Testing ejection charges

[firemanup]

I'm looking at buying a couple packs of plastic centrifuge tubes to use for ejection charges.

I'll be ground testing them first to see that they produce enough charge to seperate my rockets.

While the tubes are fairly cheap electric matches aren't. Right now for ground testing i'm considering just using my Estes launch controller and Estes igniters.

Wouldn't these be enough to light the charge, i mean they light blackpowder motors ok. The only difference I can think of is that the ejection blast may be slightly weaker than a true electric match. If the electric match produces a stronger charge then that would just be added insurance for the seperation.

Does this theory seem ok or should i be looking at other testing procedures.

I've got a 24" by 4" payload bay that I'll have to eject the nosecone off of. I'm being told that a 2 gram charge may be marginal for that much area, does this sound accurate?

Is there a general rule of thumb for the ejection charge size?

I can get a ton of 2ml micro centrifuge vials (plastic) off of ebay for very cheap but if the 2 grams isn't enough i'll end up going with the 12ml plastic vials and alter them.

Thanks for any ideas or help

 

[powderburner]

an Estes igniter should work fine (you may want to use two for redundancy--those tips come apart pretty easily)

the BP charge, once initiated, will quickly build up to temperature/pressure inside your little plastic vial, whether it's started by a 'big' e-match or a little Estes igniter

why not make some igniters of your own? nichrome wire is available all the time on ebay, and you have many options for the pyrogen tip

 

[bsexton]

Jason - You can use the Ejection Charge Calculator (Black Powder Use) on ROL INFOcentral. Looks like you are right on the bubble with 2 grams of BP for a 4"x24" payload.

 

[firemanup]

Thanks Bruce,

Checkin it out now.. may download one of the programs offerred too....

 

[bsexton]

You might also want to check out Ejection Charge Holders at Aerocon Systems.