SpudFiles

Like the title suggests, this is the best looking way I could figure to attach a coke bottle to pipe fittings. All the other ideas I keep seeing involve just epoxying the hell out of the bottle into the pipe fittings/pipe, so I just decided to throw together a how to on how to do it and make it look nice.

Tools

• A sharp utility knife
  A pencil
  A black marker (not permanent, just for ink transfer marking)
  A file
  Sandpaper (medium grit)
  A hacksaw
  A mitre box (if available)
  A ruler or set of calipers (accuracy not too crucial)

Materials

• Two or more coke bottles (they're trash, don't complain) with caps
  A scrap length of 1/2" SCH-40 PVC pipe (pressure rated)
  A 3/4" x 1/2" SCH-40 spigot x slip PVC bushing
  A 3/4" SCH-40 PVC male adapter (slip x mnpt)

Process
Like I said, this is just to make the overall connection look better. It's not exactly a revolutionary process. Some might be familiar with it, even.

To start, cut off the neck of a coke bottle with the utility knife. This isn't going to be the one to be attached to the gun/pipe, so don't waste too much time. Apply black ink (from the marker) to the end (as flush as possible!) of the scrap length of pipe. With the cap on the bottle-neck, push the pipe in from the back until it presses against the inside of the cap and leaves the ink.

Take this cap off, and discard the bottle-neck. Use the utility knife to cut out a hole the same size as the outside diameter of the 1/2" pipe (imprinted in ink). If you have one, a small gasket cutter can do this as well.

Attach the cap with the hole in it to the bottle you intend to use for the chamber. Screw it on as tight as you can. Push the pipe into the cap and bottle neck so that the bottom is flush with the bottom of the cap (out of sight). Mark this point on the pipe with a pencil.

Take a look at your bushing. It should have either a hex or round lip on the end, which will wind up (usually) flush with the fitting it goes in. Measure the length of this portion, and mark that length with pencil from the BACK of the bushing. Use a hacksaw to trim off the back of the bushing at the mark, and then use a file and sandpaper to reduce the "rim" at the front to the same outside diameter as the rest of the bushing.

Ensure that the bushing fits flush into the male adapter.

Measure the socket depth of the bushing. Subtract about 1/32" off that measurement, and mark this measurement past the mark you have already made on the pipe. Cut the pipe here, and remove any burrs.

Roughen up the inside of the bottleneck and the lower portion of the 1/2" pipe (that you measured first) with sandpaper. Clean with soap and water, and you're ready to roll.

Mix your epoxy, and apply to the inside of the bottleneck and the outside of the pipe. Push the pipe into the bottleneck until it is against flush with the bottom of the cap (or lined up with the mark you made earlier), and twist to remove any air pockets. Wipe off any excess epoxy (you can use acetone to get the surfaces really clean), and allow the epoxy to set up. This time will be marked on your epoxy tubes.

After the epoxy has set up, solvent weld the bushing onto the length of protruding 1/2" pipe. Allow this to set up for about five minutes, and then solvent weld the bushing into the 3/4" male adapter. Of course, if you have clear primer, that would be nice, but if you're using purple primer, make sure to tape off all exposed surfaces and wipe off excess cement and primer after each joint is done.

Voila! That is it. Let the entire assembly cure for 24 hours or the marked cure time on the epoxy tubes (whichever is longest), and it will be ready to use. Simply screw the 3/4" male adapter into the rest of your gun.

Additionally, some small screws can be tapped and sealed with rubber washers or more epoxy through the bottleneck and 1/2" pipe, for an extra safety factor, but as long as you take the time to prepare the surfaces beforehand, and mix the epoxy correctly (syringes suggested), then you should be perfectly fine without these screws.







Below is a picture of the final product. I am planning on making a gun like this next paycheck, and will have an updated full tutorial by then. For now, a crude drawing will have to work, along with the (I think) comprehensive instructions detailed above.

The good thing about this design is it is sooo picky. You can scale it down as much as you want, and compromise as much as you want as far as aesthetics, and the general idea still works.

that looks great; you can easily change out bottles after they explode or are dropped/damaged.

