Reloadable Motor System

Discussion in 'Mid Power Rocketry (MPR)' started by geodehunter, May 21, 2019.

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  1. May 21, 2019 #1

    geodehunter

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    What rms is everybody using now? I have been away from the hobby for quite awhile and I'm trying to get caught up on things now.
     
  2. May 21, 2019 #2

    jimzcatz

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    Only games in town anymore are Aerotech, Loki and CTI. The choice is yours.
     
  3. May 22, 2019 #3

    Wallace

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    Even though I do love my reloadables , if your intention is to save money it's not gonna happen. Single use is the way to go unless you fly a LOT or need specific motors.
     
  4. May 22, 2019 #4

    Wallace

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    Or plan on research motors.
     
  5. May 22, 2019 #5

    jimzcatz

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    Now that's just plain wrong misinformation. The exact opposite is the case.
     
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  6. May 22, 2019 #6

    AfterBurners

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    exactly how do you think you are saving money by buying SU motors?? They are always more expensive.
     
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  7. May 22, 2019 #7

    timbucktoo

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    Personally if you have a local vendor, I buy what he’s selling as you save on shipping & hazmat. As time rolls on, it’s always a good idea to expand your collection of cases and motors to other manufacturers.
     
  8. May 24, 2019 #8

    jqavins

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    Or intend to go larger than 29 mm diameter or eight or nine inches length. (Yes, this is the mid power subforum, I know.)
     
  9. May 24, 2019 #9

    JLebow

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    I guess it depends on how many flights you plan to make, if you lose the rocket (reusable motor case), lifetime of a case (no catos), and what size motor you fly.

    From the Aerotech catalog (many vendors have discounts - this example is for list price), I got the price of the DMS single use, the RMS motor case and the RMS reload. I did this for 4 sizes of motor. The break even point is higher for smaller motors. In my graph, the cost of zero flights is non zero for the RMS because of the fixed cost of the case. RMS vs DMS.png
     
  10. May 24, 2019 #10

    Wallace

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    Nice example. Well done and thank you Sir.
     
  11. May 24, 2019 #11

    jqavins

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    I retract my earlier post. (I'm about one minute past the 60 minutes time limit for editing. "Short limit, Kronk! Why do we even have that limit?") I misread the Aerotech master motor list and mistakenly believed that there were no single use motors beyond 29 mm. My mistake.
     
  12. May 24, 2019 #12

    Wallace

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    You're not the only one that hate's that time limit. It does have a purpose though, thank the turds for making it necessary..
     
  13. May 24, 2019 #13

    solid_fuel

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    Does this account for the fact that there is no hazmat shipping on many reloads where a single use comparable motor would have hazmat applied? Obviously the larger reloads will still have hazmat shipping but there are many H&I reloads that don’t require hazmat. And I know of at least one J that ships non haz.
     
  14. May 24, 2019 #14

    Wallace

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    The charts? Didn't consider that as I do not have those shipped. That is a very relevant point though.
     
  15. May 24, 2019 #15

    Wallace

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    I do know for certain that if you happen to lose and or ruin a motor case and or closures it takes a LONG time to recoup...
     
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  16. May 24, 2019 #16

    Wallace

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    A simple example being the AT m1350 which would be considered a reasonable L3 cert motor choice, not taking into account hardware/Haz shipping or case/closures(wrenches), etc. At basic retail online pricing you're looking at maybe an extra 40 bucks max for the single use as opposed to a re-load. $40 is not trivial but when you account for how many times you may actually use (and hopefully not de-purpose) that hardware... I'd love to have stacks of motor cases/closures/hubcaps/head end ignition//gen1/gen2/75mm/98mm/tailcone closures,etc. etc. etc. I totally get it that supply and demand (not taking into account certification costs of virtually everything) drives prices and I'm not placing blame on ANYONE, but for your average person that's just not realistic. Single use,Dms,Buildable or whatever you call it just makes more sense in certain(probably most) situations. Even looking on Yard sale virtually everyone is asking 95+ % of new for used hardware.
     
