British newbie seeking more power

[Aurum]

Still, nice find on the bottles etc.

Surrey? Nice place, i've got some friends renting a flat around there

[Biopyro]

It's coming along nicely. I'm using a messy, but hopefully effective silicone sealer to create the blockage, and I may epoxy a wine cork in there too. I have soldered most of the gun part except the pump attachment which I'm still pondering.

[Silence]

Fortunately it's easy to switch the pump rod and plunger with another if this one doesn't form a good seal. If silicone and a cork don't work, you could always use olives, which are the most common solution.

If the copper pipe was cut with pipe cutters, it may be deformed, which makes for trouble with inserting (and using) the pump. That said, I've only seen thin-walled, telescoping copper pipe, not 15 mm or 22 mm pipe, which is probably much thicker and more rigid. I guess you'd have a better sense of how straight the pipe is.

[SSCBen]

In my experience silicone sealant doesn't stick well enough to work as a moving seal. O-rings in wood as described in the APH guide are easy to do but you have to worry about wood rot unless you store the water gun with the pump removed. I can't suggest that enough. Mold smells bad and you don't want to be surprised when disassembling your water gun one day.

Cork seals should work but you'll probably have to worry about rot too.

All you really can do is experiment if you don't want to use one of the proven working methods.

If you want something durable you can find the right sized metal dowel and O-ring to fit inside everything without problem. The OD of the O-ring would have to match the ID of the pump pipe. The ID of the O-ring would have to match the diameter of the dowel. You can then epoxy on small strips of pipe to keep the O-ring in place. This should work well.

[Drenchenator]

O-rings in wood as described in the APH guide are easy to do but you have to worry about wood rot unless you store the water gun with the pump removed.

Completely true. Wood is good provided that you take care of it. I had to through away the wooden pump to my homemade when I got home from college because it was beyond help.

[Biopyro]

I meant the bolockage in the front handle separating the top and bottom barrel. Silicone is awful at doing anything involving serious pressure, but I have found it to make a good sealing face. I would use a plastic cork for a piston if I needed one, but I found a good hand pump for £5.
In other news I found an 8l bladder tank for £18, which I may get. The opening is threaded (not totally sure what size thread) and the opening is 20mm.

[SSCBen]

That's a good deal for a bladder tank. 8 liters is pretty huge but it'll work in your design with only a few modifications (you need to make it pump water now rather than air). Since we know so little about them if you could describe how they work, where to find them, how to build with them, etc., in whatever guide you make that would be great.

[Biopyro]

Haha no more idea how they work than you do, I'm guessing its just a rubber "balloon" which inflates with water. I'll just thread it in and have a female tap adapter nearby with a check valve.

[Silence]

I recall somebody posted a while ago that bladder tanks use rubber diaphragms, ie thick rubber sheets that stretch in one direction as water enters the tank on one side. Perhaps it's easier to manufacture sheets than spheres with thick rubber.

8 liters may not be too much for a backpack reservoir, but it's definitely a lot for a pressure chamber. I'm assuming that's 8 liters of water, with some wasted space that the bladder can't expand enough to fill up.

[SSCBen]

Haha no more idea how they work than you do, I'm guessing its just a rubber "balloon" which inflates with water. I'll just thread it in and have a female tap adapter nearby with a check valve.

In that case you'll have to remove or move the air pump too because it pumps air, not water. If the tank works similarly to other rubber CPS types, pumping in more air does nothing to affect pressure because the pressure is essentially fixed. Air with extra pressure will expand until it equalizes.

I think you can pump air into something on the top so you could move your air pump there.

I think I'll do some more research into bladder tanks now...

[aEx155]

I recall somebody posted a while ago that bladder tanks use rubber diaphragms, ie thick rubber sheets that stretch in one direction as water enters the tank on one side. Perhaps it's easier to manufacture sheets than spheres with thick rubber.

