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Should've mowed instead??

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Tbmx3

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A couple of defective F20-7w's. They both just smoked for around 10sec, then the ejection popped, then they tried to thrust and then caught fire. Besides being down a couple bucks it was kinda cool to watch. Oh well!!


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kyle

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Bummer. I mowed and did chores and broke my finger.

Should've launched instead.

What's the second rocket? I like the fins.
 

Steve Shannon

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A couple of defective F20-7w's. They both just smoked for around 10sec, then the ejection popped, then they tried to thrust and then caught fire. Besides being down a couple bucks it was kinda cool to watch. Oh well!!


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You should file a MESS report (motorcato.org) and you should turn it in to the manufacturer’s customer service department. That’s not to say you’ll be compensated, but if nothing else you might learn why it happened.
I would suspect the igniter didn’t get placed all the way forward.
 

n3tjm

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To me it sound like the delay grain ignited but not the propellant, at least not until after the ejection fired. I have seen this happened before. Most of the time I have seen this, the delay burns but the propellant never does.
 

jqavins

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To me it sound like the delay grain ignited but not the propellant, at least not until after the ejection fired. I have seen this happened before. Most of the time I have seen this, the delay burns but the propellant never does.
Seems like, maybe, this time the ejection charge was hot enough to light the propellant. By that time, the top of the motor was open, so little to no flow through the nozzle, and just a big fire.
 

Bat-mite

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To me it sound like the delay grain ignited but not the propellant, at least not until after the ejection fired. I have seen this happened before. Most of the time I have seen this, the delay burns but the propellant never does.
The way I try to avoid this is to bend the tip of the igniter down parallel with itself. That way the tip of the igniter is not touching the hole where the delay grain is.
 

NAR29996

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Looks like you might have started a little fire.

You can get nomex blankets from some rocketry vendors for pretty cheap.

I'm on mobile now, so I can't check.
 

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