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(...) Cool! Thanks for posting that. I enjoyed attending your presentation, although I admit I didn't fully understand all of it right then. I think some studying of the AND, OR, and the other type of OR (I forget what it's called- you can have one (...) (21 years ago, 15-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) That'd be XOR ;) And thanks Kevin for the PPT file, it's great! Although I do have one little query - on page 4, you say the cylinders "Expand faster than they contract" - is this correct? I thought it would be the other way round - they (...) (21 years ago, 16-Aug-03, to lugnet.technic, lugnet.robotics)
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Ross Crawford's utterance expressed in news:HJovou.1wF6@lugnet.com: (...) Definately - with more presentations like this - a whole library of good knowledge can be made :) (...) you're right.. the volume to fill with air is smaller in the shaft-end (...) (21 years ago, 16-Aug-03, to lugnet.technic, lugnet.robotics)
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In lugnet.technic, Ross Crawford wrote: <snip> (...) Rosco, The expanding and contracting behavior is described by Pascal's law that says that the force exerted by a piston is the pressure (pounds per square inch) times the surface area (square (...) (21 years ago, 16-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Ummmm yep, thats what I meant - the contract side is smaller so less force, but wouldn't that also mean it contracts faster because it needs less air? Just like the small cylinders expand/contract much faster than the big ones because of the (...) (21 years ago, 18-Aug-03, to lugnet.technic, lugnet.robotics)
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In lugnet.technic, Ross Crawford wrote: <snip> (...) I think that the smaller pistons expand/contract faster because they have much less friction, combined with the fact that they have much smaller cavities. The old large single acting pistons (...) (21 years ago, 18-Aug-03, to lugnet.technic, lugnet.robotics)
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Kevin L. Clague's utterance expressed in news:HJsMzo.4n3@lugnet.com: (...) Friction is an important factor. But just as important is the fact that if I want to fill a certain volume with air, it takes less time if the volume is smaller - therefore (...) (21 years ago, 18-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Yes. I've already acknowledged that they contract faster because of the smaller volume in a no load situation. (...) Kevin (21 years ago, 18-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Which was the basis of my original suggestion, that the smaller volume on the "contract" side of pistons (both large and small) would imply that they contract slightly faster than they expand, but with slightly less force? ROSCO (21 years ago, 18-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Yes. The contract face of the piston has less area than the expand face. (...) Kevin (21 years ago, 19-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Whew! Glad we got that worked out! But that contradicts what you say in the PPT presentation, as I pointed out originally! (URL) (21 years ago, 20-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) update. That is what I love about LEGO, learning and discovery. I'm a computer engineer, not a physicist, and the things I make are highly physical. In this case, incomplete comprehension of the theory got in the way of practical (...) (21 years ago, 20-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Happy to play my part! (...) LOL! Well I'm sure I've heard of Pascal's Law, but didn't remeber the theory, it was just a "gut feeling" that it didn't seem right! (...) I've also been a bit worried about putting a big load on the contract (...) (21 years ago, 20-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) The biggest issue when fully expanded is leverage to the side which can lead to leakage. I've experienced it once in a while. Kevin (...) (21 years ago, 21-Aug-03, to lugnet.technic, lugnet.robotics)
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"Kevin L. Clague" <kevin_clague@yahoo.com> wrote in message (...) lead to (...) Interesting, I've noticed this happens quite a lot when joing two large cylinders back to back to make a larger double cylinder, and some cylinders seem more prone to it (...) (21 years ago, 21-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) I sucked grease - by manually pulling the plunger with a dab of grease on the bottom air input - into my cylinders and they move more consistently and don't leak pressure. I used ceramic grease of the type you get for RC car gearboxes. They (...) (21 years ago, 21-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) Would not the grease eventually find it's way out into the hoses and make the hose connection a bad one because of the slippery grease? (21 years ago, 24-Aug-03, to lugnet.technic, lugnet.robotics)
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(...) I've not encountered grease coming back out. It takes a really good tug to suck it in there and you don't get the same level of airflow when in normal use. The grease is fairly thick. After a bit of initial vigorous pumping by hand to spread (...) (21 years ago, 24-Aug-03, to lugnet.technic, lugnet.robotics)
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"Tim Auton" <tim.lugnet@uton.org> wrote in message (...) I've just tried this and it does make a significant improvement, especially on older cylinders. With two old cylinders connected up in parallel, I found that the treated one would extend and (...) (21 years ago, 27-Aug-03, to lugnet.technic, lugnet.robotics)
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"Jennifer Clark" <jen@vulture.dmem.strath.ac.uk> wrote: [ceramic grease in pneumatic cylinders] (...) I hope there's no chance of damage :) I went for ceramic grease over organic as I understand it's fairly inert. I'm no chemist though and I don't (...) (21 years ago, 27-Aug-03, to lugnet.technic, lugnet.robotics)
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"Tim Auton" <tim.lugnet@uton.org> wrote in message (...) It was ceramic grease I used as well, from Tamiya. It's still working today :-) (...) Excellent! Jennifer (21 years ago, 28-Aug-03, to lugnet.technic, lugnet.robotics)
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