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

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4 posters

    Misfire-Misfire

    jds6
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    Post by jds6 Thu Mar 01, 2012 1:35 pm

    Ok guys, here is the situation. Having a tight release, I filed down the top of the sear to eliminate the distance between the sear and the notch in the roller nut for the amount of rise on the lever. Worked ok, but still had drag on release. Filed a little more, went to test shoot and it misfired. String hopped over the bolt.
    I noticed by eliminating the drag the release was a lot faster. That is good,right? So maybe I unmasked another problem is what I'm thinking. Could there be a problem in the angle of the prod, or do I need an angle at all? Is there not enough downward pressure on the tiller, in which causing the sting to hop over? Point me in the right direction.

    jds6

    PS; I have an Alchem 140# prod which has a 1/2" tip rise. Tiller cut to approx.6 degree angle
    Gnome
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    Post by Gnome Thu Mar 01, 2012 3:43 pm

    As far as I know, if your string, when at rest, is just lightly touching the track when at rest, then the angle of the prod should be correct. If that is the case, I would check the relation of the string to the butt of the bolt when in the cocked position. If the string is too high there then it would tend to skip over the bolt and misfire, which might mean you need to change the shape of the back of the fingers of the nut to get the string a bit lower, more centered on the tail end of the bolt. I've found that a slight indentation on the back of the bolt doesn't hurt much either, a minor "half moon" nock. A good photo of the rig cocked and loaded might help get to the root cause.
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    Post by Ivo Thu Mar 01, 2012 6:37 pm

    When you changed the sear engagement angle, the rest of the components followed along. (discussion in the Triggers topic where we talk about some guy who decided to* fine tune* a factory trigger...again, Pavise on point Smile )

    My guess is now the nut locks in a position where it's slightly rotated forward - this would tempt the string to sit a little higher on the teeth with all the following outcomes.

    If that is so, then I'm with Gnome on refiling the teeth so that they *hook* the string.

     Misfire-Misfire Nut10

    In fact, I would go a little further and round off the tips and edges of the teeth while at it.(third nut in the picture)

    Anyway, that's my guess and the easier solution...another being to relocate the tickler axel following the the extended radius of the nut till the teeth are angled a little back.

    Ivo

    PS: Prod angle...I never really even cared for prod angle - just as long
    as the string touches the stock it's good. Having some string pressure
    on the stock is actually there to work in your favor and the age old
    formula for that is:

    ~ Center of the tips should be 1/2 thickness of the string lower than the surface of the track
    (at least with thin modern strings)



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    Post by jds6 Fri Mar 02, 2012 7:10 am

    Thanks Gnome and Ivo for the help. Everything makes perfect sense now. ( changing the sear engagement ) I will give it a go with filing down the fingers on the nut. Would it be wise to do both, filing down nut fingers and relocating the lever pin a bit forward?
    Glad the problems I am having is on my first bow. This sure builds experience on problem solving for the future bows! Thanks again for the insight guys!
    Jds6
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    Post by Basilisk120 Fri Mar 02, 2012 12:35 pm

    jds6 wrote:Would it be wise to do both, filing down nut fingers and relocating the lever pin a bit forward?

    Probably be better off making one change at a time. That way you have a better understaning of the effect of the change and your not wondering the changes are fighting each other, or helping each other. Or something else entirely.



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    Post by jds6 Fri Mar 02, 2012 1:24 pm

    Thanks Basilisk for the info. I will try the filing on the fingers of the nut first. Have to do a list of honey-do's before I can get started. Must keep the Mrs. happy. Will post the out come soon.
    Thanks again guys for all the insight ! :
    Jds6
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    Post by jds6 Sun Mar 04, 2012 2:07 pm

    Hey guys;
    Ok, here's the update. After filing the fingers of the nut. Changing their shape as suggested. The string set much lower (bottom half of bolt).
    Cocked and loaded I gave it a test. Worked like a champ!! Smooth release, much faster release. Thanks for all the advice, insight and info to help me solve this problem.
    jds6

    PS: Ready for the next project now!
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    Post by Ivo Sun Mar 04, 2012 8:41 pm

    It's a pleasure to see something you tuned - working, but for me it is even a greater pleasure to see that this forum helped it be so.

    Good luck on the next project man, we love pictures, so post alot! Smile



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