“Sure fire” way to insure your igniter is installed properly. Pun Intended.

I’m surprised to find that a cursory search on this topic returned very little. Obviously failure to insert the igniter all the way to the top of the core is bad. Dealing with LPR, no problem since I do this at the prep table; however, doing this at the pad for HPR is more error prone: difficult orientation, bugs, sweat, rush of the launch schedule, etc…

What do some of you guys do to make sure the igniter is where it needs to be at the pad.

thx

jahall4 said:

I’m surprised to find that a cursory search on this topic returned very little. Obviously failure to insert the igniter all the way to the top of the core is bad. Dealing with LPR, no problem since I do this at the prep table; however, doing this at the pad for HPR is more error prone: difficult orientation, bugs, sweat, rush of the launch schedule, etc…

What do some of you guys do to make sure the igniter is where it needs to be at the pad.

thx

Click to expand...

Attach the igniter to a bamboo skewer that has been measured so I know when the igniter head is at the top of the motor, this works great on most 3-4grain motors, even some 5-6 grain if you can get long enough skewers, for bigger motors a small wood dowel or stick measured the same way. Just make sure nothing can clog the nozzle. If you have time and pre-planning the skewers/dowels can be soaked in a borating solution (boric acid, and borax, recipes for solution online)and allowed to dry which will render them mostly flame retardant so they won't continue burning after being ejected from the nozzle.

I just mark the leads at the appropriate depth at assembly, then I know I've sent them all the way home at the pad.

How are you sure the igniter leads have not buckled when used in larger diameter cores?

I haven't shot any larger diameter cores, and I've just stored away rharshberger's method for future reference

Most the guys at our launches fly Js and up regularly and I've seen them use the dowel method. I honestly thought that I was seeing an igniter with multiple heads when I first saw one being used. Then I figured out what they were doing. But I don't know if they leave the stick in or pull it out.

dhbarr said:

I haven't shot any larger diameter cores, and I've just stored away rharshberger's method for future reference

Click to expand...

Same with me. I would think you would have to force it pretty hard to get is to buckle in smaller cores. You would feel it.

MikeyDSlagle said:

But I don't know if they leave the stick in or pull it out.

Click to expand...

I think you have to leave it in, else risk doing the same thing you are trying to avoid.

jahall4 said:

I think you have to leave it in, else risk doing the same thing you are trying to avoid.

Click to expand...

Yep, leave the stick in the motor.

Ok, I just look at the motor and figure out about how far it is to go up. I make sure my ignitor wires are nice and straight and put it in. You don't need a stick until you hit 98's and that's a debate I think I lost once. Don't borate the stick- cause then you have a borated piece of debris who knows where. Big motors just incinerate them pretty much immediately. None of my video ever show a flaming stick.

cbrarick said:

Ok, I just look at the motor and figure out about how far it is to go up. I make sure my ignitor wires are nice and straight and put it in. You don't need a stick until you hit 98's and that's a debate I think I lost once. Don't borate the stick- cause then you have a borated piece of debris who knows where. Big motors just incinerate them pretty much immediately. None of my video ever show a flaming stick.

Click to expand...

+1 on this. Although I do use a 1/8' dowel in my 76/6000 Loki case. Only because by the time I tape the BP pellet to the ematch, it's heavy enough to bend the wire in the 1" core so it's just easier and quicker with a small dowel. I have never found a piece of stick/dowel left after a motor fired, burnt or otherwise.

The only motors I ever felt I had to measure how far up the motor the igniter went was ones that didn't have a top grain. Like some of the E & F motors in the 20/40-120 case or for example, when using 3 grains in a 4 grain EX case. Taping the hole closed in the top grain usually works well, but measuring the igniter just makes sense to me in those cases.

jahall4 said:

Obviously failure to insert the igniter all the way to the top of the core is bad.

Click to expand...

Not necessarily. Some motors require partial insertion.

rharshberger said:

Yep, leave the stick in the motor.

Click to expand...

Not recommended for high l/d ratios like some of the new Loki motors. That increases initial kn which is bad juju in erosive motors.

Binder Design said:

Not recommended for high l/d ratios like some of the new Loki motors. That increases initial kn which is bad juju in erosive motors.

Click to expand...

Good point, I was going off what I had both seen and done at various launches. High l/d motors aren't that common at most commercial flight events, but probably more common at EX launches.

Binder Design said:

Not necessarily. Some motors require partial insertion.

Click to expand...

Any "commercial" motors where the proper installation is NOT at the top?

jahall4 said:

Any "commercial" motors where the proper installation is NOT at the top?

Click to expand...

Yes, Loki 38mm reloads states the igniter should be 1/2" from full insertion when using delay grain whereas Loki 54mm reloads state the igniter should be fully inserted up against the bulkhead.

https://lokiresearch.com/Documents/38mm_Sparky_instruction_sheet.pdf

https://lokiresearch.com/Documents/54mm_J175_J525_J820_instructions.pdf

For CTI motors 54mm and below, I insert the igniter into the motor at my table, before the motor gets loaded into the rocket. I use a Sharpie on the wires to mark the depth. Remove igniter and stick it in my pocket.

At the pad, I put a A-clamp on the rail at eye level, and rest the rocket on the clamp. This allows me to see the underside of the motor. I insert the igniter and make sure it goes all the way in to the depth that I marked. Slide on the cap, remove the A-clamp, and lower the rocket.

timbucktoo said:

Yes, Loki 38mm reloads states the igniter should be 1/2" from full insertion when using delay grain whereas Loki 54mm reloads state the igniter should be fully inserted up against the bulkhead.

https://lokiresearch.com/Documents/38mm_Sparky_instruction_sheet.pdf

https://lokiresearch.com/Documents/54mm_J175_J525_J820_instructions.pdf

Click to expand...

