Homemade using 2-liter bottles

[sneakycookie]

Could you please take a closer picture at were you fill it up with air, Im having a hard time making it out realy. Thanks

[aEx155]

This is the link to my Photobucket Albums

http://s281.photobucket.com/albums/kk240/aEx155/

You can go there to see all of the pictures that I have.

If you missed the pictures earlier, sorry for the inconvenience.

UPDATE: Okay, I fixed it. Most of the pictures are back online, so, yeah... feel free to look at them.

[Drenchenator]

To answer sneakycookie's question, it looks like that the gun's pressurized through the valve at the end of the chamber section. Air is simply pumped in through there.

[aEx155]

To answer sneakycookie's question, it looks like that the gun's pressurized through the valve at the end of the chamber section. Air is simply pumped in through there.

You're right. Looking at my album of pictures, you can see a "Fill Connector" and how it connects a bike pump to the gun.

Could you please take a closer picture at were you fill it up with air, Im having a hard time making it out realy. Thanks

Update: I'm finished with my homemade check valves. I will have pictures up soon (hopefully they work... ) of the pump itself and the making of the check valves. It works well, but the fact that there is washers makes the flow really slow and turbulent. It only needs a backpack to house [the PCs], the I can get on the soaking!



There is is. Key: dark gray = PVC connectors, light gray = PVC pipe, gray = washer, light blue = hot glue gun glue (?), blue = spring, black = spring, purple = PVC cement

Hope that explains it. If you want me to make a writeup then I'll see what I can do.

UPDATE: If you didn't read it above, the pictures are back online. I just cleaned up the repeats and such.

[sneakycookie]

Thanks for the pictures, I think ill make one of these its pritty cool.

[aEx155]

I can give you a parts list and any more pictures if you want. I also have plans for making a detachable pump design.

[aEx155]

I just wanted to provide an update; sorry for bumping.

I just tried a pressure test with my first of two "spliced bottles". (For those of you who don't know, splicing is used mostly in water-bottle rocketry to increase the volume of bottles without increasing their drag. See this page)

I probably should have waited longer, because once I reached 25 PSI, the splice broke. I'm going to wait till next weekend to try my other one; hopefully it works. I wasted 4 bottles trying to make two larger tanks for my water gun.

Check back in a week or so.

[Drenchenator]

Splicing looks like a good thing to do if it holds enough pressure. And even if it doesn't hold much, you can still make a rigid backpack using spliced 2 liters because it doesn't have to take any pressure. I'm waiting for the update on this.

[Ben]

This brings back some memories. I remember Xray years ago talked about splicing. I couldn't remember what glue he used until I skimmed the page you linked to aEx. What glue did you use? I haven't spliced a bottle but from what I've been told PL Premium works great and I'd imagine the alternate glues suggested there would work well too.

[aEx155]

When I was really into water rocketry, I had gone out to buy PL Premium, along with some other parts for a Robinson coupling (see linked page in previous post). My dad deemed it too expensive, so I ended up using Liquid Nails:



I remember using this on something previously (specifically a FTC rocket) and it worked (kinda; one end leaked too much), so I decided to use it again. I know I didn't wait long enough; that's why it failed (I even wrapped the splice in several layers of packaging tape; didn't help). I'm going to wait a week to test my other one.

The sad thing is: I only have 3 2-liter bottles left.

[Ben]

You can go scavenge recycling bins in your neighborhood. I'd imagine that you'd find a good deal of usable bottles in there. Be sure to wash them though.

Looking at the technical data for Liquid Nails I can't find any mention of bonding to plastics but it does seem to get significantly stronger after a week in sheer strength at least. Waiting longer might be the answer.

If Liquid Nails doesn't work out I'd suggest reading this article to give you an idea of what else is out there that could be used to splice bottles: http://www.sscentral.org/repairs/glue.html

The hot melt glues should work well from what I've read (they'll actually melt the plastic together), but you might just want to go with PL Premium because it's known to work.

[aEx155]

From use of hot melt glue, the seem to, like you said, melt the plastic together. The only problems are 1) the melting deforms the bottles = not good 2) the bond isn't strong. The only way to melt the plastics together would be heating them up and pressing them together; otherwise, they just sit on top of each other.

I'll take a look at the link; glue seems like the only way to go...

[Ben]

That's something I hadn't considered. Melting will deform the bottle. You'll have to go with something else I suppose. General epoxies should work well but the typical amounts you can buy might be too little. If you can find a plastic welder that bonds PET plastic then that should be the best thing, but I'm not sure if a product like that exists. IPS Weld On doesn't seem to weld PET plastic.

Though, PL Premium doesn't say anything about bonding plastic well but it seems to work. I suppose experimentation is the best way to find something out.

[aEx155]

Okay, last update:

I got around to updating the setup a bit. To prevent a failure like "the incident", I didn't screw the bottles in a high degree. Instead, I hot-glued the coupler's halves together, then used copious amounts of teflon tape and thread seal paste on the bottles and made them fit. The fact that the bottles aren't screwed in as much puts less stress on the couplers. I've also dded support for multiple bottles (currently, I have three), upgraded my 1/2" flexible sprinkler hose to actual garden hose (not much improvement though) and I've added backpack straps...

...unfortunately, the backpack straps were the cause of the most recent failure. I duct-taped the straps (twine wrapped in two layers of tape like this: tape >|o| <tape and the middle is the twine) to the bottles, but that meant the coupler was under tension from the weight of the whole thing. The hot-glue came off, leaking all the pressure (and water) out...while I was wearing it. ("It's leaking all over my butt!")

I was happy with the shot time increased with a total PC capacity of about 6 liters (1.58503231 gallons) and total water amount of about 4.5 liters (1.18877424 gallons), and it's really cool to empty the gun using the fill valve connector (I believe it's a 1/2" conical-type nozzle; works really well when there's enough pressure)

One thing I've discovered is the weakness of the couplers I've been using; when the manufacturer assembles the pieces, it involves pushing a large piece (male end) into a slightly smaller piece (female end) which ends up stretching the coupler, making it prone to separation. I noticed it too on the coupler I used to connect the hose to my gun section, which means I need a way to fix it (possibly, hose clamps on the coupler, or gluing it together with PVC cement (would that work?))

Pictures:





Pictures I want to point out:

(1st col., 1st row) Multiple bottle support was achieved by using a nother tee to add things to
(2nd col., 2nd. row) The duct-tape straps are awesome, aren't they?
(2nd col., 3rd row) Looking closely, you can see the part where the hot-melt-glue was torn off and started to leak
(4th col., 3rd row) At 60 PSI, the coupler is showing signs of stress. That's the one leading to my hand help portion, like I said earlier.

[SilentGuy]

I can wait to see the pictures, but I'm wondering, did your coupling actually come apart? Or was that just a (good) observation of the plastic seams on the couplings?

Hmm...it sounds like you could easily add a pressure gauge to your tanks. Boyle's Law says that for gases, P*V = k, where P is pressure, V is volume, and k is a constant. If P for an empty chamber is 15 PSI (the pressure of the atmosphere at ground level), then P when the air is in 1/4 the volume should be 60 PSI. The pressure gradient (the difference between the absolute pressure and the atmospherical pressure) is 45 PSI. You could make markings up the side of the chamber, up to 45 PSI when the water is 3/4 of the way to the top.