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Unread postPosted: Thu Feb 21, 2008 11:13 pm
Author: jackssmirkingrevenge
I don't claim to have any original ideas, flip through
Google<sup>TM</sup> patent search and you'll know what I mean. I think the skill lies in first of all recognising existing concepts that can be applied to spudguns, and secondly having the material know-how to be able to flesh out your designs.

Unread postPosted: Fri Feb 22, 2008 12:06 am
Author: Davidvaini
I've already been a step ahead of JSR.. actually a few steps... I'm talking about baking a cake of course....

Unread postPosted: Fri Feb 22, 2008 4:29 am
Author: Ragnarok
jackssmirkingrevenge wrote:To what extend this idea actually does this remains to be quantified.

One problem that needs to be addressed is the large pilot volume that is required.

Now, here that won't limit opening time badly, but the further a piston moves back, the more energy it takes out of the chamber, which could be a significant reduction in a small chamber volume like this one.

Unread postPosted: Fri Feb 22, 2008 5:59 am
Author: Novacastrian
Here is the only pic that wanted to work of the new piston.
Image

Unread postPosted: Fri Feb 22, 2008 6:04 am
Author: jackssmirkingrevenge
The further a piston moves back, the more energy it takes out of the chamber, which could be a significant reduction in a small chamber volume like this one.


That is a factor but it can easily be compensated for in this case by adding an inch or so to the chamber volume, no big deal.

Nova, that's exactly how I had pictured it originally :) can't wait to see it in action :D

Unread postPosted: Wed Feb 27, 2008 3:18 am
Author: Novacastrian
Here i go with the vids, the first shows activation. However i am not sure that the frames portray it well. The pistons travel backwards and forwards very fast, and reseats itself. The other vids are self explanatory.
<a href="http://www.youtube.com/watch?v=J1S6ePYY03c&feature=user#">Piston</a>

<a href="http://www.youtube.com/watch?v=q3Tuu4h8now&feature=user#">Paint can</a>
<a href="http://www.youtube.com/user/TyaxComp">Water Bottle</a>
<a href="http://www.youtube.com/watch?v=h77tX1xs8GM&feature=user#">10mm thick acrylic</a>

Unread postPosted: Wed Feb 27, 2008 3:30 am
Author: jackssmirkingrevenge
yay! great stuff :D

So you're saying that the piston travels all the way to the end of the chamber, hits the endcap and bounces back?

Unread postPosted: Wed Feb 27, 2008 3:37 am
Author: Novacastrian
jackssmirkingrevenge wrote:So you're saying that the piston travels all the way to the end of the chamber, hits the endcap and bounces back?


That's it, the big or back portion bounces on acetal to acetal, the middle portion bounces metal on polyurethane, about as hard as a rubber band.

Unread postPosted: Wed Feb 27, 2008 3:50 am
Author: jackssmirkingrevenge
Interesting, perhaps a larger chamber would leave the pressure on firing higher for longer, dampening the bounce. What pressure were you firing at?

Unread postPosted: Wed Feb 27, 2008 4:02 am
Author: Novacastrian
~100psi, i am confident that the projectile has left the barrel before the piston bounces back, plus as the pressure leaves the pilot and chamber at the same time, i am lead to think that if there where still pressure in the chamber the piston would not bounce back "at all". It is a fairly large pilot for the size of cannon. Nuff talk, i'll have to wait and do a comparative test after i get a chrony :wink:

Unread postPosted: Wed Feb 27, 2008 4:06 am
Author: jackssmirkingrevenge
Only 100psi?

*cough*shockpump*choke*itcanprobablytake200psi*splutter*smallerlauncherslovehigherpressure*bark*

Anyone got a throat lozenge? :D

Unread postPosted: Wed Feb 27, 2008 4:11 am
Author: Novacastrian
jackssmirkingrevenge wrote:Only 100psi?

*cough*shockpump*choke*itcanprobablytake200psi*splutter*smallerlauncherslovehigherpressure*bark*

Anyone got a throat lozenge? :D


Fair suck of the sav! One knows that higher pressure yields more power :D I would like to get an efficient design built before i start pumping!! :P

Unread postPosted: Wed Feb 27, 2008 2:50 pm
Author: Gippeto
That works slick!

I like it, I like it a lot. :D

Unread postPosted: Wed Feb 27, 2008 8:27 pm
Author: Novacastrian
Gippeto wrote:That works slick!

I like it, I like it a lot. :D


Thanks Gippeto :)