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Unread postAuthor: POLAND_SPUD » Sun Apr 05, 2009 3:27 pm

if I had an easy and cheap source for 6mm steel bearings but they are not readily available.
AFAIK 5.66 mm ballbearings are noticably cheaper than 6mm ones... anyway 6mm ones are still quite cheap if you spend some time looking for them you can find places that sell them real cheap (in bulk)

I don't think there is any point in using a bolt on such a small bore... david's idea to use a hopper seems quite good... besides in this way you could just buy a ready made magazines (yeah I know.... heresy)

ohh I really like the diagram.... putting the magazine before the air inlet seems like a quite a good way to get rid of most of flow restictions... plus it will give you a very modern bullpup design :wink:
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 05, 2009 4:07 pm

POLAND_SPUD wrote:I don't think there is any point in using a bolt on such a small bore... david's idea to use a hopper seems quite good... besides in this way you could just buy a ready made magazines (yeah I know.... heresy)


I agree that it would probably work with just a hopper as in the attached diagram. You'd need a detent/o-ring/magnet to stop the BBs rolling out but it should work well. There will of course be dead space in the magazine but the BBs in the hopper tube should provide enough flow restriction to mitigate this, and the fact that each burst of air will agitate the BBs in the mag means it shouldn't jam.

I'll see what I can conjure up tomorrow after work :)
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Unread postAuthor: psycix » Sun Apr 05, 2009 4:25 pm

The second design on the previous page doesnt solve the problem of the first one.
Allow me:
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 05, 2009 4:35 pm

I thought about a stepped piston, but from the point of view of someone without a lathe, that introduces concentricity problems :?

edit: to hell with compressor pressures, I just ordered me one of these:

Image

No idea how long it will take to get to epoxyland from the US but when it does, I'll have 850 psi to play with in a portable bottle, this cannot be a good thing!
´
I'm worried about noise, it's quite ear splitting at 100 psi, let along 8 times as much, but we'll see.
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Unread postAuthor: psycix » Mon Apr 06, 2009 3:07 am

that introduces concentricity problems

Not if you cast this piston into the tubes it slides in. Block the small diameter step and cast it in from the back end. Use a release agent and make an o-ring groove.

----------

So you will also be using far heavier springs?

But how are you going to keep the 800 psi inside? You will have to use metal. And even epoxy has its limits...

This may be the time you have to start using ear protection.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 06, 2009 3:41 am

psycix wrote:Not if you cast this piston into the tubes it slides in.


The problem is that the piston will rotate with use and if it's not centred it will jam.

So you will also be using far heavier springs?

But how are you going to keep the 800 psi inside? You will have to use metal. And even epoxy has its limits...


I have a couple of ways to get the crucial parts welded out of steel so that wouldn't be an issue. I trust epoxy to high pressures if applied correctly, but it's better not to take risks. Also, since it's high pressure, I can restrict the porting to below the barrel diameter which would not mean significantly stronger springs.

Still, thinking about it, I'd probably start off with a cloud BBMG. We'll see when it gets here. In the meantime I want to make a clear hopper for my 4.5mm BB barrel to use with the "rattlesnake" valve, 10 round bursts are not enough :D

This may be the time you have to start using ear protection.


Or build a silencer :) the valve is only loud without the barrel fitted though, when the air has space to expand it's quieter than the impact noise.
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Unread postAuthor: psycix » Mon Apr 06, 2009 7:40 am

The problem is that the piston will rotate with use and if it's not centred it will jam.
Or instead of jamming, the nonconcentricness will simply make sure it won't rotate. Otherwise you could also try preventing rotation with a groove and a pin.
Or make sure that it can rotate by having it concentric enough and a bit of space to make sure it can.

I would recommend using a bushing or reducer to ensure its concentric. Just build the body out of standard PVC or metal parts and epoxy the piston. Because the fittings you are using are concentric, so will the epoxy you cast in be.
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Unread postAuthor: ALIHISGREAT » Mon Apr 06, 2009 7:51 am

Where did you get that tank JSR, its looks like a Ninja paintball one... and i only know of one other company that makes it and thats (c)RAP4
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 06, 2009 8:23 am

psycix wrote:Or instead of jamming, the nonconcentricness will simply make sure it won't rotate.


Experience shows that this won't be the case.

Otherwise you could also try preventing rotation with a groove and a pin.
Or make sure that it can rotate by having it concentric enough and a bit of space to make sure it can.

psycix wrote:I would recommend using a bushing or reducer to ensure its concentric. Just build the body out of standard PVC or metal parts and epoxy the piston. Because the fittings you are using are concentric, so will the epoxy you cast in be.


Valid points, I'll consider this mod for the next one which will inevitably follow :)

Where did you get that tank JSR, its looks like a Ninja paintball one... and i only know of one other company that makes it and thats (c)RAP4


It is a ninja tank, from ebay here.

Found this info on the tank:

The regulator on the pump tank is adjustable between 450 and 850 PSI by adding or removing shims in the spring pack. It is very easy to adjust and is reliable.


This would be ideal at 450 psi, I prefer less stress on the components and more shots per fill, even if at the expense of some performance.

If I manage around 800 feet per second for BBs I'll be a very happy man. Anything more will mean wasted air and extra noise.

Not too expensive for what it is in my opinion. Just a question for the better versed in paintball paraphenalia, will the valve open regardless of what I screw it into, what does the head look like? Is it a standard thread?
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Unread postAuthor: Gippeto » Mon Apr 06, 2009 8:50 am

The threads are ASA, and unfortunately, pretty unique.

The valve is a pin valve, similar to a schrader in function.

Since you'll be needing an adapter anyway, it might be worth it to have a look at some of the "remote mount" paintball regulators that have 1/8"npt outlets.

The Palmers female stabilizer (If only such a thing existed! :lol: ) has this, but it's pricey for what you get.

I think there was a link to one not long ago that was closer to $15US.

I'll have a quick look.(If you don't find it first. :) )

Edit: Found the thread, but it was an "inline" regulator, and has ASA threads on both ends.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 06, 2009 10:01 am

Gippeto wrote:The Palmers female stabilizer (If only such a thing existed! :lol: )


LOLOLOLOL 10 points! :D :D :D

Will I be ok with this?

We use BSP here in Europe though, not NPT... hmmmm.
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Unread postAuthor: SPG » Mon Apr 06, 2009 10:46 am

psycix wrote:The second design on the previous page doesnt solve the problem of the first one.
Allow me:


Image

I would have thought this would be a good compromise. If you can balance the spring weight and the mass of the piston well I'd have thought most of the air would head out the barrel. Only thing I can see being a problem is it pushing a BB up into the hopper/mag and it not dropping down before the bolt returned.

Then again, maybe a straight hopper is easier.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 06, 2009 11:30 am

SPG wrote:Then again, maybe a straight hopper is easier.


Exactly what I'm making at the moment, with a groove in the barrel for an o-ring detend and a PET preform as a hopper, convenient cap for filling and clear so I can see it in action :) It should hold around 200 BBs easily.
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Unread postAuthor: SPG » Mon Apr 06, 2009 11:46 am

Is that a sample bottle??? Aren't you supposed to wee in it???
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 06, 2009 11:55 am

No it's what eventually becomes a plastic soda bottle after blowmoulding. It's in my scrap box from my days working with a well known beverage manufacturer ;)

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