Yes, but looking at the cross section, it is still at the top of the core. I have never seen proper placement to be right up against the delay grain. The 54 has no delay, so the instructions are to get it as far forward as physically possible. Again at the top of the core, the very top for the 54. This makes the point. Absent a delay grain position as far forward as possible.

Some one please correct me, but you don't want to ignite the delay with the igniter lest you risk igniting the ejection charge without the core lighting or before the core is fully lit and burnt, correct?

jahall4 said:

Any "commercial" motors where the proper installation is NOT at the top?

Click to expand...

Ellis Mountain required 2/3 insertion on certain reloads IIRC.

Bat-mite said:

For CTI motors 54mm and below, I insert the igniter into the motor at my table, before the motor gets loaded into the rocket. I use a Sharpie on the wires to mark the depth. Remove igniter and stick it in my pocket.

At the pad, I put a A-clamp on the rail at eye level, and rest the rocket on the clamp. This allows me to see the underside of the motor. I insert the igniter and make sure it goes all the way in to the depth that I marked. Slide on the cap, remove the A-clamp, and lower the rocket.

Click to expand...

That's exactly what I would like to do, but have always assumed that inserting the igniter in any HPR motor at my table would be a violation of the safety code, No?

Binder Design said:

Ellis Mountain required 2/3 insertion on certain reloads IIRC.

Click to expand...

Interesting... Any idea why? Probably no docs online anywhere?

That's a legitimate question. The Code reads:

Ignition System. I will launch my rockets with an electrical launch system, and with electrical motor igniters that are installed in the motor only after my rocket is at the launch pad or in a designated prepping area. My launch system will have a safety interlock that is in series with the launch switch that is not installed until my rocket is ready for launch, and will use a launch switch that returns to the “off” position when released. The function of onboard energetics and firing circuits will be inhibited except when my rocket is in the launching position.

Click to expand...

I take that to mean that I will not insert the igniter into the motor, except at the pad, while the motor is in the rocket. The rocket is stable and will fly rapidly in a straight line at whatever it is pointed at. But the motor itself is unstable, and in most cases would flop onto the ground and burn itself out in the grass.

If I'm wrong, and this does violate the Code, then another option would be to pull off the forward closure (you have to do that to adjust the delay anyway), and measure and mark the igniter outside the motor, by laying it along the edge with the head at the same approximate depth as it would be inside the motor.

But to me, it's the same with AV bays. I am comfortable turning on my altimeters at the table while the AV bay is not attached to the rocket. If a charge blows, you get a poof of hot air, as opposed to it blowing with the rocket attached, in which case you get a projectile.

jahall4 said:

Yes, but looking at the cross section, it is still at the top of the core. I have never seen proper placement to be right up against the delay grain. The 54 has no delay, so the instructions are to get it as far forward as physically possible. Again at the top of the core, the very top for the 54. This makes the point. Absent a delay grain position as far forward as possible.

Some one please correct me, but you don't want to ignite the delay with the igniter lest you risk igniting the ejection charge without the core lighting or before the core is fully lit and burnt, correct?

Click to expand...

CTI says to insert igniter until it stops against top of motor core.

https://www.pro38.com/pdfs/Pro38Instns.pdf

https://www.pro38.com/pdfs/Pro54_instructions.pdf

jahall4 said:

Interesting... Any idea why? Probably no docs online anywhere?

Click to expand...

Yes. The motors that required that were high l/d ratio. The short of it is that it provides a soft start. Lit from the top, it would cato every time.

Bat-mite said:

...and in most cases would flop onto the ground and burn itself out in the grass.

Click to expand...

...but that one "case" where it CATOed I'd be setup right next to you on the flight line. Your not coming NSL this year? :wink:

Binder Design said:

Lit from the top, it would cato every time.

Click to expand...

Simply too much pressure at the top of the core?

jahall4 said:

...but that one "case" where it CATOs I'd be setup right next to you on the flight line. You coming ot NSL this year :wink:

Click to expand...

Yeah, I've already staked out a space next to you. :grin:

No, not actually going. But, like I said, if it is against code (and I am open to people's interpretations), then just run the igniter along the outside of the liner and mark where it would stop if it were inserted. Being off by as much as a quarter-inch shouldn't matter. It's that crimp half-way up the core that you have to watch out for.

jahall4 said:

Simply too much pressure at the top of the core?

Click to expand...

No. You usually can't light an highly erosive motor from the top. The initial pressure spike is too high because it comes up to pressure too fast. Even having the igniter wire still in the nozzle throat can be cause for cato.

Sorry, not understanding... if its not "too much pressure" then what are you referring to when you say "initial pressure spike is too high"?

jahall4 said:

Simply too much pressure at the top of the core?

Click to expand...

Binder Design said:

No. You usually can't light an highly erosive motor from the top. The initial pressure spike is too high because it comes up to pressure too fast. Even having the igniter wire still in the nozzle throat can be cause for cato.

Click to expand...

jahall4 said:

Sorry, not understanding... if its not "too much pressure" then what are you referring to when you say "initial pressure spike is too high"?

Click to expand...

Not to put words in Mike's mouth, but I think it's the first quote throwing things off. The way you've stated that, it appears the pressure spike is at the top of the core, which is not the case. I THINK what you're asking is if the pressure is too high when you put the igniter all the way to the top of the motor. The answer is yes.