PoSBa Build - First Pics

Discussion in 'Show off your homemades!' started by JoergS, Jan 14, 2014.

  1. JoergS

    JoergS Administrator

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    PoSBa = Perforation of Smaug Ballista

    As I said, I have started the build.

    The weapon is chambered for 240 cm shafted 20mm "arrows" that can have fours fletchings (40mm max height each). Total net draw length is 223 cm.

    [​IMG]

    Here you can see the winch box with the "maxim gun style" handles. The multiplex boards carry the load, the cheapo particle board is just for looks (will all be painted black later on).

    [​IMG]

    The trigger box will actually be pulled back by the winch. This ensures a speedy loading routine. You move the sled forward, clamp in the rope, cock it back with the winch, load the arrow from the front and you are ready to fire.

    [​IMG]

    Here you can see the "fork", a much shorter version of the four armed crossbow prod the movie prop features. This adaption will make it more effective and solid, while a part of the original design remains.

    [​IMG]

    Next, the winch mechanism. Then the weapon will already shoot - it will be time to build the mounting frame.
     
  2. Will

    Will Thread Hijacker

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    The acronym title of this new creation threw me for a minute...P.O.S has quite a different meaning here!
    This is looking truly badass! Cannot wait to see this monster in action!
     

  3. onnod

    onnod Im from Holland, isnt that weird?

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    I like looks of it allready, can't wait to see it finished!

    Sent from my GT-I9300 using Slingshot Forum mobile app
     
  4. Brazilviking

    Brazilviking Thread Hijacker

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  5. Jeremy

    Jeremy Senior member who totally rocks a pink Scout! Pink

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    So excited to see this beast in action.
     
  6. Withak

    Withak aka Whitehawk!

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    Looking good Jörg - can't wait to see the finished product. This will be a fun one. I know that laugh will be coming out when this one is fired :)
     
  7. VWscooby

    VWscooby Senior Member

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    Immense, in every sense of the word!
     
  8. coyote-1

    coyote-1 Member

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    "If it sucks, it must be an Electrolux." Accurate translation, but the unanticipated slang ruins it lol
     
  9. JoergS

    JoergS Administrator

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    Of course I know what a PoS is - are you kidding me, I have been a manager in consumer electronics all my life. I just thought that name may bring in some curious people :)
     
  10. BeMahoney

    BeMahoney Builder of things

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    This contraption looks really promising!

    can´t translate that one:

    " das muss kesseln "

    The bolt will be in a rather short,
    yet terminal mess, hopefully!

    greetings,

    Be
     
  11. rock slinger

    rock slinger I rarely shoot rocks!

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    Scary stuff there, but very creative. Can't wait to see the end result
     
  12. PaulPawx3

    PaulPawx3 Member

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    Looks like POS is international in any language :D most of the time I can't read for laughing so hard at the replies, keep them coming!!! I forgot. In honor of Joerg "thanks and bye bye" :)
     
    Last edited: Jan 14, 2014
  13. beaverIII73

    beaverIII73 Junior Member

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    Looks great, we all cant wait to see it shoot. Oh and I'm glad to see you are up and about.
     
  14. coyote-1

    coyote-1 Member

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    It's taken him months to recover from the champagne bottle incident
    ;)
     
  15. JoergS

    JoergS Administrator

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    Yes, sometimes I still get a headache when I drink too much of the stuff... MSPaint's revenge :)
     
  16. xXdoomXx

    xXdoomXx Junior threadjacker ag. J

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    Can't wait for this to be finished

    J
     
  17. JoergS

    JoergS Administrator

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    Today's progress...

    As planned I made the winch. I used a 16mm stainless steel tube, 2mm wall thickness, as a base. Then I used a big eye bolt and welded it on. I actually cut matching notches and grooves into the tube and the eye bolt so that the final part will withstand the immense torque forces later on.

    Then I made the usual cogwheel for the ratchet like function.

    The sled is drawn back by a 6 mm high performance polyprop rope. I will use a 25mm wooden dowel, 1 meter total length, pushed through the eye bolt, as a lever.

    Also put on some rubber... eight full width TBG strips per side should be OK for starters.

    Tomorrow, first test shots.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  18. xXdoomXx

    xXdoomXx Junior threadjacker ag. J

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    Loving the progress joerg, what is you aim on draw weight and speed

    J
     
  19. VWscooby

    VWscooby Senior Member

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    :eek:

    This is going to be great! Can't wait to see the test firing :)
     
    Last edited: Jan 15, 2014
  20. JoergS

    JoergS Administrator

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    200 kg (440 lb), and 70 m/s (230 fps) with the 500 gram (1,1 lb) arrow.

    1225 Joule = 904 ft-lb of energy (2 times as much as a .45 ACP)
    35 Ns momentum (8 times as much as a .45 ACP)