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Thread: Crossbow without bow

  1. #1
    Join Date
    Apr 2010
    Posts
    1

    Default Crossbow without bow

    Hi,

    I would like to know if exist some crossbow without the bow.
    I ask because for me one of the disadvantages of using crossbows is the size of it (very wide).

    The bow basically is a leaf spring, why not change it for a helical coil spring?
    Some Aluminium Pipe (similar to this one: h t t p://image.made-in-china.com/2f0j00NMmaDlvFAfrp/Aluminium-Extrusion-Profile-Aluminium-Pipe-DSAL-04-DSFT090628B-.jpg ), inside one (or more) powerful helical coil spring, cables with or without pulley system and that's it.

    This would be an compact system.

  2. #2
    Join Date
    Jan 2010
    Location
    Hamilton Ontario Canada
    Posts
    33

    Default Scorpyd "manuballista" vid....

    - is available if you pm me your email address. nothin special but a proof of concept. chronied at 175 with a 350 grain and about 45-50lbs pull.

    What I shoot during boring tv shows in the living room...dont make me none too popular with my two cats. Lousy vid I took as a test of the new webcam about three in the morning so I look pretty ruff. About 12 mgs worth of vid. or 1.35 minutes.

    One of many designs to come(or not haha).

    I know what Ivo will be building and testing soon LOL.

  3. #3
    Join Date
    Oct 2010
    Posts
    111

    Default

    got that stuffs on my site too.. visit us, we got loads of products.

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  4. #4
    Join Date
    Jan 2010
    Location
    Hamilton Ontario Canada
    Posts
    33

    Default

    Quote Originally Posted by barneth View Post
    got that stuffs on my site too.. visit us, we got loads of products.
    what ya dont got is my designs. I started with a torsion assist slingshot that adds at least 20% more velocity to any powerband. The result is my designs will always be faster and more powerful.

    If you watch the ballista slingshot vid by joergs on youtube, even he admits the design actually adds more power and speed.

    Watch for a torsion production crossbow - possibly next year.


  5. #5
    Join Date
    Oct 2010
    Posts
    111

    Default

    hhhmm... maybe you're right.. but will have something more soon

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  6. #6
    Join Date
    Jan 2010
    Location
    Hamilton Ontario Canada
    Posts
    33

    Default

    Quote Originally Posted by barneth View Post
    hhhmm... maybe you're right.. but will have something more soon

    You got lots of bows that interest me, some for themselves but mostly so I can take the limbs and riser off and replace them with torsion powered "limbs".

    I have just about talked myself into a Jackal, because I think it will be a huge seller. Dollar for dollar its a very tuff package to beat and is creating a following of admirers. Even from those with much faster bows. Your new 400 Ghost is neat because it sure makes the predator a very good value price wise and only 25fps less.

    As for me I mostly enjoy the engineering challenge in matching wits with some of the industries best while working with metal rods and a few springs from the hardware store. It is easier and much cheaper for me to build the "engine" and just bolt it on to an existing crossbow platform(rail and trigger). Chances are there will be a short draw Barnett Jackal torsion inswinger "manuballista" in my collection over the next year.

  7. #7
    Join Date
    Oct 2011
    Location
    Ashford, Kent, UK
    Posts
    4

    Default

    torsion bows , ballista. or normal compound bows still have the sticking out arms..can we get rid of them and use a tension spring instead, I think its possible, but being a newbee I am probably missing knowledge on why it wouldnt be practical..

    As a trial I made this rough model.. The idea is to replace the arms with a tension spring, keeping all the parts in the body of the riffle bow..I had some bungee rubber so used that for power instead of a spring..
    A system of pulleys gives mechanical advantage to stretch the spring ..having no pulleys I used keyrings which allow the string to slide through.. as I said its a proof of theory at the moment
    On the small model pulling the string back by 9" stretches the band/spring by 3"

    Ive seen a variation using a compression spring but mechanically I think tension is easier to work with.. The compression bow still had a cross bar limb at the front but this was fully rigid and had its pulleys fitted at the ends.. Do I need this width to get the arrow going straight? or can I keep the bow string close in?

    At the moment I am thinking of using window sash pulleys at the front.. then a vertically fixed double, then a non fixed double which is hanging on the tension spring/rubber ..All this depends on what I can find on ebay..
    These pics are of the lower side of the rifle bow The pulled string and arrow will be on the other top side..

    obviously Ive a long way to go, but when released the string certainly snaps forward quickly enough...
    I am thinking this system could allow for longer pull backs and use full length arrows, it all depends on the ammount of stretch on the spring, or bungee if you want to use that..
    Ive been looking at tension springs and you can obtain a wide variety of strengths and various ammounts of stretch for the spring..I would think that using a strong spring that only stretches a short distance will give a faster return, but that limits the pull length unlesss you use a tripple pulley system.. that will give a longer pull at the cost of less force on the arrow I presume.. however less force/acceleration over a longer pull will give just as good a final launch end speed

    please correct any of my way off mechanical missunderstandings ..dave

    pic1 front of model..pic two full view stretched spring/band.. pic3 unloaded, the band and rear pulley block..pic4 unloaded front again.. pic5 unloaded full view
    Attached Images
    Last edited by davereap; 10-06-2011 at 05:14 AM.

  8. #8
    Join Date
    Nov 2011
    Posts
    9

    Default

    has potential but seems awfully intricate

  9. #9
    Join Date
    Dec 2011
    Location
    Allenhurst, Ga
    Posts
    10

    Default

    I have to agree with lunasea. Seems very intricate. May be a pain to replace parts if failure occurs.

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