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  #31  
Old 07-14-2019, 02:32 PM
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ghrocketman ghrocketman is offline
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Stick a Q-jet D16 in that Wizard.
BT-20 based rockets are fire-n-forget.
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  #32  
Old 07-14-2019, 04:32 PM
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July 4 I wanted to test the FlightSketch mini altimeter so I pulled out a mongoose modified with a payload section and was surprised that it will take the original fat qjets with the label intact. I flew a B4-4 and the delay was long, 5.9 seconds. Then I came here and found the thread about mislabeled motors, the date code on that was 050118, the first batch I think.

Today I flew another B4-4, this batch was 100418-03. The delay was right were it supposed to be, 4.15.

See graphs below, I suspect the first motor is a 6 mislabeled as a 4, the vertical line shows where ejection occurred.

Flight altitudes were within 5 feet, 284 and 279. An Estes B6-4 flew to 286 feet.
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  #33  
Old 07-14-2019, 04:44 PM
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Quote:
Originally Posted by ghrocketman
Stick a Q-jet D16 in that Wizard.
BT-20 based rockets are fire-n-forget.


I got another at the sale, and I have a D16-8, I might do that. When AT D21s and E15s came on the market in the 90s, a bunch of turbocopters, Tracers and quest Tomahawks got the ride. Got some back too.
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  #34  
Old 07-14-2019, 09:40 PM
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While the 5/64” bit fits through the version 1 (fat) Q-jet A3s, the nozzle size has been reduced in the ones I got last week, date code 081518-02. A 1/16” bit just passes, so drilling is possible but unfortunately not with the same rig as the B4s. If you have qjet As I would love to know what the nozzle size is vs date code.

See the difference below, version 1 from May 2018 to right.
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  #35  
Old 07-17-2019, 09:54 AM
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I drilled two newer identical A3-6s a 1/16th to try to get to a four second delay using the first method with a tape stop on the bit to indicate how far to go, since only a 1/16” bit fits in the newer A3 nozzle.
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  #36  
Old 07-17-2019, 10:03 AM
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The altimeter data and video I have indicate the delay on the first flight was 4.9 seconds, which was perfect for the rocket, with an altitude of 141 feet. Using good video of the second launch, the second flight delay was exactly 5 seconds. Beware I am basing the delay from moment of liftoff to moment of ejection then subtracting the published burn time. I am not sure about the performance of the second motor because visually the flight was lower and the altimeter reported only 127 feet. If the motor pressure is low or the burn short, the delay will run long, so more testing is needed.
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Last edited by 5x7 : 07-17-2019 at 11:11 PM.
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  #37  
Old 07-17-2019, 09:39 PM
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Quote:
Originally Posted by 5x7
The altimeter data and video I have indicate the delay on the first flight was 4.9 seconds, which was perfect for the rocket, with an altitude of 141 feet. Using good video of the second launch, the second flight delay was exactly 5 seconds. I Beware I am basing the delay from moment of liftoff to moment of ejection then subtracting the published burn time. I am not sure about the performance of the second motor because visually the flight was lower and the altimeter reported only 127 feet. If the motor pressure is low or the burn short, the delay will run long, so more testing is needed.

If the propellant and delay formula are the same, you definitely have lower burn rate on the larger nozzle, assuming geometry is the same. Looks like your data goes along with it.
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  #38  
Old 07-17-2019, 10:43 PM
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I might have been confusing showing the motors with different nozzle sizes, I didn’t fly the old version nozzle yesterday, the motors are from the same bulk pack and date code, it’s just that I didn’t get quite the shortening I expected on the As so just wondering about the flight that seemed and reported much lower.
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  #39  
Old 07-17-2019, 10:56 PM
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Once 5+ people report flights it will be meaningful enough for Aerotech to put it on the website.

It appears they are iterating aspects of the product looking for a sweet spot. I hope they settle soon and run.
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