While I have been working on an adjustable nozzle flow, I have been thinking that is would be nice if it would be possible to make a spliced pair that could be taken apart and reassembled. I am thinking trying something like in this illustration.
resealable spliced pair.png (36.23 KiB) Viewed 114 times
I don't know if this is a very good idea or not. While I have nothing in the drawing on how to hold the two bottles together, I am still thinking about how to hold the two bottles together. I am thinking about using PET strap of some sort.
If you have heard of someone else trying to make something like this, please let me know.
-DogLover
-Blenderite
Check out my YouTube channel: https://www.youtube.com/c/Blenderite
it's an interesting idea, you don't have to replace the whole rocket if a part gets dammaged. You could have a pipe thruogh the centre that threads onto either end. I havn't heard of anyone attempt a removable splice.
Ascender Water Rockets
http://ascenderwaterrockets.weebly.com/
https://www.youtube.com/channel/UCS2NHXS-VFxEux70DCINR0w
While I have been working on an adjustable nozzle flow, I have been thinking that is would be nice if it would be possible to make a spliced pair that could be taken apart and reassembled. I am thinking trying something like in this illustration.
resealable spliced pair.png
I don't know if this is a very good idea or not. While I have nothing in the drawing on how to hold the two bottles together, I am still thinking about how to hold the two bottles together. I am thinking about using PET strap of some sort.
If you have heard of someone else trying to make something like this, please let me know.
-DogLover
There is a good chance that would work, but you could improve the odds by putting a strap of tape around the outside of the joint. If you use fiberglass reinforced packing tape it would probably work best. You need to keep the outside bottle from stretching, otherwise it will swell up and lose friction against the rubber seal.
I once tried to do something similar, though I really wasn't trying make it completely repairable. I think it will be difficult to get this to the point where it actually saves work over splices with PL, but that doesn't mean it's not worth a bit of dabbling.
What I tried in the past was to heat-shrink a groove for an o-ring in the inner bottle. I secured the bottle, with it's end cut off, in a power drill and had it rotating about it's axis (as fast as the variable-speed hand drill would go). Then I took one of those lighter-sized micro torches and placed the flame near the end of the rotating bottle (about 2cm back from the very edge), and it melted a pretty nice groove in place (the PET didn't really melt, just got hot and shrunk in a narrow band). The groove wasn't the ideal shape- it's hard to get the sides steep, so once it was deep enough for the o-ring, it was quite wide. I did manage to get one pair put together that held air. If I recall correctly, there was no glue at all on the joint, just an experimental fishing line wrap on the outside to keep the two bottles together. Like I said, it held air with no leaks, but once under moderate pressure (about 60 psi I think), the inner bottle collapsed enough for the o-ring to push part way out of the groove and the seal was lost.
The reason I bring up this failed attempt is that an o-ring in the properly shaped groove creates a seal that is reinforced by the pressure. Since bottles are so flexible, I think you will need such an effect to create a working seal. If I could have put a more rigid ring inside the inner bottle to support the o-ring, I think it might have worked. With your seal, as it's drawn, it's not reinforced by the internal pressure. Although, the same issues of rigidity will come up no matter which way you go. Maybe if you put a rigid ring inside the inner bottle and used a couple wraps of fiberglass strapping tape around the outside, as USWR suggest, you could make your idea work.
I was thinking about the need to reinforce the bottles. The only problem with my design is that the PLP that I used to attach the rubber in place hasn't dried. It has been almost 48 hrs now and the middle is still soft. I might try waiting a bit longer and see how it goes.
I also thought of using an o-ring but I didn't want to go buy a o-ring that big. I think the inner tube will work if the PLP dries.
-DogLover
-Blenderite
Check out my YouTube channel: https://www.youtube.com/c/Blenderite
Actually, I've been kicking this sort of idea around but using some very strong double sided tape instead of the rubber. My focus is coming up with designs that can be built and launched in 1 hour. That imediately rules out PLP. I think the trick is going to be an outer PET collar.
