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Is it possible to. Make a crossbow using 2 springs and 2 pulleys? Answered

I have this idea where you take 2 extension springs and affix them to both sides of a 2x4 and then attatch a steel cable to them which passes through 2 pulleys attatched to a 2x4 at the front of the first 2x4 the crossbow is then completed Too complicated? I will post a instructable soon Fidgety2

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Phil B

Best Answer 9 years ago

Back a number of years I have seen plans for a crossbow using a leaf spring. I have also thought about a crossbow using extension coil springs. With pulleys and cables the crossbow could be much more compact, especially in a home self-defense situation. I remember seeing a plan for a long bow using springs. I cannot provide a graphic, so I will try to describe it. Imagine a piece of 2 x 2 about 3 feet long for the center section of the bow. There is a kerf in each end of the 2 x 2. A piece of strap iron maybe 18 inches long slides into the kerf at each end of the 2 x 2. A bolt goes through each piece of strap iron and each end of the 2 x 2. This allows the strap iron pieces to pivot on the bolts. A bow string connects the outer ends of the strap iron pieces. Springs connect the inner ends of the strap iron pieces either to each other or to hooks on the 2 x 2. If the bow's pull were very strong, heavier materials might be needed.

Here is a graphic of the bow with a 2 x 2, strap iron, and springs.

bow.JPG

I've just dropped in on this thread.
Seems I'm developing something similar to what is on here. There's me thinking I've come up with a new concept. It's still being developed and altering the design as I go, but it's getting there. Plus a picture of an auto safety trigger mechanism I'm buiding too. I plan on making this a "Bullpup" design , with the pistol grip under the front of the bow. Latest idea tangent, is to make it a compound bow. Using an off the shelf crossbow pistol string. Cocking mechanism design next. No sights needed, as it will have a mounted laser for aiming.

20180404_004309.jpg20180406_142316.jpg

This is a good idea that should have been followed up on instead of forgotten. What's annoying is that every time someone who knows nothing about crossbows but has "heard" of them instantly brings up car leaf springs. Leaf springs are too large, too strong and just plain unsuitable for crossbows except maybe on a novelty crossbow on "Hillbilly Blood" that uses a giant leaf spring and a huge log to build a crossbow that's completely impractical for regular use.

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kola

3 years ago

My take.

IMG_20140727_131911.jpg

that would work if you carved into the sides of the wood where the metal would be........it should be curved

Yes you can. i have made a very simple test version and it works. the stronger the string the more the pull simple enough. i might in future try a full and large version and see how much pull i can get out of a trampoline spring cheers, jarno.

the stronger the spring not string sorry

I was thinking about using the top leaf spring to make a giant crossbow I just put a lift on my truck and was looking for a way to use the old leaf springs lol

then you could mount it on your truck like a turret that would be even more awsome