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Crossbow triggers54.118

    Crossbow triggers

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    Pavise
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    Crossbow triggers

    Post by Pavise on Wed Mar 24, 2010 11:52 am

    I often hear or read where folks are wanting to improve their crossbow trigger and in particular make the pull smoother and perhaps a bit lighter. And whilst understanding that the loads applied to a crossbow trigger when cocked, can be vastly more than those on a firearm trigger, there are some things that remain constant and are just as applicable to our needs. The following video from Brownell's wonderful website is most informative and provides much insight into how certain parts should operate together.




    Pavise


    Last edited by Ivo on Mon Feb 27, 2012 8:18 pm; edited 2 times in total (Reason for editing : Topic status: Sticky)

    Ivo
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    Re: Crossbow triggers

    Post by Ivo on Thu Mar 25, 2010 1:24 am

    Thank you Pavise for starting this topic.

    I was hesitant to start it prior to compiling a list showing the variety of trigger variations as well as the accompanying glossary of terms required for this discussion, but It won't be long now and I will be adding a link very soon.*

    The information provided in the videos is great and deals with a very important aspect of fine tuning the trigger pull weight(although there was no sound in the second video in the series, it was still great). Think this will be a great resource for those who are simply wishing to modify their store bought crossbows or fine tuning the trigger pull of the self built ones.

    Given most of us are going to actually fabricate our own triggers and all together do our projects straight from the blueprint, this topic can go much further. Many in our hobby overlook a very important factor when building the trigger by basing it on the ones seen on firearms.>>> http://webarcherie.com/forum/index.php/topic/16046-mecanismes-de-declenchement/page__view__findpost__p__397095?s=974a49821a919a39dcab46ae5e6876de

    The beautiful thing about crossbows is that we don't need the hammer to make it work..there is no primer to fire-up...so building the trigger around the idea of a "transitional lever" in my opinion is the best thing, as it will in it's mechanical simplicity reduce the pull weight considerably...and then when the trigger is built around the traditional sear design the above videos are still going to be applicable to further fine tuning the pull. What do you think Pavise, are we going in the right direction?




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    Geezer
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    crossbow triggers

    Post by Geezer on Thu Mar 25, 2010 7:45 am

    Geezer here, with observations. Even with the simple 'tickler' trigger of the one-axle roller-nut crossbow, there's much that can be done to improve release. Over the years, I have learned to position the pivot-pin the distal end in a straight-horizontal line with the sear. The further aft you put the pivot, the quicker the distal end (bit that goes into the sear) moves, but the leverage will work out to more work. The further forward you put the pivot, the easier the pull on the tickler, but the movement of the distal end will be slower... it's simple leverage. Placement of the sear in the nut effects release. A sear on the precise bottom of the nut (as shown by Payne-Gallwey) along with a very slightly arced distal-end on the tickler, will reduce the effort and smooth release. On the other hand, moving the sear back a quarter inch, so it's a bit behind the bottom-center will substantially reduce the pressure of the nut trying to rise out of it's round socket. That gives you longer lock-life and reduces the tendency of the nut to tear out the back of the socket on release.
    With the complex multi-lever releases found on sophisticated Renaissance crossbows, the sear is moved to the back-surface of the nut, so the nut is held into its socket by the cam-action of the last bits of the lever-train. That means the nut-socket, which fits the roller closely at the front, can be quite loose at the back, so there's no strain there. You will note that nut-sockets are commonly heavily reinforced with a big chunk of bone or antler at the front, but the back 'lager' block is normally much thinner, or even absent entirely. All the rear 'lager' block really does in one of these complex locks is provide a low-friction surface. Of course they hang the roller itself on the 'nussfaden' cord, to keep it from oscillating or jumping out on release, but in fact the 'nussfaden' doesn't actually bear any load when the lock is set... it only keeps things running smoothly aftger release.
    Like I say, it's complicated. .. Does the above make sense? Geezer

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    Re: Crossbow triggers

    Post by Pavise on Thu Mar 25, 2010 2:34 pm

    Hi Guys,

    Again this forum demonstrates just how good information can be conveniently shared for the common good. Some great observations and tips from Geezer as usual and another fantastic link and more from Ivo.

    Mechanism No. 4 in the link provided, is especially attractive inasmuch as it is of an overclaw type, which mitigates string rollover, and one which also minimises the trigger pull because the sear is only holding the spring powered hammer; much the same as in a firearm. What is often overlooked though is the inertia energy remaining in a nut or claw after release takes place. This momentum has to be arrested and the claws remain static and in the ready to cock position. It is amazing how these seemingly small parts will sometimes bounce only to stop halfways at times.

    We're definately going in the right direction Ivo and I look forward to seeing the additions to this topic.

    Pavise

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    Re: Crossbow triggers

    Post by Ivo on Fri Mar 26, 2010 2:28 am

    Pavise wrote:It is amazing how these seemingly small parts will sometimes bounce only to stop halfways at times.

