Yikes... Sparkling Ice 17oz bottle, 220 psi...

[Nick B]

We took a bottle and sleeved it into an identical bottle. No tape or fishing line, no fiberglass or Kevlar, no heat gun or boiling water.
220 psi so far without exploding. Not sure how much farther we can take it. We launched it at 220 and the fins sheared off. 3 launches at 175, no problem.

insane.

[Tony]

Video... or it never really happened.

[Nick B]

I don't host videos.


Many here have been mentioning Bill and Anti Gravity Research and their rockets, including wrapping in kevlar , nozzles, and fins.
Having researched his vids long ago, the renewal in interest here spurred my renewed interest. I had always wondered why it seemed like most of his bottle explosions, and my personal ones, have most often seemed to occur at the thin area of the pet bottles between the neck and sides. This area always seemed thinner to me, even though areas near the penticlaw also seem thin, and the manufacturing process seems to keep this constant. With that intrigue, I decided to take a 17 oz bottle and 2 liter and sleeve them with identical bottles. The 17 oz to keep the explosion decibels down during testing. with each one, I cut off most of the bottom of the outer bottles, and as little neck area as possible, so they would just barely fit over the neck of the inner bottles.
The 17 ounce bottle assy was tested, and this was the results. Far more pressure than I expected, since the thin penticlaw area just above the bottom is exposed, but has not ruptured. This smaller rocket has been re-fined and launched repeatedly without failure so far, and also, is using crash recovery and getting re-launched.
I expect similar results with the 2 liter, but maybe a tad less pressure limit due to the larger radius.
I had originally only expected a functional limit of about 160 psi.

[Nick B]

rocket in discussion...

[bugwubber]

I have those bottles. Hadn't tried to push the limits yet.

[Nick B]

although I have not tested the 2 liter yet, the results should be similar.

This still does not solve high pressures after splicing, nor does it for bulkheads since work to bottles for creating more pressure chambers by robinson coupling opens up the possibility of fractures. and robinson couplers are problematic at best. But it does open the door for simple, easy, higher pressure sustainers joined to simple, higher pressure 2 liters.



and that could relate to some interesting fun.




that and I love pushing limits with teenie tiny rockets.....

Maybe I can glass wrap these, n get 300-400 psi and get some new numbers for small capacity rockets....

[SaskAlex]

Nick- cool stuff. I also really like pushing the limits with small rockets and I've done a lot of "sleeving", too. I'm not too sure what exactly you are doing, though. As I gather, you are putting part of one bottle over top of an identical bottle, with no heating or bottle stretching or anything? Are you just crumpling the inner bottle while you put the outer bottle on? I always stretch my outer bottles just a little bit by pumping them up to high pressure (with water, not air), but then I need a heat gun to shrink it nicely over the inner bottle.

I also like crash recovery. It's amazing what a bottle can recover from. How much are your bottles crumpling on landing? I've always wondered how much of that a bottle can take. After a crash, I often inflate a bottle to about 20 psi and carefully take a heat gun to the creases. It greatly reduces the appearance of the creases and helps stiffen the bottle back up. I don't know if it actually helps in terms of holding pressure, but I think it does somewhat.

Alex

[Tony]

I misunderstood. When you said "no tape" I assumed you meant that you didn't use any tape. That silver stuff looks like tape.

Youtube will host your videos for free.

[Nick B]

I misunderstood. When you said "no tape" I assumed you meant that you didn't use any tape. That silver stuff looks like tape.

Youtube will host your videos for free.

I meant, no tape for reinforcement of the pressure vessel or rocket. Like strapping tape. The duct tape pictured is to hold the nose cone in place and provide some nose cone weight, for stability since the rocket is so short.


As far as hosting videos or pictures go, it's not about money. It's a choice for family privacy.

[Nick B]

Nick- cool stuff. I also really like pushing the limits with small rockets and I've done a lot of "sleeving", too. I'm not too sure what exactly you are doing, though. As I gather, you are putting part of one bottle over top of an identical bottle, with no heating or bottle stretching or anything? Are you just crumpling the inner bottle while you put the outer bottle on?

I'm just sleeving bottles with opposite tolerances, so far. So one was .010 larger than the other. I ended up with a very slight crease when overlapping the base area. That crease disappears when it is inflated with very very low pressure and is gone unless i squeeze the bottle when it is depressurized.

I always stretch my outer bottles just a little bit by pumping them up to high pressure (with water, not air), but then I need a heat gun to shrink it nicely over the inner bottle.

Sounds good. I'll need to try that.

How much are your bottles crumpling on landing?

This one is not crumpling at all when coming down about 300 something feet. The pepsi bottle nose cone does crush down though, during most landings. The bottle is just too light to receive much damage, it seems.

[NautilusRockets]

Sparkling Ice 17 oz (502.8 mL) Pressure Test

The label was removed and the ambient air temperature was 79°. The test was performed using a Clark cable tie retention method, a SKS Airbase Pro pump and a Craftsman 300 psi compression test gauge.

The bottle failed at 167 psi with the failure in a straight line from the base of the neck ring to a center point on one of the lobes on the bottom of the bottle. The failure was not along one of the two lines left from the molding process. The bottle separated completely from the neck ring and threads which were left completely intact.

Further tests are necessary to determine whether the failures begin at the bottom lobe or the neck. My thoughts are that if the failure starts at the lobe end of the bottle, reinforcement of the bottle at the bottom such as shown by Nick B could possibly account for the 220 psi failure reported.

[Nick B]

Actually, my bottle has not failed at 220 psi.


That only as far as I have gone with tests and launch pressures.



The limit may be higher, but I expect the thin bottom area between the the penticlaw and the sides to fail very soon.

[SaskAlex]

Mark- even though the ends seem like weak points, I think failures often happen from the middle. The middle often stretches the most (think of the bottle becoming more spherical). It would be an interesting experiment to just reinforce a band in the middle to reduce stretching and see how that affects failure. Of course, it all depends on the shape of the bottle. Often the neck area or base are just poor shapes and deform a lot there, too.

[Nick B]

roughly 260 psi launch 20 minutes ago with no problem.


But we maxed out our Topeak, and our current launcher gauge maxes out at 300.

[Nick B]

Well...

We lost the rocket last evening during the last high pressure launches. A wind change and change of range dropped it in a different area. It ended up somewhere in group of trees with a thicket of mallberry vines and poison sumac. We cannot locate it.


Time to move on to a 4 to 6 liter application.