An "R"-powered rocket build

Discussion in 'High Power Rocketry (HPR)' started by Rail Dawg, Nov 30, 2018.

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  1. Dec 4, 2018 #91

    Rail Dawg

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    Just ordered.

    Can a plunge router be used to cut fins?

    Also I see a sale on a Craftsman plunge router. 12 amp. Good choice?

    Thanks Rich.

    Chuck C.
     
  2. Dec 4, 2018 #92

    rharshberger

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    I use and have used a Bosch 1617EVS router for many years, its kind of a "standard" as many aftermarket accessories are made for it, the kit I originally bought had both a plunge and solid base as well as a edge guide and smaller circle cutter guide. The advantage to a plunge router is the ability to put the bit straight down into the material without using a tipping motion like solid base or trying to plunge cut without having the base in contact with the material as both situations are dangerous methods.
     
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  3. Dec 4, 2018 #93

    Rail Dawg

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  4. Dec 4, 2018 #94

    Rail Dawg

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  5. Dec 4, 2018 #95

    Rail Dawg

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    Although I'd like to have a +/- 24' total length sonotube with no breaks it's going to be best to have the lower 8 ft of the tube as a separate section so that part of the airframe can be slid easier over the 7 1/2 ft motor.

    Since I'm going to have a break there a parachute could be used just for the motor section. However I'm trying to think of a way to create a coupler at that break.

    Suggestions?

    Thanks.

    Chuck C.
     
  6. Dec 4, 2018 #96

    3stoogesrocketry

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    Ditch the coupler idea . I built a 25 foot tall 13 inch diameter 275 lb sandhawk about 10 years ago . The rock unfortunately never left the ground due to the sheer complexity and size of the rocket . The biggest mistake I made was using couplers . The parts would slide together and apart just fine , but at 90% from vertical , the weight and length made the couplers bind . Then humidity . I had it in the upper section of my parents barn , sealed from the weather , but not weather tight , and the minister durring the summer "locked" a coupler in place to the point it took two 5000 lb come alongs to pull it apart. Do as Kevin says . Flat plates and nylon self destructing bolts . Keep it simple . I would break it above the motor as you mentioned and then let the two sections come down on there own chute (s). If you are worried about the nose cone , have it deploy at 1000 foot or so with its own chute . Deploy it at the top is the safest . Aim for a target altitude of no more then 5000 feet. Then build your rocket around the motor to fit the goal. I would look into fiberglass pipe as a airframe. I will send you a couple links
     
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  7. Dec 4, 2018 #97

    ThirstyBarbarian

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    I think the consensus of people who’ve done these projects was that couplers that size don’t work well, and it’s better to go bulk plate to bulk plate.
     
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  8. Dec 4, 2018 #98

    ThirstyBarbarian

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    One question about explosive bolts. How do you access them?
     
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  9. Dec 4, 2018 #99

    OverTheTop

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    The V2 used 5" diameter pressure tanks in the central tube for coupling. The were at a pressure of 20 and 30 bar and when actuated the pressure was used to push the three sections apart. The three sections were just coupled by these tanks and there was no other form of attachment.

    [edit] You can see the 30bar composite tank sitting in the bottom of the airframe in the second pic of my earlier post. It ends up sitting half in one section (fixed) and half in the other (sliding fit). You can see me working on the wiring for the release mechanism.
     
    Last edited: Dec 4, 2018
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  10. Dec 4, 2018 #100

    troj

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    Yep! I didn't think it was that long ago. Apparently, it was! I remember some folks I didn't know out helping us at the pads. That labor was much appreciated. And BTW, we got smarter about stacking big projects as time went on. :)

    It's easy. We took a Porter Cable circle jig and extended it to make one that allows us to make large centering rings.

    Shouldn't need all-thread or cable.

    -Kevin
     
  11. Dec 4, 2018 #101

    troj

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    Sorry; forgot to answer this!

    At joints, we had a parachute bay in the middle of the bottom section. The parachute bay is exactly sized to hold the main - this is important! Sitting on top of that is a spring-loaded man-rated pilot chute for a reserve. You can buy them on eBay for cheap. That tube (we always used LOC 7.5" tubing) sits in the middle of the lower section. The upper section just has a flat 3/4" plywood bulkhead on the bottom of it. The two sections are joined together buy a half dozen 1/2" nylon bolts. The sections are brought together with the spring-loaded chute sandwiched in at the top of the parachute bay. There's a rod sticking out that holds the spring in its compressed state. We put the two sections together with that rod in, then put in the nylon bolts. Once they're partially tightened, we pull the rod out, releasing the spring. Then the bolts are tightened the rest of the way.

    Those nylon bolts are drilled out (use a drill press, not a boring bar on a lathe), filled with BP and two electric matches, then plugged with epoxy. Each match is wired to a firing board that is wired to an altimeter.

    When the rocket hits apogee, the alitmeters trigger the firing boards, which then dump an R/C battery pack into the matches. The bolts shatter, allowing the two pieces of airframe to separate. The spring is helping push them apart and once they do, the pilot chute pops up and out and pulls out the bagged main.

