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  1. #151
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    Any concerns about the thrust from the motor causing flexing between the center of the rocket (motor) and the outside of the rocket?

    To be honest, I'm seriously considering flying out (from Illinois) to see this launch. I echo what Sather says- this isn't just a "big rocket build", but more like a large engineering project that happens to have a rocket as the output.

    NAR# 99285
    Tripoli# 16283
    L1- 4/26/2015 Madcow Cowabunga- H123SK
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  2. #152
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    Having missed Steve Eves' Saturn V, this will possibly be a once-in-a-lifetime experience for me.


    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  3. #153
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    Quote Originally Posted by Bat-mite View Post
    Having missed Steve Eves' Saturn V, this will possibly be a once-in-a-lifetime experience for me.
    +1, I'm already budgeting vacation & travel fare.

  4. #154
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    Quote Originally Posted by dhbarr View Post
    +1, I'm already budgeting vacation & travel fare.
    Make sure everything is refundable. Launch slip, rain, high winds, low clouds ... anything can happen.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  5. #155
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    Quote Originally Posted by Bat-mite View Post
    Make sure everything is refundable. Launch slip, rain, high winds, low clouds ... anything can happen.
    Oh, definitely.

  6. #156
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    One thing I would suggest thinking about is to blow the chute for the rear section out the back end, rather then the top end. The V2 fin can section was quite heavy, and with the chute coming out the top it copped a bit of a bent fin on landing. Chute out the rear potentially has less damage aft.

    Two chutes might have helped for our V2, but I think rearwards would probably have been better.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  7. #157
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    Quote Originally Posted by OverTheTop View Post
    One thing I would suggest thinking about is to blow the chute for the rear section out the back end, rather then the top end. The V2 fin can section was quite heavy, and with the chute coming out the top it copped a bit of a bent fin on landing. Chute out the rear potentially has less damage aft.
    When we did our big Redstone, we took bets on how many fins would be damaged on landing - the V-2 suffers from the same issue with fins that stick quite a ways aft of the end of the airframe. Any horizontal velocity on landing and it puts a heck of a load on that fin.

    Aft deployment can present its own issues. It means a rather heavy parachute generating load on whatever is holding it in place during the thrust phase and especially when the motor first kicks in. Also if you don't get the airframe horizontal and the chute out and away, you risk the canopy coming in contact with a hot motor case. It can be done - the Arizona folks did it on one of their larger projects.

    -Kevin

  8. #158
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    OverTheTop & Kevin,

    We agree the concern for landing damage. That was a line item in several design meetings. We have some awesome CAE animations of landing strain. I will try to have that posted soon.

    Finally our approach is to let the rudders and the vane-servo boxes crush. We will make replacements part of original production. Hopefully all landing damage stops at those defined crush zones.

    Feckless Counsel

  9. #159
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    I think that's a very reasonable plan, I did the same for my foam rockets on a smaller scale, just live with some crush/energy absorbtion, it's not like you are going to fly this 20 times...better to replace a few parts and not tweak the main structure.

  10. #160
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    Sounds like a plan!
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  11. #161
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    TRF,

    Today we tested our thrust plate. It supported more than 10,000 pounds-force with ease.

    As pictured below we set thrust plate on a perimeter of bricks representing the airframe. A 1/4-inch thick steel disk representing motor’s thrust ring was bolted through four places. An 8-inch steel tube representing the motor was set upon the steel disk. Scale was placed upside down on the steel tube. Finally a 1/4-inch thick steel square was set upon the scale to distribute load to scale’s 4 feet.

    The assembly was subjected to compressive loads from an excavator.

    A first compression to 6k scale reading produced no appreciable deflection of the thrust plate. The square steel plate, however, suffered almost an inch deflection. We unloaded the assembly and the steel square returned to flat. Some audible pops were noted on initial loading.

    We added a second 1/4-inch steel square to the assembly.

    A second compression to 6k scale reading produced no appreciable deflection of the thrust plate. There were no audible pops. Noticed just a little deflection of steel squares.

    Finally we compressed the assembly to scale overload, about 10k pounds-force. Again no appreciable deflection of the thrust plate was observed.

    Thrust plate was thoroughly examined after loading. No damage was observed including plywood delamination, fastener pull out or adhesive de-bonding.

    Feckless Counsel
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  12. #162
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    Quote Originally Posted by Feckless Counsel View Post
    TRF,

    Today we tested our thrust plate. It supported more than 10,000 pounds-force with ease.

    As pictured below we set thrust plate on a perimeter of bricks representing the airframe. A 1/4-inch thick steel disk representing motor’s thrust ring was bolted through four places. An 8-inch steel tube representing the motor was set upon the steel disk. Scale was placed upside down on the steel tube. Finally a 1/4-inch thick steel square was set upon the scale to distribute load to scale’s 4 feet.

    The assembly was subjected to compressive loads from an excavator.

    A first compression to 6k scale reading produced no appreciable deflection of the thrust plate. The square steel plate, however, suffered almost an inch deflection. We unloaded the assembly and the steel square returned to flat. Some audible pops were noted on initial loading.

    We added a second 1/4-inch steel square to the assembly.

    A second compression to 6k scale reading produced no appreciable deflection of the thrust plate. There were no audible pops. Noticed just a little deflection of steel squares.

    Finally we compressed the assembly to scale overload, about 10k pounds-force. Again no appreciable deflection of the thrust plate was observed.

    Thrust plate was thoroughly examined after loading. No damage was observed including plywood delamination, fastener pull out or adhesive de-bonding.

