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Trigger design

A project log for Stickvise Crossbow

Every electronics bench should have a crossbow. First crossbow project on hackaday.io

Alex RichAlex Rich 12/08/2015 at 13:146 Comments

Research

The internet is the best. I found a nice write-up on crossbow trigger design that I'm going to try to follow:

http://crossbow.wikia.com/wiki/Designing_medieval_nut_and_trigger_crossbow_locks

The article details nut and trigger alignment, nut and stock alignment, etc. Amazing how minor differences in angles and pivot locations drastically change the function of the trigger.

Design

Here is my first stab at the trigger, side view. The main issue I see is how I will re-cock the trigger. On a normal crossbow, the string moves out of the way so you can reset the trigger, on Stickvise the trigger gets blocked by the movable jaw after firing. Hmm...

Discussions

Alex Rich wrote 12/08/2015 at 16:17 point

probably right, in fact I don't really know what the advantage of the nut is considering it just reverses the direction of the catch point.  Smoother operation maybe?  You know, getting rid of the nut will also eliminate the problem with resetting the trigger.  Maybe I will try it, thanks!

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Stefan Lochbrunner wrote 12/08/2015 at 16:34 point

Yes, operation might be smoother but I think that is only the case if the crossbow uses a string. I'd also add a spring (or springy 3d printed structure) under the trigger such that the movable jaw automatically locks when it is pulled back.

I can't wait for the first videos of this working! :)

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Alex Rich wrote 12/08/2015 at 17:53 point

Yeah definitely needs a return spring so you just pull back and it's clicked in and ready to go.  Will hopefully get it done soon!

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Stefan Lochbrunner wrote 12/08/2015 at 15:41 point

I get that you want to use the nut and trigger mechanism because it's  somewhat historically accurate but wouldn't a trigger made in a single piece be the way to go in the interest of keeping it simple and easy to assemble?

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Alex Rich wrote 12/08/2015 at 16:17 point

Doh, forgot to use reply.  Comments above

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Stefan Lochbrunner wrote 12/08/2015 at 16:23 point

Yeah, it happens from time to time ;)

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