DiaLFonZo - BeG or Staples Rocket - Build

Discussion in 'Low Power Rocketry (LPR)' started by Eric Nantel - DiaLFonZo, Oct 28, 2019.

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  1. Oct 28, 2019 #1

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    Hi All,

    So i have lost 2 rockets this weekend, don't ask my how.
    But i wanted to build one that would be cheap as well as using a body tube that i can get locally.

    So... What about a shipping tube found at Staples (Bureau en Gros in French or BeG).
    Yes i know.. it's on the heavy side.

    A little design on the CAD software and here we have some 3D printable parts for the rocket.

    BeG-Assembly.PNG

    Moto Mount:
    IMG_20191027_162055.jpg IMG_20191027_162124.jpg

    Fins:
    IMG_20191027_164621.jpg

    IMG_20191027_164740.jpg

    Tube Slot for Fins:
    IMG_20191027_180529.jpg IMG_20191027_180559.jpg

    Some initial fit pictures:
    IMG_20191028_172237.jpg IMG_20191028_172227.jpg IMG_20191028_172255.jpg
     
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  2. Oct 28, 2019 #2

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    OpenRocket Design Attached:
    DiaLFonZo - BeG - OpenRocket.png

    It will obviously require some weight in the nose as the motor mount and tube are heavy.
     

    Attached Files:

    Last edited: Oct 29, 2019
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  3. Oct 29, 2019 #3

    neil_w

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    Nice.

    It looks like there is nothing holding that motor hook tight to the mount... do you plan to wrap electrical tape around it or something? If so that might require a bit of sanding out of the TTW tabs on the fins.

    Also curious how much that all weighs, given an 18mm mount...
     
  4. Oct 29, 2019 #4

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I'll properly weigh soon and might put it in openrocket.

    I added some circles to encase the retainer and will have to cut grooves in the fins... IMG_20191028_185949.jpg
     
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  5. Oct 29, 2019 #5

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    Added OpenRocket files in second post
     
  6. Oct 29, 2019 #6

    neil_w

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    The ORK file does not look very accurate at this point (materials are not set correctly, and in this case that's important).

    You have a lot of weight in the back of that rocket. Make sure that an 18mm will actually be practical.

    In general, although it is a nifty design, I'm not sure that motor mount is worth the weight for an 18mm motor, but I'm only guessing at this point. Just keep an eye on your weights and CG.
     
  7. Oct 29, 2019 #7

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I've but cardboard for the motor mount but over estimated the dimensions (since I can't select abs) and 3D prints are not 100% filled with plastic.

    I'm new to OpenRocket maybe I can weight and overwrite the value?
     
  8. Oct 29, 2019 #8

    neil_w

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    You sure can. Go to the "Override" tab and set the mass. Usually you don't need to override the CG of individual components; CG override is most useful for the completed rocket.
    upload_2019-10-29_9-54-45.png

    Definitely put in overrides for your fins, motor mount, and body tube.
     
  9. Oct 29, 2019 #9

    mbeels

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    Beautiful design, I like that fin shape with 5 fins.
     
  10. Oct 29, 2019 #10

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I've weighted and overwritten them. (both in the second post still)
    Some like the bulkhead are have no weight as i put everthing in the motor tube to keep it's center of gravity.

    How far the CG need to be appart the CP as a rule of thumb ?
    It goes through in the simulation but barely.
     
  11. Oct 29, 2019 #11

    neil_w

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    You're aiming for stability of 1-1.5 cal, with motor. For the C6 you can get there by bumping up nose weight to 1.25 oz.

    However, at that point you're really to heavy to fly safely. The sim shows speed off the rod of about 24 fps; that is too slow to be safe. 50 fps is a target, although you can certainly get away with less than that if it's not windy. But I wouldn't fly with 24 fps.

    Things get a little better with a Questjet C12 or D16 (mainly the D16), still borderline for safe flying though.

    Bottom line: these components are all very heavy for a rocket of this size; an 18mm motor is really not the right choice to fly safely.

    If you just replace the motor mount with a standard wood-and-paper variety, you might be able to do it (in addition to reduced weight in the mount, you'll also be able to reduce nose weight). You'll still probably want to stick with C12 and D16 motors, though. Would have to see the updated numbers.
     
