Lakeroadster's Lifting Rocket

Discussion in 'Scratch Built' started by lakeroadster, Dec 27, 2018.

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  1. Dec 27, 2018 #1

    lakeroadster

    lakeroadster

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    Spent some time today on CAD working on a scratch build.... I'm calling it a "Lifting Rocket".

    It can be flown with a single 24 mm motor.. or a canted cluster of (3) 18 mm motors.

    I'm still working on this... I want to add a payload section at the bottom that locks to the body tube in place of the 24 mm motor.

    It would be neat to have multiple motor options and payload configurations.. all retrofitted onto the Lift Rocket

    I've added stiffener rings and struts to make it as "durable" as possible.

    LR 001.JPG LR 002.JPG LR 004.JPG LR 008.JPG LR 009.JPG
     
  2. Dec 27, 2018 #2

    kuririn

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    Wow. Very creative. I like it.
     
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  3. Dec 27, 2018 #3

    BABAR

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    Very cool, as usual.

    What exactly do you need a payload section for?

    Seems like when you fly three canted Cs you can put an expended D casing in the central mount, maybe it a couple drops gorilla glue to plug the nozzle. Contrary wise with a D central motor three plugged C casings in the canted mounts.

    If you fly with all 4 you may exceed the speed of balsa!
     
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  4. Dec 27, 2018 #4

    OverTheTop

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    Very nice. Consider using CF rod from your local hobby store. Might be a bit more durable, considering the bits hanging out the back, than skewers or wood.
     
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  5. Dec 27, 2018 #5

    les

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    Nice! You may also want to look at carbon fiber arrow shafts in place of the dowels
     
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  6. Dec 27, 2018 #6

    lakeroadster

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    Hence the name Lifting Rocket. A utilitarian rocket for "lifting" things to apogee... the "ute" of the rocket world.

    Perhaps things that fit into a payload bay, like a camera with a clear unobstructed view during launch...

    or things that make you scratch your head... like tethering scale car models behind the rocket...
     
  7. Dec 27, 2018 #7

    lakeroadster

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    Question.. anybody ever cut down, or sanded down, a booster motor to eliminate the area above the propellant? Might increase the possibility of a CATO if not done with great care?

    Motor Modification.jpg

    That would give a nearly unobstructed path down the center of the rocket.. thus eliminating the little edges of the boosters visible in the screen shot below (looking into the body tube, nose cone removed).

    The rocket only needs one of the three motors to have the delay / ejection charge.

    LR 011.JPG
     
    Last edited: Dec 27, 2018
  8. Dec 27, 2018 #8

    BABAR

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    1. Can’t do it a NAR launch, and would violate your NAR insurance if you get fecal turbine interaction.
    2. Is issue all three 18 mms won’t fit? Or you think they will interfere with each other. If they won’t fit, I would extend the mount or just friction fit the motors.
    3. Even if you could cut the corner safely (literallly and figuratively), you presumably have tried cutting expended casings and it is a PITB. Do you really WANT to have to do that on every launch.

    I love the idea of a rear end camera. I tried it before with engines lateral to the camera but NOT canted. The backblast from the motors ruined the lens. I think your design should remedy the problem and give you an unobstructed view. Next trick is a three point harness for your shock cord and parachute to keep the rocket from wildly gyrating when comes down under chute.

    This would work better if you had a larger body tube outside diameter upfront. The more widely spaced the three attachment points are the more stable the descent, especially with a spill hole. (Larger tube would use also give you a lot more room for your laundry, currently looks a bit scant..)
     
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  9. Dec 27, 2018 #9

    BABAR

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    Come to think of it a larger body tube up front might solve both of your problems and give you a lot more space for the forward ends of your three Canted body tube motor mounts
     
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  10. Dec 27, 2018 #10

    neil_w

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    First of all: LOVE IT.

    Second: is it stable? On the one hand, not much fin area back there. On the other hand, those canted motors should be pulling CG forward quite a bit. On the gripping hand.... aw hell I've got no clue. Where's @Daddyisabar when you need him?

