LOC Precision AMRAAM AIM 120C Build Thread

Discussion in 'High Power Rocketry (HPR)' started by TimothyAReed, Dec 21, 2019.

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Should I add a Go-Pro to this rocket?

Poll closed Dec 28, 2019.
  1. Yes

    33.3%
  2. No

    66.7%
  1. Dec 27, 2019 #31

    TimothyAReed

    TimothyAReed

    TimothyAReed

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    Build Log #6 Dec 26, 2019

    Today was a productive day finishing the base fillets for the fincan. A considerable amount of work was put into the GPS tracker mount, and the extra bulkhead was repurposed with the help of the 3018 CNC mill. I just realized that I have to order some recovery cord because the kit only came with one kevlar strap. I could use the kevlar strap for the drogue and a different cable for the main chute. However, my OCD might not let me "mix&match" recovery cords. Fellow forum dweller C.O.B.H.C. previously mentioned battle rope for recovery cord so I might go with that:

    Note: The nosecone after the bottom was cut off and the bulkhead as it came from LOC
    NOSECONE_CUT.jpg

    Note: The bulkhead was just slightly larger than the ID of the nosecone, so I milled a 3mm deep shoulder that will allow the bulkhead to seat in the nose cone (it will be epoxied in place).
    BULKHEAD_MILLING.jpg

    Note: Side view of the now modified bulkhead. Notice that one of the baffling tubes is being used for housing the GPS tracker, the mill (pictured above) also enlarged the center hole for it to fit snuggly. For those that are curious, I removed the outer wrapping for the tube so that the epoxy will soak into the fibers easier and save a little bit of weight. I did the same to the MMT tube and saved ~6 grams for comparison.
    BULKHEAD_SIDE_VIEW.jpg

    Note: The final product, sort of, I still have to drill the 1/4" eyebolt hole and figure out exactly how I want to fasten the GPS into the tube. The original thought was to 3D print a screw assembly, think Estes motor retention screws, and mount the tracker on a sled attached to the screw cap. After looking at the numbers, the method above would have been a little too cumbersome due to the size of the inner tube. I am currently thinking about printing an insert with a flange that screws into the plywood instead.
    NOSECONE_FIT.jpg

    That's all for today, thanks for keeping up with my rambling!
     
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  2. Dec 29, 2019 #32

    TimothyAReed

    TimothyAReed

    TimothyAReed

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    Build Log #7 Dec 28, 2019

    Every time I say "I make sure to post tomorrow" something happens that keeps me from posting -_-. Anyways progress is going along smoothly, and I am grateful for the schedules catchup days I scheduled ahead of time. The fincan was mounted into the main body tube, and I have completed 4/8 of the internal fillets that step should be done tomorrow. My missile works RRC3 is arriving Monday so I can then put more work into the Ebay, which will be helpful. Still undecided on what recovery cord to use. In the meantime, the kevlar strap that came with the kit was looped through the eyebolt, and the two ends were connected to a D-ring. This setup allows me to tie whatever cord I do end up using to one end and pull it through the Eye-bolt. If I decide to use the stock strap I can loop one end of the cord through the other and pull it tight(see below pictures for visual).

    Note: Kevlar strap looped through the eye-bolt but not tied
    FINCAN_CABLE_MOUNT.jpg

    Note: Kevlar strap tied to the eye-bolt.
    FINCAN_CABLE_TIE.jpg

    Note: Custom external fillet guides 3D printed for this rocket, the longer side is curved to fit the tube profile.
    FILLET_GUIDE.jpg
     
  3. Dec 29, 2019 #33

    jd2cylman

    jd2cylman

    jd2cylman

    Still not Carl... ;-)

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    I do believe that thar is purple nylon, not Kevlar, just judging by the pics. But just my $.02.
     
  4. Dec 29, 2019 #34

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd/ SEDS 2018 1st

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    Try OneBadHawk for gooood Kevlar. I haven’t been disappointed yet. It goes in all my HPR builds.
     
  5. Dec 30, 2019 #35

    TimothyAReed

    TimothyAReed

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    Thanks for the heads up, I will double-check the website. I just assumed kevlar and didn't check that's my mistake.

    Thanks for the recommendation, will check them out.
     
  6. Dec 30, 2019 #36

    TimothyAReed

    TimothyAReed

    TimothyAReed

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    Build Log #8 Dec 29, 2019

    Another productive day! The internal fillets for the fincan were completed, and the GPS tracker mount was designed and printed today. For my second catch up day tomorrow, I am going to start&finish the external fillets (I will use 5 Min epoxy for these because it retains its shape better). The Missle works RRC3 that I ordered is also scheduled to arrive tomorrow, so that is a plus. Without further ado, here are some pictures.

    Note: My GPS tracker mount for the nose cone, pretty happy with how it came out.
    GPS_TRACKER.jpg

    Note: Weighing in at 61.40 grams
    GPS_TRACKER_WEIGHT.jpg

    Note: an especially tight fit!
    GPS_TRACKER_FIT.jpg
     
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  7. Jan 4, 2020 #37

    TimothyAReed

    TimothyAReed

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    Build Log #9 Jan 4, 2020

    First of all, Happy new year! Even though I have not posted in a few days, I have been able to keep to the schedule. The GPS tracker and Canyard fins were completed in reverse order, though. All I have left to do is to order the drogue and main chute and to complete the Ebay. I will not paint the rocket until after the shakedown flight when I have a month until my actual certification flight. Tomorrow I will be mounting the RRC3, RRC2+, and going over how I want to mount the deployment charges. Any recommendations or pictures of you're Bp wells are appreciated.

