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Nothing too taxing here and I probably know the answers anyway. Thought Id ask anyway just in case.
1) I have some 5/2 valves. I want some 3/2 valves. Is it a simple case of plugging the outlet and exhaust of the unused ports?
2) Are Trevors regulators used in any heavies? Do they generally have sufficient flow rates?
Andy
1) is no problem, but Woody has better ideas on this.
2) Obsidian used a Trevor, works like a charm, but yes, the low flowrate is something to observe.
Bigger buffer tank then?
Yes ...just block off the two unwanted ports OR if you want you can re-plumb the 5 port so that it has two common inlets ...two common outlets and one exhaust....this gets you a 3 port with double the flow ( outlet ) of the original 5 port.
Drawing available should you wish to go this strange route.
The main co2 tank valve has a low flow value, therefore any regulator attached to it cannot supply enough flow of gas to feed a decent sized ram....hence the use of a buffer.
Do you need a bigger buffer? See post below.
The size of ram or cylinder used in a Flipper and the amount of energy that it could possibly deliver governs the maximum throw of a given mass....you cannot get more but you can get a lot less if your flipper mechanism and pneumatic system isnt matched correctly.
Acceleration, Velocity and Extension time equations follow for a given ram force and load.
Force to extend in Kg = 0.008 (constant) * (bore in mm) * (bore in mm) * (pressure in bar)
So let€™s take a cylinder with a 100mm bore and 200mm stroke @ 20 bar.
Ram Force = .008 * 100 * 100 * 20 = 1,600kgf
Mass to move = 100kg @ lets say a 4-1 ratio.
So the tip is taking 100 kg and moving it over a distance of four times the stroke ( 800 mm ) or 0.8 metre with a force of ...divide ram force of 1,600kg by the lift ratio of 4 ... 400kgf.
Acceleration = force in Newtons/mass to move
CONVERT Kgf TO NEWTON€™S (multiply by 9.8) = 400 x 9.8 = 3,920 Newton€™s of tip force.
So 3,920 Newton€™s /100 = 39.2 m/sec/sec...then take gravity in to account ...minus gravity 9.8 m/sec/sec = 29.4
Then calculate the velocity.
v = SQRT(2as)
Where a is the acceleration and s is the distance travelled.
v = SQRT ( 2 * 29.4 * 0.8 )= 6.8 m/sec ...this is a MAXIMUM velocity and no matter how you try you cannot get more ...only less.
Throw = v*v/2*Gravity
6.8 * 6.8/19.6 = 2.36 metres above the flipper tip.
Lets take this MAX velocity of 6.8 m/sec and calculate the ram extension time.
Solving for time t= V minus Vo /Accel = 6.8/29.4
Stroke Time (secs) = 0.23 second ..This is the quickest possible extension time for the given ram force and load.
You should now size your pneumatic system so as to keep a constant pressure under the piston and FILL this ram @ 20 bar in 0.23 sec.
Ram volume in cc (Convert ram dimensions to centimetres) = Radius * Radius * stroke * Pi.
5cm * 5cm * 20cm * 3.14 = 1,570 cc or 1.57 litres.
So to fill the ram in 0.23 of a second we must supply
1/0.23 * 1.57 litres of gas per second @ 20 bar = 6.82 litres per sec @ 20 bar.
We need this to be in litres per second @ 1 bar.. so multiply by your working pressure of 20... 136.4 Litres per second.
Cant be bothered with the Math?
Theres an embedded calc towards the bottom of my page.
http://www.teamonslaught.fsnet.co.uk/pneumatics.htmhttp://www.teamonslaught.fsnet.co.uk/pneumatics.htm
The embedded calc also outputs a Kv and Cv MAXIMUM value recommendation for your valve.
(Message edited by woody on October 26, 2008)
Woody,
Id be interested in seeing a drawing of how you do that (I assume you just switch the inlet/outlet pipes round on one side). One of the big problems on Hydra is flow. Plenty of big pipes but lots of small orofice fittings, lots of T pieces, elbows and stuff. All seems to mean gas delivery is actually quite poor (12mm pipe into a 1/4 fitting means you get the flow through the 1/4 fitting and nowt more).
Andy
Hi Sorry to steel Andys thread but can you recommend anywhere for 3 way ball valves for FP ? Maelstroms (AKA St Agro) spool valves seriously sticking since my refurb !
(Thanks to these we didnt give Andys Hydra too much hard work to get thru yesterday fight !)
