Are Estes E12 black powder motors unreliable?

Discussion in 'Propulsion' started by Underdog, Jul 30, 2019.

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  1. Oct 10, 2019 #61

    Charles_McG

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    You'd know rate vs. count. But you still wouldn't be able to compare rates unless you had the denominator of other motors as well.
    You can still do comparisons, though. They have assumptions - but I think they can still be used with care.
    Has the E12 reported CATO YTD (or month - pick a time frame) changed from historic levels. plot it like a control chart. Assumes usage hasn't changed significantly.
    Does the E12 get a different number of reports than similar motors (like the D12)? (Assumes at least a constant ratio of usage rates, though I would go further and posit that more D12s are flown than E12s)

    Data I'd love to see, but can't without inside Estes knowledge, is a list of all the E12 production lots. How many lots have reports? How many have none? In the past, when I've had a CATO, or checked the list, all the hobby shops around me have those same lots on the hangers, and they seem to stay there until they sell through.
     
  2. Oct 10, 2019 #62

    SecondRow

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    I’m willing to bet that E12 usage has increased significantly in recent months, given that E9s were discontinued sometime within the past year.

    Anecdotally, I’m seeing more reported E12 CATOs on this forum and FB in recent months. I think part of it is caused by this (assumed) increase in E12 usage.
     
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  3. Oct 11, 2019 #63

    DeltaVee

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    I *personally* have not had one CATO yet... (out of perhaps three or four packs)... however at the last launch I attended (with deangelo54) there were quite a number of them. Of course now that I said that, my next one will probably CATO. My Estes Phoenix sure flies nicely on them, though....
     
  4. Oct 11, 2019 #64

    KennB

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    I'll miss that Phoenix when Murphy's Law catches up with you.
     
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  5. Oct 11, 2019 #65

    JohnCoker

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    This we could do with data available in the motorcato.org DB. Good idea; I'll look into adding it.

    How would one define "similar"? These are both BP motors with similar average thrusts, but the E has almost twice the total impulse. BP motors near the top end of their impulse range for BP?
     
  6. Oct 11, 2019 #66

    Charles_McG

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    'Similar' is tricky, because it's so case specific. CTI Pro38 1G as a recent example - pretty narrow.
    In the E12 case, I chose the D12 because it's made by the same manufacturer, likely the same type of machine (maybe the same actual machine), is sold through similar outlets (handling), has same propellant, diameter, similar thrust. I don't think the impulse is important in this example because they are end burners and the E12s seem to CATO early - so length of burn isn't a factor.
     
  7. Oct 11, 2019 #67

    JohnCoker

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    Yeah, that's what I was pondering. It's not obvious that there is a programatic way to pick "similar" motors to compare.

    But the idea of a graph of reports over time is a good one.
     
  8. Nov 7, 2019 #68

    John Taylor

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    Why with the number of cato's and having to replace engines and kits does Estes continue to sell these engines? I know they are great about replacing kits, but what happens with an out of production model? Why don't they redesign the engines since that's where they are making the money? For everyone stating how great there customer service is, seems not so great to me if they keep endorsing a product with a significant risk of failure. Am I stating what many are thinking or am I overreacting?
    I have three E12-4 engines I am afraid to use. I don't have any models I don't care about.
     
  9. Nov 7, 2019 #69

    Nytrunner

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    Probably because the fraction of failures is very small compared to the volume of motors sold. If I didn't read the forum and only went on my own firsthand experience, I wouldn't even notice that the E12 had a problem trend

    What's the date code? Stick one in the ground and test fire it on a warm day
     
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  10. Nov 7, 2019 #70

    prfesser

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    Designs of endburning BP motors are all pretty much the same. The high level of reliability that commercial motors must have is difficult to attain. A common mode of failure is when the flame creeps up the junction between propellant and casing (there's a name for this but I don't remember it). A coreburning motor, like the old F100 or like most skyrocket motors, doesn't suffer quite as much from that problem, because there's already a large area of propellant (the core) that's aflame, and the nozzle is quite large; a little more burning surface doesn't make a huge difference.

    By contrast, an endburning motor has a rather small area of propellant---a circle the size of the i.d. of the casing, essentially--- that is burning. A little more area can have a drastic effect. I don't know how Estes solved the problem. Presumably they have some better means of bonding the propellant to the casing, I dunno. Having made a number of BP motors myself, my hat's off to them.

    There's also the size constraint. The o.d. of a skyrocket motor isn't an issue, it doesn't have to fit inside another tube. Model rocket motors are 18mm, 24mm, etc. For maximum performance the i.d. needs to be as large as possible. So special high-strength paper casings with relatively thin walls are needed. But thin casings don't do so well in endburning motors, because the casing is exposed to flame shortly after ignition. Burn-through is pretty common.

