yes johnno has def got one saw it last week
no u dont as if u use a trev valve u will be on low presure but need a low presure valve then about 16 bar i think
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yes johnno has def got one saw it last week
no u dont as if u use a trev valve u will be on low presure but need a low presure valve then about 16 bar i think
I have a 20oz bottle that the regulator fits directly onto. I don't need it now because I have other tanks for my pneumatic FW so I'm willing to sell if you want it.
How much do you want for it?
£35 plus postage.
Would you trade it for a brand new 20oz paintball bottle with pin valve and also my on/off valve?
Would you trade it for a brand new 20oz paintball bottle with pin valve and also my on/off valve?
Sorry, cash only because that's what I need.
What's the female thread on your bottle
Max?
It is this one:
http://www.store.justpaintball.co.uk/ai ... valve.html
I don't know the thread but I will try and fin out
5/8-18UNF
To fill a paintball bottle from a fire extinguisher cheaply could I take the nut from the extinguisher, turn it on a lathe to open up both sides so I can screw the paintball bottle in one side and the extinguisher on the other? Would the nut be able to cope woththe pressure? And because the nut will only be half screwed onto each bottle will it be held on enough?
I know that I should have a dump valve in-between the two bottles but i think I should be ok?
You need to have a vent valve on the filling rig. You should be able to pick one up for £20 - £50.
http://www.google.co.uk/search?sourceid ... 24&bih=588
and of course Ebay.
Hi All
We are going to be taking out first steps towards building some pneumatic machines. We got hold of 2 cylinders of Jamie a while back an I have 2 machines in mind. As we only have spinners, these machines will be for the Robotwars and other events that don't have a Class 1 Arena.
1: A 2WD flipper using a small 10 Bar, 40mm Bore, 75mm Stroke cylinder. This gives approx. 300kg of force at the tip of the cylinder which will be dropped to about 30kg over the flipper arm.
2: A 4WD (2 motors, belt driven) Horizontal spike machine with a 16 Bar, 50mm Bore, 100mm stroke. This will give around 500kg of force on the end of the piston which will have a hardened spike on the tip.
We know that spike bots have not been overly successful over the years but we want to make something different, but given some of the thin armour out there on some machines (LF3, LH3 Explosion) it might be able to do some damage.
The first issue we have is what Tanks to use. We got what looked like a 16oz paintball tank and we also picked up an empty 1kg powder fire-extinguisher which we were thinking of using as buffer tank in the Flipper.
What standard tanks do people use and what valves as well. We have, what I think is, a 3-2 valve to direct the flow in double-acting cylinders.
I just want thoughts on the 2 ideas. I am going to be putting up concepts fairly soon but I cant really do it until I know what parts are going inside. We might have some fun making an Asymmetric machine but neither machine is meant to be overly competitive, just low cost and fun.
My preferred solution is a 5/2 way valve operated system with QEV, buffer tank and spring/bungee return. I use all paintball parts for the reason that they are readily available, not expensive and properly rated. Buffer tank and main tank I'd use 12oz tanks, paintball low press regs are available as well, and they connect directly to the tank so there's no hassling with adaptors. 16bar is a bit on the high side to find LP valves and push fittings rated at that pressure.
The thing you should really take care of is making sure there are no restrictions from the buffer to the ram, that will be the difference between a flipper and a lifter!
the thin armour on LF3 is titanium sheet. You will struggle to do any kind of damage against that kind of armour with a spike.
By all means build one, but just be aware that you will likely do sod all damage.
Maybe if you rammed it with a run up...
What pressure are the push fittings usually rated to? The plan was to make the spike bot from MDF. We are not massively fussed about weight as its never going to be for competition. As it will all be fixed I was going to get parts you have to bolt together rather than push fit parts.
Also, thanks to Kane's talk at the Robochallenge awards we know his list of little tricks to get the most out of a pneumatic system, like making sure the flow its straight just to name one.
And I know what the armour is Gary. 1.5mm Grade 6 on the sides and back with 3mm Grade 5 on the front. I still think 250kg of force is enough to do something to it. (250kg as we will push ourselves back as we fire, halving the force)
250kg of force will just push the 2 bots away from each other and if your lucky make a small dent
the main issue is that they way so little and don't have a great amount of grip on the floor
No need to have the sarcastic response. Only trying to save you some time going down a route that won't work.
