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    Cheap easy crossbow build yielding effective hunting weapon

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    jaeger22
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    Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Sat Mar 05, 2016 4:30 pm

    First topic message reminder :

    Hi guys, I have been gone awhile on travel but I am home now and back to crossbow stuff and still on my mission to develop and produce low cost drop in triggers to aid the DIY Xbow builders. Especially the first time builders who may not have a shop full tools at their disposal.
    So I thought I would post my latest build with with some ideas on how someone can build a fun crossbow suitable for hunting and target shooting without investing in a ton of tools and material. Keep mind that I am no expert like some on this site. So use what is useful and toss the rest! Wink 
    To me the first design consideration is the bow. The rest of the design flows around it. Weight of course, but most important is draw length.
    So here are some bow options that I know. First, the crossbow store (online- google it) can  supply ready made bows (prods). I have used Barnett 150 lb prods from that site and they worked very well. They come with a string and ship already strung for $65. I have tested them on my bow testing rack and they pull a true 150 LB at 17" of draw. They shoot 22" 460 grain arrows at and average speed of 223 FPS. (51 Foot LB of energy) Not super speed for a crossbow but way faster than any of my homemade recurve hand bows and those recurves shot completely through deer, pigs, and elk over the years. So I am sure it will take any kind of game. They also have lower cost ($29.95) Chinese bows but they don't have a string and I have heard that they are actually much lower poundage than the advertised 150 lb, like 120# or so, but I have never used one myself.
    There are many other options, including steel bows made from car springs and ready made crossbows prods provided by artisans talked about on this site.
    But back to the CHEAP option. This bow is based on ideas posted by KenH on this site. (Thanks Ken!) The bow shown below cost me a whole $10! Now that is my kind of price ! Very Happy

    As Ken described in his post it is made of fiberglass fence tensioner rod material and is a loose stack design. I found a local supplier here in Orlando and picked up a 8 foot section for $10.  I wanted to have the same draw length as the Barnett bows (17") so I made the outer leaf 35" and the nocks are 34" apart. The other three leafs are 28", 18", and 10". I wrapped the center with strong cord and also added short wraps at each section as seen below. For the nocks, I epoxied on a short piece of walnut about a quarter inch thick at the tip and tapering down to about 1/8. I filed and sanded the shapes and then added deep nocks for the main string and a shllow inboard nock for the bastard string as seen here:



    This bow came in at 145 Lb at the 17" and gives an arrow speed with the same heavy 460 grain arrow of 208 FPS. (44 Foot Lb of energy) The difference from the Barnett being due I suspect mainly to the increased efficiency of the Barnett recurve design and the slightly lower draw weight on this one.
    The disadvantages of this bow are, 1) Width - Barnett is 28" tip to tip strung and this one is 32" tip to tip for the same draw length. 2) Slightly lower speed. (208 FPS ver 223 FPS) 3) You have to make the string.
    Advantages: 1) Fun of making your own. 2) CHEAP! 3) Having something different than the crowd. Laughing

    And here is the finished (OK near finished) cheap Xbow;



    Well this is getting long winded and I have only covered bow ideas so far so I will stop here for now and follow up with cheap easy stock and trigger thoughts soon.
    John

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Mon May 16, 2016 10:52 am

    Hi Guys, thought I would give you a quick update on the triggers. I finally got my hands on a couple of the CNC machine shop produced triggers. Man are they nice! MUCH nicer than mine. As you can see they are anodized black:


    I am starting testing now to make sure everything works well and holds up to a lot of shots. So far (first 20 shots) all is well and the trigger feel is great!  cheers
    Now I have to go shoot a few hundred arrows and then take it a part to make sure nothing is wearing out. I don't expect any issues but want to make sure. If all goes well I will push them to get them on Ebay by the weekend.
    FYI - Full disclosure- I have no direct financial interest, but my son's shop will produce and sell them.
    John
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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by JoaoLS on Fri May 20, 2016 8:11 am

    I have, Geezer. And I have to say it works out pretty neat, as after the bridles are set with some kind of glue and well tightened, you can remove the wedges with a punch and remove the bridle. It functions, as you said, as a set of bow irons. Of course it's not a neat disassemble as with the irons but it works should you need to repair or replace a stirrup, a prod, etc...without having to cut the whole thing off. I'll link to a pic of the system you described. You can see the two steel wedges in front of the square peg.


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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Thu May 26, 2016 7:34 pm

    Do you use the ancient chinese crossbow tirgger protype in your design ?

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Thu May 26, 2016 7:51 pm

    The double hooks of chinese crossbow trigger are casted as a  whole, so they are quite solid and robust.
    But they are sperate and need assembly with a bolt,I am little doubt  the displacement of double hook isn't in a line.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Sat May 28, 2016 5:10 am

    Yes the design was based on the original Chinese and the first few I made, I cut the claw out of a single piece of brass. Worked but was a royal pain to machine.

