Rocket parachute ejection

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Ves
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re: Rocket parachute ejection

Post by Ves » Tue Aug 22, 2006 10:29 am

Thanks NickC :idea:

Jim Berquist
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re: Rocket parachute ejection

Post by Jim Berquist » Sat Aug 26, 2006 7:21 pm

Just a thought!

Could you use a cylinder with a set of contacts on the top and a ball bearing at the bottom. When Rocket reaches Apex. Bearing will float. Rocket reaches apex and starts descent. Gravity takes place again and Bearing causes the contacts to work. Trips a Spring and or Rubber band to cause Trip off! Contacts need to be most close and sensitive.

I think it could work . He didn't like the use of a charge for the shoot. I don't ether. It could get burned damaged and or fail. A small 1.5 volt solenoid could do the work. Battery just a N type nicad .

Like a mercury switch, but solid. Mercury could bead up and cause it to trip.

jim
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re: Rocket parachute ejection

Post by Zippiot » Sun Aug 27, 2006 4:00 am

Or just give it a 7 second timer from when the ball leaves the contact...What if the rocket goes down nose first then the ball would never hit the switch (maybe, too many variables...)
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re: Rocket parachute ejection

Post by Jim Berquist » Sun Aug 27, 2006 7:57 pm

Ves has the right Idea! Just too much weight! . In place of relay contacts as I proposed use Ves type switch with the prongs. Relay contacts could trip on launch!!!!!!

Timers would work, But this is so simple why do you need one? At most a capacitor, battery, small solenoid and switch...The capacitor would double the battery current and insure the soenoid kicked when the switch was tickeled...A 240uf cap wieght is what? 3 grams! Doubles the battery requirement.....

Ray : I'm with you on that one, this one is about wieght!!! 200Grams could mean 200 ft.

Jim
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re: Rocket parachute ejection

Post by marksteamnz » Sun Aug 27, 2006 9:13 pm

"Greg and Richard Nakka are right, the mercury switch will trigger when the motor burns out. Not a good solution. "

This has been posted twice in various ways in this thread.

blob of mercury with contacts = ball bearing with contacts Therefore it won't work.

I'm sure Ray and Ben have given up in dispair.
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Mark Stacey
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Jim Berquist
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re: Rocket parachute ejection

Post by Jim Berquist » Sun Aug 27, 2006 10:46 pm

I was thinking that the murcury would bead up and make contacts do the thing. At the wrong time....

A solide mass like the bearing would deal with the micro gravity and hit the mark on gravity recovery!!!!!!!


Jim just at thought!!
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re: Rocket parachute ejection

Post by Ray » Mon Aug 28, 2006 1:56 pm

I haven't totally given up.

The issue is that when the motor burns out there is a deceleration that is significant, at least 2 g's. That deceleration will ALWAYS trigger a gravity type device, whether it is mercury or a steel ball bearing, ALWAYS. You could use this event to trigger a timer, or another motor, but not a recovery system. Your rocket will be at maximum velocity. Its very entertaining to see high speed deployment, but not if its your rocket.

Just stick with the tried and true, get a timer, they can be had for $25, or get an altimeter, they can be had for ~$100. Its worth it, really.

The perfect flite timer is one of the smallest I've seen, and weighs almost nothing...

NOW, I've given up.

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re: Rocket parachute ejection

Post by Ves » Tue Aug 29, 2006 3:31 pm

The first test flight of apogee-fotosensor system is unsuccesful! :oops:
The inertial switch malfunction cause a crash.

Rocket weight: 130grams (without motor)
Motor: 10N*s for low altitude flight (test flight)
Flight altitude: less than 90m (300f)

Ejection charge fires at touchdown (inertial switch makes contact)

A new test flight with repaired E45 rocket, apogee-fotosensor system and redesigned inertial switch (now with magnet on the top side) will be soon!

Sorry for my bad English! :cry:
Attachments
E45-Ready2.JPG
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E45-Survived.JPG
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re: Rocket parachute ejection

Post by Zippiot » Wed Dec 06, 2006 7:01 pm

Has anyone tried using blanks (the bullets with no bullets :) as the parachute ejection?