Normally push fittings are rated at 8 to 10 bar, I had one blow apart at 11bar. There are all metal ones good for 15bar, but they are expensive, the way round that is using small 1/8 fittings on all the system apart from the buffer and the ram, the smaller fittings cost less..... btw. it will be difficult to do away with push fittings, even if everything is fixed, as long as you're not using metal tubing and compression fittings!
Alex, there's no way you'll be able to penetrate titanium alloy, neither at 1.5mm and much less at 3mm, at most maybe you'll dent it, that's all. But you're free to prove us all wrong! ;)
Not sure if I agree on the forces generated by your rams, I think 40mm bore gives you 120kg of force and the 50mm bore gives you 300kg?
I am making a hw spike bot which I hope should be fun, I am going full pressure because I think the key to it is making it fast, so I would definatly use a big QEV to feed it and a big buffer. You'll have to use the MDF well to hold the required forces.
I would use paintball on/off valves as they are lightweight. If you can avoid using paintball tanks as buffers I would as they are much heavier than necessary.
I am not expecting to punch through Titanium. I just want to do something different. And if it doesn't work then I can build a normal flipper.
To calc the pressure I am using a converter to go from 16 Bar to 1.6 N/mm^2. From that its (25 x Pi) Squared... oh darn it... I hate using the calculator on my PC. Right... (25 x 25) x Pi = 1963.49 mm2, which gives a total of 320.4kg on a point at 16 Bar.
And the yield strength of Ti 5 is 950MPa. Ok, that is a little impossible. Oh the up side HDPE's is only about 30MPa so Explosion is in trouble.
Does anyone know what cylinder Heatwave used? It looks very similar to the one we have.
Attachment 3770
Also, can someone give me the dimensions of a 20oz Paintball CO2 tank.
Earlier in this thread mario said the 20oz bottles are 330mm long, 75mm diameter bit I haven't personally checked that.
Just checked mine, its 240 mm long (without the valve) and 64mm diameter, weighs 463gr...don't know what other tanks you could use which weigh significantly less.
Regarding the ram, I have a similar one to it on my robot, but had to modify it. The problem with those rams is that although the threaded ports might be 1/4" or even 3/8", the orifice inside will be much smaller!...that's one of the reasons restricting flow I mentioned on my earlier post.
Edit: Opps my tanks are 12oz sorry!:oops:
Edit 2: 20oz tank measurements - 80mm dia, 270mm long, weighs 830gr (incl valve)
I was going to say, 20oz are much bigger. 12oz should be enough. I have also figured out how to use the gas used to fire the cylinder to reset it without any extra gas.
The 50mm bore one has open ports with no restriction but the 40mm one has maybe 2mm dia holes a little way into the ports. Provided I am still at uni I can resize the holes to bigger ones if need be.
If it's the one you got from me, it's a 5/2 valve. And there should be both a 12V and 24V coil to offer some flexibility in operating voltage.Quote:
We have, what I think is, a 3-2 valve
A spike will indeed do minimal damage, but as long as you have fun with it, that's the important bit. My axe weapon will probably do the same, but in the short while I've used it so far, it's been fun :)
It's also interesting that whenever I mention Robot Wars or robot combat to someone who used to watch it back in the day or knows roughly what it is, the most common response is 'Do you know what would've been a really good weapon? A big spike' or 'Some sort of EMF weapon'. I'm quite well-versed in explaining the ineffectiveness of spikes and the illegality of EMFs nowadays.
Yep, no need for 20 oz tank, I use 12 oz tanks both for main and buffer with a 63 x 73mm ram, and it works well... but tbh, the there's not much of a difference in size between the 12 and 20 oz tanks.Quote:
Originally Posted by Eventorizon
Don't be fooled by the comparatively low strength of HDPE. You are looking at the solid force being put out but you need to look at impulse instead which takes into account the time the force is applied over. Ridgid metals do not deform on impact so maintain a high impulse from that force. HDPE is great at having a bit of flex and deformity, in other words it stretches out the time the impact lasts for for far longer than metal so effectively it experiences a lower force than metal does. It is what makes it such a good armour against spinning weapons because though it may have a gouge taken out it pretty much took a good amount of force out the robot. The same amount of energy is still transferred but it is the difference between putting 1kg on your robot for 1000 hours or 1000kg for 1 hour.
Also the 320kg of force is only true if you can get the flowrate high enough to keep the pressure in the cylinder up as it expands, otherwise the high pressure will only be achieved fully once the ram has finished actuating.
Now I'm not sitting here to say not to build it, just to inform you more. I myself am building an axe robot that I know is never going to properly break other robots but just hitting stuff is going to be fun! :D I would love to see you prove us wrong too (until my feather is impaled :P ), just have fun with your design and it'll be good!
