Where to put an ejection charge.

[stickershock23]

I have a new rocket, it has room for electronics in the nose cone area.

I am going to use my G-wiz in it. the rocket is 2.6" diam. If i use the nose for the electronics that means the ejection charge would mostlikeley be on top of the parachute, and harness.

I am thinking if I do it this way the charge might push the parachute more into the tube instead of pushing it out of the tube.

Anyone have experience with this? any suggestions will help

 

[kandsrockets]

I have a new rocket, it has room for electronics in the nose cone area.

I am going to use my G-wiz in it. the rocket is 2.6" diam. If i use the nose for the electronics that means the ejection charge would mostlikeley be on top of the parachute, and harness.

I am thinking if I do it this way the charge might push the parachute more into the tube instead of pushing it out of the tube.

Anyone have experience with this? any suggestions will help

I would make a charge in a centrfuge vial or a small cardboard tube with a long lead so that the charge can be place under the laundry.

 

[stickershock23]

That Thought entered my mind a few times, I pushed it aside thinking that the leads might get tangled up in the chute.

My other thought was a small drogue chute connected right to the nosecone/payload section, that way the drogue would pull the main out if it were to hang up.

 

[Pantherjon]

That Thought entered my mind a few times, I pushed it aside thinking that the leads might get tangled up in the chute.

My other thought was a small drogue chute connected right to the nosecone/payload section, that way the drogue would pull the main out if it were to hang up.

That might work..What concerns me is the airflow over the nosecone being turbulent and the altimeter not being able to detect apogee or altitude to fire the ejection charge.:confused2:

 

[DAllen]

Barometric altimeters, AFAIK are not a good idea in nose cones because as Jon already said the turbulent airflow over the cone would not provide accurate readings to the alt. However, I would consult the G-wiz manual to be completely sure. An accelerometer may be a better choice here.

I suppose you are doing this for single deploy - correct? You can also run leads to the bottom of the laundry as already suggested. I really doubt it will get tangled with the chute and harness. Try ground testing the charges a number of times prior to flight and see what happens.

-Dave

 

[sylvie369]

Barometric altimeters, AFAIK are not a good idea in nose cones because as Jon already said the turbulent airflow over the cone would not provide accurate readings to the alt. However, I would consult the G-wiz manual to be completely sure. An accelerometer may be a better choice here.

I may be confused here, but aren't G-wiz altimeters all accelerometer-based?

(for apogee deployment, anyway, and I think that all altimeters use baro for main deployment, right?).

 

[dixontj93060]

My LCX certainly is and I would expect their more complex/expensive products would be also. Easy to check (www.gwiz-partners.com).

I may be confused here, but aren't G-wiz altimeters all accelerometer-based?

(for apogee deployment, anyway, and I think that all altimeters use baro for main deployment, right?).

 

[stickershock23]

Thats what I thought too about the Gwiz, thats why I am thinking about sticking it in there. (accelerometer not Baro)

I contacted G-wiz and got the instructions for the altimeter, i used it in my 10" mercury redstone, in 2004, I have used it 3 times, so I remember how to arm it, but set up is a different story.

the area I have is about 10" long, I wonder if that could be far enough back to combat the turbulence.

Remember this was just an afterthought. my original plan was motor eject.
But with the bad results I have seen lately with Aerotech delays I kind of rethought that idea.
There were three rockets destroyed at the last launch I attended due to really short delays. one of witch was mine. my 4.0" Freaky Flyer on a I245G m went about 3 seconds instead of 10. its rear eject, so it only stripped the chute, then came in ballistic. buried it in about 8" and tore a fin off.

 

[stickershock23]

I just got the instructions for G-wiz (thanks guys thats really cool!)

It is both an accelerometer and a barometric sensor. it uses accel for apogee detect, motor ignition detect and motor burn out detect.

It seems that it only uses the BAro sensor for main deploy and altitude recording.

I think I will fly it once this way with motor eject and an extra long delay to see how well it works.

Dallen, a ground test will for sure happen, I always ground test, But i dont think that would tell me if I am going to tangle up.

If it has been done that way before, it sounds reasonable that it will work. (charge with leads under the laundry)

I also measured, I can vent the e-bay at 11.5" down from the tip of the nose cone (its a fat boy type nose cone so its pretty short)

the rocket is 2.6" diam.

