NattyDread
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- Jan 14, 2013
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Rocket: LOC V2, paper/cardboard regular LOC tube, Stretched to 8 tall, 8diameter, 26LB. Dual Deploy, 42/56 shear pins, 4 grams of black powder to separate separate/break shear pins for main chute. Weighted nose cone because its a V2 (19.7oz that comes with kit). See photo
See video, and the captures of the nose cone separation where the shear pins failed. As the video goes to close up, you will see (going from left to right), the nose cone, the chute inside of the chute protector, and the top section of airframe with altimeter bay. The nose cone obviously came off right at apogee when the drogue ejection charge went off.(this was also confirmed because at 500 feet, I actually saw the main ejection charge fire in the air with a large puff of smoke)
I have flown this before with no problems. BUT, this time, I added 6.7oz to the nose with a GPS and battery unit. This additional weight caused the nose cone to break the shear pins when the drogue chute ejection charge went off.
My guess is the drogue slowed the rocket, the top section went flying and when the shock chord tightened, the force of the jerking sheared the shear pins. With a 120 chute, the rocket took a really long time to come down from 5600 feet.
This worked fine before without the extra weight from the GPS. My guess is, I must have been really close to this happening before without the GPS. And the added weight just pushed it over the edge.
Solution Questions:
Do I add 2 more shear pins of same size; kind of a hassle with 6 shear pins?
Use 4 larger shear pins; or 2 of the same and 2 larger?
Is this just a freak accident and it wont happen again?
If I add more shear pin strength, I have to add more black powder; am I at risk of damaging the tube at some point of increasing black powder? (yes I would ground test)
https://www.youtube.com/watch?v=wJPeRrhpPJI&feature=youtu.be
See video, and the captures of the nose cone separation where the shear pins failed. As the video goes to close up, you will see (going from left to right), the nose cone, the chute inside of the chute protector, and the top section of airframe with altimeter bay. The nose cone obviously came off right at apogee when the drogue ejection charge went off.(this was also confirmed because at 500 feet, I actually saw the main ejection charge fire in the air with a large puff of smoke)
I have flown this before with no problems. BUT, this time, I added 6.7oz to the nose with a GPS and battery unit. This additional weight caused the nose cone to break the shear pins when the drogue chute ejection charge went off.
My guess is the drogue slowed the rocket, the top section went flying and when the shock chord tightened, the force of the jerking sheared the shear pins. With a 120 chute, the rocket took a really long time to come down from 5600 feet.
This worked fine before without the extra weight from the GPS. My guess is, I must have been really close to this happening before without the GPS. And the added weight just pushed it over the edge.
Solution Questions:
Do I add 2 more shear pins of same size; kind of a hassle with 6 shear pins?
Use 4 larger shear pins; or 2 of the same and 2 larger?
Is this just a freak accident and it wont happen again?
If I add more shear pin strength, I have to add more black powder; am I at risk of damaging the tube at some point of increasing black powder? (yes I would ground test)
https://www.youtube.com/watch?v=wJPeRrhpPJI&feature=youtu.be