Hi,
What kind of springs do people use to stop their QEVs misfiring when the gas is dumped? Where can you get them from?
As I see it, it has to be a very weak spring which compresses down to virtually nothing.
Also is there a reason my 5/2 solenoid valve seems to get stuck in the on position when I have the bottle turned off before a flip, I then have to put my thumb over the port where the gas come out for a while until it flicks over to the off position.
If you connect the dump valve to the buffer tank, then you should get no issues with the QEV firing when you dump the air. To dump the air from the QEV to the valve fire the weapon, it will not move provided the main supply is closed and the dump valve open. Don't know what other solutions there might be.
I've never had it fire, the pressure should drop evenly both sides of the qev.
It would be very difficult for me to put the dump valve between the buffer and the QEV but if that is my only option I will probably have to make a custom component to make it fit together in the space I've got.
I don't know why yours doesn't fire, as I see it, it is the same as switching the 5/2 valve to dump the gas in the pipe going to the QEV causing it to fire.
perhaps an option would be to severely restrict the gas flow out of the dump valve to the pressure doesn't drop fast enough to fire it, but then it would take forever to empty. I am sure Mario said to me at Maidstone I could use a small spring to stop it misfiring but I am struggling to find one suitable. The best I have come up with is using a paper clip wrapped round a large pencil to make it into a spring shape but I doubt that will work for long!
Can't you fit a Tee fitting directly to the buffer? Then you could connect the QEV to one side and the dump valve to the other. Don't know how placing a spring on the QEV will work, the way I see it once you dump the inlet of the QEV, spring loaded or not, the pressure inside the buffer tank will push the sliding seal inside the QEV and fire the ram.
Been watching back over RW and trying to spot all the little hints and tips teams give to maximise the power or efficiency of their set ups.
The one that stood out was using Liquid CO2 like in Chaos 2 and a few other machines but so far as I know we cant get liquid CO2 at events. Also it seems logical that you would end up freezing the valves as the gas expanded into the cylinder causing it to jam. But there must be ways round this if Chaos 2 can use it with no problems.
Another which Kane mentioned was to have the largest buffer tank you can, so the gas can easily flow into the cylinder. Also making the routes as direct and straight as possible so you don't waste energy in the process.
Are there any other little tips people can suggest, or correct me on these ones.
I also have this half used powder extinguisher in my flat.
Attachment 3808
Physically it is fine its just never been repressurised. Would this be alright to use as a buffer or even a main tank?
It has the following on the side...
Working Pressure: 13.5 Bar
Test Pressure: 22 Bar
The maximum our cylinders can take is 16 bar so it would be 37.5% less than the testing pressure. And if I remember right, parts must be tested to 20% more than their intended operating pressure so this would be ok.
Alex, we all use liquid CO2. George was referring to the fact that in the main bottle it will be liquid but by the time it reaches the ram it should be gas. Otherwise the whole system will freeze, nothing will work. What Kane said is exactly correct large buffer, short pipe work.
That dry powder will be ok for a buffer at that pressure yes but not suitable for a main tank.
If your system is an LP one, the most important thing is to have the least restriction possible from the buffer to the ram, that means the shortest, straightest and largest way possible, all the rest does not matter much. On a FW I would try to use 1/2" fittings if possible, couldn't manage on mine so I compromised with 3/8" fittings...results look encouraging!
Like Ed said, that tank is ok for a buffer, but surely not as a main.
What if you did something like this...
Attachment 3809
With the pneumatic cylinder we have you can take the end off. If you took that off then replaced it with a custom valve that had a diameter that was the same at the cylinder bore, I am guessing that this would technically be the best possible set up.
You would weld a custom mount to the side of the tank then have a solenoid inside to activate the valve itself.
That would be ideal but you will struggle to find a valve with that kind of bore ad if you made one it would be very heavy and would need a lot of power to switch it. You could also blow the end cap of your cylinder off by making the piston go too fast but I've never heard of that happening.
I would just use woody's QEV system as it is the cheapest way to get good flow. For the price of all that custom work you might as well go full pressure. also if you have access to lathes/milling machines (especially if they are CNC) it is not very difficult to make a high pressure ram.
Also, if this is for a flipper there is a maximum amount of flow rate you need due to how quickly you can accelerate the other robot. If its for your spike weapon then there will be a maximum due to the mass of the spike
What is Woody's QEV system?