8 liters may not be too much for a backpack reservoir, but it's definitely a lot for a pressure chamber. I'm assuming that's 8 liters of water, with some wasted space that the bladder can't expand enough to fill up.

There's a difference between bladder tanks and diaphragm tanks; there not one in the same thing. Bladder tanks use balloon shaped pieces of rubber, while diaphragm tanks use diaphragms (what a surprise, huh?). Both have air pressing against the rubber in the non-water portion and are charged to a certain pressure (EX: 25 PSI); they work just like CPS bladders but they have air added, which, I guess, increases pressure beyond what the bladder/diaphragm can exert on the water.

If you look at Dusty's gun, he said that the 2 gallon tanks he used included the air needed, so I 'm guessing that the volume rating includes the air also...hopefully I'm wrong (that would give you some more volume)

I'm no expert; that's just from what I've read.

P.S. 150 posts!!! Woo!

[Silence]

Now that I think about it, you're probably right. "Bladder" is only really an acceptable substitute for "rubber pressure chamber" in the water gun world, and it doesn't necessarily have to look like a sack. Elsewhere, it does.

150 posts - not bad. You're 41st on the list and the 1st for 2008 joinees.

[SSCBen]

First off, congrats on the 150 posts.

There's a difference between bladder tanks and diaphragm tanks; there not one in the same thing. Bladder tanks use balloon shaped pieces of rubber, while diaphragm tanks use diaphragms (what a surprise, huh?). Both have air pressing against the rubber in the non-water portion and are charged to a certain pressure (EX: 25 PSI); they work just like CPS bladders but they have air added, which, I guess, increases pressure beyond what the bladder/diaphragm can exert on the water.

I didn't make the connection in my head but it makes sense now.

I'm doing some research into cheaper bladder tanks right now. It seems they are also called "accumulator tanks." Here's a few ones I found:

http://www.jabsco.com/products/marine/w ... /index.htm
http://www.jabsco.com/products/marine/w ... /index.htm
http://www.shurflo.com/Pages/Marine/Pro ... 82-200.htm
http://www.jabsco.com/products/marine/w ... /index.htm
http://www.shurflo.com/Pages/Marine/Pro ... 00-002.htm

I'll keep searching and edit or post any new ones I've found. One of the 8 liter ones I linked to above sound like what you have Biopyro.

Edit: eBay seems to be the cheapest place to get these bladder tanks. Here's a bunch (92 at the moment) of 1 liter ones for $35 each: http://cgi.ebay.com/Jabsco-Marine-Accum ... 18Q2el1247

I think if you get two of those 1 liter tanks you'd have a damn good water gun. Now if I only had the money.

[Silence]

"Accumulator tanks"? That sounds a little like Flaming Hilt's description a while ago at Nerfhaven. I'm sure you remember that.

I'm not particularly fond of this bladder tank concept. To some extent I think homemades should be homemade to as low a level as possible (ie, to the PVC, fittings, and O-rings). My ideal homemade water gun would have a do-it-yourself trigger valve, check valves, pump, pressure chamber and reservoir. Obviously that's not always possible or desirable, but I definitely would rather build my own pressure chamber. A solar shower backpack has enough durability (after my experiences with trashbags) to justify using one as a reservoir, and ball valves have much tighter tolerances than anything you could make, even more than a homemade pull valve. But like with store-bought pumps (which aren't even usable for pumping water) and check valves (most of the time), bladder tanks have little reason to be bought, in my mind.

[Biopyro]

Perhaps if you're going more for the acheivement than the gun, then yes it all should be homemade, but realistically if I could buy a decent water gun I would, but I can't. Therefore I'm gonna make one using whatever, be it homemade or otherwise, to get a good water gun.
In the UK toolstation is still the cheapest place to get a tank like this.
Yeah looks like a pump will be a waste of time with a bladdered tank, so I'll use the mains pressure to pump it, obviously 8l of air will take quite a while to fill up!