iannucci wrote:

Now I'm really curious. No flame wars - just curious. I don't like to see anyone's rockets crash. Why do they fail? Are they just bad igniters? Then why do they work as singles for me +80% of the time? Maybe the bridgewire is like a #10 nichrome or something so it takes a huge car battery just to heat one up? Looking for answers. Larry
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Darndest thing was, IIRC, both you and I had some of Jim Turner's stuff for the launch. Heck, I still have a few left!
Robert Iannucci wrote:

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AZ Woody wrote:

I still have no idea why the multiple posts of the same thing. Sorry. Larry
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AZ Woody wrote:

Ditto here! The Fire-in-the-hole igniters have never failed once when it comes to clustering composite motors. Although, I should mention that composite clusters for me at least has been 24/29mm motors.
Bottom line, I've never witnessed, or heard, of First Fire igniters used in a successful cluster.
Ted Novak TRA#5512 IEAS#75

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Thanks for the reminder I live in Phoenix. I figured there was no chance of getting storage in the city so I had intended to ask around when I meet some HPR people here. Who are the "Hillbillies" (I remember the TV show Beverly Hillbillies), and what about FirstFires in the BDR? I'm ignorant so who is BBBBBBBB?
Larry
AZ Woody wrote:

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Larry Lobdell Jr. wrote:

"Hillbilly Rocketry" is the group that does (among other projects) the Gila Monster.
BBBBBBBB (various number of B's), is "Big Bad Bob". He lives up in Pinetop now (last I heard) but makes it down for some launches.
The "BDR" was one of SSS's first "club projects". (late 90's?) It was a tube fin bird that was built for a cluster of 2 38mm, with no electronics.. (the "Big Dumb Rocket"). It was flown many times, and BBBBBBB and I were there during that time.
If you've not hooked up with SSS or Ahpra since coming to Phoenix, you really need to. (they both fly at the same site, but on different weekends)
See sssrocketry.org and ahpra.org. Head out to the SSS launch (GHS Memorial) at the end of October, and you WILL meet some of the HPR folks...
(former TRA Prefect for SSS, and still TRA L3 here! I'm in Ahwakutee)
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AZ Woody wrote:

Thanks for the info. I think I remember seeing the Gila Monster on Discovery TV - Rocket Challenge. I plan on taking my 2-stage to the GHS SSS launch next month. But if I read the web right you need your own launch equipment. I used the club stuff back in MI so I don't have a pad like I will need for this rocket (4" x 10' & ~20#, rail buttons for 1-1/2" rail). I wrote to James Brill and he forwarded it to the SSS group mail but I haven't heard from anyone yet. The 1st stage has a 54mm main mount with 2 38mm permanent strap-ons, and the sustainer has a 54mm mount. For the first launch I intend to use 2 I357T & an I435T staged to a I212SS. If that goes ok I want to try a J540R with 2 I435T air-starts staged to a J180T. I also have a LOC EZI-65 that I could bring.
Where is Ahwakutee? Larry
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Larry Lobdell Jr. wrote:

It's the part of Phoenix that is located on the south side of South Mountain. It's really Phoenix, and it's south of what is normally called "South Phoenix". (think Ray or Chandler Blvd and I-10, but on the west side of I-10.
Where in the valley are you located?
Both SSS and AHPRA go by the "missfire alley" launch methods (last I knew). Normally, everyone has their own pads and launch controllers, but most folks will allow you to borrow theirs.
You'll be "pushing your own button" for the launch. Once you get used to it, you won't want to go back!
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