    This method has worked very well for us and it's stupid simple.

    -Kevin
     
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  12. Dec 4, 2018 #102

    troj

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    A router table big enough to cut 24" - 30" diameter rings will be expensive.

    We use 2x4s laid over two sawhorses, a piece of 2" foam over that, then drop the sheet of plywood we're cutting on the top of it. A plunge router with a circle jig and you can whip out rings and bulkheads all day long.

    One word of warning - sonotube is not precision material. You'll need to cut custom sized rings. Concrete forms are shipped with one inside of another, both of which will be sold as the same diameter.

    -Kevin
     
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  13. Dec 4, 2018 #103

    Rail Dawg

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    Ok this all makes a lot of sense. I like the idea.

    You mentioned fiberglass pipe. I’ve been looking at all sorts of pipe... If you’ve got a link to something suitable for a rocket I’m all ears.

    Thanks!

    Chuck C.
     
  14. Dec 4, 2018 #104

    Rail Dawg

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    Thanks Kevin for being a part of this discussion. You’ve got good experience and it’s needed.

    Going to get the Bosch router and if it’s sonotube your caution about diameter is noted.

    Chuck C.
     
  15. Dec 4, 2018 #105

    Rail Dawg

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    Bam! Great idea!

    Chuck C.
     
  16. Dec 4, 2018 #106

    ThirstyBarbarian

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    How do you access the bolts during assembly? Are they accessible through a hatch in the outer "skin" or tube? Or is the skin added after the bolts are tightened?
     
  17. Dec 4, 2018 #107

    ThirstyBarbarian

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    Any info on the motor in terms of average thrust, burn time, or even an estimated thrust curve?
     
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  18. Dec 4, 2018 #108

    boatgeek

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    There's a bunch of manufacturers out there. This one popped up on Google: http://www.corrosionfluid.com/fiberglass-pipe-smith-fibercast/red-thread-pipe-frp-piping.aspx. 24.3 lbs/ft for 24" material, filament wound, 3/8" wall, probably way overkill for our purposes, sold in 40' lengths.
     
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  19. Dec 5, 2018 #109

    troj

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    Holes in the side of the airframe.

    With our building method, the tubes are 100% non-structural. We can cut as many access holes and hatches as we need.

    -Kevin
     
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  20. Dec 5, 2018 #110

    Rail Dawg

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    Good question.

    This is being worked on by Pat G.

    He's got the casing dimensions and before too long should have some good working numbers.

    It's going to be cool to see what he comes up with!

    Chuck C.
     
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  21. Dec 5, 2018 #111

    Rail Dawg

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  22. Dec 5, 2018 #112

    ThirstyBarbarian

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    That makes sense. Thanks.
     
  23. Dec 5, 2018 #113

    ThirstyBarbarian

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    That’s going to be really interesting!
     
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  24. Dec 5, 2018 #114

    tomsteve

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    im thinkin youre lookin at 30" diameter" ( think somewhere above ya mentioned 30" sonotubes)if so you will probably have to make your own circle jig for the router but it is pretty simple.
    i had to cut some 48" circles a few years ago. i started with an 8' rip of 3/8" ply the width of my router base. mounted the router onto the end then plunged my straight bit through( i think i used a 3/8" straight bit with a 1/2" shank on this one) then measured off the edge of the hole to get the pivot point for the jig. worked great.

    circle jigs wouldnt be necessary for a tetrahedron.:)
     
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  25. Dec 5, 2018 #115

    tomsteve

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    that would have quite a large base,wouldnt it!
    houses get moved down roads on flatbeds. ;)
    theres alway this,too
     

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  26. Dec 5, 2018 #116

    Bat-mite

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    Is that Captain Ahab hanging off the side with a harpoon?
     
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  27. Dec 5, 2018 #117

    Rail Dawg

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    How does one add a motor in Open Rocket?

    Chuck C.
     
  28. Dec 5, 2018 #118

    Bat-mite

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    There are three tabs, one for design, one for motors, one for simulations. Your MMT has to be designated an MMT or else it won't let you add a motor.

    Click the motors tab, then click to add a motor. Select the motor from the chart on the left.

    From memory and no OR in front of me. Sorry. BUT --

    There are no Q motors there, since only commercial motors are listed. So, you need a motor file generated by BurnSim or something similar, and then in your Preferences, you will find the directory where motor files are stored. Drop it in that directory.

    Hope this helps. Sorry I don't have it in front of me.
     
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  29. Dec 5, 2018 #119

    Rail Dawg

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    That’s helpful. Can I put in a MMT and just say it’s 200 lbs?

    Working on CG and CP.

    Thanks.

    Chuck C.
     
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  30. Dec 5, 2018 #120

    ThirstyBarbarian

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    You could put in a motor mount and call it 200 pounds — that would work. Or you could put in a “mass object” of 200 pounds.
     

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