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Dual Deployment

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solrules

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Heads up mods: feel free to move this to the techniques section, I am unsure of where to post this.

Anyway, I am thinking of using a dual-deploy system made of a copular, with a copular bulkhead and body tube bulkhead on each end, held together with threaded rods, holes drilled for wires, U-bolts, etc. and a small section of body tube glued in the middle of the couplar. Now, that couplar is placed inbetween 2 body tube sections, so that I can run wires down towards the motor for the drouge, and wires up to deploy the main. Now here's the questions: at apogee and ejection, what is to keep the main section from coming loose from the copular, maing the main deploy at apogee? I was thinking of using shear pins, but that would be hard on phlexible phonealic (body tube might get damaged over time). Is there any way besides friction fit? Thanks!
 

solrules

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Ahh! I get it now! Thanks for the advice, hokkyokusei. I was thinking of having both sections seperate at the copular section. This way make a lot more sense.
 

powderburner

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I have wondered if there was a simple way to adapt dual deployment for low-power rockets without having to get into electronic timers and BP ejection charges (and the LEUP that now comes along with the use of BP).

Could be kinda nice to have a low- or mid-powered rocket also come down quickly and then deploy a main 'chute.

Can you share any more details?
 

havoc821

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I am doing the EXACT same thing for my high power ANDRUS 1. I use a couple of layers of masking tape to get a tight fit, then a plastic rivet on each side of the tube for both tubes. You could however change the design of the rocket and create a baffle ejection that would seperate at the coupler, but that would be more difficult.

Powderburner,

The only other way than using an altimeter an BP, Pyrodex, etc. is just choosing a long delay so that it deploys 20ft. off the ground going 100MPH!!!!! :D :D :D :p Just kidding of course. :p I am interested in finding a way to do that. It would be neat because Estes/LPR rockets seem to drift far easily.
 

Stewart32

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why have dual deployment? Why not just on chute deployed at an appropriate altitude for safe touch down. What purpose exactly does the drouge chute serve? Juz wonderin?
 

shockwaveriderz

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the drogue chute/steamer slows the rocket down from hi altitude in addition to acting as a recovery beacon of sorts..
 

cls

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I have wondered if there was a simple way to adapt dual deployment for low-power rockets without having to get into electronic timers and BP ejection charges
how about this: a cluster rocket with different delays on the motors, and stuffer tubes to different deployment bays?

I am thinking something like E9-4 and E9-8, parallel clustered in a BT-80. two separate bays at the top of the two MMT tubes... streamer in the 1st bay, a nice big silver mylar parachute in the 2nd bay ... hmmm, have to try that!
 

Rocketmaniac

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Originally posted by Stewart32
why have dual deployment? Why not just on chute deployed at an appropriate altitude for safe touch down. What purpose exactly does the drouge chute serve? Juz wonderin?
Some people use dual deployment without using a drouge...... The altimeter fires the apogee charge and breaks the rocket into two parts ...... Then at a set altitude (I use 250') the main charge fires and the chute is deployed.......
 

powderburner

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Originally posted by Stewart32
why have dual deployment?
I want to try two-stage deployment to get my rocket down fast and minimize drift, but still have it touch down softly to minimize damage. I would like to improve my percentage of recovered models, even the small ones.

I hate like the dickens to watch a rocket sail away in the wind, and it always seems to be windy around here in north Texas (I should take up kite flying). And the winds aloft always seem to change every ten minutes.

cls has a good idea, the same thing I was considering for a multi-engine design, but I was hoping some of you guys would also have an idea or two that would work for single-engine rockets.
I just can't see a way to do this (for single-engine design) without stepping up to the cost/complexity of on-board timer electronics. My best idea to avoid an extra BP charge is to use the timer to set off an Estes-type igniter to burn through a thread, releasing a parachute package held between the streamer and the rocket. I just don't like the extra junk on board but there might not be another way?
 

hokkyokusei

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Originally posted by Stewart32
why have dual deployment? Why not just on chute deployed at an appropriate altitude for safe touch down. What purpose exactly does the drouge chute serve? Juz wonderin?
As other's have said, it's to slow down the rocket so that deployment of the main doesn't occur at too high a speed. Having said that it is possible to do it. I've done it myself and it worked fine. You need to be confident that whatever you do at apogee spoils the aerodynamics enough to avoid a ballistic descent!
 

hokkyokusei

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Originally posted by cls
how about this: a cluster rocket with different delays on the motors, and stuffer tubes to different deployment bays?

