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assassin



Joined: 27 Jun 2004
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I think I may have found a direction I want to go for my next bot after the next one Laughing

I would like to try out another concept I discussed a while ago improving the efficiency of the gas used within a pneumatic ram.

What I'm looking for help finding is a cloth like material capable of containing 800psi of force, I don't think it has to be 100% air tight but that would be nice. The other need would be it has to be a cone in shape.

I've ran out of time gtg to work, I'll post more detail later....

Anyone know much about air bag material?
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Post Mon Sep 21, 2009 7:46 am 
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Knightrous
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Not sure if it's any good, but maybe see if you can find out what car airbags are made from. They survive a large pressure surge while they expand, so it might be close to what your chasing.
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Post Mon Sep 21, 2009 8:04 am 
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Woody



Joined: 07 Oct 2004
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Here's a quick possible for you .

http://www.rubbersheetroll.com/neoprene-rubber-cloth-inserted.html

http://www.warco.com/pages/products/sheet/engineered.html

Post Mon Sep 21, 2009 8:30 am 
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assassin



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Yes yes airbags from cars are something to look @. I don't want a rubber type material thanks Woody, mainly because I don't want expansion. So a high tensile material that's thin, like a airbag from a car. The shape would need to be cylindrical and tapered(like a cone) with one large orifice(about 60mm) and one small(about 15mm) and about 100mm in length.

So I would be after a material that's meets these specs and a way to manufacture it to the desired shape or a complete solution already done(say out of a car airbag).

I've never seen a airbag and don't know if there porous and/or up to 800 psi. I would need to look into it.
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Post Mon Sep 21, 2009 5:26 pm 
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Woody



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Which of the laws of Physics are you trying to improve/alter ?

Energy = Force x Distance
Force = Pressure x Area
Distance = Volume / Area
So...
Energy = Pressure x Volume
( psig x cu-in => in-lbs )

Power = Energy / Time
Power = Pressure x Volume / Time
( Units = in-lbs/sec)
and Flow rate = Volume / Time
So...
Power = Pressure x Flow rate
( Psig x cu-in/sec => in-lbs/sec )

Are you trying for heat transfer to the gas whilst it's in transit from the bottle to the ram thus negating ..to some extent ...the pressure drop?

Woody

Post Mon Sep 21, 2009 6:33 pm 
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assassin



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hhaha

I'm keeping to the laws, the one in particular is FORCE = AREA X PRESSURE. I would like to test my theory one day keeping to that law but decreasing the conventional ram volume with a mod/consept.

I've discussed it before and from memory most didn't think it was possible, but I tell you IT IS! I'll prove it!
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Post Mon Sep 21, 2009 6:52 pm 
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Woody



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Ah yes..
I read an article two or three years back.

Let's see if I can find it ......Yup here it is.

Dr W... chamber volumes ..

I'll not post the article URL.Smile

If you wish it drop me an email.

Woody

Post Mon Sep 21, 2009 7:13 pm 
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assassin



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It's no secret, I discussed the concept and posted links in this thread. Still most didn't think it would work.

I'm just after any info on what I have posted above, thats all.

Seems car air bags are woven nylon, I wonder if it could be suitably joined. Creating a airtight, collapsible/folded part.
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Post Mon Sep 21, 2009 7:31 pm 
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Woody



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That's probably where I originally got the information ..just forgot the connection to this thread.

Woody

Post Mon Sep 21, 2009 7:37 pm 
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shreddy



Joined: 09 Jan 2009
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mmm, this keeps reminding me of the kevlar strip that the whyachi leaf spring flipper used to wind down its arm. that handled some pretty high tension levels.
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Post Mon Sep 21, 2009 10:16 pm 
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Knightrous
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Maybe take a walk through all the air muscle technology. Most of it is low pressure, but surely someone in that field has experimented with high pressure.
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Post Mon Sep 21, 2009 11:30 pm 
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Nick
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I really doubt you will find a thin fabric that is strong enough; airbags expand really fast but I don't think they hold the sort of pressure you want. The other problem with a bag is that you need some way to automatically fold it up as the ram retracts.

I'm happy to admit that I know almost nothing about pneumatics, but couldn't this arrangement work as well or better?




It has a massive conical ram surface area (almost 50% of the total surface area when the ram is closed) and would be easier to make than a fabric ram. I'm not saying it will work, just that its conceptually fairly similar to the conical airbag ram. My take is that if Energy = Pressure x Volume, then none of these schemes are going to work very well Confused

Post Tue Sep 22, 2009 2:23 am 
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Rotwang
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The freezing cold will potentially affect the bag material.
Possibly making it more brittle and stiffer if your using CO2.

The low thermal mass of a bag rather than an aluminum cylinder will work against the expanding of the gas, after all the energy your trying to use is the heat present in the bot at the start of the fight and what can be soaked up through convection, conduction and radiation during the fight.

The thinner and lighter the buffer tanks and bags the sooner the pressure drops of.
OK if you only need a couple of launches but a lot of our arenas don’t have death zones and most bots now days can survive being bounced off the roof
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Post Tue Sep 22, 2009 6:42 am 
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assassin



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Thanks for the diagram there Nick but no, the concept is to keep the conventional area on the piston head with the same pressure. The bag is to reduce the amount of volume used, increasing gas efficiency.

Rotwang(Gary?) I thought the change from liquid to gas of Co2 sucks the heat mainly from the supply bottle, not the ram so much.

I believe the concept really needs to be tested, and I'm happy to try it out one day.

So instead of all this gas-bagging(get it? Laughing ) about the theory(only kidding I'm happy to talk about it) any input into design of the bag is what I'm looking for. Thanks for the interest guys.
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Post Tue Sep 22, 2009 7:39 am 
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assassin



Joined: 27 Jun 2004
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quote:
Originally posted by assassin:
I've started to design a different pneumatic ram. Does anyone know of any collapsible tubing which could handle 1000psi. And when I say collapsible I mean it can constantine flat. Thanks.

Edit:

This study has given me some ideas:
http://www.liv.ac.uk/researchintelligence/issue29/pneumaticactuators.html

As we all know:
Force = Area x Pressure
Area = (1/2 Bore)^2 x Pi

We only need to apply the force to the face of the piston head. The rest of the cylinder doesn't need to be filled. The ways I can think of @ the moment are a collapsible tube or a upside down(if you like) telescopic section. I have started designing a telescopic version in CAD.

The advantages of the effort, extra weight and more moving components are great. Less gas used, smaller tanks needed, less flow required with smaller valves needed and of coarse a faster return stoke with less gas to waste.

Yes it could be 50% less volume to fill, with the same force and travel of a regular RAM.


Heres my original post a year or two ago.
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Post Tue Sep 22, 2009 7:43 am 
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