    Last edited: May 24, 2019
  17. May 24, 2019 #17

    Wallace

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    Rant over...At least until flaming begins.
     
  18. May 25, 2019 #18

    solid_fuel

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    the cost for an M motor is very different than most motors more commonly used. in all motor sizes there are also the motor characteristics and the fact that the single use category is more limited in choice, And when contemplating buying an M motor I don't think there are that many Single use choices

    buying only from your on field vendors tends to even further limit your motor choices. Unless you're lucky enough to have multiple or one of the larger vendors attend every launch.
     
  19. May 25, 2019 #19

    kuririn

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    Wallace, I agree with you on some points regarding the economics of RMS vs SU. What I don't see mentioned is the convenience and ease of SU motors: no assembly and no residue cleanup. Prep it, fly it, chuck it.
    On the other hand some of us actually enjoy assembling and cleanup of our casings and motors.....
    OK nobody enjoys cleaning up. But some enjoy assembling.
    And this will be a necessary skill when moving up to the larger motors.
    Whether or not SU or RMS is more economical depends on your personal situation, as previously detailed.
    Also, consider this: if the resale value of used casings is 95% of retail, what is the real cost to you?
    You cannot resell a used SU motor.
     
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  20. May 25, 2019 #20

    mbeels

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    Actually, there are a few exceptions where single use motors cost less than comparable reloads. The Economax F67 and G74 cost less per Ns of impulse than similar impulse reloads for the 29/40-120 hobby line case. (compare purple triangles and yellow squares in this plot). The F67 is also HAZMAT free. (Sale prices from Sirius Rocketry. The costs of cases was not included in these numbers.)
    motors.png
     
    Last edited: May 25, 2019
  21. May 25, 2019 #21

    Wallace

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    No one in their correct frame of mind truly enjoys cleaning cases;). But if you look at it from the other perspective, even if your used "stuff" sells for asking price you're still out that 5% plus what, if any you spent on shipping. I did preface my original with the fact that I do actually love reloadables, just bothers me that "I" personally cannot justify(or usually) afford them..
     
  22. May 25, 2019 #22

    jbr

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    reloadables in research make a big difference
     
  23. May 25, 2019 #23

    Wallace

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    Correct me please if I'm wrong, but can't you then easily also make your own snap ring cases and graphite nozzles? I do own a lathe and have regular access to mills,surface grinders, cnc stuff, etc. Being both NAR and TRA L2 I should know this but have yet to delve into that rabbit hole...
     
    Last edited: May 25, 2019
  24. May 25, 2019 #24

    Wallace

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    I do also own close to a thousand dollars in reloadable hardware (only up to 54mm so far) yet still find myself searching for a single use alternative for fear of "something" going wrong. Regularly find myself considering selling it off while it still has value(I.E. before I break or lose it) If that makes any sense?
     
    Last edited: May 25, 2019
  25. May 25, 2019 #25

    jbr

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    my 29mm set [​IMG]
     
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  26. May 25, 2019 #26

    mbeels

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    By far, I use my Aerotech 24/40 RMS case the most, I can fly it locally without having to drive far for a HPR field. It's definitely my favorite. "H" and above is Cesaroni for me. I'll use the single use Economax to fill in the F and baby G gap. As through Ds are Estes BP. So I like a bit of everything.
     
  27. May 25, 2019 #27

    mbeels

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    Did you make those? What impulse range can you fly with them?
     
  28. May 25, 2019 #28

    jbr

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    38mm cases upload_2019-5-25_9-32-52.png
     
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  29. May 25, 2019 #29

    jbr

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    54mm cases upload_2019-5-25_9-33-51.png
     
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  30. May 25, 2019 #30

    jbr

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    98mm cases, the full M case is not in this pic upload_2019-5-25_9-35-1.png
     

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