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new valve :) feedback appreciated!

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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new valve :) feedback appreciated!

Unread postAuthor: Link=UN= » Sat Jun 25, 2011 12:55 pm

new valve for my air rifle -
<a href="http://s148.photobucket.com/albums/s37/Zero_413/?action=view&amp;current=_MG_0034.jpg" target="_blank"><img src="http://i148.photobucket.com/albums/s37/Zero_413/_MG_0034.jpg" border="0" alt="Photobucket"></a>

this is my new hammer valve (unsure if hammer valve is the correct term) for my air rifle build.

the diameter of the 'T' is 2.5cm and is reduced smoothly inside to a diameter of about 1cm so I should hopefully get a decent air flow.

the diameter of the barrel when finished is going to be 4.5mm and will hopefully shoot .177 cal pellets quite well.

changes i made from the original:
- much stronger spring to keep the seal 100% airtight
- sealed on both ends of the valve to stop leaks
- I used a lot of epoxy resin around all the joints to minimize leaks and some chemical metal on the inside to hold all the plastic parts together.

any feed back would be great :)
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Last edited by Link=UN= on Sat Jun 25, 2011 6:51 pm, edited 1 time in total.

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Unread postAuthor: jakethebeast » Sat Jun 25, 2011 4:47 pm

umh, aint that little big for .177cal? just a thought...
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Unread postAuthor: Link=UN= » Sat Jun 25, 2011 6:28 pm

whats too big for .177cal?
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Unread postAuthor: jackssmirkingrevenge » Sat Jun 25, 2011 6:50 pm

Depends what pressure you're using, lower pressure needs a bigger valve.

A diagram of the internals would encourage more opinion ;)
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Unread postAuthor: Link=UN= » Sat Jun 25, 2011 6:55 pm

well im hoping to get it up to around 200psi, possibly higher.

i only mentioned the .177 pellets earlier as they are the ones i have. It will fire any 4.5mm round.

Ill put up a rough diagram in a bit....
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Unread postAuthor: Link=UN= » Sat Jun 25, 2011 7:18 pm

red - rubber washers to seal the air flow
the black L shapes inside the pipe on the right are to keep the rod central

<a href="http://s148.photobucket.com/albums/s37/Zero_413/?action=view&amp;current=valveinternal.jpg" target="_blank"><img src="http://i148.photobucket.com/albums/s37/Zero_413/valveinternal.jpg" border="0" alt="Photobucket"></a>

when the spring is compressed the valve is opened and air can flow through.
the washer on the other side of the 'T' seals the gap so the air dosnt leak out. (its a prety good fit anyway so their wouldnt be a massive ammount of leaking to stop)
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Unread postAuthor: jackssmirkingrevenge » Mon Jun 27, 2011 1:03 am

Looks good, make sure you make your hammer adjustable in terms of spring strength, weight and travel in order to be able to tune it to give you good power without wasting air.
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Unread postAuthor: Link=UN= » Mon Jun 27, 2011 4:22 am

yeah, im having issues finding a big enough / powerful enough spring.
im from the uk, any tips?
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Unread postAuthor: jackssmirkingrevenge » Mon Jun 27, 2011 4:27 am

Link=UN= wrote:yeah, im having issues finding a big enough / powerful enough spring.
im from the uk, any tips?


Ducky Lip ;)
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Unread postAuthor: Link=UN= » Fri Jul 01, 2011 9:08 am

ooookay

air tank is on and had a few test shots, so far pumped it up to 10 bar and it sounds pretty powerful

shot it at a steel sheet with my .177cal pellets and it left a nice dent, i think if i got some heavier steel bb pellets it would go right through as the ones i have are lead and are a bit soft.

only a single shot atm, and i think i might keep it that way.
it takes no time to pump up and its a bit fiddly to put in a new pellet so not really much point!

had a cool idea for breach loading as well
ill put up some pics as soon as the chemical metal is dry
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Unread postAuthor: Gippeto » Fri Jul 01, 2011 11:05 am

Well done! :)

Be VERY careful with steel bb's...they have a rather HIGH tendancy to come right back at you...(ricochet)...you'll stop having fun if you lose an eye...I promise. :wink:
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Unread postAuthor: Link=UN= » Fri Jul 01, 2011 11:14 am

haha
thats kinda put me off them a bit then.

maby ill make a dart or arrow instead!


are there any issues to be caused by bending the air tank?
i bent mine upwards so that it meets the barrel at the end, just wandering if any one had had problems...
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