    Feckless Counsel
    Well, congrats! You know you're hardcore when you need an excavator to build your rocket I REALLY hope I am available to see this go up!
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  13. #163
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    I enjoy that the steel plate showed far more strain than your wooden thrust plate.

  14. #164
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    Nytrunner,

    We were "impressed" by that as well. Attached is zoom from picture 2 above. Really gives one a sense of relative stiffness.

    Feckless
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  15. #165
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    27th July 2014
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    very nice! Now you should submit it to the hydraulic press channel on youtube
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  16. #166
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    Very nice worst case scenario since your actual vehicle will be free to accelerate instead of sitting there resisting the entire motor force .

  17. #167
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    Congrats on the successful test!

    Honestly, I'm not too surprised by the plate defection. All that FEA though, and no one ran a quick deflection calc on the plate?

  18. #168
    troj's Avatar
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    Quote Originally Posted by Feckless Counsel View Post
    Thrust plate was thoroughly examined after loading. No damage was observed including plywood delamination, fastener pull out or adhesive de-bonding.
    I'm not surprised. That construction technique is incredibly strong and works quite well. You've also got a nice, wide thrust ring.

    Something else I just thought of that may help on your timing of altimeters... We held the sections of ours together with explosive bolts (nylon bolts drilled out and filled with BP and ematches). We also had spring-loaded pilot chutes and the chute bays were sized such that the bagged main and pilot chutes just fit. This meant that if the sections separated, the pilot chutes were coming out - there was not stopping it.

    In our case, we recovered in three sections, which allowed us to put the altimeters in the upper tube. For the capsule we used timers with switches that detected the separation of the capsule from the upper airframe section. That way we allowed the capsule a couple seconds to fall away from the tube, so we had less risk of entanglement between the two. We also chose to fly without the tower (it was easily removable) to reduce entanglement risk from the tower itself.

    This is a really cool project and I hope it's very successful.

    -Kevin

  19. #169
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    TRF,

    Attached is a link to video from our load testing. This video is recorded from a gap in the brick perimeter. Note the count up to 10k pounds ends in scale overload. Light appears between bricks and thrust plate as the assembly is unloaded.

    https://youtu.be/4b1iArZZwMI

    Video courtesy Bob at Rockets Magazine.

    Feckless Counsel

  20. #170
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    Quote Originally Posted by Feckless Counsel View Post
    TRF,

    Attached is a link to video from our load testing. This video is recorded from a gap in the brick perimeter. Note the count up to 10k pounds ends in scale overload. Light appears between bricks and thrust plate as the assembly is unloaded.

    https://youtu.be/4b1iArZZwMI

    Video courtesy Bob at Rockets Magazine.

    Feckless Counsel
    I watched that entire video with no sound thinking, "When are they going to start compressing it already?"

    Incredible work!
    crmrc.org

  21. #171
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    Quote Originally Posted by rstaff3 View Post
    Well, congrats! You know you're hardcore when you need an excavator to build your rocket I REALLY hope I am available to see this go up!
    2 of my last 4 HP flights, I've needed an excavator to recover....
    Phill Ash
    SouthEastern Virginia Rocketry Association (SEVRA)
    2016 Tot Impulse: 3819.2 Ns (L2, 47 motors, 43 flights)
    2017 Tot Impulse: 4605.2 Ns (L2, 45 motors, 44 flights)

  22. #172
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    18th December 2010
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    TRF,

    There have been so many discussions regarding adhesives. Please let us throw another log on the fire?

    Project Redstone’s skin is about 850 square-foot. That is entirely too much surface area to prepare with abrasives, solvent cleaning or chemical etching. Instead we want a self-preparing adhesive. We believe that is entirely the domain of methyl-methacrylate adhesives (MMA).

    MMA are frequently carried by toluene, carbon tetrachloride and other aggressive solvents. Those solvents promote surface adhesion with little to no surface preparation. The strength of MMA are about 4,000 PSI lap-shear, approaching the strength of toughened epoxy.

    MMA are moderately expensive. Parsons Partite MMA costs about $35 per system-liter. US composites 635 medium epoxy costs about $20 per system-liter. Ten liters of adhesive are required for the project.

    Is our research complete? Can anyone suggest a “better” zero surface prep, high strength and moderate cost adhesive?

    Feckless Counsel
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  23. #173
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    Something else I just thought of that may help on your timing of altimeters... We held the sections of ours together with explosive bolts (nylon bolts drilled out and filled with BP and ematches). We also had spring-loaded pilot chutes and the chute bays were sized such that the bagged main and pilot chutes just fit. This meant that if the sections separated, the pilot chutes were coming out - there was not stopping it.
    We did a similar method in our V2. The sections were separated using pneumatics. Compartments were made in the central 5" ID tube to hold the pressure tanks and valves, and form a piston/cylinder arrangement at one end of each tank. Pressures were 20 bar and 30 bar (one composite tank and one aluminium). The valves were triggered by a manual command via radio, with backup being an RRC3 altimeter in each section. The tanks actually performed the coupling function for the stack.
    Click image for larger version. 

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    The parachutes were in buckets with a car airbag under them, facing the bulkhead on the opposite section. You can see the white bucket in this pic:
    Click image for larger version. 

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    The tops of the parachutes were tied to the opposing section with a small piece of Velcro. The idea was that as the sections separated the chutes would be dragged out. "Plan B" was to have the airbags triggered to throw the chutes out into the air a short time later.

    Deployment was entirely nominal. Radio triggered separation and the Velcro did the job. The chutes were already in the air when the RRC3 altimeters (backup plan) fired the airbags.

    TRA 13430, Level 3

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