First Time Crossbow Building Questions

I have always been a fan of crossbows, often preferring them over bows in games. I have decided that it would be interesting and awesome to actually build and have one. As for the crossbow I want to create something that is detailed for display but still has a decent force. I want to make a steel prod crossbow that can put out 250-300 pounds of force. 

My question is what the dimensions of the prod should be as well as how far back the string would have to be pulled with said prod to achieve the amount of force. I have tried to find a formula to solve this myself but have been unable to figure anything out. Also it would be nice to know what kind of string would be suggested. Beyond this though I feel the rest would be much easier to figure out. Alternatively if someone has schematics for a steel crossbow that will reach 250-300 pounds of force that would be greatly appreciated. If you think purchase of a premade prod would be better, then I will gladly take a look at links to those as well.

Also as for loading mechanism I am assuming goats foot lever would be good for this amount of force?

Dan here,

First of all, welcome to the forum. I'm quite new here as well but people here have been a great help. For the prod, there are a couple of sellers I know of. There's Slobows : http://www.slobowscrossbows.com/

Also Alchem : http://www.alcheminc.com/crossbow.html   (although I heard that you have to be petient when ordering there

Tod's stuff in the UK : www.todsstuff.co.uk/crossbows/crossbows.htm

There's Darkwood armory that sells crossbows as well but I'm not sure if they sell just prods.

So, unless you have some skills and knowledge in metal working and also access to a metal shop, I'd stongly suggest you stick with already made prod or try your hands on a wooden prod (you won't get as much draw weight though). I am on my first build as well, neraly completed. Beware though, building these shooters are addictive and I find myself with countless other projects in mind.

For the string, here's a useful link : http://crossbow.wikia.com/wiki/Making_simple_endless_loop_strings

Again, welcome to the guild ! Cheers !

As for how far back to get that force, that depends on the prod.  Some will have a shorter length and other a longer draw length.  Unlike longbows and recurves there is not a standard draw length at which the pull weight is posted.  This is also an important consideration in that a longer draw length at a lower weight can have as much or more stored energy then a heavy prod at a short draw length. 

And of course welcome.

Good thinking Basi. Your right on here . To start ,you have all these thoughts to,put into your "pot", so to speak.When starting out there are a lot of points to consider. It's a double edge sword also. Not hard to do but, too bad if you make the wrong pick. You'll either smile ,or, grump. Take time ,research , research , and some more.Pick out one or two of the pros here and talk . Take your time , that's the only thing that don't cost much.Being on this site is one of the bargins now days.A stranger has access to an amazing group of people located here.