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Adjusting Delays - Q-Jet
I have been adjusting Aerotech delays for over 25 years using their approved drill method, which has been officially incorporated across most of their line. They have released at least three tools through the years to make it easier to do.
Quest released its A through D Q-Jet motors, and second generation packaging dropped Quest from the label and the motors are branded Q-Jet by Aerotech. In line with other Aerotech products, I thought it would be simpler to buy the longest delay if it could be adjusted. AT single use motors are adjusted through the forward touch hole but this is problematic for Q-Jets because the ejection charge cap is down pretty far, and although others have gotten it out, I don’t think it would be worth while to have cap removal, then dump, drill, replace and recap as a good option, In addition, drilling from the forward end causes delay grain to remain after the change goes off and that still burns, barbecuing the rocket above the motor. I found a 2” long 5/64” diameter bit fits through the nozzles and reaches the delay. As a first test I took a 1/16th off a B4-6 to make it a four. The flight went great with just over 5 seconds from liftoff to ejection which confirms to me the regular delay material is being used. The pictures show the bit, with tape marking the depth to drill too, and the delay removed. Try this at your own risk, the drilled hole is small so there is a chance if the hole is not cleaned out well you will get the normal delay. A bigger bit should fit in Ds and Cs. If you try it take note that every motor needs to be measured, where the delay is in relation to the nozzle can vary even between motors of the same class and delay. The other thing to remember is the delay is rubbery but it is holding back the pressure in the motor so don’t cut it under 4 seconds or the shortest delay offered. Getting the longest delay is nice because there is no Estes equivalent. Flight Video Last edited by 5x7 : 06-17-2019 at 07:50 PM. |
#2
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Excellent !
I will only order the long delays from now on. Only really interested in their 18mm D, which is a good substitute for the old 18mm Cox D8.
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When in doubt, WHACK the GAS and DITCH the brake !!! Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't ! Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY. ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC ! |
#3
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I just ordered a 3 inch bit and a stop collar from McMaster Carr that will make this a 30 second job.
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This is very interesting. I’m not sure I personally would act on this information, but I appreciate knowing this. Thanks.
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Bernard Cawley NAR 89040 L1 - Life Member SAM 0061 AMA 42160 KG7AIE |
#5
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Quote:
Don't be scared . . . You won't "blow your hand off" - LOL ! Dave F. |
#6
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Not too worried about that.....
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Bernard Cawley NAR 89040 L1 - Life Member SAM 0061 AMA 42160 KG7AIE |
#7
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Quote:
You bet, I personally wouldn’t start with Q-jets if you had never shortened a delay,the 24-60 case has model rocket motors with adjustable delays and you get a better feel for it when you can see what you are doing. I got started when the 24-40 reloads long delay were the full length and the delay spacer for the next shorter delay was a hard fiber disk that would survive the flight and could be reused. So to make a 7 into a four, you would hold the spacer next to the delay and slice off that length, then use two spacers instead of one. When AT switched to thin paper spacer rings it was back to drilling. |
#8
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I'm familiar with drilling delays in the context that I fly 24 and 29mm CTI motors. I also have the tools for both the new RMS motors (such as the 24/60 loads you allude to) and the other one that uses a similar but different tool (I forget what AT called that one). But I've not thought of drilling delays on SU motors through the nozzle....
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Bernard Cawley NAR 89040 L1 - Life Member SAM 0061 AMA 42160 KG7AIE |
#9
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I think the universal delay drilling tool that's not universal unless I am missing something.
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#10
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Here is a simpler way to do the drilling with a longer bit, a depth stop and 1/32” washers, sold as shortening shims. Procedure is
1) Stack as many washers as you want seconds removed on the nozzle, plus one to drill on. 2) Put depth stop loose on bit and bit into nozzle. 3) with depth stop resting on washers, tighten depth stop. 4) Remove all washers except the one against the nozzle. 5) Drill until stop bottoms on washer on nozzle and clear shavings. First the items: Last edited by 5x7 : 06-18-2019 at 10:02 PM. |
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