hmm I would have thought (and I think I've tested) that the relief valve on the soda stream would be at a lower pressure than that, as it is the pressure that the glass bottles are pumped up to!
They are inside two layers of polycarbonate, but I'd still be surprised at a 200psi blow off.
Maybe the valve body is designed to leak pretty at that point?

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I would be happy if we could show that the tubing leading to the ram always fails at or below the working pressure of the lowest rated component. This test would obviously need to bedone behind a polycarbonate screen.

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"hmm I would have thought (and I think I've tested) that the relief valve on the soda stream would be at a lower pressure than that, as it is the pressure that the glass bottles are pumped up to!
They are inside two layers of polycarbonate, but I'd still be surprised at a 200psi blow off."

I tested one of the 3 that I have just before posting .....it was some 6 years ago since I last tested one and wanted to refresh my memory.

200 psi is the pressure that I got on the gauge to get it 2 open .......BUT ..It's always possible that the pressure I got is in error .....

I should perhaps test another to be sure.

Regards Woody

BUT ......thick glass bottles can easily take high pressures.


"A chemical engineer for the Owens-Illinois Glass Company and its Pacific Coast subsidiary, maker of Coca Cola bottles, explained how glass is manufactured and the methods used in testing and inspecting bottles. He testified that his company is the largest manufacturer of glass containers in the United States, and that it uses the standard methods for testing bottles recommended by the glass containers association. A pressure test is made by taking a sample from each mold every three hours--approximately one out of every 600 bottles--and subjecting the sample to an internal pressure of 450 pounds per square inch, which is sustained for one minute. (The normal pressure in Coca Cola bottles is less than 50 pounds per square inch.) The sample bottles are also subjected to the standard thermal shock test. The witness stated that these tests are "pretty near" infallible. "

well that's pretty impressive really!

It wouldn't have done me much good to use the 200psi relief valve and ~100psi piping then

I think they could be modified to drop the pressure. They have a pin which can be pushed in to open the valve manually too (which the sodastream machine does when the glass bottle is not in place).
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The Engine Whisperer - fixer of things

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Originally posted by DumHed:
I'm really surprised actually that this has all been brought up so far down the track after the event, but it is quite valid since there are a few more CO2 bots around these days.

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Durrrr....i dont supose they read and fully understood that the holes are there as a safety valve so the cylinder can never get full pressure after the ram is extended....

yeah I think the rule writers, be they engineers or not, have missed the point a lot of the time.

If every bit of non standard pneumatics gear needs independent testing, what about all the high rpm spinning weapons, etc which are also potentially dangerous?
Also, is there any pneumatic equipment that is rated for robot combat use?

It sounds to me like most of the proposed "tests" will be far more dangerous to perform than combat use of the bot!
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The Engine Whisperer - fixer of things

Dont you also have a vent valve that makes the system always open until the actual bottle valve is depresed and that operates with the same power as the activate valve?

I have a similar device on vertex's selfrighting arm, its a solonoide wired in paralell with the compresor motor. When the motor is switched on the solonoide holds a spring against needle valve that closes a port against the presure so the ram extends once its fully extended the neddle valve releases presure as it is pushed off its seat againt the spring with the system presure .As soon as the compresor motor stops the needle valve opens and lets the ram back down .

yep, exactly like that.

Whenever there is power the vent solenoid is open. (actually I think I added a switch that turns it off when the ram is fully retracted, so save power)
It closes while the ram is being fired, and opens as soon as the ram reaches the end of its stroke, or the fire button is released.
So, turning the controller off will make the system default to vent mode, and in a complete loss of power the main valve won't be able to activate anyway.
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The Engine Whisperer - fixer of things

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Originally posted by Totaly_Recycled:
Durrrr....i dont supose they read and fully understood that the holes are there as a safety valve so the cylinder can never get full pressure after the ram is extended....

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hehe it doesn't bother me, that's why I have a stupid screen name

I wouldn't be at all worried about the pressure on a hot day, as the sodastream bottle is designed to handle transport and high temperatures, and has an integral relief valve, which is brand new each time you get a new cylinder.
So, the pressure available from the bottle will be fairly stable, and shouldn't make too much of a difference to the bot's safety.

I can understand the concern about someone building the same sort of system without experience or safety, but that is a problem with any weapon design (or any potentially dangerous thing built at home).
This is where I see a benefit in things like vacuum line being used, because it's not really possible to misuse it in a way that it will not blow under high pressure conditions.
It would be easy for someone to damage or incorrectly install a pressure relief valve so that it wouldn't work.

If a rule was made that low pressure handling lines must be used in the system then there's a crude but effectively fail safe way of ensuring that massive pressures can't build up in parts that can explode dangerously.
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The Engine Whisperer - fixer of things

People just seem to have trouble getting used to the idea of non-traditional safety devices like using low pressure hose. If you had it stamped "certified for xxx psi" then there would be fewer problems

Has anyone mentioned exactly what happens when this tubing bursts? I would imagine its noisy but essentially harmless...
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

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*POP* hissssssssssssssss

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I just thought of something: On a hot day the plastic would be a little softer and would burst at a lower pressure, making it even safer - compensating for hotter gas tanks nicely!
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

yep.

it does get cooled down by the gas, but only while firing, and even then it's not much.

I get slight condensation on the pipes after a lot of flips, but no frost or anything.
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The Engine Whisperer - fixer of things

If you were writing a rules set for this class of weapon, what wording would you use so that, if a new builder turned up with this style of system, you would know it was safe for everyone there.
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So even the rain that falls isn't actually going to fill our dams and our river systems