    Third: why are the intruding motor cases a problem? Doesn't look like they're intruding very much, still plenty of airspace there for the main motor ejection I would think. Also, as pictured, the canted motor tubes look *way* longer than an 18mm motor, why would they be intruding at all?

    Fourth: did I mention I love it?

    Took me a minute to parse this. ;)
     
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  11. Dec 27, 2018 #11

    Wallace

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    Don't forget to block the ejection ends of the motors accordingly so you don't end up with unintended forward end ignition...
     
  12. Dec 27, 2018 #12

    neil_w

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    Can you explain that?
     
  13. Dec 27, 2018 #13

    Nathan

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    Reminds me of this video I made 5 years ago. An oldie but still fun to watch.
     
  14. Dec 27, 2018 #14

    Wallace

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    I you were to use say two 0 delay booster motors and one with a 5 second delay for deployment you stand a fair chance of the booster motor(s) burn through igniting the delay motor from the unprotected top end. Make sense? Common cure is dog barf and tape over the open top end of the delay motor...Yes, modern BP motors have a clay cap (instead of paper) at the delay end but a little added protection couldn't hurt...
     
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  15. Dec 28, 2018 #15

    neil_w

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    Makes sense, thanks for the explanation.
     
  16. Dec 28, 2018 #16

    Wallace

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    No problem. This is especially a potential issue with booster motors since there is unprotected BP at the fore end..Just something to keep in mind when clustering.
     
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  17. Dec 28, 2018 #17

    lakeroadster

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    Thanks everybody for the suggestions and comment.

    Back to the drawing board... I updated the model to the bigger body tube, which throws off the entire perspective of the rocket.

    Then I updated the body tube ahead of the canted cluster transitioning from the BT-50 to a BT-55, then back down to a BT-50 for the nose cone. That looked a bit like a python that ate a pig.

    I really like the clean lines of a single body tube from the bottom to the top. So the current plan is to scale everything up, going from a BT-50 body tube up to a BT-60. This will make the rocket proportionally the same, give adequate space for recovery components and make the model much easier to build.

    I'll post up some photo's when I get the model updated.....
     
  18. Dec 28, 2018 #18

    BABAR

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    I REMEMBERED that! So at least some of my gray matter is still working. Very cool!
     
  19. Dec 28, 2018 #19

    BABAR

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    1. Input is great but remember a camel is a horse designed by a committee.

    2. How did it look if you kept the upper body tube constant and just went with a BT-60 nose cone? Also, if room for recovery is tight, just lengthening the tube a bit gives you space for wadding and a less folded chute of same size. But will put proportion off.
     
  20. Dec 28, 2018 #20

    lakeroadster

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    Curious what the trajectory looked like from your vantage point? Did the camera make the rocket arc over?

    Everything I tried in that regard looked worse than the original.

    A little nose cone gives the illusion of a big rocket. A big nose cone makes the rocket look smaller.

    Making the body longer takes away from the "lifting" concept.. and it's my understanding that having the canted motors as far forward as possible should help with stability.

    At least that's my maniacal thoughts on this design.

    I'll post up some screen grabs.
     
  21. Dec 28, 2018 #21

    lakeroadster

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    Screen Grabs

    Lifting Rocket, BT-50 main, with BT-55 parachute bay. Perhaps call this one "The Python"... cause it looks like a "Python Ate A Pig". :D

    The issue here (or perceived issue) is I'd like the CG to be below the clustered canted rockets, to help ensure stability. But I think this design would work fine with a payload section that is attached via the lower 24MM location (no 24mm motor) just lifting via the cluster. The lower payload section thus shifting the cg downward. LR PYTHON 001.JPG LR PYTHON 002 CG.JPG

    ___________________________________________________

    Here's a stretched version of the same design. The body tube has been increased to ensure the CG is well below the canted cluster.

    The cool thing about this design... the rocket could be built using various pinned tube couplers that would allow multiple main body tube length configurations, depending upon the required lifting task.

