hey all from Illinois

Found this forum while searching handmade medieval crossbows.  I'd like to try my hand at one but have some questions. The first one being if it would be possible to make a crossbow prod from a piece of burned out plate.  I always see people take barstock or some kind of steel and then form it to the shape but what if I drafted in CAD the shape and then had someone waterjet or even flame cut the shape out?  It would be plain A36 steel say 1/2-3/4 inch thickness and I'd make the prod 1/4" thick all around.  
Does anyone see any possible issues?  I may try it out with one of my shop guys flame cutting it and see how it goes.

You can't make a prod that way . You can't use plain steel, it would have to be "high carbon steel. Something that would be heat treatable.Regular steel like your talking about would just bend and stay bent. It would not make a "spring" . I'm not smart enough to tell you what number steel you would need, but I'm sure there are those here that can.

You could cut the prod out with a waterjet, surely.  But then the steel would have to be spring tempered, otherwise it's just a 'hunk o steel' not a spring.

You are missing the point here. you can cut high carbon steel with a hack saw BUT, it has to be high carbon steel. You can't make high carbon steel out of a piece soft flat stock. Also all shaping and work has to be done "Before it's hardened ". The prices they chg. for a prod,-- fully warrantied, with a high performance, and looking great are nothing compared to making something that "could bat your brains,or your friends brains all over the floor. I would not attempt it. Make all else, it's what this forum is all about.

c sitas is absolutely right,you obviously have access to some high level metalworking technology.Where you seem to be deficient,is in the metallurgy department.Spring steel is  a high carbon steel,and most likely has other additives,ordinary mild steel won't work.
                                                      Unless you have access to a skilled blacksmith with hardening and tempering experience,or a commercial hardening and tempering facility,or intend to adapt and use a vehicle leaf spring,I would forget about trying to make a metal prod,there are companies that sell them.
                                                               Hermit.

Considering all the work that goes into making a safe, workable steel prod, it's much more economical and efficient to simply buy a prod from a professional shop.
From my point of view, I can see only two reasons to make your own: Either you can't purchase the type of prod you want or you simply want the experience and satisfaction of doing it yourself.  Note that I don't include cost in the reasons to build your own.  Because by the time you've got your steel and all your tools together and spend several hot, sweaty days fuming and cursing over the project, a 75 dollar prod from Slowbows or Darkwood is going to look mighty cheap.
Geezer.

Hello from Il, as well.
There are tempering places in the western 'burbs that will toss a prod in with a job, and you can get the 5xxx steel from Admiral in Alsip, but when I was looking to make 3 prods for the 7th grade stonebow project, the cost was too high, much more than the Slobow prods. My advice to another novice is to use a known prod, make a bow that functions safely then think about making the prod. It is nice to have at least one known variable the first time out. Having made flintlock springs, I can tell you it is not as easy as it seems. Now take the 3" spring I made and multiply the length by 10. That 24-32 inch span has to be heated and cooled evenly, or it could (read 50/50 chance) break and hurt you pretty bad. Not to dissuade you, but realize the potential energy locked into that steel. I find it easier to work on the lock and stock and worry how that works than the prod.

A final note, you might get the feeling that we are jumping on you pretty hard about the risks and value of making a prod. Bear in mind we don't want anyone getting hurt. I was sent a strong "don't you effing dare" message when I was designing pellet shooting bows. I took it to heart, and still have all my eyes because of it. Use the collected experience here as a guide. If we seem gruff with safety items, someone probably got hurt in a similar way, and doesn't want it to happen to another.

Ha ha I'm pretty thick skinned so I don't feel jumped on.  I was actually debating a prod from slowbos but figured I'd ask around.  I recently got into crossbows and I'm a tinkerer so naturally want to make one for myself just to have something I made.  I eventually want to make a self cocking full size crossbow similar to the Barnett Commando.  I'm sure I'll ask a lot more questions before I ever get started.
Thanks
Ed

Hey Ed; I found another spot you should check out for prods. Digitarc.com. They advertise on the right hand panel. Their stuff looks great and the prices aren't that bad either.

Does anyone know where to get a fiberglass prod with a draw of 100# or less?
I know there are some British websites that sell them but I was wondering if there are any based in the US.

http://www.thecrossbowstore.com/ has them. I used the little 80# ones for the stonebows. They have an ebay store too. The ones I used are little, about 12" or so if memory serves I'm not at home. If you don't mind MINI CROSS BOW written along the front you're all set for about ten bucks. They have other sizes too. The minis pack a good punch and took a fair bit of abuse.