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  #1  
Old 03-18-2009, 04:56 PM
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Default "Nuclear" ejection charge splits nose cone!

I tried a little lunchtime launching today including the maiden flight of my BMS Astron Gyroc clone, with an Estes A8-3. At 0.4 ounces without a motor it got off the pad in a hurry and hooked into the breeze pretty severely. Because of the hook it was already headed "downhill" when the ejection charge went. I don't think I've ever seen a motor ejected so far before! Now I know what you guys have been referring to as the "nuclear ejection charge" is really like.

Once the flaps deflected the Gyroc came down VERY slowly (much as I remember from away back when) but when I went to collect it from where it touched down I found the nose cone was cracked along its long axis very nearly down the centerline. No way it cracked from the touchdown. Air can leak now from inside the body through the cone.

The only explanation I can think of for this is that the ejection charge was so violent that it cracked the cone. Is this plausible? The cone is, for those who aren't familiar with the Gyroc, a BNC-20B which is glued into the top of the body tube. This particular cone was quite light and therefore made from fairly soft balsa. The motor was just slipped into the body tube - no tape or other aids to retain it.

I didn't have my CA with me or I'd have sealed the break and perhaps tried again...but will it split again?

Is the ejection charge in Quest motors so violent? I could try a Quest A6-4 next time.....
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Old 03-18-2009, 07:26 PM
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Quote:
Originally Posted by BEC
The only explanation I can think of for this is that the ejection charge was so violent that it cracked the cone. Is this plausible?
Yes. A nuclear T-motor did this to one of my Zoomies Doug.


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Old 03-18-2009, 07:42 PM
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Sounds to me like the motor fit way to tight. Did you use tape to friction fit or did you just slide in the motor? I not, try sanding the inside of the tube a little to help keep it from happening again.
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Old 03-18-2009, 07:44 PM
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Holy cow, Doug. That does it. I'm leaving this thread RIGHT NOW! That was more than my eyes could handle.
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Old 03-18-2009, 08:26 PM
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Quote:
Originally Posted by Intruder
Sounds to me like the motor fit way to tight. Did you use tape to friction fit or did you just slide in the motor? I not, try sanding the inside of the tube a little to help keep it from happening again.


As I said in the original post
Quote:
Originally Posted by BEC
The motor was just slipped into the body tube - no tape or other aids to retain it.


The motor ejected a good half a soccer field's length when it came out. It was NOT tight in the tube....but I suppose I could shoot for "it would fall out if I picked the rocket up" loose.

Doug, compared to you I got off easy, though my nose cone was not hollowed as you had apparently done. Are the 13mm motors even worse somehow?
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Old 03-18-2009, 08:29 PM
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Sorry. I get "selective reading" sometimes.
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Old 03-18-2009, 08:39 PM
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Here's a little Google Earth and Powerpoint illustration.....
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Old 03-18-2009, 08:45 PM
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Quote:
Originally Posted by BEC
Doug, compared to you I got off easy, though my nose cone was not hollowed as you had apparently done. Are the 13mm motors even worse somehow?
Can't recall if I hollowed it out, or if it came that way, or if the hot ejection charges somehow factor into it.

I've seen the nuke blasts on 18mm A's and B's, but it seems more common on the 13mm motors. I often find myself digging deep into my stash for really old 13mm 1/2A3-4T's just to avoid killing one of my older (more precious) 2-stagers.

Doug

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Old 03-18-2009, 08:49 PM
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That was more than my eyes could handle.
In what way? Do you find it horrifying? Or pornographic?

Doug

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Old 03-18-2009, 11:52 PM
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I just put a little LED light down the BT of the Gyroc and see that the cone is partially hollowed as well....that seems to be a feature of BMS cones. It now has thin CA in the cracks from the outside and thanks to a pipette dropper also around the base of the cone on the inside.

I do believe I'll try a Quest A6-4 next in this one, though....since I have a half-dozen of them.
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