Cheers Ian
Old archive pic link....
http://web.archive.org/web/20040814181807/http://www.teamonslaught.fsnet.co.uk/S5-2.gifhttp://web.archive.org/web/200408141....fsnet.co.uk/S 5-2.gif
Yes we both seemed to have complete failures on the pneumatics in that one :blush:. Found out what our problem was. Someone (probably Paul cos it couldnt possibly be me :mrgreen:) forgot to screw down the speed controller so it was fouling the pipes and fitting........DOH!
Andy
Ball valves.
http://www.yateson-stainless.com/yateson03.htmhttp://www.yateson-stainless.com/yateson03.htm
Scroll down the centre panel for some pdfs.
Watch out for the opening torque ratings for these ball valves ...youll need a DECENT actuating ram to get the valve to open QUICKLY!
http://www.valves-online.co.uk/acatalog/Three_Way_Ball_Valve.htmlhttp://www.valves-online.co.uk/acata...all_Valve.html
(Message edited by woody on October 26, 2008)
Andy ...Use the calc on my page and get a guesstimation of your required flow rate for both your flipper and axe.
The ratio is simply the flipper tip travel divided by ram stroke or Axe head travel divide by ram stroke.
Some sort of a starting point is needed to refine your system.
Will do Woody. Have already decided that it needs redoing. It never caused a problem before but as Lukes getting better at driving its become more apparent that we need to get more out of it.
Thanks
Andy
Actually Woody, just had a look round that and its a fabulous little tool. Need to take some details of the geometary and then play with it a bit.
Andy
http://uk.youtube.com/watch?v=Bp9SWUoRxJchttp://uk.youtube.com/watch?v=Bp9SWUoRxJc
Theres a T port in there ;)
got my one from valves online too.
looks good suren, tryed a self-righting test yet? wouldnt do it in the living room though lol
I only got it working on sunday! Didnt think i could fire the ball valve fast enough with the actuator ram i have, but it seems to work ok. Wont know if its going to lift anything untill i put some weight at the end of the arm. That will be this weekend ;)
And the u tube video isnt that good, The arm its actually moves faster. Couldnt work on the robot in the garage as the builders were round, got kicked out the kitchen so the living room was the only other option!
You could of tried flipper one of the armchairs!
Can anyone explain to me the difference between magnetic or non-magnetic cylinders (apart from the obvious:))?
Simple, if youre talking about aluminium , bronze or stainless steel bodied cylinders, the magnetic part is a ring around the piston, between the sealings, that makes it possible to detect the position of the ram with a simple reedcontact on the cylinders body.
Otherwise youre talking about lineair electromagnetic accelerators, and thats an entire other story.
Thanks Mario.
Just one more thing. If I were to use a 1/2 2/2 valve (Burket or similar) on the upward stroke of the cylinder can I just fit a quick exhaust valve on the cylinder. I recall Woody mentioning that this wasnt desirable but at the time we were talking about using a 5/2 valve.
I suppose the alternative is to keep the 5/2 valve in place and tee it into the feed making its primary function an exhaust.
Andy
Andy
Andy,
Working on the assumption that you need a flow increase ...Id probably recommend a 2/2 valve with a flow rating suited to your setup on the extend side of the ram ... combined with a small 1/8 port 5/2 and a self relieving regulator + QEV Exhaust on the retract.
Note that the 2/2 Burkert valve hasnt an exceptional flow rating.
Some data on your setup ... bore , stroke ,flipper tip lift and working pressure would help with a recommendation.
Woody
In the original turbulence when it was first built we put a burket on the fire.. it was pants.. wouldnt even selfwright.
We changed to a variation of woodys Q.E.V firing idea and it turned it from a rubbish lifter to quite a competitive flipper.
out of curiosity whats involved in converting a hydraulic ram to operate as a full pressure pnuematic ram?
any internal mods or just enlarging the ports in the ram itself?
cheers
Not a total answer to your questions but worth a read.
http://www.fightingrobots.co.uk/discus/messages/9/845.htmlhttp://www.fightingrobots.co.uk/disc...ges/9/845.html
Cheers woody,
ive stripped the ram down and found its 5mm wall thickness steel and the piston itself is actually using a metal seal on it like a piston ring.
its next to impossible to move the piston by hand. is it okay to replace the metal ring with an o ring seal to lower the resistance?
thanks again.
Replacing the piston seal with an O ring should be fine....Id go for a very light fit.