Wisdom of using two ignitors in a CTI 54 motor

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curtisheisey

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Hi, I've been launch an Upscale Deuce's Wild!, and I am preparing a 54 mm version. I was just wondering what the wisdom is on using two igniters held in position with an 1/8 in dowel rod in a CTI 54 mm motor. Will this obstruct the nozzle flow in a harmful way? I am just looking at reliability of light (not that I've had issues with CTI, just want to be really sure). I know pyrogen dipping is an absolute no-no. Thanks.
 
I have use two e match style ignitors in a 54mm motor. But I did not use a dowle to hold them it. The stiffness of the solid core wire did the just fine.

Also, Why is pyrogen dipping a no-no. I have seen and done it several times. Homemade ignitors are all dipped.
 
In my opinion , I wouldn't use a dowel to hold your igniters in place. that thought just doesn't settle in my stomach well
My biggest fear is you turning your engine into a boomer, maybe use some wadded up tissue and masking tape.
 
I have heard of using a thin dowel. But that is for the sustainer stage of a two-stage rocket. Where you do not want the igniter falling down under booster thrust. And yes to large of a dowel could cause your motor to go boom.

The only downside of one ignitor at the pad, is having to walk back out there and replace it when the first one doesn't work.
 
CTI motors light extremely reliably with the e-match provided. if you have found a consistent deficiency in being able to light CTI motors, I would suggest contacting them to let them know. The rest of us seem to get them lit with a single e-match.

If you are not having trouble lighting them, as I think you are indicating, then why try to solve a problem that doesn't exist?

The danger of using too big of an igniter in any motor is overpressurization, leading to cato.

As for dowels, I use them on large motors (75mm and 98mm). But CTI motors come with that nice cap to hold the motor in. I don't see the need for a dowel in a 54mm.
 
I have heard of using a thin dowel. But that is for the sustainer stage of a two-stage rocket. Where you do not want the igniter falling down under booster thrust. And yes to large of a dowel could cause your motor to go boom.

The only downside of one ignitor at the pad, is having to walk back out there and replace it when the first one doesn't work.

Or in the OP case..he needs and wants to lite both (2) motors in his Upscale Deuce's Wild. Having only one lite could be more then just a long walk issue.

Tony
 
In this picture, you can see the dowel protruding from the nozzle. This was a 76mm Loki L930. Loki reloads don't come with starters, so I use Frankum Performance. This particular motor used a FITH (fire in the hole) starter.

I wrap it around a thin dowel, and set the tip on top of the dowel. I use a few pieces of masking tape to hold the wire to the dowel. Once inserted, I bend the dowel back toward the launchpad, which causes it to stay in, and tape the dowel to the launchpad. There's really nothing left of the dowel, tape, or starter after ignition.

Reminder: I do not do this for CTI motors. Shove in the match, put on the red cap. Done.

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Also, Why is pyrogen dipping a no-no. I have seen and done it several times. Homemade ignitors are all dipped.

Thanks for all the info and replies. The pyrogen warning is for CTI motors. In terms of the pyrogen, there has been a case of CTI motor failure where someone had dipped the supplied CTI igniter in pyrogen. It had slipped down in the motor. Instead of lighting the grain and powering up the motor, it lighted the bottom grains. They just burned and did not pressure up, and the motor case just melted and destroyed the rocket.

Yes, to some extent this is a problem that doesn't exist, especially when using the checklist and checking the igniters with a multimeter before installation. And also carefully measuring the length. You can put a little loop in the bottom and hold it in place with the yellow cap.
 
Thanks for all the info and replies. The pyrogen warning is for CTI motors. In terms of the pyrogen, there has been a case of CTI motor failure where someone had dipped the supplied CTI igniter in pyrogen. It had slipped down in the motor. Instead of lighting the grain and powering up the motor, it lighted the bottom grains. They just burned and did not pressure up, and the motor case just melted and destroyed the rocket.

Yes, to some extent this is a problem that doesn't exist, especially when using the checklist and checking the igniters with a multimeter before installation. And also carefully measuring the length. You can put a little loop in the bottom and hold it in place with the yellow cap.

That problem was incorrect igniter placement, not because of pyrogen. I guess you could argue that without the pyrogen the electric match would have just popped without igniting the lower grain, but the real problem was placement.
 
It's OK to use a narrow dowel to support your igniter, I do it all the time with sustainers and larger motors (75mm). In the case of the sustainer, you need to keep the igniter in place during boost; for the 75mm, you want to make sure it's in the right place (the igniter wire by itself can bend due to the larger core and length of the motor). You need to match the size of the dowel to the nozzle diameter, though; if it feels the least bit snug then it's way too big. You should be able to feed it easily into the motor, use the cap to hold it in place (I test-fit it at the worktable and snip the end off the dowel just past the end of the nozzle). I've used 1/16" basswood stringers in 38mm sustainers and never had a problem, with 75mm's I typically use 1/8" basswood stringers.
 
I use 1/8” dowel rods all the time. 54-98 motors. Not sure what wadded up tissue paper is for and how it would be used. I wouldn’t stick a dowel rod up a K300 because of the thin core opening and almost zero core at the top.
 
I've been flying a 54 mm Deuce for 15 years. With CTI motors, use the supplied igniters. They are all based on low current e-matches. I have never used a dowel in 54 mm motors but have used them in 75 and 98 mm motors. I posted a rebuild thread (replace LOC body tube, add camera mount between motors) here https://www.rocketryforum.com/threads/54-mm-deuce-rebuild.4380/ I also built a 98 mm version https://www.rocketryforum.com/threads/bigger-deuce.47449/ but it shredded after 5 flights. The 54 mm is still flying after 45 flights. I had to reduce the cant angle from 15 to 12 deg to allow motors up to 4 grain.
Ground and onboard views of a flight with a CTI K454 and AT K456 These motors were ignited with thermite.

 
Hi, Rocketjunkie, awesome!!

I built a 2x29 mm 3G out of bluetube in 2011. It's got about 30 flights on it, but is starting to get beat up from some hard landings. I made a new one using a 3d printed MM also out of blue tube, but I haven't had the opportunity to fly it yet. I extended the 29 mm tubes from 3G to take 4G motors.

I built a 2x38 mm 6G out of fiberglass last year. I used 3d printed nylon to make the motor mount. On the 3rd flight, the 7.5 in fiberglass tubes must have bound, because the charges didn't blow it open, and it lawn darted. I am in the process of rebuilding it.

I am also making a 2x54 4G. The 2x38 and 2x54 bases are both 7.5 FB, so I can use the same alt bay, payload and NC.

On the two larger rockets, I put two 29 motors on for airstart.
 

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