 

[sylvie369]

Again, as far as I know, ALL altimeters use baro for main deploy altitude detection.

I believe (correct me if I'm wrong) that the advice about keeping it away from the nose cone and other external turbulence-producing stuff is all about getting a good apogee detection. When it's trying to detect main deploy altitude your altimeter bay is tumbling around like it were a nose cone anyway.

In short, I don't think there's any reason to avoid putting a G-Wiz in the nose cone. All of the reasons to put avoid putting an altimeter in the nose cone apply only to altimeters that use a baro apogee detection. The G-Wiz uses accelerometer for apogee.

Again, I'm not dead sure of this, but it's what my understanding has always been. I've not done it myself, but I've certainly seen people successfully fly accel-apogee/baro-main altimeters mounted in their nose cones.

Re. your I245 early eject: did you put the motor together well before the launch? I had an early ejection this summer that I attribute to having done that. Some of the propellents interact with the delay grain, and IIRC, Mojave Green is one of them (mine was a G motor, whichever Mojave Green G fits the 29/40-120 casing - with all the new motors, I can't keep 'em straight anymore).

 

[stickershock23]

Sylvie,

Thank you for the input, that seems to be really sound. I think I will be good. I am only using it for main at Apogee!

I think a long set of leads and a squib will work out. I was just a little nervouse of a tangle. its a big rocket, but smaller tube. I think I am going to need about a 48" chute (just a guess right now) in a 2,6" tube.

as for the I245. It was assembled 15 mins before the flight. it was NOT a drag sep. (rear eject, no way it was drag) and no way it was pressure, I have a 1/4" vent hole. almost too big. and besides I never saw another pop after the first event.

This was not the only REALLY short delay I have seen lately, I saw one on a j2something (54 mm 2 grain) it went about 4 seconds, and it was a backup, so it was supposed to be an extra long. and a few more. I really am steering away form AT motor ejects. they really are not consistent.. actually I am steering away from AT period, once I burn up my supply, I think I am done with them.

 

[Buckeye]

"Turbulence" is not really the problem with the airflow around the nose cone. Rather, it is the steep pressure gradients along the curved cone that can affect a baro altimeter on the way to apogee. The recorded peak altitude will be fine, but the shape of the ascent curve may be incorrect.

If you put the vent holes through the shoulder of the cone (also need aligning holes in airframe), you will be fine. This location will be a couple inches below the "curvy" part and in the "straight" part, where a static pressure reading will be good. I do this in my Minnie Magg.

I use long ematch leads to go under the laundry along with long leads for a burrito-style DD setup. No problems with tangling, yet.

Good luck.

 

[sylvie369]

I really am steering away form AT motor ejects. they really are not consistent.. actually I am steering away from AT period, once I burn up my supply, I think I am done with them.

I don't do much motor ejection on high power anyway - guessing at the appropriate delay seems far too iffy for me. It didn't take too many dual deployment flights before I felt much more comfortable with that than I do with motor ejection.

If you put the vent holes through the shoulder of the cone (also need aligning holes in airframe), you will be fine. This location will be a couple inches below the "curvy" part and in the "straight" part, where a static pressure reading will be good. I do this in my Minnie Magg.

Remember that he's not using baro at all. Accelerometer-based main deployment at apogee, no other event. Sounds fine to me.

 

[stickershock23]

"Turbulence" is not really the problem with the airflow around the nose cone. Rather, it is the steep pressure gradients along the curved cone that can affect a baro altimeter on the way to apogee. The recorded peak altitude will be fine, but the shape of the ascent curve may be incorrect.

If you put the vent holes through the shoulder of the cone (also need aligning holes in airframe), you will be fine. This location will be a couple inches below the "curvy" part and in the "straight" part, where a static pressure reading will be good. I do this in my Minnie Magg.

I use long ematch leads to go under the laundry along with long leads for a burrito-style DD setup. No problems with tangling, yet.

Good luck.

I actually am NOt putting it in the nose cone, I am right below it. I have about 10" of Payload bay. 10 " may seem long but the entire rocket is 7 foot tall. Bottom line I do need a vent for Baro so I will give it 3 holes as low as I can get them. about 10 inches down (4 inches below the nose cone)

Thanks for the info about the tangles. that was my only concern with long leads below the chute.

