grouch
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That's so freaking cool it hurts to look at it!
Two-stage HPR design build
- Thread starter SteelyEyed
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Thanks. Glad you like it grouch. But, it's was a good news/bad news kind of thing at FITS over Memorial Weekend. After the booster test went so well I was going to fly the sustainer solo for a shakedown test (with motor delay backup, the RRC2-mini, and the WRC+) before I stacked it in two-stage configuration. I powered up and installed the Garmin dog collar GPS in the nose cone, prepped the two RouseTech CD3s with two e-matches in each one (one from the alt and one from the remote for both the drogue and the main), installed the fully prepped av-bay, the drogue, main, kevlar shock cord, shear pins, etc. It was all ready to go laying on the table at my camp site. The good news... it looked awesome and I was exceedingly proud of it... the bad news... I proceeded to power up the two MissileWorks units to confirm the power up sequence and continuity beeps for the e-matches, and test my two magnetic switches (which BTW are mounted too close to eachother and sometimes when I run the magnet by them, one powers up and the other doesn't, then when I try to just turn the one on, the other turns back off... frustrating... a bad layout choice on my part... which I have to fix)... about 10 seconds after power up both deployment charges fired... almost blowing the nose cone and main chute into the adjacent camp (halted by the 20 ft shock cord... I did make sure no one was standing in harm's way when I powered up... something to always remember)... the drogue did not deploy because I did not yet have a motor installed... so the drogue CD3 pressure vented out the motor mount tube, otherwise the fin can would have been thrown off the table in the opposite direction of the nose cone.
A bit startled, it took me moment to realize what had happened. Then I remembered a couple of years ago or so reading in Sport Rocketry that the MW RRC2-mini was subject to unplanned event execution (premature firing) due to RF interference with the Garmin Astro mounted near by. So now I have to rethink this bird and make some changes before I can fly it. So for now I'm going to work on the alternative sustainer and rework the av-bay (change out the mag switches and probably use a CommSpec radio tracker instead of the Garmin and see if that works... if not replace the RRC2-mini with a Raven or Adept or something... stand by for updates.
Any sage advice from others experienced with this issue would be welcomed!
Bret
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bandman444
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God man. You are lucky
Exact same thing happened to me with my Garmin astro, and a Perfect flight MAWD back in October 2011. My altimeters were off and I had just finished putting in the apogee charges (3, and 4grams) and as I was putting the parachute into the tube, all I remember is a flash. Both of my eyes completely torched.
The ER doctor said that if I had not been wearing contacts I would have been permanently blinded no doubt, the scratches and burns on my contacts were extreme he said.
I will never touch a bp charge without safety glasses, EVER.
Scary stuff man, scary stuff.
CarVac
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Be careful with safety glasses too: I let go of the left arm of my safety glasses when taking them off, and it sprung back and poked me neatly in the very center of my eye. Good thing I was also wearing contacts, because that had a scratch on it for the rest of the day!
Close call bandman. Glad it turned out okay. Given that there have been a number of these cases documented, I'm surpised NAR and TRA haven't issued a safety advisory notice... or maybe they have and I've missed it.
One important item to note, the RouseTech CD3 is not nearly as hazardous as BP charges (a cold CO2 blast in the face would be bad, I would choose it over the situation you experienced).
AlphaHybrids
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Beautiful build - I really enjoyed all of it.
I do have a comment on the Garmin Astro setup. For my L3 I had dual mounted RRC2-Mini's and a DC-20 transmitter. I had all this in a 2.5" airframe with about 9" of vertical separation between the DC-20 and the RRC2-Mini's. The DC-20 was in the nosecone. I had heard of this happening, and tested for this condition. I found that the RRC2-Mini's didn't fire in my hour long test of them. I powered them up and down and left the DC-20 transmitting. Just for extra insurance after the tests I put aluminum tape on the outside of my e-bay to create a psuedo-faraday cage. I flew the rocket 3 times, and never had an issue with any interference. I know it can happen, and don't know the exact circumstances of what causes it. I do know that I had the DC-20 set on the lowest frequency that it had and the most frequent update interval.
