JACKS SHED.

Adam · Posted: Sat Oct 24, 2009 12:52 pm Post subject:

Looks like those bands aren't going to be stretched enough for full power :(
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Adam

julesj · Posted: Sat Oct 24, 2009 4:08 pm Post subject:

Hi Adam, this is just a test set-up!!! I am working on an extendible version to enable variable length of pull.

gtavares · Posted: Mon Oct 26, 2009 12:00 am Post subject:

fcuking Jesus !!!!!!!!! I love this slingshot rifle !!!!!!!
Congratulations bud !!!! I really enjoy it !!!Congratulations !!!!!

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Keep slingshooting ------------- O

julesj · Posted: Mon Oct 26, 2009 12:34 am Post subject:

Thanks Gtavares, I really appreciate your enthusiastic comments!!! I test fired it yesterday, and it proved to be quite accurate at short range, but I need to tweak the firing mechanism a little for a crisp let-off. It's still a work in progress; I intend to change the broom handle 'barrel' for some kind of extendible version, when I can stop shooting this beauty long enough to design one!!!

gtavares · Posted: Mon Oct 26, 2009 10:03 am Post subject:

Leave it a little longer, have more power...like this one: http://www.slingshotrifle.com/ *Video( http://www.cmt.com/videos/misc/27...xtra-clinging-to-my-toy-gun.jhtml)
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Keep slingshooting ------------- O

Adam · Posted: Mon Oct 26, 2009 10:22 am Post subject:

Hmm... instead of extending the 'barrel' why not move the anchor point of the elastic closer to the trigger and run it forwards to a pulley before coming back to the trigger again?

That way you increase your draw length but without having to make the rifle too long?
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Adam

julesj · Posted: Mon Oct 26, 2009 11:00 am Post subject:

Adam, I like your idea of a pulley system. I have never used this on any of my designs; how effective is a pulley in increasing power output, and where and how would you mount it, if you were me, so as not to spoil the lines and make it look 'clunky'? I have limited engineering knowledge, and I only use off-the-shelf components!

julesj · Posted: Mon Oct 26, 2009 11:36 am Post subject:

Could the fixing points be on a sliding rail that locks in to position to enable cocking/ tensioning of the bands maybe?

Adam · Posted: Mon Oct 26, 2009 12:24 pm Post subject:

Joerg has some pulley designs in his latest video if I remember correctly.

You want the pulleys at the 'muzzle' end of the rifle so the band starts at the trigger, goes forward to and around the pulley and is just slack enough so you can load the pouch and pull the bands back to the trigger.

I'll draw something, photograph it and send it you. Might take me a while as I have a physio appointment in an hour.

Cheers,
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Adam

JoergS · old man o'the woods Yes Joined: 20 Jun 2009 Posts: 154

What you could use is not a pulley, but a simple set of rollers. You could keep the "barrel" a bit shorter, but the limit is about 1/5th of the total draw length.

Let's not forget that you need to draw the rubber out to about 500% of the original (relaxed) length. So if you would attach the rubber at the trigger you would only get 200%.

Rollers work, but the mechanical stress will shorten band life, though. Maybe it is best to just go ahead and use a little longer "barrel".

Jörg