Igniter dimensional constraints?

Question

I've never done AP (I keep trying to resist the pull), but I have been experimenting a bit with igniter construction. So here's my question.

For a generic igniter, what would be the maximum acceptable thickness? In other words (I think), what is the narrowest throat/slot/whatever that AP motors typically have?

Phil Stein · Accepted Answer

It depends on the motor.  Small ones are  1/8" - 1/16". Some cool onesare  around 3/4" and use BLue THunder propellant from a small motor tolight the motor.

bit eimer · Answer

Thanks Phil,So there are really motors with a 1/16" throat or core (that's pretty small), or did you mean 3/16"?

Phil Stein · Answer

There are some that are that small.  The small AT18mm & 24mmcomposites  use them.  Also, Quick Burst makes real small ones.Remember that the ignitor has to go way up the nozzle & on smallmotors, the throat of the nozzle is pretty small.

lovs2fly · Answer

Phil, did you get a chance to go down to MDRA launch? I saw that 90%Harpoon. After seeing that flight I'm rethinking if I want to do my ownHarpoon.Dennis

default · Answer

Ditto.  The smallest will be from the BlackJack loads.  The nozzle on the F39, a24mm blackjack reload, is tiny.steve

Jerry Irvine · Answer

7/64 DEF5/64 BCD

Phil Stein · Answer

No.  I was going to just go watch but buy the time I was at a pointwhere I could leave, I would have gotten there at 3:00.  It didn'tseem worth driving 4-5 hours for 2 hours of flying.  I took mydaughter to the luncj & the mall & still had a good time.

Andy Eng · Answer

The Apogee D3 and B7 have ridiculously small nozzles...IIRC, Tom Binford built something like a 13mm D motor with a real tinynozzle.

Zak Orion · Answer

I have some F39 reloads and they are Blue Thunders.  But I know the F12 is a black jack reload for the 24mm case.

default · Answer

Yep, my mistookie. F39 has a huge nozzle, it is the E11J I was thinking of. Reminds me of a period in time when there were some quality control problems coming out of Las Vegas. Some nozzles had no hole drilled in them at all, but worse yet, I had some E18 reloads delivered with E11J nozzles. That would have been an overpressurizing experience for sure.

steve

Jim Yanik · Answer

"default"  wrote innews:     If the nozzle diameter spec were part of the motor datasheet,then one could select a drill bit of the correct size to be certain you have the right nozzle or enlarge a too-small nozzle throat.

Igniter dimensional constraints?

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