Coke bottle rocket

[Jon GibbsParticipant @jongibbs59756]

Well I'd consult NASA… **LINK**

Yes, really

Jon

[davebParticipant @daveb17630]

Posted by SillyOldDuffer on 11/10/2016 14:24:51:

As the thread is about Coke Bottle Rockets, I wonder if the group could put their minds to optimising CBR performance? For starters:

• What's the burst pressure of a 2L coke bottle?

You can check this with our aeromodelling colleagues. 2L coke bottles used to be used as gas tanks for CO2 motors. I don't recall the figure but it was very much higher than I expected.

Dave

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jon Gibbs on 11/10/2016 15:33:27:

Well I'd consult NASA… **LINK**

Yes, really

Jon

Thanks Jon, very useful link!

As guidance it suggests a distance of 102m at 80psi, also that bottles should never be pressurised above 90psi. (As there are children involved, I assume this implies a safety factor of 2 or 3, and that bottles will fail somewhere between 200 & 300psi )

I'm just off to see if I can get the simulator to work: it appears to be the last word on bottle rockets.

Dave

[SillyOldDufferModerator @sillyoldduffer]

Posted by duncan webster on 10/10/2016 15:55:19:

Posted by SillyOldDuffer on 10/10/2016 13:35:09:

Posted by SillyOldDuffer on 10/10/2016 12:46:57:

Posted by Robin Graham on 10/10/2016 00:49:41:

…

but for simpler solutuion, which actually does the arithmetic for you as well see SmathStudio.

…

Duncan,

Many thanks for the link to SmathStudio which has filled a gap in my software armoury.

It fired up straight out of the box on Windows 10 and experiments with it have all been very positive. Not too difficult to drive and it even does units. If only such a thing had existed when I was struggling with maths at school – mankind has come a long way from my error-prone fights with a slide-rule and 4-figure Tables.

For linux fans, it runs as a mono application. Ubuntu 16.04 automatically downloaded and installed the mono run-time but then SmathStudio crashed with an exception equivalent to 'missing DLL'. This was easily fixed by manually installing the complete mono package with 'sudo apt-get install mono-complete' Limited testing hasn't found anything wrong with the mono version on Ubuntu.

The chief shortcoming is that the display is utilitarian. Perfectly understandable but nowhere near as good looking as latex. The two complement each other though: do the sums with SmathStudio, and type them up with latex when you need publication quality.

Thanks again,

Dave

[DanielParticipant @daniel]

More basic and very little precision,

I made this bottle launcher for the children, a little while ago

Not quite ready for a moon trip yet . . .

[SillyOldDufferModerator @sillyoldduffer]

Like it!

[Neil WyattModerator @neilwyatt]

The great Aeromod Doug McHard used to wrap his bottles in fibreglass tape before installing them inside model aircraft.

Neil

[duncan webster 1Participant @duncanwebster1]

SoD,

I'm glad you founf SMath useful, Mathcad gives better presentation, and draws graphs, which SMath seems to struggle with. If you're really into it it can do programming as well, but that makes my head hurt, I'd switch to C for that

On the coke bottle front, several clubs have in the past had a competition for how far you can get a rail vehicle to travel with the stored energy inside a coke bottle. The pressures quoted frightened the life out of me! Plenty of scope for reaction rockets, little air motors whatever

[HacksawParticipant @hacksaw]

Cripes !! Those kids haven't got eye protection or hard hats !! And the rocket' going to hit the upper window!

Edited By Hacksaw on 12/10/2016 22:21:00

[Mike StaceyParticipant @mikestacey71444]

"Made the launcher for the children"……I've used that excuse too!

[DanielParticipant @daniel]

[DanielParticipant @daniel]

Posted by Hacksaw on 12/10/2016 22:19:39:

Cripes !! Those kids haven't got eye protection or hard hats !! And the rocket' going to hit the upper window!

Edited By Hacksaw on 12/10/2016 22:21:00

It's trajectory was erratic, to say the least, due, mainly, to it's complete ommission of a nose cone

However, it's "fuel" did always get it over roof height, after which they were tucked under the rather generous eave.

As long as they didn't move, they were reasonably safe

All the best,

Daniel

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