Yet another one

Hello everyone !

A couple of weeks after finishing my second crossbow, I built myself a little crossbow pistol made of mahogany with an ebony roller nut (the prod is tension bar fiberglass wrapped in hemp string though (I feel like I cheated a bit)

I just wanted something so I could shoot quickly.

Nice!  What's the draw weight?  How does it shoot?

I don't know the draw weigth yet but it's stiff. I had to make a stirrup. I did shot a couple of bolts. I don't have the fps speed yet. I'll probably drop by the archery store in the next few days. I'll keep you updated.

Cute!

Aunt Entity's impressed too

http://www1.pictures.zimbio.com/mp/OomPG-3Y9WTl.jpg

YAY for anuti. Quite a beast,---the thing in her hand. Really cool project Danny. Good lookin job on the bow.

Hehehe Thank you Aunt Entity ! I'm not quite familiar with the character though, I just know it's from Mad Max.

Anyway, the little prod snapped yesterday, I already made the replacement and I'll install it tonight. I went with a loose laminate this time (just two layers). I'll keep you guys updated.

Is there anyway we can put a video here ?

Très joli travail, Daniel Levesque, je le verrais bien dans les mains du personnage de votre avatar...

Merci Jocky ! En fait, le personnage de mon avatar, c'est moi-même.

Anyway, the replacement prod snapped again, seems like I'm not that good with fiberglass... oh well. At least, It wasn't expensive. Bought a cobra replacement 80 lbs prod from amazon. At least I know this one will work.

Danny, your not over drawing are you?

I'm drawing 7 inches total and the prod is 18" ntn... is that too much ? I guess I should go at something like 21" ntn to be at triple the total draw length. That's what I'm doing for my wood bows.

Also , the second laminate is 5"... it's basically just to prevent the center of the prod to flex too much

What do you think ?

Can highly recommend making reliable, short stocky prods from a brick layers trowel.

Very springy steel of effective thickness, easy to cut and drill. Could be layered and bound, and possibly made 15"ntn... if you can find a trowel long enough.

Daniel Levesque wrote:En fait, le personnage de mon avatar, c'est moi-même.

Tonnerre de Brest, j'ai vu plus juste que je ne le pensais. À l'abordage !!!

Hey Daniel, nice pistol! I like how burly it is, I usually make my mini crossbows too light and get a lot of hand shock when I fire them. Regarding the issue with your prods breaking, I'm wondering a couple things- I don't see a photo where the prod is strung to see how much down-force there is on the string. Not that the pressure of the string on the bolt track would increase stress on the prod, probably the opposite, but since the fiberglass lathe you've been using is straight, it would need to be angled quite a bit to provide adequate clearance, and maybe there's to much twisting action when fired for the fiberglass to take. The other thing is the weight of the bolts you're using. Maybe they are too light for the draw of your prods? I've learned that heavy projectiles are much safer when working the kinks out of a new design. Too light and it's just as bad as dry-firing.
Gnome

Thank you Gnome,

I succeeded, at last, to make a decent prod (it is 21 inches ntn and as a second laminate layer of about 8 inches or so). It is sturdy enough, not too hard to draw back but still is an adequate shooter. I don't think to draw weight would be that much, maybe 80 - 100 lb or so. For a pistol, it's not too bad.

I honestly don't know how to bend fiberglass without weakening it though... if you have some pointers, I'd greatly appreciate if you'd share

Cheers !!

You can't bend poltruded fiberglass bars after the fact -- nature of the beast.  Gnome was talking about the angle of the prod to the deck of the tiller.  

To keep the string from dragging down the deck of the tiller when you release, the prod is not set at 90 degrees to the deck, but at a shallow angle (depending on the powerstroke) so that when cocked the string sits at the middle of the bolt in its track, and when at rest the string just touches the deck.  If the string drags all the way down from the catch to the rest point, you lose a tremendous amount of energy to friction; as well as cause a LOT of wear and tear on the string.

Oh okay... didn
In fact, the bow IS tilted (about 15 degrees or so). There's not much pressure from string to the tiller when it's at rest. It doesn't show a lot on the picture tough. Maybe it's just the angle I took the shot.