Just for reference, I have built a 2.6" Estes solar sailer.

Sylvie, I use electronics quite a bit, and am moving towards using it all the time. but it is nice to have a rocket or two that you dont have to worry about electronics. just stuff in a chute and a motor and fly. (like that will ever happen perfect every time LOL)

thanks for the great input guys I think I am good to go!

 

[stickershock23]

Well, I finished her up. Figure with all this talk I might as well post a pic.

It's about 7 feet tall. weighs in at 8 or so lbs (good guess) I think it will go up on a Cesseroni 38mm 4 or 5 grain Red! I really can't wait to fly this one. it was quick and fun to build. and I did it all out of scraps I had laying around! (FREEBIE ROCKET! WOO HOO!)

The gold box is a window to see in and see the Gwiz led's. the bottom of that is a tiny bit above bottom of the payload section. also note the hole in the bottom left of the gold window. that is one of my vent holes. thats pretty much bottom.

EDIT: now looking at the pic, you cant really see the vent hole. the big screw is holding the payload section closed.

 

[daveyfire]

Mark, that's way cool!

(For the record, I always run my deployment charge leads underneath the recovery system in the booster. Never had a tangle problem, either.)

 

[stickershock23]

Mark, that's way cool!

(For the record, I always run my deployment charge leads underneath the recovery system in the booster. Never had a tangle problem, either.)

Awesome Davey, thanks. I Have done it, but only in LARGE recovery sections.
this is small thats why I asked!!

 

[stickershock23]

Well, I finally got to fly her...

Kind of weird recovery. I used an XL motor delay as a back up. the ejection happened late. (about 14 seconds counted in my head)

When I recovered, it was zippered about 3" no biggie, the Gwiz ejection charge had fired. and it looked like it fired from the inside (not motor eject lighting it from the outside)

Heres the weird part, the GWIZ was still flashing armed... the only thing I can think. A) it didnt detect launch and motor eject did ignite my charge. (but it really does not look like that) B) the Gwiz did fire, but something "bounced" my arm switch and it reset it's self.

anyways no harm (not major anyway) so I am happy with the flight, but I am not 100% sure about the Gwiz. I may have to throw it in another rocket with electronics, and try it again!

 

[Handeman]

Awesome Davey, thanks. I Have done it, but only in LARGE recovery sections.
this is small thats why I asked!!

My L1 rocket is 2"ID and I've always used a charge on top of the motor and connected to the av-bay above the drouge. I have 9 flights on it an I've never had a tangle, other then some twisting while falling, but nothing ever affected the recovery.

The GWiz uses a remote battery. Any chance the battery connections opened during flight? Did you use a 9V battery? I only use Duracell 9V. I've heard that other types can open internally during heavy G loads. That's only my recollection so take that with a chunk of rock salt.

Glad to hear the damage was only minor.

 

[stickershock23]

My L1 rocket is 2"ID and I've always used a charge on top of the motor and connected to the av-bay above the drouge. I have 9 flights on it an I've never had a tangle, other then some twisting while falling, but nothing ever affected the recovery.

The GWiz uses a remote battery. Any chance the battery connections opened during flight? Did you use a 9V battery? I only use Duracell 9V. I've heard that other types can open internally during heavy G loads. That's only my recollection so take that with a chunk of rock salt.

Glad to hear the damage was only minor.

the Gwiz has 2 9v batteries, one for the "Computer" one to fire the charge. Although you can fly with one battery. (I never have)

My batteries were set up really simple. 2 snap on connectors, about 8" of lead, they hung out the bottom of my E-bay, I wrapped them in Foam rubber and slid them into the "coupler" below my e-bay. there was plenty of slack on the wires. so I don't think they would have come un done, but it is very possible.

I think they were energizers. but I can't be sure untill I open the bay back up.

As for loss of power, it was more likely the SWITCH I used. cheapie radioshack toggle. It's what I had on hand. if I fly it again, I will change that out to a rotary switch. or some kind of positive connection.

I wish the G-wiz had some kind of data storage, so I knew if it did fire or not.

One more thing, I am pretty sure it didn't accelerate hard enough that it might have caused a problem. it was only an I284W. (38mm 5 grain white)
Hey but you never know..

 

[ben_ullman]

that thing was going fast enough by the looks of it

Ben