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    Bolt Flight

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    jds6
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    Bolt Flight

    Post by jds6 on Tue Mar 19, 2013 5:33 am

    Greetings all;
    I have just completed a new build for the wife( pics coming soon). Took it out for a test shoot, and wasn't pleased at all. The flight of the bolt was high and to the right. Thought it might have been the bolt so I tried multiple bolts. Same thing, high and to the right. ( good grouping though).
    What would cause this problem? Prod not square with tiller? String doesn't sit in fingers of the nut properly( evenly)? String sits to low on the bolt?

    Any thoughts and help would be a great help. This is my fourth build and first time to come across this problem.
    Thanks
    jds6
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    Taxus
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    Re: Bolt Flight

    Post by Taxus on Tue Mar 19, 2013 4:45 pm

    I think you've hit the nail on the head with some of the potential problems. Here are a few things to check....

    The bolt shooting high could be the string hitting the bottom of the bolt rather than the centre. This may mean the groove is not deep enough. Have a look where the string is on the butt of the bolt before shooting one. A thicker string would reduce this somewhat too.

    As for shooting to the right: make sure the prod is centered in the socket and that the socket is as even as possible (not deeper one side than the other)
    This will ensure the string is square with the tiller.

    If you made your own prod make sure the limbs taper evenly. If one side is thicker it can shoot to one side as the prod isn't bending evenly.

    It is possible to draw the string unevenly so you could mark the string centre and check it is centred between the nut fingers when drawn.

    Also canting the crossbow while shooting can cause them to shoot to the sides. Worth bearing in mind although you havn't had this problem shooting your other crossbows.

    I look forward to seeing some pictures,

    Taxus
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    jds6
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    Re: Bolt Flight

    Post by jds6 on Tue Mar 19, 2013 8:58 pm

    Thanks for the insight Taxus, I did check out the prod to see if it was not square with the tiller. I was off just a hair. Adjusted that problem.Shooting straight, but still high. being that I have no bolt groove, I guess the problem lies in the finger of the roller nut itself. Maybe the string sits a little to low on the fingers? Probably can adjust that by reshaping the fingers itself if all possible.
    I will post some pictures of the trouble maker in a new topic. Let me know what you think.
    Thanks

    jds6
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    robert.collard.5
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    Re: Bolt Flight

    Post by robert.collard.5 on Wed Mar 20, 2013 1:17 am

    Nice Pics, now to the subject. It would appear you have no "Sights" so I wonder what you are judging elevation by? If you leveled the deck you should also take into consideration the bottom of the ramp you put in the front inlay, then there is the range. Different bolts or arrows are possibly not the same weight or length. As your string stretches it will vary too, and the new prod might settle in. My point is: there are too many variables and not enough information. When I got my Working Mans Medieval Crossbow from Todd, he had already made some calculations that helped me figure out where the arrow should shoot. I believe it was chronographed at 196fps with 815gr arrow. Doing some math that would give me three inches high at ten yards and almost dead on at twenty. I tried to use the arrow holder as a rear sight and found it shooting 5" high. After a little Kentucky windage I got a sub one inch group of three arrows at ten yards, bullseye. Nice looking crossbow, BTW.
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    jds6
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    Re: Bolt Flight

    Post by jds6 on Wed Mar 20, 2013 4:02 am

    Thanks Bob for that info. Will do some more testing and see what I can come up with. Thanks for the kind words on the pics.

    jds6
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    Taxus
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    Re: Bolt Flight

    Post by Taxus on Wed Mar 20, 2013 4:39 pm

    Just had a look at your other post...
    With bolt rests you need to make sure they are not too high or the bolt may be pointing upwards too much ,thus shooting high. Keep it deep enough at the front so there is just a small clearance from the rest of the table.
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    jds6
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    Re: Bolt Flight

    Post by jds6 on Wed Mar 20, 2013 6:12 pm

    Taxus if you look close enough it really doesn't have a rest so to speak.
    What you see is just a guide for the bolt. From the front of the tiller to the fingers of the nut is totally flat. I am still trying to figure out the darn problem.
    Maybe some mathematical thing with trajectory!
    Thanks for your insight, any other insight would be great.

    jds6
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    mac
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    Re: Bolt Flight

    Post by mac on Thu Mar 21, 2013 8:16 am

    JDS,

    Are you sure that there really is a problem? When you say it is shooting high, what are you comparing it to? How high is it shooting, and at what range?

    Most importantly; are the bolts coming out straight? If the bolt is straight, but the groups are higher than you expect, perhaps it is just a better bow than your others. After all, all things being equal, higher is better....n'est pas?

    Try shooting through some paper at different distances from the bow and see from the shape of the hole whether the bolt was straight. The range I used to shoot at had a frame made of PVC that held a roll of cheap white paper for this. It will take a couple of hours and a few bucks in material to make one, but they are a valuable diagnostic tool.

    Mac
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    jds6
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    Re: Bolt Flight

    Post by jds6 on Thu Mar 21, 2013 10:07 am

    Mac, thanks for the info. I will test all when I get home this evening. The target range will be 10 yards and will post my results.
    Thanks again

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    Re: Bolt Flight

    Post by Taxus on Thu Mar 21, 2013 11:06 am

    Mac has a point here, 10 yards is very short range for a bow with a draw weight of 110lbs.
    If the bow is shooting flat at that range it will make accuracy more difficult should you want to shoot longer ranges.
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    Re: Bolt Flight

    Post by jds6 on Sat Mar 23, 2013 3:31 pm

    Greetings all
    After the last post from Mac I decided to do as he suggested. Set up a sheet of paper at the target so see if the bolt was flying straight.Shot three different groups of 3 bolts at different ranges to check the trajectory of the bolts. Using just the bolt tip and target as line of sight this is what the results were. At 10 yards the bolts were at approx. 4-5" high(group 1). At 15 yards at approx.7-8" high (wind blowing pretty strong at that time, group 2 ) At 20 yards much dead on target. (group 3).
    All bolts seemed to be straight in flight.
    Here is a picture of the range test. Any thoughts on this would be great.


    =http://www.servimg.com/image_preview.php?i=79&u=17025010]

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    Re: Bolt Flight

    Post by mac on Sun Mar 24, 2013 9:20 am

    JDS,

    I am sorry that I did not write clearly enough. The idea is to place the paper somewhere in between the bow and the target (but closer to the bow) so that you can see if the bolts are flying straight.

    For example, if the paper is one yard from the bow, you might find that the bolts make a vertical tear rather than punching a round hole. The shape of the tear could tell you if the bolt were leaving the bow "nose up" or "nose down". By changing the distance that the paper is from the bow, you can see how the bolt oscillates in flight, and when it finally damps out and flies straight.

    In an ideal situation, the bolts will make a round hole in the paper no matter how far it is from the bow.

    Mac
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    Re: Bolt Flight

    Post by jds6 on Sun Mar 24, 2013 12:28 pm

    Thanks mac

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