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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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I doubt it..
You need more information on the ram to say for sure.. a manufacturers pressure rating, The force will be proportional to the working pressure and the bore diameter.
Then you need to take into account how far you need your flipping arm to move to effectively flip most designs, and given that most flippers rams are "geared up" so that the rams stroke length results in more end-of-flipper travel, you need to divide the maximum cylinder force by the arm ratio.
EG - if you have a ram that can generate 100Kg of force, but you have attached it to an arm at a point that doubles its travel, then you only have 50kg of force at the end of the arm.
Given that one you linked to is only designed to close doors cheaply, Its not likely to be designed to put out massive amounts of power, and pneumatics are one thing in robots you *dont* want to run over their specification or capabilities.
If you keep it down around 100 Psi of compressed air, then you arent necessarily required to show safe ratings on your all your pneumatic components. If you go above that, and it looks dangerous, then you might need to get your door-closer pressure tested to show its not going to explode when you fire 145 Psi into it suddenly.
Theres some information on cylinder sizing here http://www.bimba.com/techctr/techtip3.htm - or google searching for these terms.. 'pneumatic force bore diameter pressure' should turn up lots more info for you to read and learn about so you can do this safely rather than just asking someone else "will this work ?" _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Mon Jan 10, 2005 1:36 pm |
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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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If you read Dumhead's new bot thread, you will see that there is a junkyard up geelong way that apparently has some stock of 2nd hand pneumatic rams..
There might be one closer to home if you hunt around.. we need to find some good junkyards around melbourne.. commercial rams would be a much better place to start if you want to run high pressure.
If you want to stay with low-pressure to keep it safe and free of approval-requirements, then all you need to do is add more or bigger low-pressure rams (which effectively increases your bore size).
4 cheap rams (bicycle pumps, door closers, whatever) at 100psi should (I think) generate as much force as 1 equivalent bore-size ram at 400psi.
It might work out to be heavier, since you need more mounts, plumbing and so on, but if you want more power, its either that, or learn how to do the high pressure stuff safely. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Mon Jan 10, 2005 2:12 pm |
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DumHed
Experienced Roboteer
Joined: 29 Jun 2004
Posts: 1219
Location: Sydney
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I wouldn't worry about the pressure, just figure around the 100psi mark for simplicity.
If you need more lifting power you can use larger bore rams (foot pumps are already huge) or more rams.
The larger the ram the more air it will use, but that's the same with anything.
Coke bottles work well as pressure tanks, and will handle around 100psi without strengthening, but you'll need to make up an air valve and do a fair bit of piping.
I found a small fire extinguisher that works really well, but different types use different fittings, and most don't seem to be easy to connect hoses to.
The nice thing about the extinguisher is that the valves are very quick acting, so all you need is a servo or solenoid to pull the lever and you get very quick flow into your ram.
Jeff's setup on El Bravo works very well though, using a cheap air gun valve activated with a servo.
The problem with the extinguisher tanks is that they're not very big, so they won't hold enough air for heaps of flips. El Bravo has two 2L bottles, so it's about 4 times the storage of a single small extinguisher. _________________
The Engine Whisperer
- fixer of things
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Mon Jan 10, 2005 3:28 pm |
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kkeerroo
Experienced Roboteer
Joined: 17 Jun 2004
Posts: 1459
Location: Brisbane
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There ae a few thing you have to realise about drive axe weapons that might be a little helpful. There are 3 different ways of driving them that I have seen and thought of, pneumatics, electrics and springs. Each one requires a different setup. Actually springs are like pneumatics.
Anyway, hammers and axes are all down to energy and power. The energy in a pneumatic (and spring) weapon is all potential. In order to get the most out of the gas you need to use it as quickly as possible. Also the more gas you use the more energy you get. This is why you should use short, fat rams over long skinny rams. The shorter rams doesn't take as long to reach the other end and therefore wastes a lot less of the energy. You also need the rest of the axe and linkage setup to be fast which means you need a light axe, such as a thin preicing point, rather then a sledge hammer which would just slow the system down and waste the energy.
So thats how you choose the ram and axe. The linkage on the other hand is a different story. I'd prefer a four-bar linkage over a rack and pinion as you use less of a stroke of the ram and you end up with an acceleration curve more suited to an axe swing (force at the start, speed at the end) where as a rack and pinion has a constant curve. Not to mention an effect rack setup would be heavier, but requires less room.
And before Aaron starts going on about the Judge, it runs of 3750psi Nitrogen and where are you going to get that from? _________________ Get Some!!!
Secretary of the Queensland Robotics Sports Club inc.
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Wed Mar 09, 2005 10:05 pm |
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