All you would need is a timed release on a pin that you cock, would take almost no energy and hopefully the blank gives off enough expansion to blow out the parachute and not destroy the rocket.

Just a thought.
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re: Rocket parachute ejection

Post by Ray » Wed Dec 06, 2006 7:58 pm

Wondering how you'd keep the pin cocked in an acceleration rich environment?

10 g's is normal, 20 g's is common, 30 g's isn't unheard of...I've had flights in excess of 70 g's.

Would take a pretty robust pin system to stay together.

An ematch or christmas tree bulb etc, with a bit of black powder works great. Rouse Tech CO2 ejection systems work into space...BP has trouble over about 25k ft.

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re: Rocket parachute ejection

Post by Zippiot » Wed Dec 06, 2006 8:29 pm

I cant get black powder, and any mix of charcoal (pyro grade not bbq stuff) and kno3 doesn't give enough of a push to get the nose off...

I doubt I would actually rig a bullet to a rocket, just wanted to see if anyone has tried it.

The rapid change in atl doesn't make the co2 cylinder blow apart? Must be strong stuff
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re: Rocket parachute ejection

Post by Jim Berquist » Wed Dec 06, 2006 11:33 pm

Zippiot:

Bad Idea! Mechanicals would weigh to much. Even a .22 cal blank like used in a nail gun would be to much.....

A small charge in a one end closed cylinder and a flash bulb may work. Like a small mortar type fire work.

Could be set off with a pendulum switch or mercury switch on appajee.

Dajavue: this is on some other thread some place. Mercury beads up and activates ignition prior to Appajee. Newton's law , the feather falls as fast as the mercury!!!!

Jim
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Zippiot
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re: Rocket parachute ejection

Post by Zippiot » Thu Dec 07, 2006 5:30 am

What about a timer activate by mercury. The switch goes off once the motor stops burning (according to some reading I did on mercury switches) which activates a timer based on how fast and large the rocket is. For a C class maybe 7 or 8 seconds for a long delay (reading off the side of my C class estes sitting near the computer).

So we dont need to make sure that we have the flight time accurately mapped out, a little 10 second delay activated by a motion or mercury switch might do the trick.

22cal blank really weighs that much?
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re: Rocket parachute ejection

Post by heada » Thu Dec 07, 2006 6:25 am

Mercury switches are notoriously unreliable and problematic. I would suggest a g-switch based timer or an altimeter (either barometric or accelerometer based)

The g-switched based timer is going to be the cheapest route to take (a good one will run about $30) but is limited to whatever time you select. Since it is g-switch based, it will detect launch and start the timer after that. Once the time that you programed has passed, it will fire the ejection charge. Altimeters are better because they will sense when the rocket is at apogee and deploy the recovery device then. I would highly suggest looking at the perfectflite altimeters and timers. http://www.perfectflite.com

I don't think the weight issue with the .22 cal blank is the problem as much as the device that would be required to fire such a blank. The blank, firing pin (rim fire, not center fire) and control of the firing pin would be considerable. Keep in mind that in order to fly this rocket without an FAA waiver, you must keep the entire rocket (motor and airframe) below 1500g (3.3 pounds)

In most deployment systems, the requirement is FFFFg black powder but you can use other things as well. FFFg powder, pyrodex and other smokeless powders can be used if prepared correctly. There is also the Rouse-Tech CD-3 deployment system which uses CO2 to deploy the recovery device (which will survive a flight to over 100,000 feet and still function correctly) If you are looking into something like pyrodex, you use slightly more than you would with black powder (i.e 1g of black poweder equates to 1.5g of pyrodex) and you pack it tighter than you would normal black powder. If you still can't obtain powder, you can (with EXTREME caution) take an Estes motor, extract the black powder from it, grind it (BY HAND! in very small amounts) to a small granule size and use that.

If you have issues with obtaining e-matches (a LEUP, or Low Explosive User Permit, is required) then you can make you own deployment charges using Christmas tree light bulbs (a string of 50 bulbs for $1.00 puts each charge near the $0.02 each range) http://www.jamesyawn.com/ignitors/jimmyfire/index.html Pratt Hobbies has a product that you might be able to use as well. http://www.pratthobbies.com/proddetail. ... d=WEC%2D5B

-Aaron

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