Pneumatic

[woody]

As the current FRA rule set stands Stealth appears illegal on 2 points ........a seperate shut off valve and a low pressure PRD ......with the possibility of a 3rd infringement with the vent valve rating.

8.6.
Gas cylinders that do not incorporate a valve (for example: the gas is released as soon as the cylinder is screwed into it€™s mating pneumatic connection) such as found on disposable welding bottles and €˜fizzy drinks€™ machines must have an additional remote isolation valve accessible from outside of the robot.

And
8.8.
A certified pressure relief device [PRD] must be installed in each part of the pneumatics system where a different operating pressure is used (operating pressures separated by a pressure regulating device).

So it needs to be argued that the additional remote isolation valve isnt needed in this instance.

A PRD is in my opinion a must .......it isnt possible to quantify a bit of low pressure rubber tube that will rupture @ ??!!** psi as a safety device.

If it had a Low Pressure PRD and a vent valve to match the PRDs rating ....Id be happy with it.

Woody

Edit
It should be possible to combine the function of pressure dump valve ...... in the unlikely event of the flipper being locked down ... with the vent valve IF it has a manual overide.

(Message edited by woody on September 21, 2006)

I dont think you have ever seen a Sodastream bottle - It screws in to a fitting yes, but it also has a release valve built in to the tank. In Stealth the valve in the bottle is the firing mechanism and everything past the valve is vented and low pressure. Fitting a second valve after the tank makes the system LESS safe as there is now a section of pressurised tube between the tank and the valve.

In this bot, there is also a dump valve just before the ram that is open at all times other than during the firing cycle; it opens to retact the ram and stays open until the next firing. I believe it failsafes open by spring tension.

[woody]

I dont think you have ever seen a Sodastream bottle ........

Who is the you in that sentence?


(Message edited by woody on September 21, 2006)

Err, obviously that would be Woody? Im not saying that tanks like those refered to in rule 8.6 dont exist, but the tank in Stealth does have a valve and so 8.6 cant really apply.

[woody]

Nick ....Perhaps I can interest you in a visit to one of my webpages ?
http://www.teamonslaught.fsnet.co.uk/co2_info.htmhttp://www.teamonslaught.fsnet.co.uk/co2_info.htm



(Message edited by woody on September 21, 2006)

[maddox]

The original valve in a sodastream bottle is a pin valve. Turn the bottle into the socket and the valve opens.

If something is wrong then, it will go wrong with the hand in the robot. If a seperate isolation valve is used this risk a lot less. Especialy the screw valves we recomend have the advantage that you can open the system very gentle.

Nick, Woody was using sodastream bottles in the earliest days of Robot wars, and probably before. This means at least 10 year of experience.

There are many people on this forum who have an enormous amount of experience with pneumatics. You read the name and you know that you can respect the information they give. It does take some time to learn who you can trust.

A seperate manual valve is essential for pin valve bottles.

Not only does it make the system safer for arming, but pin valves often freeze open. A manual valve means the bottle can be isolated and safely removed.

[woody]

@ Nick .....
Ill try and explain my earlier post.

As the current FRA rule set stands Stealth +1>appears illegal on 2 points

Im fairly sure that rule 8.6 is applicable to Sodastream bottles with pin valves and should perhaps have the addition of ..... see words in red.

8.6.
Gas cylinders that do not incorporate a hand operated valve (for example: the gas is released as soon as the cylinder is screwed into it€™s mating pneumatic connection) such as found on disposable welding bottles and €˜fizzy drinks€™ machines must have an additional remote isolation valve accessible from outside of the robot.

So it needs to be argued that the additional remote isolation valve isnt needed in this instance.

The basis for this is .. as you pointed out ... the gas isnt released as soon as the cylinder is screwed into it€™s mating pneumatic connection.

My finishing line of that post....before the additional edit ...

If it had a Low Pressure PRD and a vent valve to match the PRDs rating ....Id be happy with it.

I must point out that I have NO official standing in the FRA.

Regards Woody

A soda stream, and most, if not all legal CO2 (and N2O) bottles have a burst disk, rated at +/- 200 bar- except for older bottles, who can have lower rated burst disks at 135 bar.
If you can get 70 bar/1000 psi burst disks to replace the 200 bar ones, these will be accepted as a PRD in the FRA rules (as far as I understand). Problem is, once it goes, say bye bye to all the CO2 on board.

Using a rubber tube with a estimated burst pressure around 1000 psi is not accepted.