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Originally posted by Ajax:
@kkeerroo

Your system is going to be around 100 psi. But that is not the only factor for the rules. It will totaly depend on your pneumatic configuration to determine what rules comply to your robot and which ones don't.

This is the hard part with pneumatics. it is the hole system that needs to be reviewed not just parts of it.

As some parts could be safe in one configuration but unsafe in another configuration.

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To all . Ignore him. He must be grumpy today.

Andrew, SHUT UP!

ROFL surely you've worked out what ever you're arguing about... go build a robot or something
6 pages XD
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YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH

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Originally posted by Daniel:


To all . Ignore him. He must be grumpy today.

Andrew, SHUT UP!

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Originally posted by Woody:

As to the locking pin ...... over in the UK we prefer the raised flipper arm approach.

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Originally posted by Ajax:

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I didn't use the SodaStream's relief valve because I had no easy way of connecting a hose to it, and figured that it wouldn't offer any more reliability than the rest of the system.

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Pesonaly I think it should be a normaly open vent used.
Apply power to close the vent.

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Improve safety. Try and build systems to be in a safe state when no power is connected.
An open vent would do this.

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Yes but at some time the robot needs to be turned on.
If there is a locking pin in place, it just adds that little bit of extra safety.

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At the moment if Stealth is fired and never makes it to 75% extention, for instance stuck under rail. fight would stop then kick it to resolve problem.

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but if there was a manual over ride or timer in place then you have control to reset pneumatics and continue with out stopping the fight.

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Dumhed, your system wasn't built to the rules, which is pretty stupid

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If I recall correctly a central locking actuator fires the bottle valve.

The sort that has a small PMDC motor and spur gear reduction driving a rack.
These actuators only require the lightest pressure to move them when they aren’t powered up.
The spring loading in the bottle valve is more than sufficient to return the actuator to the off position and it is only when the actuator is powered up that it can open the valve.
If the bot is electrically powered down and undamaged I think a misfire is virtually impossible.
Combing this with parking the flipper in the extended position and if feasible a venting valve that is open at all times when idle and there is not a lot to worry about.

Using the soda stream PRD is an obvious choice and is the way to go but as I haven’t got my hands on one yet I wont 100% endorse it.

I hope we aren’t all bidding against each other on e bay.

One reason I think formalising the Soda stream sitch is that they are still readily available, my local supermarket sells them and has gas bottles.
So for a low powered flipper there is potential for a safe entry-level CO2 system at a low cost. $100 at the supermarket gets you a new unit with one 40 litre bottle and $130 gets you one with 2X 40 litre bottles on line New.

Ask around there is a lot in the back of kitchen cupboards.

Personally the vac hose appeals to me as it combining the function of over pressure protection cushioning the shot of gas and connecting things that would need piped up anyway, simplifying and using things that have to be there anyway is the way I like to build. After all you could put a stronger spring in a PRD just as easy as cheat and use reinforced hose. Be a bit obvious if you start Launching opponents with a sodastream bot

Brown Teck as Brett calls it “ Mote in Gods Eye”.


One other point, AFAIK the normal failure mode of commercial rams used in Bot flippers is to pop the ends off them.

The tube doesn’t burst; this is aggravated by heavy flipper attachments not wonting to stop.

I think Stealth has an extra bump stop between the piston and the end of the ram. Its flipper is very light and of corse venting the gas slightly before the limit of travel also reduces the shock loads on the ram, Not necessarily all points to try and legislate but more proof that Andrew understands the forces involved.

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Originally posted by DumHed:
It will prevent things like the ram being blown apart, but with a ram rated for operation at 150psi I don't think it's going to blow up before that unless it's been damaged, in which case I'd be just as worried at 100psi as I would be at 200psi.

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Originally posted by Rotwang:

I hope we aren’t all bidding against each other on e bay.

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Modifying the ram will certainly void the certification, but it's still a fairly safe bet that in general it's still the same ram and will handle the same sort of pressures.
If the weakened area is under pressure at all, the vents will also be open, so I don't think it's really reducing the safety of the ram.
I'd be wary of anyone putting massive holes in a ram, but it's not necessary (and will cause the seals to die very quickly so it's not preferable to do in the first place)

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I think Stealth has an extra bump stop between the piston and the end of the ram. Its flipper is very light and of corse venting the gas slightly before the limit of travel also reduces the shock loads on the ram

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Here's some Sodastream valve flow information based on a rough test that I've just done.

The test was conducted with the std Sodastream lever valve attached but without the small bore pipe........ and was performed twice using a full cylinder for each time.

The bottles were weighed before and after ...the result is an average of the two.

Depressing the valve for 15 seconds caused 0.15kg of liquid to be converted to gas .

This equates to 0.55 liter of gas per second @ 150 psi or 0.825 liter @ 100 psi .... Giving the Sodastream valve a Cv of around 0.003.

A good ram fill time is down in the tenths of a second.

An excellent match for this flow would be a 50mm x 50mm ram assuming you that can actually get the valve open quickly enough .

Cheers Woody

I think from memory Stealth still uses the small bore pipe as a flow restrictor .

I won an old Soda stream for $12 on ebay, + postage, around $25 all up.
The supermarket has changeover bottles for $11 so Ballistic might be in for a refit soon.

We were planning an all-electric replacement for the current version of ballistic but as the Soda stream setup is so compact we will have a play with the soda stream in the old version and have a think about it.

Thanks for doing those flow tests Woody, all good information.

At the moment I am thinking adjustable timer to fine-tune the shot of gas.

The door lock actuator takes time to move and the firing valve will take time to close, I don’t wont to waste gas and if the flipper is jammed under the arena edge I would be happier if only the set pulse was fired rather than vent excessive amounts of gas.
A limit switch as a back up is a possibility but they can be damaged easily.

oh yeah on Stealth the valve is only open while I hold down the fire button *and* the limit switch is not reached, so if it's jammed under something and doesn't extend, the gas is still turned off as soon as I let go of the button. I may have not made that clear before.
So, it does have a timer, which is me
The system is controlled remotely, but the limit switches make sure it doesn't waste gas if I hold the button too long or the control stops working (although it does default everything to off if it loses signal)

I think the sodastream setup could work very well in Ballistic!

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I think from memory Stealth still uses the small bore pipe as a flow restrictor

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I don’t think I totally trust Matt to take his finger off the button in the heat of battle.
If any of the electronic types out there wont to help me out with an adjustable 555 timer type circuit, I would be thinking of it driving a changeover relay so the vent valve is powered up as soon as the bot is turned on.
A problem with relays of course is they take time to work but as everything is going to take time it probably doesn’t mater.
Just turn the knob till it fires reliably.

Bottle temperature, bottle volume, if the bottle is venting liquid or vapor, I can see that the manual control has a lot going for it. Maybe the 75% sensor is the go.