    Note: 3D printed alignment guides for the canard fins
    CANYARD_FIN_ALIGNMENT.jpg

    Note: The tape for the fillets placed and epoxy was just laid down.
    CANYARD_FIN_FILLETS.jpg

    Note: A front view of the fillets
    FILLET_VIEW.jpg

    Note: Brand new RRC3, very excited for future projects with this guy RRC3_PACKAGE.jpg

    Note: Finished some work with the Ebay, these are the mounts for the Missle works screw switches. Notice how the switches are aligned with the centerline of the ebay. EBAY_SWITCH_MOUNTS.jpg
     
  8. Jan 13, 2020 #38

    TimothyAReed

    TimothyAReed

    TimothyAReed

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    Build Log #10, Jan 13, 2020
    I was able to meet the schedule and Complete the test flight on Jan 12, which was a success. I will post a more detail retroactive build log along with an AAR tonight, but for now, here is a video of the launch.

    NOTE: launch at 0:22
     
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  9. Jan 13, 2020 #39

    swatkat

    swatkat

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    Which motor? Looked like it turned a bit off the rail. AMRAAMs are typically pretty stable.
     
  10. Jan 14, 2020 #40

    TimothyAReed

    TimothyAReed

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    I195J-10, the rocket weighed 8Ibs, The chutes that I purchased from the vendor were heavier than I was expecting, plus some high winds caused the weather cocking. This video angle also makes it seem more extreme than it was. I updated my OpenRocket file, and with the chute, the rocket had a stability of >3.0 Cal. For my cert, I want to use a motor with an average thrust of +250N so that I can have a higher off rail velocity.
     
    Last edited: Jan 14, 2020
  11. Jan 14, 2020 #41

    Nytrunner

    Nytrunner

    Nytrunner

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    Average thrust means little. Look at the thrust curve of the motor, specifically the first 1/4 second while its on the rail.

    If you have a progressive burn, rhe avg number is deceptively high. If you have a regressive burn, then the avg number is lower than actual on-rail thrust
     
  12. Jan 14, 2020 #42

    TimothyAReed

    TimothyAReed

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    That is Correct, to clarify the I195J-10 has a peak thrust of 415N right at the 1/4 second mark. I am looking at buying 54mm Loki Research hardware and specifically a 54-2000 with a K250 reload. This would bring my stability to under 3.0 and have a max thrust of 800N. The predicted apogee is ~5,500 ft however depending on how smooth the final paint job is it could be more.
     
  13. Jan 14, 2020 #43

    Nytrunner

    Nytrunner

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    Great selection process! Whenever someone mentions designing by the average thrust, I start to worry
     
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  14. Jan 14, 2020 #44

    swatkat

    swatkat

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    Dang that's heavy! PML is ~3 lbs lighter!
     
  15. Jan 14, 2020 #45

    TimothyAReed

    TimothyAReed

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    I was also including the motor weight plus I had Nomex parachute protectors on each chute. But definitely a pretty heavy rocket.
     
  16. Jan 15, 2020 #46

    TimothyAReed

    TimothyAReed

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    Build Log #11, Jan. 14 2020

    Because I was unable to keep up with a daily log, I am going to document some necessary build steps and tests retroactively. This build Log is going to focus on the Ebay. I settled on using a Missle works RRC3 as my primary and an RRC2+ as a backup. For the "Shakedown" flight, I also had an ejection charge set on the motor to go off 3+ seconds after Apogee, therefore, giving me double redundancy on the drogue deployment. This is a stand 4" Loc Ebay kit that has been modified with 3d printed parts and some light CNC milling. Without further ado, here are some pictures.

    Note: Milled the RRC3 mounting holes plus a 3.5 mm deep recess for the nylon bolts to go into. This allows me also to reuse the standoffs as I can still unscrew them and move them to another Ebay.
    EBAY_RRC3_MILL_MOUNT.jpg

    Note: The battery side of the Ebay, it is set up so that the battery terminals are facing the Aft end of the rocket. This orientation reduces the chance of the batteries separating from the case during the boost stage of the flight. The two green wires are for the RRC3 because it has a separate terminal for the switch.
    EBAY_BOTTOM.jpg

    Note: The top of the Ebay. The Blue and Yellow wire indicates two things; the main bulkhead of the Ebay and what altimeter they go to. The Drogue bulkhead is not epoxied to the sled like the main is, so two JST connectors are used to allow for easy separation. These were mounted by epoxying the female side to the sled and then fasting the drogue bulkhead to the Ebay and then connecting the Male side and epoxying it in place. I also super glued the wires in place so that they won't move around and keep a neat appearance. Once again, I deny any accusations of me having OCD.
    EBAY_TOP.jpg

    Note: The main bulkhead, remember that the Yellow wire goes to the RRC3 and the Blue to the RRC2+
    MAIN_BULKHEAD_EBAY.jpg

    Note: Notice the semi-rectangular holes, made with a rotary tool and files, that the male JST connectors were slotted through and then epoxied in place.
    DROGUE_BULKHEAD_EBAY.jpg

    Note: For those that are curious, I am using centrifuge vials for BP canisters. They are made by cutting a small hole for the E-matches and then applying a small amount of 5-min epoxy at the base of the match and then sliding it to the bottom of the vial. The vials are then taped in a vertical position, and the epoxy is allowed to dry. The BP is weighed and poured into the vial. Any space left is filled with "dog barf" packed tight, and then the vial is closed.
    BP_CHARGES.jpg
     
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