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


    Trouble with my Gafa

    Share
    avatar
    msalazar2310
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 11
    Join date : 2015-04-19
    Age : 73
    Location : Mexico

    Trouble with my Gafa

    Post by msalazar2310 on Mon May 21, 2018 1:21 pm



    By trying to span the bow, applying force with a long lever, two things happen:

    1.- The string goes far above the nut making impossible to cock it. Geezer suggested me to go  further back passing the nut and than slowly go back and the string goes down by itself. This I did it and finally the string was in place

    2.-The force I need to pull the string back is too much, (nothing to do with Tods videos where he pulls the Gafa lever with two fingers).

    My bow is 900mm. long, 40mm. wide in the middle, and 11mm. wide at the tips, the bow is made of automotive spring steel, with a thickness of 6.4 mm.6.4mm. 

    I would appreciate if you make me your recommendations for I am sure that I have done somethin wrong, possibly in the geometry of my gafa, or the bow with these meassures has got a draw weight far above to be cocked with it and I need a cranekin.

    Manuel Salazar
    Dark Factor
    Dark Factor
    Tinkerer

    If there is a will, there is a way.


    TinkererIf there is a will, there  is a way.

    Posts : 65
    Join date : 2017-10-16
    Age : 35
    Location : Belgium

    Re: Trouble with my Gafa

    Post by Dark Factor on Tue May 22, 2018 12:05 pm

    What's the bow draw weight? I've never used this kind of lever but only the wooden one (from the stirrup) and with it we have about 2-3 times more force, not more.
    Force with 2 fingers doesn't mean a lot. I shoot 60lbs bows with 2-3 fingers. Stronger seems impossible for me but a friend of me can draw 130lbs bows with 2 fingers too and it doesn't seem hard for him !
    avatar
    msalazar2310
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 11
    Join date : 2015-04-19
    Age : 73
    Location : Mexico

    Re: Trouble with my Gafa

    Post by msalazar2310 on Tue May 22, 2018 6:27 pm

    I do not know thw draw wight, I assume it may be 200 pound
    avatar
    msalazar2310
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 11
    Join date : 2015-04-19
    Age : 73
    Location : Mexico

    Re: Trouble with my Gafa

    Post by msalazar2310 on Wed May 23, 2018 2:07 pm

    https://youtu.be/iIkxyjVu9gc

    This is what I mean by "holding the lever with two fingers"
    avatar
    c sitas
    Crossbow Junkie

    I live here!


    Crossbow JunkieI live here!

    Posts : 496
    Join date : 2012-11-24

    Re: Trouble with my Gafa

    Post by c sitas on Wed May 23, 2018 4:07 pm

    yes ,that is all well and good. Notice where the fingers of the lever set when starting out. He has lots  of leverage this way. The way your's are setting ,you have no leverage at all. Fingers are too long.
    avatar
    msalazar2310
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 11
    Join date : 2015-04-19
    Age : 73
    Location : Mexico

    Gafa

    Post by msalazar2310 on Thu May 24, 2018 8:47 am

    Thanks a lot, I made the fingers longer as necessary in order to have "room" for corrections, one ting I also can do is to relocate the pin, however I will have to guess in what direction, this prior to modify the curve of the fingers, whtever ideas you got, let me know
    Manuel
    Dark Factor
    Dark Factor
    Tinkerer

    If there is a will, there is a way.


    TinkererIf there is a will, there  is a way.

    Posts : 65
    Join date : 2017-10-16
    Age : 35
    Location : Belgium

    Re: Trouble with my Gafa

    Post by Dark Factor on Thu May 24, 2018 10:18 am

    Not sure the length of the 2 fingers of the lever are a problem. If it's longer than necessary, there is no problem.
    But is it the final lever or an old picture ? I mean there is no lever limb. For me, the length of the limb is the force multiplier... the longer the better for multiplying the force.
    That's only physics... if the final distance between the nut and the lever axis is 4 times smaller than the distance between your hand and this axis, you multiply force by 4... if more, this will be easier
    Geezer
    Geezer
    Master Crossbowyer
    Master Crossbowyer

    Posts : 1075
    Join date : 2010-01-12
    Age : 71
    Location : Austin, Texas, USA

    Re: Trouble with my Gafa

    Post by Geezer on Thu May 24, 2018 12:31 pm

    Certainly the lever in the photo has no upper limb.  That's what gives you the 'leverage'.  Also note that the 'fingers' on the illustrated lever are mounted on a thru-axle (Yes, Payne Gallwey's pattern does it that way) but in fact plenty of 'gafa' or 'goatsfoot' levers hang the fingers on two rivers, with no axle.  The advantage to doing it that way is that the axle doesn't limit the range of motion on your lever.  I have seen a few period bows with marks on the stock where the axle for fingers would end up stricking the top, but I've also seen lots of these bows (Padre Island bow or Maltese bows) with no such marks. 
    In some cases, the missing upper limb is immovable, but most of them swivel, so the lever can be folded when not in use.  Geezer.
    avatar
    drawknife
    Fresh Blood

    Doesn't mean
    I'm new to crossbows


    Fresh Blood Doesn't meanI'm new to crossbows

    Posts : 21
    Join date : 2011-02-11
    Age : 69
    Location : Barnsley, England

    Gafa/Goatfoot lever

    Post by drawknife on Fri Jun 15, 2018 2:56 am

    Hi,
    Just to add what has been said;
    The shape of the bent levers near the claws is not the correct shape, See Payne Galways goatsfoot lever design. (should be on the internet).
    Your device needs an extended lever forward of the  bars that you use to pull the device back. this will give you more leverage.
    The smoother you can polish the sliding surfaces the easier it will be to pull.
    I made one of these to (almost) Payne-Galways design and it worked but still lifted the string. It is all in the shape of the curved legs.
    Hope this helps

    Sponsored content

    Re: Trouble with my Gafa

    Post by Sponsored content


      Current date/time is Tue Feb 19, 2019 6:22 pm