    Very true, I've also been taught that the claw should stop after it has traveled it's path and remain in that position until once again cocked. The opposite goes for the other parts as we want them to cock
    automatically once the crossbow is cocked.

    Geezer wrote:Like I say, it's complicated.

    Soon we might need to start posting pictures in order to keep track of this.



    Before I created this forum I was a member of this one other crossbow forum... not the French one that Kali introduced to me(where that link came from), but a Russian crossbow forum. The latest of the triggers displayed there have been simply amazing in demonstrating the use of the "transitional lever"(if my terminology is correct) that I mentioned earlier.

    Credit for presenting this trigger goes to Сергей(Phoenix) >>>Build details



    and this trigger was fabricated by Zmeelink >>> the actual crossbow is still in the works.



    I'd say more, but I'm still looking through the gunsmithing books to find the terminology I need.




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    Terminology

    Post by Ivo on Fri Mar 26, 2010 2:41 am


    By the way, for those who would like to help in putting together a dictionary of terms PM me for more info.  
    All help is appreciated.




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    Re: Crossbow triggers

    Post by Todd the archer on Sun Mar 28, 2010 3:30 pm

    I would like to build a crossbow with a sophisticated trigger in the future, but for now I am going to put together a more primitive design. Something along the lines of a southeast Asian style. Having said that, how do they release the string from the notch in the stock/tiller. It does not appear they use the medieval push up peg system. I have looked at various pics but is not completelty clear. maybe someone know better how their trigger works.

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    SE Asian trigger

    Post by Geezer on Mon Mar 29, 2010 9:30 am

    Geezer here: Uhhh, guys, I'm familiar with the simple southeast Asian trigger. It's a very chancy thing... a notch with a funny little lever at the front, that lets you change the incline and alout the string to slip out. I cannot recommend it for security. If you want to do a simple notch-lock, look at one of the push-pin models, either with a lever on top or underneath. Geezer

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    Re: Crossbow triggers

    Post by Todd the archer on Mon Mar 29, 2010 11:52 am

    Thanks Geezer, having described how it works it makes sense on what I am seeing. I will not try it for the reasons you stated. I do have my own idea for a variation of it though. Will post pics when finished.

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    Re: Crossbow triggers

    Post by Ivo on Mon Mar 29, 2010 6:56 pm

    I know of only one Chinese crossbow trigger. Is this the one we are talking about? >>>Link

    Our French friend did an excellent job on presenting how it functions.





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    I have seen that one before

    Post by Todd the archer on Mon Mar 29, 2010 7:25 pm

    Thats not the one I am thinking of. Geezer understands. The one I am talking about isn't Chinese but is more Vietamese or Tiawanese style. I am trying one simular to number 9 in that link above.

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    Re: Crossbow triggers

    Post by Ivo on Wed Mar 31, 2010 4:50 am

    #9 follows the same principal as the one I'm working on ... only it is a bit simpler(no transitional piece, no automatic safety).


    ....from what I "imagine" this one might indeed be a bit "chancy" as Geezer said... without a transitional piece it might just roll back into release unless of coarse this action is blocked with a special pin or even an over all interior shape of the housing.

    What do you think about this design from Robin Allen's site?



    There is absolutely no chance of roll-back.




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    S.E. Asian lock

    Post by Geezer on Wed Mar 31, 2010 7:03 am

    Geezer here: Yup, the S.E. Asian locks I have seen are more like no. 9 mentioned above, but substantially cheesier. Not for strong bows and not for the faint-hearted.

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    Re: Crossbow triggers

    Post by kiwijim on Fri Apr 02, 2010 7:07 pm

    Hi Ivo,
    That trigger from Robins site is a very good design. Good enough to be standard issue for Excalibur and Tenpoint crossbows. I think tenpoint call that design "power touch".
    I was lucky enough to score a couple of Excalibur locks and have used them on some heavy weight crossbows. Even at a high draw weight (+300#) they are still crisp, have a short and easy pull and a couple of hundred shots later, have shown minimal signs of wear on their sear sufaces .
    I researched the specs on these locks before I used them in a high weight crossbow and decided 300# is still well within their margin of safety, although, for obvious reasons, I cannot reccomend that other people do the same.

    Very good thread guys, Some excellent information here.

    Regards
    James

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    Re: Crossbow triggers

    Post by Ivo on Thu Apr 08, 2010 8:27 pm

    I've recently had to move so I had to take a shovel to my shop in order to dig my way through it...guess what I found.>>> Kasenit

    And because this trigger is really dependent on good hard steel for the sear - Kasenit might just allow me to use it on my next
    crossbow.

    There was an interesting topic on Russian forum about these triggers where a guy was tuning them a bit...I'll be back with some interesting pictures/info as soon as I find that topic.




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