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    Draw stroke limit of a prod

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    Draw stroke limit of a prod Empty Draw stroke limit of a prod

    Post by War Song on Sat Nov 30, 2013 10:49 pm

    Are there ways to determine reasonably, the maximum stroke that you can safely operate and draw a prod back?

     I have a 28 inch loose laminate prod made from tension bars, I can't really tell if its stacking at the 9 inch stroke point, or if my muscles are just wussing out. I was really hoping for more of 10-11 inch power stroke, but afraid that might be near the limit of my prod. At 9 inches, its drawing at about 70-80 pounds.

    Suggestions?


    EDIT: I do not know why the title was "target shoting x-bow", sorry about the mislabeling. Brain is dying on me in old age.


    Last edited by War Song on Tue Dec 03, 2013 9:18 pm; edited 1 time in total
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    Draw stroke limit of a prod Empty I delete and starts a new thread

    Post by Loosenuts on Tue Dec 03, 2013 3:35 am

    I delete and starts a new thread.


    Last edited by Loosenuts on Tue Dec 03, 2013 7:59 am; edited 1 time in total
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by kenh on Tue Dec 03, 2013 6:02 am

    Loosenuts -- Birch makes a great tiller, and it looks like you're doing good work.

    IMHO, however, it would be better for all of us if your post you work in it's own thread, rather than dumping it into War Song's thread about prod draw limits and strength...
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by kenh on Tue Dec 03, 2013 6:09 am

    WarSong;  You can certainly draw more than 9 inches! 

    The loose lam tension bar prod in my Avatar pic is two lams -28" and 16" - and draws well over 200# at 13".  Bare handed I can draw it maybe 9"-10", but I need a wippe or other booster to go the distance.  If you can draw it, that prod should be able to go to 14" (half it's length).
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by Loosenuts on Tue Dec 03, 2013 7:57 am

    kenh wrote:Loosenuts -- Birch makes a great tiller, and it looks like you're doing good work.

    IMHO, however, it would be better for all of us if your post you work in it's own thread, rather than dumping it into War Song's thread about prod draw limits and strength...
    Thats so strange? I started a new topic. I dont know how it could be? How can War song have the same title? Now i got two topics with the same title ??? 

    Can a moderator delete my post here?
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by Rizzar on Tue Dec 03, 2013 9:46 am

    I was trying to reply on this topic yesterday or the day before when I could not find it anymore.
    But when Loosenuts made his thread It was youst there again but unter the new title.
    Obviously some kind of Bug.


    In general it is really hard to say anything about your prod.
    You didn´t give enough information on it.

    One needs to know the measurements of the laminates, the number and length of each resulting in its alignment.

    Besides in my opinion a loose laminate prod is very hard to calculate, so you should hope to get with the above mentioned information to somebody who built a similar one.


    Concerning the alignment, those laminates can be layered together to result in an even bending or, when done wrong, with stiff areas resulting in an uneven bow with changed power draw.


    90# would be similar to a very lightweight wood prod, so relatively low.



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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by Loosenuts on Tue Dec 03, 2013 10:06 am

    Thanks Rizzar. I thougt it was me or we haved the same topic title.
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by War Song on Tue Dec 03, 2013 9:33 pm

    Maybe I copy and pasted Loosenut's title by accident? Well I fixed the title, sorry about that Loose.


    Kenh, thanks for replying! Your tension bar build was really great stuff, saved me having to tiller an oak board (which I definitely do not have the patient for Rolling Eyes ). Can't believe they had these things just lying around at Home Depot, seems wasted on fences...

    In anycase, I based my prod on yours, except I could only find the 1/2 inch ones. No problem, I cut a pair of 28 inch and 24 inch bar, taped long to short, then taped both of them side-by-side to form a wider prod. I know one 28/24 prod pulled 58 pounds at 11 inch, so two of them ought to give me ~120 pounds at 12 inch.

    If your drawing at 13 inches with the same prod length, I'm guessing I won't have to worry about the prods snapping and hitting me in the face, right? smack
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by kenh on Wed Dec 04, 2013 6:09 am

    Your bars are 1/2" x 1/4"?  I think that, rather than stack two prods one atop the other to make it 1" x 1/4", I would have gone the other way -- 2, 28s, then 2, 24s, 2, 16s etc.  leaving the prod 1/2" wide and say 3/4 or 1" from back to belly.  This was very common in Chinese prods where they might layer a dozen bamboo lams together. and the prod was deeper than wide.  Take a look at the illustrations in this Chinese Crossbow manual.  The drawing are accurate -- the prod slots are deeper than they are wide: 
    http://www.atarn.net/images/ming_xbow/ming_xbow.htm
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    Draw stroke limit of a prod Empty Re: Draw stroke limit of a prod

    Post by War Song on Thu Dec 05, 2013 4:46 pm

    The first prod I had already laminated together, but the draw weight was too small, so I made an identical one and mounted them side-by-side them together. Also, I figure friction on the laminates would be lower on a side by side design than with a very deep multi-laminate prod.

    Draw stroke limit of a prod 20131205_1747111_zpsac7313b0
    Draw stroke limit of a prod 20131205_1747271_zps88451935

    Progress so far, just missing the rails and full tickler. 9 inch stroke, anymore and I can't hand draw it. On top of that, I'm using a wooden nut; risky I know, but I lack metal working tools and it happens to be a circular cut of support timber my father had drill out from the basement - too tempting for the improviser in me to pass.

    It seems strong enough, my chiesel could hardly dent it when cutting the bolt slot. Might cast a proper nut from aluminum once I get a furnace running in the spring.

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