Crossbow Bows ??

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ghostman01
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Sun May 11, 2008 4:41 am

Hey peoples, this is my first post in the Non spudgun area. Hope im not breaking any rules.

I was thinking about making my own crossbow for target and small game and i cant work out what kind of bow to use. Or where to get it. ATM i have a bout 50-60 cm piece of 10mm fibre glass rod from an old fishing line that i used on my old cross bow that i made when i was 12 or so and could put a bolt about 50m or so and it has since broken and ive got older and i want something a bit more powerful and with a better trigger system. I would like something for a bow that is cheap and easy to get in south Australia. If i cant find anything ill use my fibre glass, im just hoping for some feed back from more experienced guys and gals on which way i should turn. Im sticking with cross bow because its silent and ive got heaps of pneumatics and stuff so pls dont tell me to make one.

Thanks
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hotknife ralphie
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Sun May 11, 2008 5:50 am

Hey, I've no experience with crossbows but I was looking around for info a while back and found some stuff about an arbalest (really kickass crossbow with a steel prod) and thought that if you can manage to find a reasonably light leaf spring (http://en.wikipedia.org/wiki/Leaf_spring) and use a windlass (http://en.wikipedia.org/wiki/Windlass) to cock the bow, you may be able to create a hopefully moderately powerful crossbow/arbalest thing. I was going to do this I just haven't found a cheap leaf spring.

PS I've never encountered a leaf spring in person so for all I know they may be far too stiff, I think I remembered reading somewhere that they are tempered as well but don't quote me on that one.
Just an idea. Goodluck.
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Carlman
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Sun May 11, 2008 6:44 am

hey mate, i was also looking into doing this and then thought of getting one froma shop instead to save hassle and so i can actually own a non-homemade weapon if tht makes sense.

do you need a licence in aussieland for 1?
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hotknife ralphie
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Sun May 11, 2008 6:58 am

http://www.ausbow.com.au/crossbow.htm .Pick your state, damn nsw, everything is illegal here.
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Carlman
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Sun May 11, 2008 7:05 am

yay for WA, ima get myself a cross bow! :D

(sorry for jacking, back to your normal broadcast)

how about lots of bamboo sticks joined together?
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Antonio
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Sun May 11, 2008 9:21 am

What I used for my crossbow was a bed plank. The ones that are arc like. They have pretty good bending properties. I also made this mechanism of steel to hold the string, but I gave it to my friend so ill c if he can make a picture of it. The problems that I had with bows were that the projectile never flew straight and always tumbled in the air.
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STHORNE
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Sun May 11, 2008 9:32 am

Cut some strips from aluminum sheet and spot weld them together.

make them about 3 inches wide x 12 inches long..
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bluerussetboy
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Sun May 11, 2008 4:24 pm

STHORNE wrote:Cut some strips from aluminum sheet and spot weld them together.

make them about 3 inches wide x 12 inches long..
Some aluminum is too brittle for a crossbow prod. Spot welding 3"X12" strips will just snap from very little use. Several people have been successful with 1.5" x 0.25" 7075 T6 51 aluminum bar stock cut to 36" long for a ~90 lbs@~10" pull.

If you are leaning towards a leaf spring prod, you should go to your local junkyard and look for spring packs that have more than 3 or 4 springs in them. These leaf springs are softer and will be easier to bend. If you use the longer leaf springs found in Ford trucks(3 spring spring packs) they can be re-arched for a softer feel, basically reheated. You shouldn't need a cocking lever if you keep the spring rate under 100lbs.

You can also order prods and other crossbow parts from the link below
http://www.alcheminc.com/
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Antonio
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Sun May 11, 2008 4:35 pm

I think leaf springs are too heavy. I matters what kinda of ammunition you are using. But a light projectile needs a short energy burst'' a heavier one needs a longer one. Impulse= m*v= F*t ... so in terms of long and short I mean the time. Thats how you get optimum efficiency on a bow. Light bow> light projectile, Heavy (leafspring bow)> heavy projectile. A heavy bow will not fire a light proj. well as the proj. will shoot away before the bow has exerted all its energy. Something like that :)
bluerussetboy
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Sun May 11, 2008 4:53 pm

One of the nice things about leaf springs is the ability to give them a softer spring rate. Four wheelers have been doing this for literally decades for softer spring rates.. If the rate is too stiff, heat up the spring and re-arch it. You can't do that with wooden or fiberglass prods.
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Antonio
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Sun May 11, 2008 4:57 pm

bluerussetboy wrote:One of the nice things about leaf springs is the ability to give them a softer spring rate. Four wheelers have been doing this for literally decades for softer spring rates.. If the rate is too stiff, heat up the spring and re-arch it. You can't do that with wooden or fiberglass prods.
Ah k, yeah that sounds really interesting:) I didnt know that was possible. But I think the mass of the bow is still big factor and steel is heavy..
bluerussetboy
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Sun May 11, 2008 5:17 pm

No denying the weight of a leaf spring. That is why you look for spring packs with plenty of thin springs as opposed to lesser count spring packs. They might both carry the same weight, but more thinner springs translates to a smoother/softer ride.

I've only helped friends build their crossbows. They build crossbows like some of members here do spudguns....religiously. Some like leaf springs, others like aluminum bar stock, and one guy likes carbon fiber. I personally want one that will throw 20" bolts out of 1" rebar @ 300 fps. It''s going to have to be from leaf springs. Probably not going to happen. :(
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ghostman01
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Mon May 12, 2008 1:33 am

wow thats alot of replies, im going to try and use my fishing rod first and if i cant get good power outta that im going to go for the save up and buy real one lol.
Keep the ideas a coming
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THUNDERLORD
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Mon May 12, 2008 1:53 am

I made a really good crossbow with a bullpup stock.
I can shoot it like a pistol or shoulder fire it.
But the limbs I used were off a compound bow that was old.

I took the pulleys and handle off. With fixed string it had 100+lb.s pull and about 14" inch draw.

But one limb was cracked so I may build something using surgical tubing or the same type tubing but from an exercise kit sold frequently in discount retail stores (Ross or Marshals in USA)

The interesting part on my design is the trigger.
I built it by removing the bolt from a trigger for compound bows.
And drilling a hole and bolting that to sheet metal.
Then I extended a rod to press the trigger on it.

I plan to cut a slot in the sheet metal and add a pin so when I cock the string back and it presses the trigger back and locks onto the string by pressure.(as it is now I have to close the trigger manually) But it would be simple to do.
Then I could add a magazine if I wanted.
I could post some photos in non spud related maybe or here later.
Also I want to post a how to on arrows when I have the time. :wink: 8)

EDIT:BTW, your avatar reminds me of myself when I use a bike pump. Guess my hairs gotten long. :lol:
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Hydra
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Mon May 12, 2008 3:11 am

PVC is actually really good for the "cross" bit where the string is attached. Forgot what you call it.
If you're gonna use wood you should use woods like ash, yew, birch and that kinda stuff.
There are some really good tuts on Instructables.com...Most of them are by wannabe medieval kids and they have almost no knowledge of archery and swords etc.. not saying i DO. (They probably play too much Runescape or something...)
I actually a mini crossbow like 30cm (1ft) long and it shoots about 30-40m lol (30-40m=90-120 ft)
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