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assassin



Joined: 27 Jun 2004
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@ work now...

I know what I need to do, make a low pressure prototype, to test the theory.
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Post Tue Sep 22, 2009 8:09 am 
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kkeerroo
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Joined: 17 Jun 2004
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my understanding is that to make a flipper throw a robot as high possible a lot of energy is needed.
the energy ouput by a ram is proportional to the pressure and the volume of the ram.

so a long stroke/small volume ram will throw a robot as far as a short stroke ram if both have the same bore and pressure.
but as always flow rate is key.

may be useful if you are limited in how much flow rate you can get.
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Post Tue Sep 22, 2009 8:52 am 
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Daniel
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Thats an interesting design for an industrial ram but it only seems useful for a lifter.

Force = Area of pistion x Pressure
Energy = Change in Volume x Pressure
Speed = Energy / Force

So if you had two rams that put out the same Force at the same Pressure but one only used half the Volume of the other it would only move a target at half the speed

Remember that what is fast for industry is slow for robots. That idea seems really great for running 50 rams on a production line for 24 hours a day but I wouldn't put one in a robot. A bit of a waste of time and money.

Post Tue Sep 22, 2009 8:56 am 
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Woody



Joined: 07 Oct 2004
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It appears to be the calculation of energy transfered and energy that is left still contained in the cylinder / ram at stroke end.
A conventional cylinder at stroke end has it's total volume full of wasted energy that is ultimately exhausted to atmosphere.

The "bag" ram is supposed to transfer the same ammount of force thru out it's stroke but uses less gas volume to do so.

How ...F.Nose

Post Tue Sep 22, 2009 9:15 pm 
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Rotwang
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Joined: 15 Jun 2004
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Think a lot of air bags are just Nylon.
Not very exciting.

Still a little concerned with the thermal aspects, probably a result of playing with N2O for engine boosting year’s ago.
Very important to keep bottle temperatures just right. Mad

If your running a full pressure system why should the phase change only take place in the gas bottle?

Yes CO2 is weird stuff in that it has no liquid state below 5.1 atm but the vapor that gets to the ram / bag will be at higher pressure than this so there could still be wet vapor trying to suck in heat.

Even dry as in vapour co2 can still be very cold and the temperature of the various parts of the system affects the pressure.

So I don’t know what low temperature does to nylon.

Air bags have big holes in them and are meant to deflate very quickly, might have one at work if it hasn’t been thrown out if you wont one to play with.
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Post Tue Sep 22, 2009 10:25 pm 
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DumHed
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I have an air bag. It's fairly porous.
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Post Wed Sep 23, 2009 11:27 pm 
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assassin



Joined: 27 Jun 2004
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Thanks guys, I'll make up a low pressure ram one day out of PVC tubing and do some tests with and without the sock. The low pressure ram would be larger, any ideas for that simple/easy bag? Maybe canvas. Once again it would be a tapered bag small @ the bottom, larger @ the top.
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Post Thu Sep 24, 2009 7:25 am 
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Philip
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How thick would 7075 need to be to replace brass to handle the same pressure?
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Post Wed Oct 28, 2009 7:18 am 
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assassin



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Give me some dimensions. A cylinder I'm guessing? Give me OD ID and length and I'll post some spec/pics, for ya. Also pressure.
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Post Wed Oct 28, 2009 8:37 am 
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assassin



Joined: 27 Jun 2004
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Or

http://www.matweb.com/search/DataSheet.aspx?MatGUID=d3bd4617903543ada92f4c101c2a20e5&ckck=1

http://www.matweb.com/search/DataSheet.aspx?MatGUID=9852e9cdc3d4466ea9f111f3f0025c7d

Look @ the Density and maybe the Yield Strength. You will see that the 7075-T6 is a lot stronger for a given weight.
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Post Wed Oct 28, 2009 10:10 am 
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Philip
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I am looking at a Burkert 5404 http://www.burkert.com/COM/buerkert_products.php?type=5404&sk_id=2 Would 7075 aluminium need to be thicker or thinner to replace the brass components?
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Post Wed Oct 28, 2009 8:30 pm 
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assassin



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Thicker it has a lower yield strength, but its much lighter.
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Post Wed Oct 28, 2009 10:15 pm 
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maddox



Joined: 21 Dec 2006
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7075 ali has a reasonable high yield strength. About 25% higher than normal brass. So, it's not only 3 times lighter, but also stronger.

With a small mill it's perfectly doable to copy a brass valve body in ali. And for a Burkert 5404 you can gain up to 130 grams, if all brass is replaced.

Post Thu Oct 29, 2009 2:22 am 
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Philip
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Thanks to both of you.
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Post Thu Oct 29, 2009 4:56 am 
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maddox



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We did think about it to have a double or triple body CNC milled in 7075 ali, to have a smaller , lighter valve with more flow.

Another solution is to copy the Burkert 5404 but larger, and use a normal 5404 as pilot valve. But that's for heavyweight applications.

Post Fri Oct 30, 2009 1:04 am 
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