Eh... no.

You'd have to build an entirely new bottle/adapter assembly if that happened, unless you have a magic way to melt epoxy.

But, 20-oz bottles shouldn't explode unless you're using a lot of pressure (over 80 PSI).

oh, I misinterpreted that the 3/4 adapter went over just the cap. silly me

perhaps it is time for a 1" and some thinwall 1" pvc(or filed-down-on-the-inside sch40) as a bushing.

With this design, the 1/2" SCH-40 is epoxied inside of the bottle neck.

markfh11q wrote:Eh... no.

You'd have to build an entirely new bottle/adapter assembly if that happened, unless you have a magic way to melt epoxy.

Actually, epoxy is very heat sensitive and (at least w/ metal), a torch, heatgun or similar device is very effective at thinning epoxy. However, given the circumstances, it probably would not work in this application for obvious reasons.

Well written howto. Only downside is that coke bottles have the known safety issues and thus I'd rather see people just use PVC instead.

I don't see anything wrong with a 20-oz coke bottle at 80 PSI. They've been used before with very good results. I'd rather just use PVC as well, but Coke bottles add a certain something to small cannons. (Don't say shrapnel and contusions)

It's interesting to see how opinions on construction materials/practices change in this community over time.

markfh11q wrote:I don't see anything wrong with a 20-oz coke bottle at 80 PSI. They've been used before with very good results. I'd rather just use PVC as well, but Coke bottles add a certain something to small cannons. (Don't say shrapnel and contusions)

It's interesting to see how opinions on construction materials/practices change in this community over time.

nothing wrong with coke bottles, you can fibre wrap them as well if you want something more durable.

markfh11q wrote: But, 20-oz bottles shouldn't explode unless you're using a lot of pressure (over 80 PSI).

Usually, 80 PSI isn't considered a whole lot of pressure. Yes, Coke bottles are cheap and readily available, but plastic shrapnel is not fun. A PVC tank will only cost you around ~$5-6, and is MUCH safer than a Coke bottle.

nothing wrong with coke bottles, you can fibre wrap them as well if you want something more durable.

Actually, a fibre wrapped Coke bottle will probably end up being more expensive than an equivalent size PVC tank.

Actually, a fibre wrapped Coke bottle will probably end up being more expensive than an equivalent size PVC tank.

Agree on that one.
You could also fibre wrap PVC for even MOAR strength. (Or just go metal )

Well, I finally built a prototype (the actual cannon it's going on is almost done as well).

I think what you guys don't realize is that, yeah, a PVC chamber is just as cheap, but sometimes it's fun to try new things and experiment. I made a combustion out of a JIF peanut butter jar and it wound up costing me more than a comparable sized PVC spudgun, but I was fine with that because, well, it was a freaking peanut butter jar and a piece of a 2 liter bottle....

Anyways, enough blabbing, on to pictures.

Its peanut butter spudding time!

That budweiser bottle sleeve looks funnny on it.
Though the clear plastic is just the one thing in which soda bottles are superior to pvc: you can look at the combustion flames and sparks on a combustion or water vapour on a pneumatic.
Yes, I know clear PVC exists but that is very expensive for most of us.

My method of attaching the PVC bottle to the pipe probably isn't so aesthetically pleasing, but it's a lot simpler.

I simply filed the bottle threads off until the bottle made a tight fit into the fitting. Once so, the part of the bottle going into the fitting would be epoxied and the bottle stuffed in. The other end of the fitting would then be connected to a valve or to something else eventually connecting to a valve somewhere. Any gaps in the epoxy could well be filled by more epoxy later on.

http://www.spudfiles.com/forums/simple- ... ter,0.html.

I made 4 such guns for trials purposes. I don't ever recall having a leak with the guns except for defective schraders lol (another problem in itself). They are being phased out of service.

However, I don't really understand the need to connect a soft drink bottle unless you're trying to be innovative or pipe is expensive in your area. As far as my case is concerned, extra PVC pipe for a chamber costs about the same as the extra fittings needed to adapt the bottle to the pipe. Higher pressure tolerance and looks more professional too, a big thing when I'm recruiting for my science club.