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piston question

A place to ask general spud cannon related questions.
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Unread postAuthor: MrCrowley » Fri Jan 11, 2008 6:58 pm

pvcmaster wrote:The original topic of this post was sealing faces, so I thought I would slip in a question. My piston has a diameter of 2" and it is sealing against a piece of 1.5" pipe. Is the difference between the O.D. of 1.5" (Which is 1.900") and the piston enough to open the valve?

Yeah it'll be fine, technically you can have no 'open' area on the sealing face to make it work, but it's always good to have some.


spudy buddy wrote:ok it was just an idea. most people somehow keep the bbs from falling out of the barrel anyone know how?

Do you mean out the back of the barrel where the piston seals?

Just put a tiny blob of epoxy or hot glue at the back.
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Unread postAuthor: spudy buddy » Fri Jan 11, 2008 7:07 pm

no i alredy plan on doing that but some how some guns are able to shoot at a target that is on the ground while the person is holding the gun standing up which means that there must be some way to stop the bbs from rolling out or are the bbs just a really tight fit?

Edit: if they are a really tight fit then what can you use as a push rod to get them to the back of the barrel?
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Unread postAuthor: MrCrowley » Fri Jan 11, 2008 8:19 pm

Hmm not sure how they do that in a co-axial, because usually you just put a layer of hot glue in the barrel, but that only works if you breech load.

You sure the cannons you saw are co-axials? Otherwise i'm not sure how you could achieve the same effect in a co-axial unless you have a tight fit.
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Unread postAuthor: spudy buddy » Sat Jan 12, 2008 1:03 am

no i don't think that they were co-axials, i'm pretty positive that they weren't co-axial but i was just wondering if there was or if they fit really tight.

for those green 6mm bbs what size of a barrel do i need cause it doesn't have the diameters in mm but in fractions?

Edit: for a fraction to mm the closest i get is 1/4 to 6.350mm. is the brake line that i need to buy or what?
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Unread postAuthor: MrCrowley » Sat Jan 12, 2008 1:30 am

Tight fit, or they put some glue infront of the projectile on a breech-loader.

You need brakeline, if you're from the US, go on http://www.mcmaster.com and look for some pipe that's really thin, it should have the real I.D to fractions of an inch.

1/4" is the nominal diameter of the pipe it means nothing to you, the real I.D could be about 9mm.

Do some searching, what brakeline you need for 6mm BBs has been discussed many times, i've answered loads of pages of questions, so just do some searching this time. There is an answer, so just find it.
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Unread postAuthor: spudy buddy » Sat Jan 12, 2008 1:52 am

ok i will search the 177 pages of posts to find the answer if its the last thing i do. lol just kiding :D
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Unread postAuthor: anthony5640 » Sat Jan 12, 2008 8:50 am

ok im realli new to the airgun stuff and spudgun stuff eventhough i got a airgun that shoots at 30psi through 1/4 inch plywood what the heck is a pistol valve? can you please explain how it all works and give an animation on it?


ahahhh i sorta get it so u need 2 valves? i have 2 a big one and a little 1 will that be a problem? little 1 for fill valve and big for a quick exaust, i think that will be quite effective.

but how does this piston thing realli work how do u know how big it has to be.

i realli need help b4 i kill miself with this lol and ill make it properly none of this cutting out the next size up pvc pipe to make a reducer or woteva im gonna spend some cash for some decent parts if i get some knowlage on this piston valve thing.
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Unread postAuthor: spudy buddy » Sat Jan 12, 2008 12:46 pm

post number 4 has 2links in it. the second one will show you how they work. go to the first page of this topic and its the 4th reply down.

what exactly is the diameter that i'm looking for cause theres a lot and idk which one needs to be 6mm. this is brake line from napa auto parts.

Brake Line - Universal Steel Hydraulic



Item#: BK 8131201

Price: $1.99
tax and shipping not included

Disclaimer: The stated price may vary from the in store price and may change at anytime.


Attributes:
Diameter:3/16"
Length:8.0"
Size:3/8"-24 x 3/8-24
Features & Benefits:Replacement Brake Line For Hydraulic Brake Systems
Seamless Steel For Longer Life
Universal Design
Material:Copper-Fused
Tin-Coated
Bendable:Yes
End:Double Flared
Contents:Brake Line Assembly Adaptor
Manufacturer:American Grease Stick Company
Mfg Part Number:BLX-308BK
Fittings:Yes
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Unread postAuthor: MrCrowley » Sun Jan 13, 2008 12:51 am

I have no idea because i'm not sure if 3/16" is the nominal or real diameter.
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Unread postAuthor: spudy buddy » Sun Jan 13, 2008 1:00 am

ya thats what confused me too. any idea why it wouldn't let me deleat that double post? i tried like six times :?
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Last edited by spudy buddy on Sun Jan 13, 2008 1:53 pm, edited 1 time in total.
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Unread postAuthor: MrCrowley » Sun Jan 13, 2008 1:02 am

Not sure, I had the same problem earlier on, working now, hence me deleting that double post, just give it a few days I guess. :?
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Unread postAuthor: spudy buddy » Sun Jan 13, 2008 1:13 am

ok ty for doing that i was gona ask you to delet it but you did it before i could ask so ty. i guess when i go there i'll take a bb and see which one it fits in. i just hope that they aren't packaged in a box cause that would screw me over compleatly. oh and in the pics they all have like a threaded cap but not realy a cap cause it goes on over the pipe but i was wondering if it was to conect the pieces together?
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Unread postAuthor: spudy buddy » Mon Jan 14, 2008 5:33 pm

hey in the topic about piston sliding room you wrote that the piston needs to slide 1/4 if the barrel ID. my barrel is gona be 6mm so the piston only needs ti move 1.5mm ???? am i mxed up or is that right cause that seams a bit little?

also if i want a servisable piston, and i do, how do i make it? just use a plug without glue then drill holes through the pipe into the plug and wrap screws in teflon tape, tighten them in the wholes, and hope it wont leak?
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Unread postAuthor: ALIHISGREAT » Mon Jan 14, 2008 5:44 pm

spudy buddy wrote:hey in the topic about piston sliding room you wrote that the piston needs to slide 1/4 if the barrel ID. my barrel is gona be 6mm so the piston only needs ti move 1.5mm ???? am i mxed up or is that right cause that seams a bit little?

also if i want a servisable piston, and i do, how do i make it? just use a plug without glue then drill holes through the pipe into the plug and wrap screws in teflon tape, tighten them in the wholes, and hope it wont leak?


well mathematically 1.5mm should be right yes but i don't see any harm in making the piston travel a bit bigger something in the region of 5mm i would use. and if you want to make the piston serviceable then just use threaded fittings :)
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Unread postAuthor: spudy buddy » Mon Jan 14, 2008 7:20 pm

ya it wouldn't hurt to make it more.

the threaded caps ive seen thread into something smaler than the barrel like this:

also how hard is brakeline? if you hold one end will the oyher end droop? would an arow shaft be a beter idea?
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