Small pistol crossbow

A couple of days ago i came across a bundle of coiled steel sitting in a dumpster. Said bundle turned out to be a broken bandsaw blade. Logically, living in a city where metalworkers are rare, i took it home, cut it to pieces, filed away most of the teethy parts and assembled a miniature loose laminate prod.

The whole thing measures 31cm in lenght, bends smoothly to a 18cm draw, and, despite its mighty 8# weight, is obviously stockless and therefore pointless.

Today, some more filing and chiselling turned into a wee little roller nut.

Next step is to carve out a pistol stock out of some sapele i have lying around...

Any advice on designing the trigger and/or the stock is most welcome!



The prod!



The tiny nut!



And the tiniest sear plate.

Awwww that's cute!   If it were me, I'd make a miniature tickler 'trigger'.

  Kenh, that would be cool, though i was thinking more along the lines of a vertical trigger, since even low leverage ratios aren´t really an issue with this armor shredder i got here 

She is a cutie, though

News update on the build progress:

Original prod seemed too narrow to fit the design i had in mind, so took the angle grinder and cut some backsaw blades so size.



Nocks are crap, but i'll figure it out later on



Stock design is taking shape, so is the trigger. Sorry kenh, had no room for a tickler here 





Any thoughts?

Lookin' really good there.  Except for those nocks .  Even a kiddie power crossbow deserves good nocks.  You could cut pin nocks and then dip them in liquid 'handle plastic' so they won't shred strings.

Quick question: Being that the individual laminates are stressed individually, one could add a couple of leaves to the outer side, to add some poundage, and still have the same draw length safely, right?

Kenh, the groove u see on the nock pic is the first cut of the pin nocks, though i'm thinking of going with some leather wrapping instead of plastic, purely out of aesthetics. Great thought though, hadn't thought of that!

You can add leaves to either the inside or the outside, or both without changing the draw length.

Now I see your pin nocks! Duh?

Thanks for reassuring me man! In my mind that made sense, but since this is my second laminate bow, never a bad thing to ask the man. Now that opens up some room for this to become something a bit more serious, as i do have another blade and a half lying there on the shelf, looking sad in their unbent state. 

Don't know exactly how much poundage i'll get, but experiments are in order. 

By the way, stock is taking shape and lookin' good. Got to find a 24mm drill bit tomorrow, for the nut socket...



Dem elusive nocks eh?

Got some more work done this week, the trigger is almost done, still lacking sideplates though. Going to cut up some some saw blades to strenghten the prod a bit, hopefully soon!

Lookin' good!

I loves me some pistol crossbows, watching this with interest. I like your stock design quite a bit. I'm a little concerned that you don't have much or any mechanical advantage in your trigger. Guess you won't know how stiff the pull is until you decide how stiff to make your prod. Keep us posted!
Gnome

Hey Gnome! I kind of like it too, and it feels good to hold. 

So, i beefed up the prod a bit, with 2 more laminations, and things are looking better. Haven't measured it yet, can't find my scales, but on the 3# mini scale, the 3# mark is at the 4cm draw (including the 1.75cm low brace height), so i expect a bit of an increase from the original 8-9#...

I foresee a bit of a problem with the sideplates, as there might be a lot of string wear with the string resting on their edges. ( Since my nut is only 4mm narrower than the stock. 2mm on either side might be too thin, even if sanded glass smooth.) But i'll cross that bridge when i come to it. Sideplates are cut out, i'm adjusting the axle position, so the nut is centered. I'll post some more on that in a few days. Meanwhile, pics!  





There are your nocks Kenh! 

You need to angle the place where the prod meets the tiller such that the string is in the notch at full draw but just touches the deck at brace.  The angle is usually around 6-7 degrees.   Of course with such a low weight the issue is drag on the string, not wear and tear of the tiller.

I will angle it Kenh! Yeah, i reckoned as much; not worth wasting any of my already limited power on string/tiller friction. 

Gnome, forgot to mention the trigger business. I realise the leverage is almost non existant, but i think it'll be manageable for the weight im going for, which should be below 30#. 

What do you guys suggest for the prod mounting? I just finished a binding on another crossbow, hemp and artificial sinew, with leather padding; was thinking of going that way with this one, using a dowel instead of a hole, like Kenh's avatar pic. 

Here's a pic of the other binding i mentioned:

I did a pistol bow a while back with a similar roller nut design, that is, the roller nut being the full width of the stock. I filed down the side plates until the string made no contact:

If were to do this build again, which I may well do since I have enough parts, including a roughed out stock of the same wood, I think it would be better to add wood to the side panels to beef up the lock area. If you have scraps of the same timber you cut your stock from and shaved them down to just a quarter inch or so, it would look better and you would have more bearing surface for the axle of your trigger. Just my 2 cents.
Gnome

I've done both the hole an the dowel, and I gotta say I prefer the dowel.  It's less "fiddly" since you aren't passing cord ends back and forth through the increasingly small hole.

Just make sure that the binding cordage doesn't look "out of scale" with the rest of the build.  Since this isn't a magnum power build, I think I would find some nice packaging string and just a thin slip of leather wrap.

I'll keep an eye out for that Kenh, that is part of my fears regarding a binding. 

That's a very nice bow you got there Gnome, i think i'd seen it before on my wanderings around here. The whole "binding side plate" is appealing, though i don't have enough wood to make it properly i think.

Took your advice on the wood bits, and after sanding a milimetre off of each side of the nut, managed to get a good fit. Looks pretty good as well! Thanks man.

I need to find some decent screws, a new file and some quiet time to make this one really shine!

Beginning to like this piece quite a lot,   i'll keep you posted. 
As always, pics!

Nice work can't wait til its finish. I'm doing a 29" crossbow for a first build, its not done but adding pic as I go so everybody can see my progress.
Euell

Hey guys! Just did a test shoot after tying the prod, and I like what i see! My flimsy 16cm homemade bolts (made for the first pistol crossbow i made a while back) work like a charm, though i think they are way to light for this. One of them pierced through 5mm high density resin MDF though. 

Out of camera battery, but i managed to film another shot. String is crappy still, so are nocks (need to cover them sharp edges.) but it already promises fun! 



Trigger is still lacking a spring, there is no trigger guard, no final shaping, no lots of stuff. Still, couldn't resist trying the little thing!  

Hurrah!  I love it when a plan works out!

Here is the shot i mentioned, managed to salvage and edit it.

Sooo here's where it stands at the moment:

I'm working on a bolt clip, a trigger guard and a small plate to cover the trigger mortise just right, so the trigger itself doesn't wiggle a bit. So far, the mech works pretty good, and those wood strips on the side really helped tone down the string wear, so many many kudos for that Gnome!

Can´t wait to get it finished so i can really make that grain shine, i'm getting to like this wood a lot!