I am thinking something like E9-4 and E9-8, parallel clustered in a BT-80. two separate bays at the top of the two MMT tubes... streamer in the 1st bay, a nice big silver mylar parachute in the 2nd bay ... hmmm, have to try that!
Well it would work, but of course your main would be deployed just 4 seconds after your streamer, which wouldn;t normally be enough, I would guess.

What might be cool would be to have a "motor" that was all delay and ejection charge. You can sort of do this with fuse and BP of course.
 

llickteig1

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It is also important to understand that not only does the drogue slow down the rocket a bit it also serves the purpose of keeping either half of the rocket from becoming stable and coming down ballistic.

You can split the rocket in two at apogee and not use a drogue, just be certain that neither of the two pieces can become stable on their own.

--Lance.
 

prowlerguy

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You could use the normal ejection charge to deploy the streamer and a mechanical timer and spring-actuated piston to deploy the main chute. The devices can be rather small and no battery or BP is needed. No that I have actually done it, but I have read about it on other models.
 

powderburner

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Originally posted by prowlerguy
You could use . . . a mechanical timer and spring-actuated piston to deploy the main chute.
So, who knows all about these things and is willing to teach the rest of us?
 

prowlerguy

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Here are some links to G. Gassaway's web page. He used a mechanical timer to delay the deployment of the chutes on his SRB's.

http://members.aol.com/narshuttle/pix1.htm

There is this quote
Why a wind-up timer in the SRB's instead of electronic/pyrotechnic charges? Electronic systems for the SRB's would add additional weight, the mass of the timer and whatever mass of the batteries needed to fire a flashbulb. And such mass is doubled since there are two SRB's. There is also a problem in trying to devise a means of arming/safing the electronics to avoid accidental firing.
I don't have the time to find it right now, but I recall it was a wind-up motor from a small toy that was used, with a wooden disc calibrated to provide the delay needed.
 

Ryan S.

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Originally posted by llickteig1
It is also important to understand that not only does the drogue slow down the rocket a bit it also serves the purpose of keeping either half of the rocket from becoming stable and coming down ballistic.

You can split the rocket in two at apogee and not use a drogue, just be certain that neither of the two pieces can become stable on their own.

--Lance.
this is very true, you could get some serious zippers. The nosecone on my V2 is stable and comes down pretty straight. However, this is not a problem because the body flips around so much it causes the nose to shift back and forth and therefore slow down.

I have seen rockets where the parts are stable and it isnt good, it is essentially like there was no apogee deployment at all bvecause the booster is traveling almost as fast as it would be by itself but do to lack of nosecone drag slows it down a bit
 

havoc821

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About the spring/piston thing, there was an article in an old Sport Rocketry that talked about how to make one that was activated by a servo rotating which unscrews a nut holding the spring down and when the nut comes off, the spring/piston shoots foward and deploys everything, but is kinda complicated.
 

Guest
You have described my dual-deployment system to a "T". That is exactly how I did mine. The bulkhead and coupler bulkhead should be glued together to form a cap for each end of the alt. bay. I ran wires using nuts and bolts thru each bulkhead to make permanent e-match terminals. I used a U-bolt at each end, with one piece of 1/4-20 threaded rod running up the middle to tie it all together. The bay also has a slice of body tube on the outside like you mentioned, this gives a place to mount a switch for the altimeter. When the bay was complete, I poured a thin skin of 30-minute epoxy in the bottom of the bay (drouge end) to seal it tight. You don't want drouge ejection pressure bleeding in the bay and freaking out the altimeter. I also affixed a 3/4" PVC caps the outside of each end of the bay to contain the powder charges.

To retain the payload section to the alt. bay, I installed the payload section on the main side of the bay, drilled three equally spaced holes lower (closer to the ring of BT on the outside of the bay) and epoxied nuts corrisponding to those holes on the inside of the alt. bay. Drill your holes for static ports above these holes. That way there's no distrubance of airflow in your static ports.

As for shear pins, I have found that 2-56 nylon screws are hard to beat. I used three on my 4" rocket, but two would do.

You can view some specifics on my webpage:

http://home.alltel.net/jm44316
click on 'My Rockets', then 'Level 2 rocket' near the bottom of the page.
 

wyldbill

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Originally posted by solrules
... seperate at the copular section....
Hope you're not flying this at a family oriented launch.... ;)
 
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