Some simple pneumatic questions

[widow_twanky]

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

[maddox]

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.

[widow_twanky]

Bigger buffer tank then?

[woody]

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.

[woody]

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. = 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, 200

[widow_twanky]

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

[Ianshock]

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

[woody]

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

[widow_twanky]

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 ) forgot to screw down the speed controller so it was fouling the pipes and fitting........DOH!

Andy

[woody]

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, 200