Hydraulic pneumatic questions!

I am looking at running a high pressure pneumatic system using off the shelf hydraulic cylinders, which as I understand can be used as long as they are down rated by 50%

For off the shelf hydraulic parts, can these be modified, and to what extent, and does this required re-certification?
For example, boring out ports for faster flow rates.

If I were to manufacture my own cylinder, the rules state that all custom components 'must be pressure tested and certified to 120% of working pressure.'
Are there many places that will do this, and what are the typical costs involved?

Also the very best of luck to everone up filming at the moment!

I don't know what's possible in the UK, but on my island the only hydrostatic testing facilities are scuba or fire extinguisher companies, and they only test cylinders of known origin.
Even if I had to use their service, it's not just a matter of applying pressure up to 120% and that's it - expansion of the component has to be measured etc, ie specific data related to that particular component you designed.
This topic has been picked up before and from what I gathered, as long as the pneumatics don't look dodgy, and you know what you're doing it should be fine. Of course any EO will have the final say, so it's always a good idea to keep them in the loop on what you're building, as they and other experienced members over here may help you with any potential issues.

Hi,

I am also trying to make a robot using Hydraulics.

I think I am somewhat behind the curve on the need to know slope though...

I fI buy a hydraulic pump what do I need for the valve/switch thingy? How easy is it to connect one part to another and where do I go for those bits????

And then how do you show that it has been tested to 120% of the opperating pressure?

P.S. And how do you get the cost of it past the wife.....

I have a hydraulic pump and directional valve for sale, I'm going to get pics on at the weekend.

Quote:

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Originally Posted by terry

I have a hydraulic pump and directional valve for sale, I'm going to get pics on at the weekend.

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Ah, that sounds like the thing i need...

How much, what capacity, and stuff...

Thank you for your posts
I probably caused confusion by calling them cylinders, I am more referring to actuators (rams) than cylinders (fire extinguishers etc.)
I have a feeling the standard 3/8" ports on the off the shelf hydraulic rams are not large enough to allow the flow of a full pressure system. Am I correct?

For our hydraulic set up in Andron4000, we bought an all in one unit from related fluid power. It has a 2 liter tank, 5l/m and runs 24V from a solenoid, so we have a turnigy relay switch to throw it on and off.
The valves are attached to the all in one unit and I think from memory we plan to use another switch to throw them too.

I should probably add that we are yet to get any of this working yet as we are still waiting on our weapon parts to be manufactured!

http://www.relatedfluidpower.com/products/power-units/
https://hobbyking.com/en_us/turnigy-...-switch-1.html

The testing and certification was a concern for us on these, so we went for new, off the shelf parts and read the rules very carefully, and made sure to stay within them ie, no stored pressurisation, invertable, incorporated pressure releif valve, test gauge point

On topic, how have you solved inverted hydraulic reservoir problems? I've got a vary basic low tech method in mind, just wondering if there's a better (more reliable) option?

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Originally Posted by ThreeFingeredJack

On topic, how have you solved inverted hydraulic reservoir problems? I've got a vary basic low tech method in mind, just wondering if there's a better (more reliable) option?

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I am planning to use the pressure vessel reserve thing that exists in the hydralic world to be the reservoir rather than a tank but I hope that I can use the much cheaper plumbing expansion vessels. I don't know if the hydraulic flid will corrode the rubber air bladder in the expansion veseel....

The pump draws from the middle of the reservoir. As long as we arnt on our front we shouldnt draw in too much air.
We did think about expansion vessels, but thought technically a closed system might be considered pressurised...

Some of the heavies use an accumulator bladder.
Others have used a pneumatic ram, the piston just follows the oil.

Heard about 1 using an 8" inner biketyre.

Now that I have my idea all modeled up with the hydralic cylinders in place, I think I'm leaning more towards the idea of a low pressure (16bar) system.

I am worried about the hydraulic components being quite heavy and expensive, as well as the forces from the hydraulic cylinders self destructing with reactant forces.

I'm also concerned about freezing, as the port sizes seem relatively small for a full pressure system, and I don't really want to get into re-certification for modified parts where possible.


I can use a 50bar fire extinguisher co2 tank, or possibly this if it's allowed?

http://www.workshopping.co.uk/produc...LiEaAj_B8P8HAQ


...Through a regulator, (which I am struggling to source. BOC have quoted £280 for one)
into a 16bar low pressure buffer tank.

This should combat freezing and also the reduced force may mean I don't tear myself apart


In regards to the actuator, Norgen cylinders have an operating range up to 16 bar,and an 80 bore cylinder from norgen weighs less than a 60bore hydraulic cylinder.

Festo and SMC cylinders would be much cheaper to me as we use them all the time at work, however their operating pressure is 10bar I think, thought they are tested to 15.
edit: (Just had a check, they are proof tested to 15bar, fittings to 30bar, is this ok to use at 15 bar or do we need to stay at operating pressure?)

I am sure they are capable of taking the forces, where would I get these tested/ certified to stay within the rules?
We do CE mark at work, and use a lot of pneumatics.