    "Why don't they make coreburning motors instead?" All sorts of reasons. For example a coreburning BP motor is more fragile than an equally sized endburner; the hole up thru the center means the propellant can crack more easily.

    Aaaand that's probably a lot more than you wanted to know... :)

    Best -- Terry
     
  11. Nov 8, 2019 #71

    John Taylor

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    I've seen them blow up. I haven't seen any other hobby motors blow up. It happens a lot. Way more than any other hobby motor. Mess statistics are impressive.
    I believe it's a money thing. It would cost Estes a lot to buy back all the engines out there, retool or whatever it would take to change the manufacturing and design of the current E12 engins. It's cheaper to let a bunch blow up and replace them and a few kits.
    The stopped the E9 engines. They weigh out there decisions based on expected gains and losses.
    There in buisness to make money not necessaraly to make friends.
     
  12. Nov 8, 2019 #72

    John Taylor

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    In all my years (I'm 61) I've never had or seen an Estes motor Cato before.
    These Estes E motors are blowing up at a high rate compaired to the D's or smaller motors.
    Just my observations.
     
  13. Nov 8, 2019 #73

    John Taylor

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    I appreciate the intelligent responses and help.
    Thanks
     
  14. Nov 8, 2019 #74

    DeltaVee

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    Well as far as design goes (I speculate...), I imagine that the nozzle shape probably is key... not to mention the importance of the propellant being bound to the walls of the casing. I think maybe the latter here is significant... if the bond to the walls break then the only thing you can do is pick up the pieces. One thing Estes did was add 1/4" to the casing for their E motors (remember the E15??) which probably helped the bonding issue. I don't know what's used for the propellant-paper interface be it glue or just a ton of pressure on manufacture. We had quite a few E12 catos last Saturday, and someone said that they seem to feel that we get more E12 catos when it gets cooler (which it was)... but I don't think it was really cool enough to make a difference.
     
  15. Nov 8, 2019 #75

    Nytrunner

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    What was the temperature outside?

    Advice I've received has been don't fire the Es if the temperature is 30 deg below the warmest temperature it's been exposed to. That's why I only fly them in the summer
     
  16. Nov 8, 2019 #76

    John Taylor

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    Why only the E motors? I've never had an issue nor have I witnessed with A-D engines. Numerous E failures seem to abound.
     
  17. Nov 8, 2019 #77

    John Taylor

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    How are supposed to know the warmest temperature they have been exposed to before we purchased them? It's not like
    "Brewed cold, kept cold"
     
  18. Nov 8, 2019 #78

    Arsenal78

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    I’ve flown a lot of A-D and the only cato I’ve had myself was a B but I’ve flown about 10 E9/E12’s and all but a few catoed. Estes knew something was up with the E engines but they never bothered to look into it, hence why the E12’s are doing it as well. Haven’t seen any 29mm BP motors cato yet but who knows. If you’re going above a D, just fly composite, especially if it’s a kit you like.
     
  19. Nov 8, 2019 #79

    Nytrunner

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    Don't know, I'm not a motor guy.
    My engineering spitball is that the longer casings experience greater deflections than a D during thermal cycling and are more subject to separation when the slug and case expand at different rates.
    24's have thinner casings than the 29mm BP motors which haven't had this issue. It may be that they can only get 24mm casings in that thickness, and are making do by honoring their warranty when requested.

    Ah, anecdote time! I've witnessed an A10 and a couple C6's blow too.

    We can't. However, I know they're made in the colorado desert and shipped in hot trucks, so when I go out to launch this weekend in the low 50's, guess which motors I won't be flying.

    Rocketry is all about personal preference. I mitigate what I can, and spin the roulette every time I put a rocket on the pad.
    A wise rocketeer once said "If you don't want to lose it, leave it on the shelf"


    *edit post button is open for a short while so you don't have to throw multiple posts up one after another
    **you can quote multiple people on one post too
     
  20. Nov 8, 2019 #80

    DeltaVee

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    At least in the mid to upper 40s I'd say...

    We even had two b6-4s have a problem (nozzle issue... the rocket just sat on the pad sizzling)
     
  21. Nov 8, 2019 #81

    Nytrunner

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    Oh yeah. That's E-boom weather for sure
     
  22. Nov 9, 2019 #82

    John Taylor

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    I paint them real nice, lookin good before 1st flight. It's no big deal when one crashes due to my fault which happens from time to time.
    However if my model blows up due to no fault of my own, with a store bought main brand SU motor, then I am NOT a happy camper.
    IMHO, Estes could and should do better.
     

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