Edward
I do have a comment on the Garmin Astro setup. For my L3 I had dual mounted RRC2-Mini's and a DC-20 transmitter. I had all this in a 2.5" airframe with about 9" of vertical separation between the DC-20 and the RRC2-Mini's. The DC-20 was in the nosecone. I had heard of this happening, and tested for this condition. I found that the RRC2-Mini's didn't fire in my hour long test of them. I powered them up and down and left the DC-20 transmitting. Just for extra insurance after the tests I put aluminum tape on the outside of my e-bay to create a psuedo-faraday cage. I flew the rocket 3 times, and never had an issue with any interference. I know it can happen, and don't know the exact circumstances of what causes it. I do know that I had the DC-20 set on the lowest frequency that it had and the most frequent update interval.
Edward
Edward,
Glad you appreciated the build and thanks for taking the time to describe your experience with the Astro/RRC2 mini. I lost momentum on this project following the RF interference issue but will be getting back to it in the next few weeks. I still need to complete the alternate sustainer design as well as solving the aforementioned problem.
Bret
Thank you DM,
It's always great to hear from folks you appreciate the rocket designs I post. Designing interesting and unique rockets is my favorite element of the hobby... like I have said many times before... I quickly get bored with 3FNC designs. For whatever reasons, I'm partial to military/weapons systems-looking designs. Glad you like it.
Bret
freddiejojo
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I dont mean to hijack the thread but on the Garmin Astro, I have a DC-30 I use and my altimeters are a Raven and a HiAlt45k. I have not had any issues yet, but just to be on the safe side, what precautions should be taken? One of my latest builds has the antenna of the Astro pointing straight down out of the nose cone and pointing to the altimeter bay. Should I redesign this? Would wrapping the av bay in aluminum tape help to shield it? Any thoughts?
If the antenna has a pattern anything like a whip antenna, having it "pointed" at the av-bay would actually make it pretty quiet from the av-bay's point of view. For the Raven, you should test it with the Garmin running, and either do a simulated flight if you can connect a USB cable in that configuration, or do a test where you jerk the rocket upwards to trigger liftoff with no BP installed. In either case, look at the Raven recorded data for signs of interference in the baro or accel data that could affect the deployment logic.
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sodmeister
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I want to hear the 3FNC crowd ( or general lower order of people or mob)chime in on this one and state their case 
You make us proud with your fine design and work.....I could not do better as yet ,but does give me goals to set and hopefully achieve !
As always Bret ,another fine piece of work.
Sincerely
Paul T
You make us proud with your fine design and work.....I could not do better as yet ,but does give me goals to set and hopefully achieve !
As always Bret ,another fine piece of work.
Sincerely
Paul T
Thanks Adrian, will do.
Adrian, I too would like to thank you for taking the time to reply. One of my optional solutions to this problem is to replace the RRC2mini with my Raven and give that a try. If that's the route I take will give your suggestion a try. Another is to keep the RRC2mini in place and fabricate, install, and test some sort of an RF shield similar to the one described in the aforementioned Sport Rocketry article.
Also, if anyone else out there in TRF land has any prictical experience and/or good suggestions... please post 'em.
Bret
Thanks Mason, glad you like the design. I wish I had time to start such a business, but 1) it would be EXTREMELY unlikely that I could make a go of it given the demands of my day job and 2) I would probably get into a mode where the hobby that I love became a JOB (not good).
BTW there is a vendor that has talked to me about kitting the sustainer stage of this design... but those things are a lot easier to talk about than to actually accomplish (so don't hold your breath).
Bret
I agree they would be successful, but understand the lack of time.
I want to hear the 3FNC crowd ( or general lower order of people or mob)chime in on this one and state their case
You make us proud with your fine design and work.....I could not do better as yet ,but does give me goals to set and hopefully achieve !
As always Bret ,another fine piece of work.
Sincerely
Paul T
Thanks Paul, your feedback is always sincerely appreciated. I'm looking forward to seeing the designs you dream up... bring 'em on!
Bret
A nice idea, but in my case I use aluminum tape inside the airframe and copper tape on the av-bay to form the electrical leads to the ingniter wires that fire the sustainer motor. Adding tape around the av-bay would short out the circuit...
Could you not use a thin layer of epoxy to insulate the two? Or aluminum tape inside the av bay instead of outside?
I can't put any more tape on the outside of the av-bay, because as it is now, the existing tape (inside the airframe and outside of the av-bay) provides two raised surfaces that create a nice solid electrical contact with a tight fit. If I add more tape the fit will be too tight to insert and remove the av-bay. Interesting idea to put metal tape on the inside though... I will give that some serious thought. Thanks for the recommendation.
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