Hey everyone, I'm not exactly new here, I've been stalking these forums for a bit in preparation for making my full scale medieval 100% working crossbow ^.^ But I HAD to make an account to post a pretty nifty idea I had yesterday.
Well, I basically I made a 1/3 scale crossbow as a sort of prototype for my big one next week. And yeah I used a 30cm metal ruler as the bow part (prod) !!
It works beautifully. If anyone wants to make one, it's really easy and infact I made it in less than an hour while watching Criminal Minds last night.
To make, I found a suitable piece of wood in the back yard to use as a stock. With the ruler, it's just a regular 20cm metal ruler which I drilled an extra hole on the other end. Then I (With the help of a drill) made a slit at the end of it to fit the metal ruler nice and tight. I then secured it with superglue. So then I used a rasp to make a rail for the bolt to run down and strung the bow nice and tight. After checking how far it could be cocked, I made a 90 degree cut for the string to rest on after being pulled back and drilled a hole down to the bottom of that to have a trigger mechanism. You dont need a trigger mechanism, you can just push the string up with your fingers, but triggers are always cool
Here are some pictures:


http://imageshack.us/f/69/dsc0935q.jpg


http://imageshack.us/f/802/dsc0932.jpg

Pretty good for an hours work aye

You guys will probably think I'm silly, but its just something you can whip up if you're looking for a few laughs at school maybe. Be careful though, I broke 7 pens and made a guy bleed today (He told me to shoot him, I'm not sadistic..)

EDIT: Seems like the pictures arent coming up so I posted the link instead

Shooting people with crossbow-propelled pens has to be a bad idea almost no matter what.

But the crossbow design, thats cool.  I`ll have to take a look at metal rulers tomorrow. 

I`m thinking... a long one, a shorter one behind it, and maybe even an even shorter one behind that one... I`ll have to look into metal rulers

timann

Now I'm looking at my 18-inch rulers thinking "Hmmmm....I know I use those all the time, but...."

Using an automotive leaf spring is a possibility, but requires a lot of work to do right.  A leaf spring is not "tillered" properly.   It has to be ground careflully so that, like any bow, it bends progressively.
This generates such heat that the spring must be re-tempered after grinding.

Much easier to simply buy a professionally made prod from Alchem:

http://www.alcheminc.com/crossbow.html

A hacksaw might let you taper the profile of the spring, but it still would not be tillered.
If you look at historic steel prods, they are progressively tapered as to thickness just as a longbow would be.
Tapered in profile would be better, but not optimum.

johnny108 wrote on Dec 26^th, 2011 at 1:49pm:


I've already got the leaf springs from my neighbor's truck.
I just can't cock the stupid thing. Seems they're rated at 7,000 Lbs.
And no, I don't want to shoot pens.