EJECTION CHARGE!!??

Discussion on ground control/GSE and recovery equipment. This includes launch pads, triggers, chutes, streamers etc. Includes other items such as simulation and other computer software, etc.

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03flyer
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EJECTION CHARGE!!??

Postby 03flyer » Sat Apr 07, 2018 8:27 pm

I don’t find the ejection charge in my reloadable motors very reliable... just wondering if I can buy spare charges from AR?
Something like this..

Image
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Re: EJECTION CHARGE!!??

Postby kopius » Mon Apr 09, 2018 12:01 am

03flyer wrote:I don’t find the ejection charge in my reloadable motors very reliable... just wondering if I can buy spare charges from AR?
Something like this..

Image

Firstly, what was not reliable about them? Timing or quantity or something else?

We can provide BP, however that requires the explosives license.


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Re: EJECTION CHARGE!!??

Postby 03flyer » Mon Apr 09, 2018 10:52 am

kopius wrote:Firstly, what was not reliable about them? Timing or quantity or something else?

We can provide BP, however that requires the explosives license.


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Nothing, i lied. Don’t understand how I can buy rocket motors without a license but need a license if I want a spare charge for them. I just want to get into dual deployment and don’t see how that can happen down here. I’ve spoken to WorkSafe Tasmania on several occasions and they can’t give me any advice on hobby rocketry laws.
The best they can offer me is a fireworks permit so I can set of some firecrackers on one specific day. I’m done trying to deal with them.
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Re: EJECTION CHARGE!!??

Postby SpaceManMat » Mon Apr 09, 2018 4:43 pm

You might be able to join a shooting club to get access to black powder.

Possibly a better option for you would be to look at using servos or other non pyro means like co2.

George (air.command) does some pretty serious water rockets all with servo eject. Do a search here or check out his web page http://www.aircommandrockets.com
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Re: EJECTION CHARGE!!??

Postby 03flyer » Mon Apr 09, 2018 11:34 pm

Thanks for the advice SpaceMan.

Think I’ll try removing the charge from the reload and transfer it to an ejection canister connected to an altimeter for apogee deployment, and a Jolly chute release can do the rest. Good news is that there will be only one separation, bad news, I can’t ground test it and there is no back up.
Do you think it might work?
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Re: EJECTION CHARGE!!??

Postby SpaceManMat » Tue Apr 10, 2018 9:18 am

If you’re using the same size charge then provided you pack it well then you should get the same bang. I do recommend you use a decent length charge well and stuff tight with dog barf. It is important with black powder that the charge be contained as long as possible as it explodes.
QRS: 124
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Re: EJECTION CHARGE!!??

Postby 03flyer » Tue Apr 10, 2018 1:21 pm

SpaceManMat wrote:If you’re using the same size charge then provided you pack it well then you should get the same bang. I do recommend you use a decent length charge well and stuff tight with dog barf. It is important with black powder that the charge be contained as long as possible as it explodes.



Found this on the Cesaroni website..

How do I remove the ejection charge if I am using electronic recovery deployment?

The ejection charge is retained by a thin plastic cap held in place by a couple of drops of adhesive. You can pry out the cap with a small screwdriver or similar tool, then tap out the ejection charge and use this powder in your deployment system.

Pro38 motors contain 1.3 grams of FFFFG black powder
, Pro54 motors contain 2 grams.

You really don't need to plug the hole but you can put in a drop of epoxy or CA if you wish.

NOTE: If you have previously adjusted the delay setting with the ProDAT tool, AND have decided to use the motor without ejection charge in a different application, then you should plug the hole as the delay will burn for a few seconds after it reaches the flash hole. Some delay combustion products could vent through the flash hole and discolor or damage the motor mount tube or airframe components ahead of the motor.


I will be using a 38-1grain motor and have some nice aluminium canisters, 2.5g and 4.5g.
Which size do you recommended I should use and how should I place the E- match?
Should I place it at the the bottom of the powder, middle or top before tightly packing it with dog barf?

Thanks for your help, I appreciate it.
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Re: EJECTION CHARGE!!??

Postby OverTheTop » Tue Apr 10, 2018 4:33 pm

How much BP? The right amount to do the job. Ground testing normally confirms the correct amount when using electronic ejection. Since you are BP limited you don't get that option easily.

If you take the volume of the parachute compartment and get the numbers for diameter and length in inches (empty), then use those numbers for a reasonable estimate: diameter x diameter x length x 0.006 will give you the number of grams BP required (approximately, and usually a good number to start with)

In the spirit of "blow it out or blow it up" I would add 50% as a safety margin if you are unable to test. A chute not in the air is worthless!

Where for the eMatch? Think about where the pressure is and what is burning. If you put it under the BP it will scatter the unburnt powder. If you put the match on top of the BP (assuming BP well facing up) it will burn at the top, and all the way down, with better proportion of BP turned into gas.
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Re: EJECTION CHARGE!!??

Postby SpaceManMat » Tue Apr 10, 2018 8:06 pm

What motor have you already flown it on? I would think 2.5g is plenty of capacity.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: EJECTION CHARGE!!??

Postby 03flyer » Wed Apr 11, 2018 10:27 am

I’ve mostly been using the G69-14A Skidmarks on a LOC IV - Also got a few G46-11A Classics and G79-13A Smokey Sams.
I plan on building something much lighter than the Loc using 2.6 or 3.0 tubes, have a few spare kits lying around. Just need to order some E-Matches when I’m ready.
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