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Crossbows - Everything about Building, Modding, and Using your Crossbow Gear

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» Ancient Crossbow Reproduction 120lb@28"
by stuckinthemud1 Wed Oct 06, 2021 12:41 pm

» Ball shooting Crossbows worth the bother
by c sitas Sat Sep 25, 2021 7:34 pm

» Chu Ko Nu - repeating chinese crossbow
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» Skew of tiller
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» tiller desgin
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» Want to build modern target crossbow
by ora8i Fri Aug 13, 2021 1:20 pm

» starting a 1400's replica
by tghsmith Wed Aug 11, 2021 10:25 am

» New Medieval just about finished
by Dark Factor Mon Aug 02, 2021 6:41 am

» How do I tune this
by stuckinthemud1 Sun Jul 25, 2021 3:14 am

» Plans and materials for my first build
by c sitas Sat Jul 03, 2021 7:39 am

» Bolt rest
by stuckinthemud1 Mon Jun 14, 2021 3:24 pm

» Collotiere a Charavines crossbow
by stuckinthemud1 Sun Jun 06, 2021 2:25 pm

» ash lath and pin-lock crossbow
by stuckinthemud1 Wed Jun 02, 2021 7:56 am

» Late medieval tournament distances?
by stuckinthemud1 Thu Apr 15, 2021 8:20 am

» Cutting delrin straight by hand?
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» Other forums like this one?
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» new find in china, terra cotta warrior site
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» Crossbow Books
by Andy. Sun Mar 14, 2021 3:46 pm

» 95lb ancient crossbow shot faster than 960lb medieval
by Fangbows Fri Mar 12, 2021 11:36 pm

» best type of horn to use..
by kenh Tue Mar 09, 2021 3:16 pm

» re-introduction
by tghsmith Sun Mar 07, 2021 3:15 pm

» 4 fletch question
by 8fingers Fri Feb 05, 2021 3:14 am

» fix bolts
by MPDVM Tue Feb 02, 2021 7:40 pm

» Reverse draw compound bow build
by c sitas Tue Feb 02, 2021 7:20 pm

» New Build for 2020
by Gnome Wed Jan 27, 2021 6:19 am


4 posters

    Alphabetical evolution

    hullutiedemies
    hullutiedemies
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    Post by hullutiedemies Wed Apr 03, 2013 11:22 am

    After the H-bow it was obvious to try the fashionable backwards design.
    This let to K-bow
    Alphabetical evolution J_k_proto
    , wich works quite satisfactorily, but with 6 limbs and massive riser section it is uneconomical to build.

    I soon found out that split limbs were not necessary, also got rid of the the backwards facing "cross-bow".

    So after X-bow comes the Y-bow:
    Alphabetical evolution J_y_1

    This makes a durable and lightweight construction as the limbs are separate bows holding their own tension. So the assembly only takes the final draw-weight.

    Added pulleys to the arms out of tarpaulin buttons with acrylic cased stonewall nails as axis.
    Alphabetical evolution J_y_2
    This allows twice as long power stroke
    Alphabetical evolution J_y_3
    Accuracy is surprisingly good, arrows are going were they are pointed, despite limbs being badly off-balance.

    Unlike the the usual backwards scorpyrd-daVinci bows, this is a true in-swinger. When triggered all moving parts collapse inwards and forwards. So this can be safely shot while in contact with users body or other obstacles on the flanks.

    And the best part
    Alphabetical evolution J_kurve
    F/D-curve is fat like a singing lady. This is a true compound bow.


    Coming up next
    - Limbs steamed to matching curvature
    - Second set of pulleys for 50% longer power-stroke
    - Trigger mechanism
    - Stock & bolt rail
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    kenh
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    Post by kenh Wed Apr 03, 2013 2:27 pm

    Yer startin' ta skeer me now, Nerd.....Alphabetical evolution 207946 Fascinating..... keep it up!

    Since my initials are K and H that means I gotta build two paleobows. I need to have a talk with the seagrape tree in my girlfriend's backyard....
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    Post by kenh Sun Apr 07, 2013 6:17 am

    I sort of expected you to create a Y bow that features a single forked branch rather than the two interlaced bows design. Not complaining, mind you... just a thought.
    hullutiedemies
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    Post by hullutiedemies Mon Apr 08, 2013 3:58 am

    That would require a symmetrical forked branch that has inside suitable for bow back.
    It is easier to make two separate limbs - especially composite material limbs. Plus pulling off that cable-bridge allows the device to be folded vertically for transport. Besides stresses would tear a forked or split log apart unless reinforced with wrappings anyway.


