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

Latest topics

» 8mm or 10mm for pivot
by stuckinthemud1 Yesterday at 12:03 pm

» Hola a todos
by juanjo nippers Wed Feb 13, 2019 3:54 am

» 3D crossbow design
by dutchbow Sun Feb 10, 2019 11:53 pm

» For Sale: Masai Huntsman Crossbow
by TonyU Wed Jan 30, 2019 8:32 am

» profile of medieval composite prods?
by Armbrustier Sun Jan 27, 2019 5:46 am

» can you point me in the direction of a post on nut-making
by stuckinthemud1 Mon Jan 21, 2019 11:25 am

» Need some help with a Reverse Draw Crossbow
by JacobL Mon Jan 14, 2019 4:02 pm

» hello from new mexico
by kenh Mon Jan 14, 2019 5:01 am

» WTB custom crossbow
by Osterreichische Thu Jan 10, 2019 8:21 am

» Laminated Medieval Tillers
by Rpastor248 Mon Jan 07, 2019 4:27 am

» Introduce myself
by oscar Mon Dec 31, 2018 7:37 am

» lever cocking bow for sale on IMA
by phuphuphnik Mon Dec 31, 2018 4:10 am

» please critique this tiller/stock dimensions
by stuckinthemud1 Fri Dec 28, 2018 3:15 pm

» Help identifying a Crossbow
by TheNuclearkirk Fri Dec 28, 2018 2:55 pm

» Bullpup light crossbow
by Gnome Wed Dec 26, 2018 1:54 pm

» Finished Crossbow - Thanks to all - here some pic and if anyone wants info let me know happy to help .
by c sitas Sun Dec 23, 2018 8:36 am

» Model Aeroplane Rubber
by c sitas Sat Dec 22, 2018 10:57 am

» Making a wooden prod
by stuckinthemud1 Fri Dec 14, 2018 9:28 am

» 'mastic' in medieval crossbow decoration - what is it?
by kenh Thu Dec 06, 2018 5:51 pm

» Welcome! Welcome! Welcome!
by kenh Sun Dec 02, 2018 7:57 pm

» Geezers finnish crossbows?
by Geezer Tue Nov 27, 2018 7:50 am

» Miniature Cross Bows.
by stuckinthemud1 Sun Nov 25, 2018 1:35 pm

» My first Crossbow Tell me what you think!
by kenh Mon Nov 19, 2018 5:50 am

» G/Day from Queensland Australia
by Andy. Thu Nov 08, 2018 3:15 am

» Here I go, overthinking again
by stuckinthemud1 Wed Nov 07, 2018 10:15 am


    Crossbow Lock Sideplates

    Share
    avatar
    benjaminh123
    Techno Weeny

    Lets put a laser on it!!!


    Techno WeenyLets put a laser on it!!!

    Posts : 54
    Join date : 2015-02-23

    Crossbow Lock Sideplates

    Post by benjaminh123 on Sat Mar 28, 2015 3:00 pm

    Hi everyone,
    I'm about to begin building my first crossbow; a big thank-you to all you great guys here that have helped so much.

    One design question though; If I decide to make a drop in lock (like this one, just from aluminum) how thick should the side plates holding the sear and trigger pivots be?
    mac
    mac
    Master Weaponsmith
    Master Weaponsmith

    Posts : 560
    Join date : 2010-12-23
    Location : Near Philly USA

    Re: Crossbow Lock Sideplates

    Post by mac on Sat Mar 28, 2015 5:15 pm

    Ultimately, it's all about restoring the strength of the tiller which is lost by removing wood to make room for the nut and lock.  As such, it comes down to a question of "how strong must the tiller be?"  That is largely a function of the spanning method and the draw weight. 

    A bow which is spanned by putting your foot in a stirrup and drawing the string with your hands or a belt hook does not need much strength through the nut well. 


    By contrast a bow which is spanned be a mechanism that attaches on the "user side" of the nut, will put the tiller into a bending load, and the sides of the nut well have to be up to resisting that load.  So bows that use a goat's foot, a craniquin, a windlas, or a hook and pully need strength here in proportion to the strength of the prod.

    A bow that spans with a wippe falls somewhere in between because although the wippe pushes against a ring on the "prod side" of the nut, the tiller is used to steady the bow against the effort applied to the handle.




    Mac
    avatar
    benjaminh123
    Techno Weeny

    Lets put a laser on it!!!


    Techno WeenyLets put a laser on it!!!

    Posts : 54
    Join date : 2015-02-23

    Re: Crossbow Lock Sideplates

    Post by benjaminh123 on Sat Mar 28, 2015 5:39 pm

    I'm not sure if you really are understanding my question; lock plates that I'm speaking of (look at the link in the first topic) are just holding the pivots for the trigger and the sear in this mechanism that I plan to use:

    The nut will have its own separate side plates; what I'm speaking of will just have the trigger and sear putting weight on it; would 1/8" aluminium work?
    avatar
    jaeger22
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 153
    Join date : 2013-03-15
    Age : 70
    Location : Orlando, FL

    Re: Crossbow Lock Sideplates

    Post by jaeger22 on Sat Mar 28, 2015 6:47 pm

    Yes 1/8" should work fine for bows up to 150 lb. or so. The two factors that it depends on on are the type of aluminum and the pull weight of the bow. If you use a 1/4" axle the area resisting  the force is 1/4"  times 1/8" times two (two sides) or .0625 inches squared. So even if you use soft aluminum with a yield strength down around 5000 PSI per inch, it still should not fail until you hit 312.5 pounds of pull. So a safety factor of 2 for 150 lb pull. Most aluminum will be stronger. Pure aluminum is only 4000 psi but hard to find any pure.
    However if you want to build a 250 lb pull xbow, not so much!
    avatar
    benjaminh123
    Techno Weeny

    Lets put a laser on it!!!


    Techno WeenyLets put a laser on it!!!

    Posts : 54
    Join date : 2015-02-23

    Re: Crossbow Lock Sideplates

    Post by benjaminh123 on Sat Mar 28, 2015 6:59 pm

    Thanks Jaeger22,
    That was just what the information I was looking for; how much space around a 1/4" pivot would be  "safe"? How close to the edge of the aluminium could the pivot be? Please bear in mind that I am only speaking of the trigger and sear, NOT the nut. You could refer to the drawing above, in my last post.
    avatar
    jaeger22
    Workshop Savvy

    Did you see my tool collection?


    Workshop SavvyDid you see my tool collection?

    Posts : 153
    Join date : 2013-03-15
    Age : 70
    Location : Orlando, FL

    Re: Crossbow Lock Sideplates

    Post by jaeger22 on Sun Mar 29, 2015 5:14 am

    It looks like there will be only a little less stress on the shear so I would leave at least 1/4" of material around it and the trigger is lightly loaded so if you needed to for your design you could go as low as 1/8" . More is always better but those are what I would as minimums.
    Good luck and please post your progress.
    That is a very interesting trigger design. I may have to build one myself!

    Sponsored content

    Re: Crossbow Lock Sideplates

    Post by Sponsored content


      Current date/time is Tue Feb 19, 2019 6:05 am