In Progress Medieval-style Crossbow

[Dane]

Thanks for the kind words and your opinion. I would not have know that. And, things can be changed and adapted and fixed before they break, so to speak What kind of steel or other material do you recommend for the sear? Any type of metal is fine with me, as this is not an exact replica but a medieval-styled weapon.

I believe that they used to fit a steel or iron wedge into the bottom of the rolling nut to act as a sear, and I don’t see this being a problem to achieve. I imagine I will simply cut a slot into the nut and epoxy in some sort of more robust metal. The guy who did the build-along does make, to the best of my knowledge, relatively low weight weapons for light target work and SCA events, stuff like that, and I do plan to shoot this a lot if it turns out as fun as I think it will.

This crossbow will rate about 175 – 190 lbs. with an 8” draw. I do have a nice piece of hand forged iron, about 1/8” or a bit thicker (a tiny plate about 2” x 3”) – would that be suitable? I imagine if I do go that way, I will still keep the threaded rod, but just epoxy it in the nut.

All in all, it is maybe a very good thing we had 10” of snow and ice yesterday preventing me from picking up that epoxy.

Dane

[gstoneberg]

Sounds like a good suggestion to me.  Couldn't you just remove the threaded sear from the rolling nut, heat it up red with a torch and then quench it in oil?  That's what we did in college to turn our mild steel rod into a center punch after taking it off the lathe.  The tickler will be hardened some from the hammering it gets I would think?  If you were worried about it you could just weld a thin layer on the end of it and the heat from the weld would harden that.  You'll have to be gentle with the grinder to keep from annealing it.  But, the easiest solution would be to find a local metal shop and, after you get everything working the way you want,  take the threaded sear and tickler to them to be heat treated.

George

[Holten101]

Like gstoneberg suggest I would try some selv tempering of the bolt...and make sure that you can replace with relative ease the sear and the trigger. In commercial trigger systems (which are not of the highest quality) the contact surface bears the full load and can (and will in my experience) be worn to a degree were the crossbow is unsafe to handle...especially while loading the arrow/bolt (I have the scars to prove it;-).
The systems that I have worked with are in principle similar to yours...but instead of a rolling nut they have small, pivoting plate.

If you dont self temper it, you could opt for a high quality machine bolt....the kinda that will actually take some stress (yours could be good enough....but if it was easy to file down, then it most likely is not):-)

Cheers....looking forward to more:-)

[Dane]

Guys, Thanks! This is all good advice.

Holten, do you recommend a manufacturer for high-quality bolts, ie. not Chinese stuff you get at Home Depot? Buying just a few bolts rather than in bulk is desireable.

Baring that, I can try home heat treating. Any suggestions of what kind of oil to use for the oil bath to cool the parts? I have a hand held propane torch, but am not sure it can generate the heat I need to get the parts hot enough. They are very small parts, though, so maybe what I have will suffice?

BTW, the tickler will be easy to remove from the tiller should I need to later. Once I epoxy the sear bolt into the nut, if I had to replace the sear, I'd need to make a new nut, but that is doable if it comes to that.

Need to ask again, do you think making a sear out of that iron plate would be a good alternative? It would be relatively easy to make the part and inlet it into the nut.

Dane

[Pat B]

Dane, an auto parts store will have hardened bolts that should work for this. Maybe even threaded studs that would work.
  Cool project, BTW     Not my cup of tea but I love watching others and their projects. This is actually way above my experience level. 

[gstoneberg]

That's a good point Pat.  You can even get grade8 bolts at Lowe's.  It will make your cutting and shaping/filing a little harder, but the metal is much harder.  I'm afraid there's nothing that can be done with the tickler other than heat treating it, welding it or doing a lot of hammering on it to harden it.

Good luck,
George

[Dane]

Pat, good day.

Great tip! I’ll pick one up this weekend, in fact, or even today, as we are getting another snow storm starting tonight, so I may (sadly), be stuck at home and in my shop.

I agree, it is fun to see other projects unfold on PA that one wouldn’t take on themselves. I reckon that if you wanted to build something like this, you have more than the artistry and skills.

Until fairly recently, I’d never even considered building a crossbow, so I am on a sharp learning curve here. It is so much fun, I expect to build others after this one. A bigger, more powerful military bow would be fun, as would one with a composite prod, but that is a whole ‘nother subject entirely.

George, heat treating the tickler should not be that hard. I have a nifty little book called The Home Machinist’s Handbook. He recommends using a Mapp gas torch and bringing the part up to a dull red, then quenching the part in water, not oil. Would not a handheld standard propane torch get the needed temperature? The end of the tickler is a very small area that will be heat treated.

Dane

[gstoneberg]

Dane, the problem you will have using the propane torch on the tickler is that, while the part that needs heat treatment is small, the remainder acts like a heat sink drawing the heat away from the tip.  If you chuck it in a vise, the metal vise jaws will also act as a heat sink.  Mapp gas is quite a bit hotter burning, but I don't have a mapp gass torch so I don't have first hand knowledge.  It may still work, probably depend on your torch tip design.  The torch would probably work on the threaded rod as it is a lot smaller.

George

[macbow]

I think you can buy a mapp gass bottle to fit a hand held torch at a regular hardware store.
Ron

[fishfinder401]

what woulde you recomend for a very SIMPLE fireing mechanism, as ni am very limited in what i can do and what time i have, school always getting in the way of building stuff,
btw if you want to make a very powerful crossbow a prod you could use is a car or golf cart suspension spring, you can get new ones on ebay.
this crossbow should be awesome looking by the time its done, where did you get the moos antler for the nut

[Dane]

Good news is that my torch is in fact a Mapp torch. Hurrah. I had it in a drawer for a long while, so I had to dig it out to check it out.

Bad news is that my local auto parts store doesnt carry any threaded hardened rod. I may consider other options, too.

Fishfinder, school does that, eh? Some guys have built super cool, super simple primitive crossbows, with a peg pushed up through the tiller that pushes the string up and behind the bolt. I will look around for some examples that have been posted here tomorrow. So, they can be all wooden weapons.

I got the moose antler from Moscow Hide and Fur. Love that place. It was wicked expensive, but worth it.

Dane

[Dane]

Well, I think I solved my sear and tickler hardening challenges.

I just placed an order for Kasenit from Track of the Wolf, and if they recommend it, I think it should be a good product, and looks like a simple way to case harden stuff. I'll be using that in combination with a Mapp torch for both the sear area of the bolt and the trigger end of the tickler.

I found some 3/8" Class 8 bolts, rather than Class 5 bolts, and would not have known about those if it wasnt for this thread, so thanks to everyone.

Arg, now I have to wait for the Kasenit and of course, the prod, tickler, and stirrup. In the meantime, I'll be ordering some crossbow quarrel heads and making a set of quarrels. I can also make a leather or wicker quiver and belt for the spanning claw.

Dane

[fishfinder401]

i did make one reletivley successful one, it was around 90 lbs and all it was was a slot that would hold the string a i would have a piece of wood under it to leverage it out
can wait to see how this one comes out, looks great so far

[Dane]

Thanks, Fishfinder.

That slot arrangement with the peg pushing up the string is exactly the simple type I was referring to. Some guys here have made ones like that, they look like fun. One of the big problems with that system is that the sting slams forward into the base of the bolt.

Dane

[Knocker]

I am enjoying your thread Dane.  It strikes me as ironic that slingshots are outlawed where you live, and you are building cross bows and siege engines!  :-)  I am guessing the local politicos will be passing some new ordnances when you roll your stuff out of the shop!!!!   

Keith