    But of course the limbs could be permanently glued or riveted at lower end. That way a cable-bridge would not be necessary. And if I get to make one out of metal , it probably will be bend from a single bar.
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    Post by Oppenheimer Mon Apr 29, 2013 5:52 am

    You´re amazing Nerd Flintstone! First of all I like your primitive and cheap way to design your bows. Also your ligts highspeed arrows are really fun. Tried them and think they are nice to play with my children this summer. Then we have your frictionless limb resulting in high speed. Even if they were mounted on a normal lever axis, they will reduce friction and get precision. Where do you get all ideas from?

    By the way -whath homemade trigger do you use. Do you have any close upp picture on it?
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    Post by ferdinand Mon Apr 29, 2013 9:31 am

    beautifull. Really. Post a movie!!!
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    Post by hullutiedemies Mon Jun 17, 2013 10:03 am

    Oppenheimer wrote: Where do you get all ideas from?

    As I probably mentioned in my introductory message,
    my hobby interest is not so much building crossbows but more into developing them.
    So I try to consciously think "out of the box". I also actively follow advances in modern military technology and try to think ways applying these to muscle powered homemade devices. And since I do not have a professional level workshop with good tools nor the skills of a pro craftsman, I am forced to figure out easy ways to implement my designs cheaply with simple tools.

    Besides having studied machine construction in polytech and written my masters paper on applied mathematics, one exercise project for my undergraduate class was programming laser sensors for ESA weather satellite - so I guess I technically sort of am what Americans call "rocket scientist".

    Oppenheimer wrote:
    By the way -whath homemade trigger do you use. Do you have any close upp picture on it?

    Alphabetical evolution Liipai10
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    Post by Oppenheimer Sat Jun 29, 2013 5:08 am

    Thank for your answer Nerd F. It took a while so I tought you disliked the questions. Your interest seems to be exactly mine too. I think Further development of crossbow-making can be made ​​and by aplying technicues and physics from other branches I believe efficiency can be DOUBLED. Too many thinks in too traditional ways and the companies owning the market dot Newbies want to steal parts of it. The result is no development made ​​and just the same devises in different collours of the Year.
    One area you have just opened up is to get an almost frictionless devise, not needing more power input like stronger limbs, etc. Another thing you point out is simplicity like in your trigger.

    Now I wonder what model of yours has the best eficiency? I miss the discussion about energy efficiency in the forum.
    hullutiedemies
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    Post by hullutiedemies Tue Jul 02, 2013 2:34 am

    Oppenheimer wrote: It took a while so I tought you disliked the questions.
    No, just time and stress management. I usually do not even read replies to my postings until I know I have time to write a response. Photography, editing and uploading of pictures adds couple weeks extra to response time.

    Oppenheimer wrote:
    Further development of crossbow-making can be made ​​and by aplying technicues and physics from other branches I believe efficiency can be DOUBLED.
    Doubled in what way ?
    Any compound system of half decent quality can achieve decent bolt speed with 90% input/output energy efficiency.
    I usually like to think in terms of dry fire speed , the theoretical upper limit should be dictated by speed of sound in material the acceleration system is made of.

    Oppenheimer wrote:
    Too many thinks in too traditional ways and the companies owning the market dot Newbies want to steal parts of it.
    I have been browsing discussions at crossbownation board, and it seems that the industry is not really interested in "open-source" solutions. They want patentable designs they can license. Thats where the money is.

    Oppenheimer wrote:
    Now I wonder what model of yours has the best eficiency?
    With any style, it boils down to minimizing the speed of energy storing spring and minimizing the inertia momentum of the primary string that is pushing the bolt.

    I have a recent new a idea that has not yet been properly tested- scale model was promising though, but there is potential for tripling the bolt speed. ( And awfully simple one - wonder why nobody has ever tried this before )
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    Post by kenh Tue Jul 02, 2013 5:53 am

    NF -- I really look forward to seeing the results of your new idea.

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