  12. Oct 29, 2019 #12

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I can go bigger for the engine (mount) and ditch the clip fin approach as well.

    I'll model it...
     
  13. Oct 29, 2019 #13

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    What about lowering the CP with more fin surface?
     
  14. Oct 30, 2019 #14

    neil_w

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    Good, but unlikely to really solve your weight problem. Also it looked pretty nice the way you had it. :)

    But certainly feel free to experiment!
     
  15. Oct 30, 2019 #15

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I've quickly designed and guess the weigh in cad of a D12 and it's way better.. Might go that route
     
  16. Oct 30, 2019 #16

    Ablative

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    Could you not skeletonize the tube section of your motor mount and reduce weight that way? The tubular section the engine slides into doesn’t need to completely solid to do its job. The mount looks like a really great design!
     
  17. Oct 30, 2019 #17

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    Here is a LIGHT version of the motor mount and some data. (OpenRocket V0.3 uploaded)

    DiaLFonZo - BeG - LIGHT Mount.png
    Estimated: 13.24g
    Real: ???

    DiaLFonZo - BeG - HEAVY Mount.png
    Estimated: 25.72g
    Real: 20g
     

    Attached Files:

  18. Oct 30, 2019 #18

    neil_w

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    That's certainly an improvement, but the whole rocket is still too heavy and too tail-heavy. I just took a look at those fins: you have them overridden to 1.3 oz; if they were made of balsa the whole set would be a bit over .2 oz according to OR. That's over an ounce of extra tail weight in the tail, which is a *lot*.

    Your new motor mount comes out to .47 oz; built from traditional materials would be closer to .16 oz. That's another big difference.

    Finally, the body tube is 2 oz, whereas a standard commercial BT would be about .9 oz.

    So you're just fighting a tough battle from front to back. You can certainly build a rocket using these materials, but it really should have a 24 mm motor mount, and then you'll need either (a) more nose weight, or (b) larger fins.
     
  19. Oct 30, 2019 #19

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I understand all that - This is not an attempt to build a powerful rocket but to build one using the Staples tube.
    Unfortunately it's hard here to find material, it has to be ordered only.

    I'll port all that to a standard hardware very soon and will make files available as well so anyone can do their own.

    :)
     
  20. Oct 30, 2019 #20

    Eric Nantel - DiaLFonZo

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  21. Nov 1, 2019 #21

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    The last post was done on my phone and it ... didn't work right.. sorry

    The new motor mount with some skeleton shape as suggested by @Ablative:
    IMG_20191030_170013.jpg

    Here is the two motor mounts side by side on the scale:
    IMG_20191030_170252.jpg IMG_20191030_170752.jpg

    Nose as i will use it:
    IMG_20191101_135304.jpg IMG_20191101_135307.jpg IMG_20191101_135311.jpg

    I will not use it but you can see a payload compartment option. (will use that on other models)
    IMG_20191031_172908.jpg
     
  22. Nov 1, 2019 #22

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    Just a coat of primer IMG_20191101_190142.jpg
     
  23. Nov 2, 2019 #23

    Ablative

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    It looks badass I think you should throw stuff up and see what sticks. I think that with an 18mm motor and a launch space that’s not inside an elementary school classroom you can feel free to push the boundaries a bit.
     
  24. Nov 2, 2019 #24

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    Thanks - I'll try to do that this weekend but we had crazy winds the last two days.

    I've started modelling on a standard BT-60 tube and cardboard motor mount as well as balsa fins.

    It's still borderline in openrocket regarding the speed off rod.
     
  25. Nov 3, 2019 #25

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    Ok I flew it.. If enough people want to see I'll share the video
     
  26. Nov 3, 2019 #26

    neil_w

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    Videos are great, but at the very least some sort of flight report would be welcome. What motor did you use, and what happened? What was the final weight of the rocket?
     
  27. Nov 3, 2019 #27

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    I was already aware of the weigh and everything so it was a fun try...

    I'll get you the final weight but.. Too heavy...

     
  28. Nov 3, 2019 #28

    neil_w

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    What motor was it?
     
  29. Nov 3, 2019 #29

    Eric Nantel - DiaLFonZo

    Eric Nantel - DiaLFonZo

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    The only one I had on hand B6-4

    IMG_20191102_171052.jpg
     

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