    Being an engineer, I can't leave any design alone. LOL  Laughing When I first thought about making the claw out of 3 pieces, I had the same concern about keeping the claws aligned. But then I realized that because the string pulls evenly on each side, it actually forces them into alignment. I have built a bunch of them and it has never been an issue. I even deliberately left the bolt loose as a test and it still stayed strait. It is also held in alignment by the 5/16" axle in the back that it rotates on. So it can't get out of alignment.
    I put one of the CNC machine shop built ones in my latest build to test it and so far I have over 200 shots (150 Lb bow) with no issues. I take it apart every 50 shots of so and check for wear but so far none is showing. The shear surface still looks brand new. I don't think I could wear one out in my life time. cheers
    The machine shop did not have time to finish the first run up this week. Crying or Very sad  (This is fill in work for them.) But they hope to get to it this week if no more high $ interruptions come in.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Sun May 29, 2016 8:17 pm

    Thank you for your deep explanation and hard test。

    I think the Qin dynast crossbow trigger is best on the appearance and might short on the strength。

    Here is a link of crossbow trigger auction,the price is not too high compared with your CNC
    mechanical working.

    http://pai.sssc.cn/item/511749

    Here is a reproduction of original Qin/Han dynasty crossbow。
    http://atarn.net/phpBB2/viewtopic.php?t=17&highlight=trigger

    Hope they are useful for your project。

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Sun May 29, 2016 10:57 pm

    Shen-bi-nu / Divinced arm crossbow  replica (not good job)

    http://www.bilibili.com/video/av2639985/
    http://tv.cntv.cn/video/VSET100239490650/2576dbf6adb24670a5e8fa01e27b7670&

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Mon May 30, 2016 4:26 pm

    Thanks for the links. Interesting reading!
    " the price is not too high compared with your CNC
    mechanical working."

    I don't read Chinese so I may not have understood the one for sale. It looks like the price is 1,150 Yuan. A quick search gave 15 cents to the  Yuan so I get $172.50 American and it looks like that is just the inside parts without the case. Is that correct? If so, the CNC ones will be WAY cheaper.  But then the CNC are not meant to be authentic looking. They just use the basic Chinese design as a starting point.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Tue May 31, 2016 9:59 pm

    Maybe you can have a bargain on the price,there are too many crossbow triggers digged out in  northwest china whre it was the capital of ancient empire。
    I still have a problem why you don't tie the end of the shorter bow?
    If you tie the ends,the power will increase greatly。

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Wed Jun 01, 2016 9:11 am

    Yes I think they will be a bargain. But one man's bargain may be another man's rip off. Shocked LOL
    I expect they will be around $40 but that will be up to the machine shop once they figure out how much total touch time is involved in each one.
    stm2010 wrote:I still have a problem why you don't tie the end of the shorter bow?
    If you tie the ends,the power will increase greatly。

    Please explain. I would love to get more power out of them but don't understand "tie the end of the shorter bow"
    Any pointers you can offer would be greatly appreciated. Any pictures?
    Thanks,
    John
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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by septua on Wed Jun 01, 2016 1:24 pm

    Are you including the trigger return spring for production ones? The click is reassuring and it says the intermediate part is seated.
      
    Tom

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Wed Jun 01, 2016 1:57 pm

    Tom, yes the spring is included. On my home made ones the spring was just captured in a slot I cut in the stock behind the trigger but the CNC made ones will have a extra back wall with a screw or pin that captures the spring so no extra slot in the stock is needed.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Fri Jun 03, 2016 2:45 am



    They are not the good place for increase the power of the bound bows marked with wrong symbol。

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Fri Jun 03, 2016 5:02 am

    Thanks for the picture! That makes your point very clear. I will experiment and report back. But I have to say I am skeptical. I think I originally tried it that way on the first one I made but the bindings slid off when the bow full bent, or at least after a few shots. In this loose leaf design, the leafs are NOT glued together and must slide some.
    But I will experiment as soon as I get time.
    Thanks again,
    John

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Sat Jun 11, 2016 3:02 pm

    It looks like stm2010 is correct! I did a test on a bow I built a while back. First I measured the draw force with the bow as is with the bindings in the middle like so:


     
    With the draw pulled to a tad over 17". my rusty trusty old bow scale read dead on 75 Lb but due to the 2 to 1 reduction pulley, that is actually 150 Lb.


    Then I added bindings at the end of each short limb or leaf as you can see here. I left the original bindings in place.


    As you can see below, the scale reading went up right at 2.5 LB and with the 2 to 1 reduction, that means the bow now pulls 5 Lb more or 155 Lb.



