Holding air start ignitor in place - Airstart 101

[Dustin Lobner]

Hi everyone,

In the super early planning stages for an air start rocket (my first, hence the question).

How do people hold the ignitor up inside the motor? I've heard of small dowels being used - how are those supported?

If I had to try something on my own, I would say the smallest "sturdy" dowel, the end of the ignitor taped to the dowel, and a bunch of masking tape across the nozzle to support the dowel.

The airstart motor is (at the moment) an AT J450DM or potentially an I280DM...yes, DM sparkies are hard to light, but after seeing what Wildman's BigUn did to an I280 on the ground, I have no concerns about it lighting if the ignitor is held in place.

Thanks in advance everyone!

Dustin

 

[cerving]

I like balsa or basswood stringers, they bend a little bit which sometimes makes it easier to put them in. If your motor has a plastic nozzle cap you can use that to hold it in, otherwise leave a bit sticking out and use masking tape to hold it in. A lot of masking tape.... and don't forget to poke a vent hole in it.

 

[Cameron Anderson]

Hi everyone,

In the super early planning stages for an air start rocket (my first, hence the question).

How do people hold the ignitor up inside the motor? I've heard of small dowels being used - how are those supported?

If I had to try something on my own, I would say the smallest "sturdy" dowel, the end of the ignitor taped to the dowel, and a bunch of masking tape across the nozzle to support the dowel.

The airstart motor is (at the moment) an AT J450DM or potentially an I280DM...yes, DM sparkies are hard to light, but after seeing what Wildman's BigUn did to an I280 on the ground, I have no concerns about it lighting if the ignitor is held in place.

Thanks in advance everyone!

Dustin

Big uns take a lot of juice to ignite...what are you using to fire it off?

 

[heada]

Ematch threaded though the hole of a pyrodex pellet and then bent over so that the pellet is resting on the ematch head. Ematch leads are then taped to a bamboo skewer. Leads and skewer taped to the nozzle.

- Low energy ematch works with nearly all electronics.
- Pyrodex pellet gets even stubborn motors to ignite (similar to what CTI uses in the forward end of their motors) You should be able to (maybe sometime in the future) find them in sporting good stores that sell muzzle loading supplies. 100 pack cost me $25 few years ago.
- Bamboo is stiff and resists bending and breaking but is narrow and cheap (cheaper and stronger than most hardwood dowels). It is either ejected at motor start or burns up at motor start.

(edit for grammar)

 

[Dustin Lobner]

Big uns take a lot of juice to ignite...what are you using to fire it off?

The plan was an Eggtimer Proton set up with a LiPo dedicated to the deployment channel. I'll talk with Tim (Wildman) and see what it needs, and then talk with Cris at Eggtimer and see if a 2S LiPo can get it done...

 

[AllDigital]

I used to fly an airstart cluster a lot. It was smaller, with a 54mm in the center and three 38's surrounding it. I'd light the 54 on the ground and then airstart the three 38's. My trick was to use aluminum HVAC tape to protect the other three igniters and cover the nozzles of the 38's. I made sure there was a small vent hole and didn't put the aluminum tape on too tight over the nozzles, but I did put it on tight around the outside of the nozzle and on the blast plate to hold down the igniters. For the long 38's (I think 6XL) I did not need to use a dowel/stick, but for a 54mm I probably would.

 

[Dustin Lobner]

Heard back from Wildman, airstarting a Big Un is a no go. He too recommended an ematch and pellet.

 

[cerving]

The plan was an Eggtimer Proton set up with a LiPo dedicated to the deployment channel. I'll talk with Tim (Wildman) and see what it needs, and then talk with Cris at Eggtimer and see if a 2S LiPo can get it done...

I'll get out a Big Un and see if a 2S/500 mAH in the Proton will light it, the Proton can source 10A safely. Alternatively, you can dip an ematch with Quickburst dip or something like that.

 

[cerving]

Well, as usual Tim was right. I tried both a 2S and a 3S LiPo, the Big Un didn't even smolder, with a 4 second on-time setting. On the bright side, I didn't have to sacrifice a Big Un...

BTW, I did check the Proton before and after with an ematch... no issues there.

 

[tfish]

a pyrogen system that will work with an ematch...

http://quickburst.net/qb/procast-order-page/
Tony

 

[JimJarvis50]

I've always used the PML magnalight and it works fine. When I run out, I'll try the quickburst.

For 54mm and smaller, I don't think a dowel is necessary. For 75mm and up, I use a dowel. The technique I use is to glue a nylon string onto the bottom grain or the top of the nozzle. The string hangs out of the nozzle. At the pad, I put in the igniter, wrap the string around the dowel and add a few drops of superglue.

Jim

 

[ksaves2]

I think ematch with pyrodex is the easier/safer way to go like Tim recommended.
In the past, I experimented with an ematch augmented motor igniter as I was thinking I'd like to try air starting/staging eventually and the entire time I was nervous as the pyrogens were allegedly pretty sensitive.
I did have success as the ematch augmented igniters burned like hellfire sparklers though I never got the chance to fly one. I did manage to get hurt by one though in testing.
I was using an ARTS2 deployment altimeter with its software connected to a laptop to set off the ematch augmented igniter.
The igniters were burning well at 100% success rate but I lit one and instead of burning, it popped and burned.
The bad deal is stupidhead here was too close as he didn't have long enough leads and the thing popped "up" in the air and ended burning like hellfire in my ear!!
I did see it coming though and put out my arm. The wire curved over and still caught my ear for a split second. Caused a painful burn that didn't require going to a doctor (though I is one) but I was picking at crusty scabs for 6 months.
Trust me. Airstarts with ematches and pyrodex is the safest way to go. I was burned by the alternative.
BTW, I did use the small batch of my "airstarting" igniters for primary ignition for launching of rockets. They worked but I didn't do a continuity test as I was paranoid the current would pop the igniter.
If I ever get to staging or air starting, I'll have to become friends with a firearms guy as I don't have a FOID card. Unless one can get pyrodex without a FOID card.

Kurt

 

[llobdelljr]

For air-starts, and ground started clusters, I use a Triple 7 .50 caliber pellet. During reload assembly they fit nicely into the top grain of 38mm AT motors, and 54mm motors with a little more effort to hold them in. I use ematches (now unregulated MJG) up the throat to ignite the pellet. I don't use anything to hold them in - the ematch leads must be strong enough. This method has been 100% reliable since 2006.
If I am successful at an L3 try later this year, I'll have to find something that can air-start 75mm motors Any ideas?
Larry

 

[Cl(VII)]

Slightly off topic, but if I wanted to airstart a more stubborn motor (Loki Red K627 for example) would it be helpful/permissible to paint the top grain itself with pyrogen before motor assembly to give it that extra get up and go insurance?

 

[Cameron Anderson]

Slightly off topic, but if I wanted to airstart a more stubborn motor (Loki Red K627 for example) would it be helpful/permissible to paint the top grain itself with pyrogen before motor assembly to give it that extra get up and go insurance?

I've done that with success several times.