The only thing I don't like about the double sided tape is that it would probably be hard to take it apart. It might be interesting to try some sort of sticky tape on the seam around the outside. That might help seal the edges. I hear that Gorilla tape is a super sticky duct tape. That could work very well. I might try using duct tape or electrical tape to help seal the seam. I will be experimenting this afternoon.
-DogLover
-Blenderite
Check out my YouTube channel: https://www.youtube.com/c/Blenderite
DogLover wrote:The only thing I don't like about the double sided tape is that it would probably be hard to take it apart. It might be interesting to try some sort of sticky tape on the seam around the outside. That might help seal the edges. I hear that Gorilla tape is a super sticky duct tape. That could work very well. I might try using duct tape or electrical tape to help seal the seam. I will be experimenting this afternoon.
-DogLover
We have seen Gorilla Tape, but have never tested it. It looked just like ugly colored duct tape. Are you saying that it is better than regular duct tape?
DogLover wrote:The only thing I don't like about the double sided tape is that it would probably be hard to take it apart. It might be interesting to try some sort of sticky tape on the seam around the outside. That might help seal the edges. I hear that Gorilla tape is a super sticky duct tape. That could work very well. I might try using duct tape or electrical tape to help seal the seam. I will be experimenting this afternoon.
-DogLover
We have seen Gorilla Tape, but have never tested it. It looked just like ugly colored duct tape. Are you saying that it is better than regular duct tape?
Yes it is much stronger/ stickier/heavier. Unless I'm going for decorative purposes, it's the only version I've used for several years now. Here's PM's evaluation..http://www.popularmechanics.com/_mobile ... ts/4306415
DogLover wrote:The only thing I don't like about the double sided tape is that it would probably be hard to take it apart. It might be interesting to try some sort of sticky tape on the seam around the outside. That might help seal the edges. I hear that Gorilla tape is a super sticky duct tape. That could work very well. I might try using duct tape or electrical tape to help seal the seam. I will be experimenting this afternoon.
-DogLover
We have seen Gorilla Tape, but have never tested it. It looked just like ugly colored duct tape. Are you saying that it is better than regular duct tape?
Yes it is much stronger/ stickier/heavier. Unless I'm going for decorative purposes, it's the only version I've used for several years now. Here's PM's evaluation..http://www.popularmechanics.com/_mobile ... ts/4306415
You should send that link to Mythbusters, so they can use it in their next great Duct Tape myth!
[quote="U.S. Water Rockets1"][quote="bugwubber"]Coke/mt dew splice with grease, zipties. failure: The inner bottle collapsed inward in two places as pressure was applied.[/quote]
Do you have a drawing or photo of the setup and failure? It's not exactly clear what was happening and why it should collapse like that.[/quote]
Sorry, my more detailed comment self destructed.
The bottles actually do better without grease. I use coke with mt dew because the coke bottle will go inside the mt dew without heat shrinking.
Interesting, just string (no grease) tied neck to neck collapsed the bottom neck but kept pressure.
I am attempting the same type of thing (using the same bottles, too ). I recently added an inner seal (of Sikaflex 11fc) on the inside of the outer bottle where the lip of the inner bottle will seat. Hopefully this will keep air pressure out of the space between each of the bottles.
Inner Seal
100_6671.JPG (1.33 MiB) Viewed 42 times
I also added two bulkheads to the inner bottle to help prevent it from crushing. One where the outter bottle ends, the other near the end of the inner bottle.
Inner Bottle Bulkhead
100_6673.JPG (1.32 MiB) Viewed 42 times
I will test it under pressure on my next launch date. Sadly, rain is expected all this week.
). I recently added an inner seal (of Sikaflex 11fc) on the inside of the outer bottle where the lip of the inner bottle will seat. Hopefully this will keep air pressure out of the space between each of the bottles.