With the low pressure system I should be able to use pretty standard pneumatic valves/ fittings/ lines


I get about 740kg running high pressure, and 400kgf with low pressure but much less risk and less self destructive.

Regulators go for paintball stuff, there are shimable ones which you can adjust to your required pressure. I doubt you'll be able to find any compact solenoid valves rated 16 bar tho, that said I have successfully used a 10 bar rated 1/8 bsp ported solenoid valve with pressures in the range of 16bar, after sealing the endacaps, because thats from where they leak...don't ask me about certification tho :uhoh:

Take care.
Normal pneumatic regulators that can regulate 70bar+ to 8 - 16 bar cannot handle liquid CO2.

Paintball regulators have a very low flow, and don't fit on Industrial CO2 bottles.

Can the paintball regulators handle liquid co2? Could the low flow rate be combatted with a reasonable sized buffer tank?
if not, does anyone want to sell me some pneumatic stuff?? í ½í¹‚

I don't know how paintball regs handle the liquid CO2. Never used them.

But for most pneumatic setups, a decent buffertank (3 times the volume used by the setup) is a good addition.

I used a cheap china paintball reg and it worked ok, it will handle Co2 fine ( its a purpose built reg to run on Co2).
I was going for this: http://www.rap4uk.com/MYTH-P3-3000ps...r-p/g-2428.htm before I opted for a full pressure system. Its adjustable to 19bar lowest. Low flow of the reg is not an issue as you anyway need a buffer tank..., now it does not matter if the buffer takes two seconds to fill, whats important is how fast you're going to empty it if you're building a flipper.
As for bottles you could use paintball stuff, there are different sizes to chose from.

That's great, thank you.

I would imagine that the paintball stuff is fine, the rules just state appropriate design, specification and certification.
Paintball equipment should satisfy all of these?

Most of the components we use have an operating pressure, and a published proof pressure.
For instance, Festo cylinders are rated to 10 bar operating pressure, but 15 proof pressure.
Am I required to stay within operating pressures, or is the published proof pressure enough to show they are rated/ tested to maximum pressures in that part of the system?

I just do not want to design and build something that will not be able to compete.


I have done a quick sketch of the circuit components.
Attachment 6362

Does the dump valve empty the whole system (including co2 tank?)

Paintball regulators will be able to handle liquid CO2 for a while, although I'd recommend avoiding the Ninja Pro V2, as the ball inside can freeze up and cause no end of havoc - this has happened to me while playing, I had to wait around 5 minutes for it to warm back up before putting a new 12g in. The Myth G2's (linked above) are ok, but have a tendency to not entirely screw into EU spec bottles.

I would recommend the Sly HP regulators - you'll get around 800PSI output (55ish bar?) (although I'm not too sure if you can get them anymore, paintball politics n'all means that Sly are now a subsidiary of Valken). If Sly don't make HPRs any more, you can get high & low pressure kits for PMI regulators.

For a system dump valve, look no further than the Planet Eclipse POPS ASA - they're well designed for purging the system completely, and I'm sure that Jack (the designer) would love to see them used on 'bots.

Thank you. Does the dump valve empty the main tank too?
I think 55 bar might be too much if i run a low pressure system, but i have seen a few that can supply 10-16bar to my buffer tank
i am not too worried about fittings as i can get these turned up to fit.

No, that purge valve will only take pressure out of hoses and any connected buffer tanks, but will keep pressure in the main tank.

Co2 adjustable tank regulators are difficult to find, HP air regs might work, construction is similar to Co2 reg.
You'll need a Co2 tank, a regulator ( HP burst disc is integrated in it) on/off valve, quarter turn valve (vent), safety valve (PRV) set at the lowest pressure your components can handle ( your operating press). Then you'll need a buffer tank, solenoid valve probably a QEV and some fitings and piping.
Have a look at this thread for more info on LP pneumatics:
http://www.fightingrobots.co.uk/thre...hlight=Liftoff

Thanks Chris
I have found a few lower pressure co2 paintball regulators, but yes, most of the lower pressure paintball stuff is HPA.

I have sent a few messages to clarify the ruling on the 'lowest pressure components can handle'. Is this the regular operating pressure, or the proof pressure?
As soon as i figure this out it will decide if i run a 10bar or 16bar system.
I would obviously prefer 16, as the cylinders are then smaller, lighter and cost less!
As of yet i cannot find a suitable 16bar rated 5/3 solenoid valve to run my cylinders double acting, though i would think they are proofed to~15 if regular use is 10bar

'lowest pressure components can handle' I take it to be the rated pressure of a component, ie the operating pressure. And although the rules say so I'm almost sure that most of the custom built rams and valves which are operated above their rated pressure are not independently tested. This issue has been discussed at length a couple of years ago and from what I gathered it seems that the event organizer has the final say, so they might accept a custom built HP system which was not pressure tested if they deem it well built.

As for solenoid valves, most are rated at 8bar but will handle more pressure. It's not going to explode, but it might leak at the end caps where the pilot valve is.