    Not huge but an additional 5 LB of pull for just adding bindings at the end of each leaf
    is a good deal in my book. cheers  Thanks stm!
    I am doing some work on the stock for this bow but when I put it back together I will fire some arrows through the Crono to see if it made a noticeable difference in arrow speed.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by c sitas on Sat Jun 11, 2016 3:46 pm

    Jeager please ; could you post a diagram on how you hooked up your scale with the 2 to 1 advantage . I'm brain dead today.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Sat Jun 11, 2016 10:30 pm

    It is easy to understand since Jaeger use a movable pulley to draw the bow。


    Your  use four separate bows bounded as a whole. It remind me of chinese song
    dynasty's chuan-zi-nu (triple crossbow, ox crossbow). It is the father of modern
    compound crossbow. It doesn't increase the pull power but increase the pull
    length, W=F*S, so the final energy stored is improved.







    Chinese crossbow replica



    As a reference :
    https://myarmoury.com/talk/viewtopic.php?p=284513

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Sat Jun 11, 2016 10:43 pm

    A chinese guy named "bldx000"  is clever as "Donald Duckman" on the youtube.
    I think their ingenious inventions on the bow and crossbow  is Top 2 on the youbube.
    Their jobs are full of more innovation and wisdom than other's.


    Unfortunatelly, "bldx000" always hide the full view of his inventions in order to keep
    secret, may be he want to apply for patents.
    Anyone smart can speculate its mechanical struture and make a copy.

    https://www.youtube.com/watch?v=7LkIXFQU9B0


    https://www.youtube.com/watch?v=XDAisqtQ-0c

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Sun Jun 12, 2016 4:10 am

    sitas wrote:Jeager please ; could you post a diagram on how you hooked up your scale with the 2 to 1 advantage . I'm brain dead today.

    Here is the back end of my bow testing rig. Wench rope goes to the pulley then back to the scale. The black rope on the left ties to the bow string.
    My scale only goes to 100 Lb which was fine for my hand bows but for the Xbows I needed the 2 to 1 reduction.


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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by c sitas on Sun Jun 12, 2016 8:04 am

    Hey my friend , you have a real touch of genius in you . Thank you for the view. I'll be setting myself up the same way  as I have your same problem . Thanks again. Anything further on the trigger yet?
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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by Onager Lovac on Mon Jun 13, 2016 6:12 pm

    Jaeger22 a 150 Pound bow with a 17" draw?!, Awesome!, whats the brace height on that bow?

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Tue Jun 14, 2016 4:08 am

    Onager Lovac wrote:Jaeger22 a 150 Pound bow with a 17" draw?!, Awesome!, whats the brace height on that bow?

    They are a bit over over 4 inches. I just measured the two I build and one is 4 1/8"and the other is 4 3/8"or so. I was thinking they were 5" so it has a bit longer power stroke than I thought.

    c sitas wrote:Anything further on the trigger yet?

    Sorry this dragging out so long. Embarassed  I slowed things down this week because I requested a small change.
    As part of my testing, I wanted to make sure it would not fire accidentally. It is a bit of a fine line to get light trigger pull yet safe for all kinds of use. One test I came up with was to hold the cocked Xbow with an arrow in it in front of a target in my left hand and then hit the but with my right hand to see if I could make it go off. First with just my hand and then with a 3 Lb rubber hammer. Surprised   Now at some point it WILL go off if you hit it hard enough, as will ANY trigger, due to the inertia of the trigger mass holding it back as the stock rapidly moves forward. But it should not fire with a light to medium  hit. It was not bad and it took a hard hit to make it go off. Not unsafe at all but could I make it better?  scratch I realized that if I reduced the mass of the trigger, it would make it much harder to make it go off with a hit to the stock. I hand machined out material from the middle of my test trigger to lighten it and repeated the test. Now it takes a much harder hit to make it go off. I could not hit it hard enough with just my hand to make it fire but can still get it to fire if I hit it with the hammer very hard. But as I say, any trigger on any cocked gun or xbow WILL fire if you hit the rear hard with a big hammer. Unless you have a safety and it is on.
    Sorry for the long winded explanation but that is why I ask the guys at the CNC shop to modify the trigger to reduce mass. 
    They came up with the solid works model below.


    So now just waiting for a machine and operator to free up and run a batch of them.

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by stm2010 on Wed Jun 15, 2016 10:24 pm

    Hi,jaeger22, there is a very usual ancient chinese crossbow trigger which has been reported by Stephen Selby。。
    http://www.atarn.org/letters/ltr_aug03.htm

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    Re: Cheap easy crossbow build yielding effective hunting weapon

    Post by jaeger22 on Tue Jun 21, 2016 2:33 pm

    Thanks for that link! Yes that is a very interesting trigger. It is kind of a cross between the normal Chinese and the roller nut type. The guy that wrote it up said he thought it was for lighter weight bows and I would agree. It is simpler because it has one less part but it looks like it would have to have long and heavy trigger pull and high shear ware. . . .

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