#261
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#262
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I wonder if, in haste, some motors were either mis-labled or had the wrong delay charges installed (or if the tolerances [or settings] of the equipment that made/installed the delay charges might have been off).
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#263
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I strongly suspect that my “B4-4”s are mostly mislabeled B4-6s based on data I have in hand. But a couple of them - one from each of the two date codes I have - have been correct.
Since all the ejection charges have been far more than needed I wonder if there was simply too much specified....perhaps thinking based on other Aerotech products for much larger models. I agree that tolerances of both delay grains and ejection charges need to be looked at.
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Bernard Cawley NAR 89040 L1 - Life Member SAM 0061 AMA 42160 KG7AIE |
#264
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Ejection charge is now under control.
Initial amount was .5 grams. Combined with the caplug retainer, this is too much for any model capable of being launched with such low thrust motors with 4 or 6 second delay times. in other words, the only models these motors will work in are BT-20, BT-50 and lightweight BT-55 and the volume is too small to withstand a .5 gram blast. As soon as they got the feedback, they reduced them to .3 grams. i do not have a date code cut-in, but the first date is obviously .5 gram (050118). Contact them if you need to report delay issues and maybe they can figure out what happened. After all, if they made or cut 1000 6 second delays and 1000 4 second delays and they made and shipped 1500 "-4" motors, and 500 "-6" motors then they should be able to determine what happened. if they made exactly the correct amount for the number of motors made and shipped, then they have to do more root-cause/corrective-action. Quote:
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-Fred Shecter NAR 20117 (L2) Southern California Rocket Association, NAR Section 430 |
#265
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Good--thank you for reporting their ejection charge mass reduction. The original Quest also had motor problems, which to their credit they quickly corrected. My first Quest motor, an A6-4 (black powder, of course) flown in a Quest Pipsqueak, fired its ejection charge as soon as the propellant burned out, at top speed, which resulted in a Kevlar cord "zipper" of its body tube. The motor either lacked a delay charge, or a void along the side of the grain (or maybe a crack) allowed the flame front to instantly rush forward and ignite the ejection charge. I contacted them and submitted a MESS form, and they replaced my motor pack (and also the kit, if memory serves). I used many Quest motors after that, and never had another one fail.
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#266
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Quote:
I have contacted them....this was before the 5 flights on Saturday and 9 on Sunday. I was actually expecting a call back today but so far it hasn’t happened. Here are the five flights for which I have onboard data via AltimeterThree. For those who are unfamiliar with the device, it carries a three-axis accelerometer as well as a barometric sensor and the delay time is based on accelerometer data. (I’d have had two more but the battery connector was not seated fully inside my other AltimeterThree and it shut itself off during the coast phase on those two flights. I probably did that myself as I had pulled and reconnected it during an attempt to troubleshoot a different issue a few months ago.) Of these five flights one four second and one six second delay was about right. The other three were all long. Visually, just watching from the ground, all the others were long to some extent. I flew one B4-4 on Saturday in an Alpha III that had a perfect flight profile - so I know it can happen. But so far it’s not the norm. The B4-6’s ejection charge was so violent it ejected the motor in spite of the motor hook (yet, fortunately, didn’t rip the motor tube by pulling down the top of the hook). My son found the casing a few minutes later in the grass....and it was bent a few degrees in the middle as if it were soft and flexible when it hit the ground. That surprised me because these generally have seemed to not be any hotter than an Estes motor on the outside at recovery and not as hot as Chinese Quest BP motors. The Tripoli cert letters for the As and Bs certainly don’t show the delays as running significantly long, which is why I suspect mislabeled motors.
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Bernard Cawley NAR 89040 L1 - Life Member SAM 0061 AMA 42160 KG7AIE |
#267
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Model rocket motors are allowed to go to 200 degrees C. Estes virgin kraft thick paper cannot ever do that and besides BP burns at half the temperature of APCP. The polycarbonate cases Q uses (insert derogatory term I often refer to Aerotech as), are much thinner, have more than 2x the combustion temperature and are so optimised in material usage they actually made the case 0.006-0.01" bigger OD than useable.
Tech Jerry |
#268
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Back to case measurements for the moment...
I was looking at the PDF of the 1962 (61?) Estes catalog (on the Estes website) and their drawing of a typical model rocket engine showed a diameter of "0.69 +- 0.025" . Whew, really loose tolerances back then!
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Roy nar12605 |
#269
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Quote:
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#270
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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").
__________________
Bernard Cawley NAR 89040 L1 - Life Member SAM 0061 AMA 42160 KG7AIE |
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