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  #271  
Old 06-21-2018, 01:18 AM
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A Fish Named Wallyum A Fish Named Wallyum is offline
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Quote:
Originally Posted by BEC
Since you brought it up, here it is.

I still think, subjectively, that Q-Jet cases are as not hot post firing as Chinese Quest BP motors - especially the Cs. But the plastic cases must be hot enough to be deformable immediately after firing. None have felt "soft" when pulling them out of a normally recovered model (well, as near normally as you can what with the delay and ejection charges outside of what we'd consider "normal").

There's a TV commercial about that.
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  #272  
Old 06-21-2018, 03:04 AM
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Quote:
Originally Posted by BEC
Since you brought it up, here it is.

I still think, subjectively, that Q-Jet cases are as not hot post firing as Chinese Quest BP motors - especially the Cs. But the plastic cases must be hot enough to be deformable immediately after firing. None have felt "soft" when pulling them out of a normally recovered model (well, as near normally as you can what with the delay and ejection charges outside of what we'd consider "normal").
Whoa...at first glance (in the small thumbnail image, just before I read your posting), I thought it was a pickle! I guess the combination of its heat-caused relative plasticity, its rapid (gravity plus backward [downward?] ejection out the back of the rocket) downward travel, and the hardness of the ground where it hit may all have contributed to its deformation.
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  #273  
Old 06-21-2018, 11:14 AM
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Except for the last factor, yes. Sixty Acres Park is primarily a soccer facility and was being groomed for a week-long event as we were there. It's one of the softer places one can land rockets (or bits or rockets).
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  #274  
Old 06-22-2018, 05:32 PM
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Quote:
Originally Posted by BEC
Except for the last factor, yes. Sixty Acres Park is primarily a soccer facility and was being groomed for a week-long event as we were there. It's one of the softer places one can land rockets (or bits or rockets).
Thank you. To "forensically examine" this incident as much as it can be, was it found on the surface, or had it punched into the ground (even if it bounced back out, leaving a "dent" in the soil)? If the latter was the case, that would suggest that the motor case was quite plastic (in the way that "plastic" refers to the hot rock inside the Earth--heat-softened and pliable) at the instant of impact.
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  #275  
Old 06-22-2018, 08:06 PM
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My son didn't say...but it wasn't hard for him to find it. From that I'm inferring that it wasn't buried in the ground or even leaving a dent. As light as they are I don't see how one could do so on that site.

Yes, I'm thinking that the case is quite plastic in that sense immediately after firing, but when held in a motor tube you can't really see that unless you get to a just-flown model really quickly.

Another that was flown without the label shows a little shrinkage of the case about 1/2 an inch down from the top of the 18mm diameter portion. I checked a couple of others - I've flown 19 of these now - and can see a little of that on some of them.
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  #276  
Old 06-22-2018, 10:07 PM
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Quote:
Originally Posted by blackshire
...And that's not even considering their performance tolerances (the static test stand instrumentation back then might not even have been electronic, but mechanical or electro-mechanical). If Estes was still using firework piece casings then, that might account for their looser dimensional tolerances. I just hope that the "wall thickness-trimmed" new batch of Q-Jet motors won't be too heat-deform-able (like the bent ejected casing that BEC reported), or transmit too much of the heat to their casing surfaces.


Vern has said their "test" stand back then was a small postal scale, poorly damped, which lead to such anomalies as the B16 motor, as in 16 *pounds* average thrust, which was later corrected to three pounds thrust. The B3 (predecessor to the metric B14) could floor the undamped scale by inertia, leading Vern to believe that it was indeed producing 16 pounds of thrust.
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