drink maker brainstorming

[Andrew]

How does one seal the gap between the "straw" leaving the T fitting and the T fitting itself? Would it make sense to use a T-fitting with male threads in conjunction with a threaded end cap that I drill (and seal) a hole through?

Sorry, missed this.

If you use a straw then the option that springs to mind is glue. You could use a hose barb and run the straw through that and then glue (kinda like atvan's idea but the other way round). You'll have more contact surface so it should hold more pressure than just gluing it straight into an endcap.

Also, your most recent design will not have any purty bubbleses.

True, and some would consider that the best bit!

[briancof]

@Andrew:

You're talking about just connection to a two-liter bottle, right? The biggest challenge I have is of how to get liquid out and gas in through the same fitting. Conceptually, it's no problem (and one could CAD up a part that would very obviously do the job) but it's tough putting something together with off-the-shelf parts that gives you any degree of pressure confidence. Not that the pressures in question are extreme but, you know. The right side of my T fitting, yes, would have to be somehow sealed exactly as you've drawn it.

@Atvan:

I'm sort of following your idea with the hose barbs, but might need a picture to fully understand. How does the barb interface with the T fitting?

Thanks all!

[atvan]

Sorry, I was a bit rushed earlier, I kinda figured It would be confusing. Basically, it was a way to make your picture work. I know for a fact that all the materials exist in my design, always a plus. After some testing in my basement, I figured out what works. If you can find a tee that has a 3/4 female threads in | of the T and 1/2 female threads in the __ of the T, that would be perfect. If not, a 3/4 female threaded tee with one of the __ ends reduced down to a half inch female thread will do. I discovered that a hose barb for 3/8 vinyl tubing with 1/2 inch male threads will actually accept 3/8 tubing in both ends. A hose clamp will hold the one end, while you will need glue for the other. This, however, will allow one to essentially thread a tube through a fitting with a good seal.

[Andrew]

You're talking about just connection to a two-liter bottle, right?

I don't think I was?

I meant use a straw, or vinyl tubing, to keep air and liquid seperate. The straw goes right to the bottom of the bottle (to drain the liquid) and the compressed air comes in through the t fitting (around the straw of liquid). if you're worried about the strength of a straw, in relation to pressure, you could run a smaller PVC pipe back into the t fitting connected through an endcap (using a male threaded coupling) and connected to another piece of PVC pipe on the other side (using a female threaded coupling) with washers to seal.

It may even be better to turn the design upside down so all of the liquid drains out through the t fitting and air is pumped in through the smaller PVC pipe. You get to use all of the liquid and get the bubbles aswell then!

[briancof]

Sorry, I was a bit rushed earlier, I kinda figured It would be confusing. Basically, it was a way to make your picture work. I know for a fact that all the materials exist in my design, always a plus. After some testing in my basement, I figured out what works. If you can find a tee that has a 3/4 female threads in | of the T and 1/2 female threads in the __ of the T, that would be perfect. If not, a 3/4 female threaded tee with one of the __ ends reduced down to a half inch female thread will do. I discovered that a hose barb for 3/8 vinyl tubing with 1/2 inch male threads will actually accept 3/8 tubing in both ends. A hose clamp will hold the one end, while you will need glue for the other. This, however, will allow one to essentially thread a tube through a fitting with a good seal.

That makes sense, thank you. In theory, if the T had a long enough female thread run, one could attach barbs for 3/8" hose to both the inside and outside, but glue probably does the trick in the likelier case where there's room only for one. Any intuition on best glue type for (eg) vinyl to brass?

[briancof]

@Andrew

I can almost picture what you're describing with the PVC/endcap interface but am a little bit dense/new-to-this and might need a diagram to fully grasp. In the short term, I think the current "straws" (not drinking straws, of course, just seemed like an intuitive label for them) are of small enough diameter in relation to the pressures in question that they're so far holding up. That may not be the case if we want to move to higher flow tubing, though, for (eg) beer.

[atvan]

There would be no way to attach a barb to the inside of the fitting.

If you can get some plastic hose barbs, that would probably be better. Where are you again? They should be pretty easy to find in the US.
Epoxy might work, but anything to seal it should be fine, it holds together fine on its own.

[Andrew]

I can almost picture what you're describing with the PVC/endcap interface but am a little bit dense/new-to-this and might need a diagram to fully grasp.

Ask and ye shall receive:

You can probably tell, that's quite a few washers and connectors (and possible areas for leaks!). Whilst drawing this diagram (and the similar one for CPS1200fann) and from reading atvan's posts on tubing barbs and threaded tees, I couldn't help thinking how over-complicated my solutions were becoming. The following drawing is simpler, should hold more pressure, should be less prone to leakage, uses up more of the liquid, and lets you have the cool bubble effect!

The dark grey piece in the threaded tee is just a plastic disc (anything waterproof will do really). You might not need this, it may only need to be smaller, or it may need to extend further into the neck of the bottle, depending on how quickly you want the liquid to be dispensed. It just 'encourages' the incoming air to travel upwards into the bottle rather than straight into the exit tubing.

The tee is (as atvan suggested) a threaded tee. I don't know exactly the size you'll need though. The barbs are threaded directly into the tee (you can use reducers if you need).

As long as the exit and entry tubing reach a point higher than the level of liquid in the bottle, the liquid will not be dispensed until the bottle has air pumped into it. The only extra thing you need is a stand of some description (two plant pots glued together with a hole in the bottom of each?) but that shouldn't be too much of a problem.

[atvan]

If you use a 3/4 threaded tee, you won't even need that cap adapter.

Now that I think about it, unless you draw out the drinks at a very high flow or a very low air flow rate the extreme bouyancy of the bubbles and pressure in the air tube should remove the need for any type of straw or seperator.

[Andrew]

If you use a 3/4 threaded tee, you won't even need that cap adapter.

Even better! I'm pretty sure you can get 3/4" hose barbs as well, so that means one less place to leak.

By the way, how did boring the cap go? It'll probably be fine for the prototype, and you could use the more recent ideas for the finished thing (Or you could make one prototype of each design and describe the benefits and disadvantages of each?).