Steel prod on a crossbow

Hello everyone !

I got my new forge ready and I'd like to make a new crossbow with a steel prod. I was able to put my hands on a decent springsteel (5160) from a semi-truck leafspring blade... they are hefty though (about nearly 1/2 of an inch thick) and I know it's waaaaaay too much for a crossbow. You think it would be possible to forge it to about maybe 3/16 to 1/4 of an inch thick and re-temper it after ? Is there someone who has done that already ?

BTW, I want to get a decent power out of it and cock it with a goatfoot maybe (in the ranges on 400 lbs maybe). Also, I know all about Alchem and Slobows that sells prods but I like to do things entirely by myself.

Any advices would be appreciated !

Hey Daniel, will watch your project with interest!

Have you considered using the leaf spring from a golf buggy or similar? Much less work

I would use them but I don't have any and in Canada, they seems to be hard to come by... 

Anyway, I found a 5160 flat bar supplier yesterday, in the very city I live in !! Never thought that would be possible. So I'll get a 3/8 of an inch thick, 2 inches wide and 60'' long flat bar (good enough for 2 prods I'd say). That'll be much better since I won't have to cope with the hole you'd find on a leafspring.

Will post photos, the nut will be made of brass (I know steel is lighter but I don't have a steel round bar around, just a brass one) and the tiller will be made of Cherrywood. All iron component will be hand forged by myself... can't wait to begin my project.

Try a local spring and brake shop. They can give you a good guesstimate to get the target weight you want. Build a swedge to get matching tips.

I got two springsteel flatbars today. both are 2 inches wide and 60 inches long. One is 3/8 of an inch thick and the other is 1/4. The good thing is, they are already deflexed since they are originally made to be leafsprings. I'll just cut them to the right size with an anglegrinder (I'll be sure to not heat the bar too much by doing that of course), taper them to about 1 inches at the tips, cut the notches in and voilà !!

Ok, me again. I cut the two different prods, one on the 3/8 of an inch, the other on the 1/4 and MAN… how will I be able to span them ?? Even the 1/4 is STIFF !!! Both are 28, 5 inches total length (26,5 NtN), 1 inches wide at the tips, 2 at the center and of even thickness all along the prod. I guess I'll need some mechanical help just to string them. For now, I'll settle with the 1/4 thick. Any advices would be appreciated ! Thanks !

Hi Daniel,
I'm no expert on prod geometry, but it sounds like you still have a beefy hunk of steel there. I checked my stiffest Slobow prod and it goes from a little less than 1.75" at the center down to about .5" on the tips before it flares out for the string pegs. It's a little thinner, just 3/16" but still draws over 200 lbs. Like I said, I'm no expert, but I think I'd be tapering it down a bit more to hit the 400 lb neighborhood.

BTW, how are you planning on forming your tips to hold your string, just cutting the profile or doing some forging?

Regarding stringing your beast, there are a few methods, this is one I came up that works well for me. I think I'd design something sturdier for the 400 pound range, but you get the idea. The scissor jack is now bolted to the frame and I use cargo straps as a security measure to keep the tiller in line, and leather pads on finished tillers and prods to keep from marring the finish.


Good luck and keep us posted,
Gnome

This sort of spanning jig gets the Geezer seal of approval.  My journeybeing, Lightly uses a similar one.  Medieval 'ziebanks' were similar in concept, but deployed horizontally in a table.  A vertical one will save valuable shop room.  With a scissors or bottle jack and some discrete padding, you should be able to span any reasonable crossbow.  Geezer sez build this!

For the prod, I just cut the profile like you said... it's my first one and this way, I won't have to re-harden it. I mean, I do have a forge and everything but with that much power, I'm worried about limb failure and getting injured. I got some more though so eventually, I'll try to make the flaring tips like those of Slowbows or Alchem and reharden it.

If you're worried about breaking an untested steel prod, do what medieval bowyers did.  Run a length of leather, @ 1/2 inch wide down the back surface (faces the target, not the belly) of the prod, from end to end. Lash it at the ends (around the nocks as well, and about mid-span on each limb.  That won't keep the prod from breaking, but if it should break, it won't spin out and hit you.  Some medieval bows have a woven strap of leather, or possibly even of hemp.... a flat braid would work just fine.  If you like the looks, do a nicer lashing at mid-span on each limb, and attach some colorful pompoms.  They did that too.  Geezer.

Thanks Geezer, I though about that too, the leather strip I mean. It's probably what I'll do since I have a couple of leather scraps lying around. I'd definitely like that better than having half of my prod stuck in my eye.

It's called a 'sicher' strap (sicher for sure, or safety)  Geezer.

So if somebody in Germany asks if the Pope is a Catholic, or a bear poops in the woods, you can simply answer 'sicher'.
Geezer.

Oh and one more question here (that was Columbo right ?). I know most prods on either Alchem or Slobows have a draw length total at 11,5 inches. My prod is the same length (28,5 inches but NtN, let's say 26,5 inches). Would 11,5 inches seems like a fair draw length or should I aim a bit shorter than that ?

Daniel, don't forget to build wheels for your spanning jig,eh eh , your gonna need it to cock that animal. Gonnna need an awesome string on it also. Actually the whole stock and lock will have to be stronger.Keep up the good work, you'll end up 
being proud of yourself and  your bow.

I saw rollers at Princess Auto that looked like they could be repurposed for your prod press wheels.  For bows, I use the formula; Bow length =2.2 X draw length and if in doubt, add more length.

look at the digitarc website. They make any strength prod you will need in steel. you can choose from traditional ends to pulleys. Purchase one from them and use your time to build a stock and release.

Hey Todd, good to see you here. I follow and watch your projects. Thanks