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    Loose Laminate Pinlock Build

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    kenh
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    Loose Laminate Pinlock Build

    Post by kenh on Mon Mar 04, 2013 8:32 am

    Thought I'd share some build-along photos as I make my first full size crossbow. The materials are a bit different and hopefully will inspire others just starting out.

    The Prod is 3 "loose laminates" of 3/4" x 1/4" fiberglass chainlink fence tension bar. Lams are 28", 24" and 20". The 6ft bar cost $7 in my area; less in others I know. The lams will eventually be held together with binding of heat-shrink tubing instead of painters tape. The nocks are two thicknesses of 1/4" Phenolic that I had laying about, glued with Locktite Go2 glue. Not the prettiest things in the world, but they should clean up nicely.



    The Action is a 'tech-tweaked' Skane pinlock, with 5/16" Delrin rod for the pin. The face of the action where the string sits will be reinforced with a block of Lignum Vitae, one of the hardest woods in the world, which can be sanded super smooth.



    The Tiller is 1-1/8" thick 75 year old southern yellow pine heartwood, hard as the proverbial rock. The shape is that of a 17th century harquebus stock.

    Here it is on a tillering tree with a bastard string. That's as far back as I can horse it. Will definitely need mechanical assistance getting it back to that third notch so I can slip on the working string when I get it.



    Last edited by kenh on Sat Mar 30, 2013 8:22 am; edited 2 times in total (Reason for editing : Change topic title)

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    Re: Loose Laminate Pinlock Build

    Post by rolynd on Mon Mar 04, 2013 3:22 pm

    Definitely an interesting build i will surely follow.! Steel bows are hard to come by and using a readily made chinese replacement fiberglass prod is too easy. I always like to see alternative approaches.
    When I look at the tiller of the bow in the last pic it seems to me that the tips of the bow stay fairly straight while most of its bending happens in the middle. I think you could shorten the second and third layer a little to get the ends of the arms working a little more or add a 4th, shorter layer to stiffen the center.
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    kenh
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    Re: Loose Laminate Pinlock Build

    Post by kenh on Mon Mar 04, 2013 6:34 pm

    You're right. I hadn't really looked at the tiller of the prod. Could certainly cut back those lams and get more tip action.
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    Re: Loose Laminate Pinlock Build

    Post by stoneagebowyer on Sat Mar 09, 2013 4:42 am

    This is kind of a cool combination of medieval Swedish and ancient Chinese weapons, plus early firearm stock shape. I am thinking of the repeating crossbow prods made from multiple bamboo lams. I agree with you both, the prod can bend more evenly, and will perform much better. Any idea what kind of power you are getting with this, ie. the pull weight?
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    Re: Loose Laminate Pinlock Build

    Post by Gnome on Sat Mar 09, 2013 8:49 am

    Interesting, I like the combination of elements you've chosen. I'll have to pick up some of that fiberglass lathe to play with.
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    kenh
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    Re: Loose Laminate Pinlock Build

    Post by kenh on Sat Mar 09, 2013 9:53 am

    Pull weight Who knows...I only have a 50 lb fish scale. Much stronger than I can pull by hand to cock. My muscled neighbor could barely pull it back with a bastard string to test fit the regular string.

    No glue I've tried will hold the phenolic nocks I made. Sieways pressure is too much for otherwise good holding power.

    Plan B is underway - I'm cutting conventional pin nocks, and then re-enforcing them with the epoxy putty we use to repair boats. Essentially make my own tip covers like the commercial fiberglass prods have; only mine will be epoxied in place.

    Thanks for the comments, guys. More as the project develops.
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    Re: Loose Laminate Pinlock Build

    Post by Gnome on Sat Mar 09, 2013 12:14 pm

    kenh wrote:
    No glue I've tried will hold the phenolic nocks I made. Sieways pressure is too much for otherwise good holding power.
    I thought that looked like it might be a problem. I've wondered about the method you're going to try next, can't wait to see how it turns out.
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    kenh
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    Re: Loose Laminate Pinlock Build

    Post by kenh on Sat Mar 09, 2013 5:41 pm

    The Chinese made many styles of loose laminate prod crossbows, not just the repeater. Take a look at the Ming Dynasty "waist braced" bow that I found here:

    http://thearbalistguild.forumotion.com/t748-ming-dynasty-non-repeating-chinese-crossbow-build-it?highlight=chinese
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    kenh
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    Update -- The Final Product

    Post by kenh on Fri Mar 29, 2013 8:49 am

    Update Time;

    So three laminations were 'way more than I wanted to mess with. In fact, two lams -- 28" and 20" are over 200# draw. I tied that prod to the rafters and hung my 200+ lbs off it and only pulled three-fourths of the 12" power stroke! Even with a wippe it's a major pain to cock. Not comfortable = not fun in my book.
    Maybe that makes me a wimp, but hey, I turned in my Superman cape a loooonggg time ago

    I'm wondering how much, if any draw weight reduction I'd get by shortening the inside lamination by say another 4 inches -- giving me a 28" lam and a 16" lam... Having the tips more flexible might make cocking with the wippe a bit easier -- ya think?

    The prod tip with Plan B nocks:

    ...
    The Whole Thing. The bolt is fletched with thin slices of blue spalted Black Pascheco some Peruvian hardwood I happened to have laying about. The shaft and tip are from some arrows I obtained which were much too heavy for any of my bows. The prod has a 3.5" brace height, 12" power stroke.

    ...
    The front end. The braided cord loop is for the wippe.
    The prod tie system is based on the 2000 year old Chinese Han Dynasty attachment method.


    The back end.

    ...
    Pinlock details. The tickler has a 1/8" dowel pivot pin. The pin is
    5/16" delrin rod tied to the tickler with waxed cord.
    The small block between the tickler and the tiller just holds
    the assembly in the cocked position for photos. A similar block will be used as a simple safety device.


    Last edited by kenh on Mon Apr 01, 2013 5:08 am; edited 4 times in total
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    Re: Loose Laminate Pinlock Build

    Post by Gnome on Fri Mar 29, 2013 11:28 am

    Strong work! Your "Plan B Nocks" look like a simple and elegant solution. I think you should trust your instincts and shorten your secondary leaf a bit to bring the pull down to something you're comfortable with. Once you've got a shooting history and are confident that everything is working soundly, you can always ramp it up again. That's a real advantage working with a loose laminate prod, easy to tinker with.
    Overall a clean, interesting design handsomely executed, can't wait to to hear how it shoots.
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    Re: Loose Laminate Pinlock Build

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