    LR PYTHON STRETCHED 002.JPG LR PYTHON STRETCHED CG 001.JPG
    __________________________

    Thoughts?

    I'm off to make a new CAD model based on a BT-60 main body tube... which should eliminate the "Python Ate A Pig" look.
     
    Last edited: Dec 28, 2018
  22. Dec 28, 2018 #22

    neil_w

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    If you move the forward ends of the dowels onto the payload area (or, even better, onto the front end of the transition) it might look better. Dunno if that would mess up your separation point though.

    Of the two you just posted I like the stretch version.
     
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  23. Dec 28, 2018 #23

    BABAR

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    Okay waaaaay outside the box
    R.e :Last 2 pics
    Glue in nose cone. Use rear eject if you use forward motors.

    Use forward eject if you use rear motor.

    I am taking the liberty of Consulting daddy is a bar on this I hope you don't mind.
     
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  24. Dec 28, 2018 #24

    lakeroadster

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    No worries... the rear eject isn't possible with the aft cargo bay... not sure I made that clear.
     
  25. Dec 28, 2018 #25

    lakeroadster

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    So here is the BT-60 based Lifting Rocket. I've attached some screen grabs with and without the aft cargo bay, shots showing center of gravity
    and a drawing. Motors shown are all 24mm, but the mounts allow 18mm or 24mm.

    The larger forward recovery bay behind the nose cone I added just because it looks better IMO. Plus it adds capacity. Likely separation will be between the back transition and the recovery bay.

    Plan is to attempt an open rocket simulation. I'm pretty sure I can get a good run with the single bottom motor.

    It looks to be unstable without the aft cargo bay unless the canted motors are removed. The CG in the last screen grab below includes the canted motor weight For single motor launches it might be a good candidate for an e-motor, but I worry about cato's.

    BT-60 LR 002.JPG BT-60 LR 003.JPG BT-60 LR SIDE CG 001.JPG BT-60 LR 004.JPG BT-60 LR SIDE CG 005.JPG Lifting Rocket Study Drawing.jpg
     
  26. Dec 29, 2018 #26

    OverTheTop

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    Love the look of the struts to the cargo pod!
     
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  27. Dec 29, 2018 #27

    neil_w

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    That aft cargo bay is wackadoodle. :confused: :cool:

    I'm a bit confused by this:
    The aft cargo bay will pull CG backwards but not CP. How does removing it make it less stable, in any scenario?

    This thing could use a good sci-fi paint job.
     
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  28. Dec 29, 2018 #28

    Daddyisabar

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    Put your canted motors as far forward as possible. If three ejection charges are too hot just reinforce the tube above the mount or plug a 0 delay motor or two with a nice glob of epoxy. All you need for the motor mount is an old centering ring and a few drops of superglue. There is more than enough surface area on the body tube to get a strong and durable superglue bond on the motor mount tubes. Drag most any asymmetrical payload up attached to the rear end. Tell the RSO the pendulum theory is still good. Put some cool looking fins way up front. Most folks don't know that you have one of the most stable rockets at the launch. It being kinda funny looking keeps up the scare. Just need all three motors to light. Love tractor motors. So much more fun to pull than to push. Not many do it, but you can fly what you like, Ekranoplans, Stukas, worms, dragons, or just pull up silly payloads. So it is not conventional in construction or bends some rule, but it works and is not boring. Keep up the good work.
     
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  29. Dec 29, 2018 #29

    Nathan

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    As I recall it flew pretty straight up. But the camera broke loose when the ejection charge fired. Landed in soft grass and wasn't damaged.

    Every once in a while I think about trying something like that again but on a high power rocket.
     
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  30. Dec 29, 2018 #30

    Daddyisabar

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    A slung camera pointing up under clustered tractor motors would be cool. Just a little soot to wipe off the lense after a nice stable flight and soft recovery .

    A globe of go pros, 360 degree views hauled up with high power clustered tractor motors. Say it ain't so!
     
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