My 1st Q-Jet experience

[shockie]

Didn't have any problem straightening out the igniter.
When I tried to push the igniter down the throat, it met some resistance in the core, wouldn't go.

So I took a toothpick and it pushed up all the way. It sure felt like the throat was just a little too narrow, but it went in with no resistance or large force.

Then had no problem pushing the igniter in. I have about 1/4" of the black part of the igniter sticking out of the nozzle.

I'm assuming this is correct.

I think I may get a .020 to .050 carbon fiber rod in the future to test the throats.

Q-Jet A3-4

I'll report back on how it works.

 

[Art Upton]

I don't recall any pyrogen sticking out the nozz of the Q-Jets I have flown. Now there is a black shrink wrap that sticks in the Nozz to hold it there, is that what you are talking about ? Many times that can move around and you put the starter up the nozz till it stops and move the wrap to the nozz to hold it in place.

 

[BEC]

It is also possible, especially with the As, to put the "initiator" in and then miss the slot in the propellant and therefore not get it all the way to where it is supposed to go as the rest of the case below the propellant is empty. In general I have the black heat shrink on the igniter leads just aft of the nozzle when the igniter is properly placed. I've missed the slot, had to pull the igniter out, straighten it again then put it back in. In this situation, often the pyrogen gets knocked partially or completely off. The igniter will work just fine anyway, for both Black Max and White Lightning Q-Jets.

I'm not quite sure what Art is talking about - of all the Q-Jets I have had since they started including the heat shrink for igniter retention, that tubing has been either red or orange. The black on the leads is an "insert till about here" marker.

 

[shockie]

I've attached a photo of what mine looks like if anybody cares to comment.

 

[BEC]

That looser red tube is supposed to be slipped off and then stuck in the nozzle beside the igniter to retain it. On the As and Bs this is kind of problematic—the tubing really needs to be a little smaller. Insertion depth looks about right.

You aren't really going to fly that Astrocam on an A3-4 are you? I'd guess maybe ~125 feet and maybe the 'chute will open before it gets back to the ground with a full four second delay.

 

[shockie]

That looser red tube is supposed to be slipped off and then stuck in the nozzle beside the igniter to retain it. On the As and Bs this is kind of problematic—the tubing really needs to be a little smaller. Insertion depth looks about right.

You aren't really going to fly that Astrocam on an A3-4 are you? I'd guess maybe ~125 feet and maybe the 'chute will open before it gets back to the ground with a full four second delay.

yes, I read the instruction about sticking that red tube into the nozzle to retain the igniter, but that igniter is in there pretty tight, not sure it will fit . If the igniter is in there tight, is it required for proper ignition?

 

[heada]

I think the red tube does 2 things, 1) hold the igniter in place and 2) closed off the nozzle opening some so that it's easier to build up pressure.

It's similar to the red/yellow cap on the nozzle of AT/CTI motors

 

[BEC]

yes, I read the instruction about sticking that red tube into the nozzle to retain the igniter, but that igniter is in there pretty tight, not sure it will fit . If the igniter is in there tight, is it required for proper ignition?

In my experience the requirements for getting a Q-Jet properly lit are the same as for other motors....as long as the hot bit is in the right place at ignition (and the nozzle's not completely blocked) it will be OK. So if yours igniters stay in place with the pull of the ignition leads on them they will be fine. I've flown Q-Jets with the tube, with a ball of wadding in the nozzle, tape on the nozzle....all work.

As I mentioned, that red heat shrink won't fit in A or B Q-Jet nozzles anyway. It's tight on the Cs and works great for the Ds (both Black Max and White Lighting).

 

[shreadvector]

I think the red tube does 2 things, 1) hold the igniter in place and 2) closed off the nozzle opening some so that it's easier to build up pressure.

It's similar to the red/yellow cap on the nozzle of AT/CTI motors

Actually it is NOT there to close off the nozzle and build up pressure. It is there to provide a vent to allow gas to escape while the igniter is burning. Otherwise the pressure will spit out the igniter before the composite propellant ignites. Once the propellant ignites, it will spit out the igniter and the bit of tubing holding the igniter in place.

 

[heada]

Actually it is NOT there to close off the nozzle and build up pressure. It is there to provide a vent to allow gas to escape while the igniter is burning. Otherwise the pressure will spit out the igniter before the composite propellant ignites. Once the propellant ignites, it will spit out the igniter and the bit of tubing holding the igniter in place.

Venting gas or keeping part of that gas in place to help the propellant ignite is basically the same, no? You neither want fully restricted (CATO) or unrestricted (igniter falls out with first gas movement). If it was only there to hold the igniter in place, you could use a small rubber band around the outside of the nozzle like the SU 29mm motors do/did. Either way of looking at it, the igniter and tube are ejected once the propellant ignites.

 

[AeroTech]

Actually it is NOT there to close off the nozzle and build up pressure. It is there to provide a vent to allow gas to escape while the igniter is burning. Otherwise the pressure will spit out the igniter before the composite propellant ignites. Once the propellant ignites, it will spit out the igniter and the bit of tubing holding the igniter in place.

This ^^^^