Pumping with pneumatics?

[Billfred]

Alright, so I got my haul of pneumatic parts from eBay today. (now if only I could get some hoses that work!)

I was thinking about the operation of the cylinders, and it hit me. If you connect two cylinders at the lower port with one extended, then push on it, the other goes up. So if I were to take, say, two cylinders, connect them at the same ports, stick t-junctions somewhere in between, and put an alternating force on both (as in one is pulled up, the other's pushed down, and it rotates between the two), then I'd have myself a Lego-grade compressor, right?

(On a tangent, I have found out that the small pump is quite possibly the wimpiest thing in all existence. It took about a pump and a smidge on the large pump to get a large cylinder all the way out--on the small pump, it was more like twelve.)

[Max Lobovsky]

I believe this was discussed earlier except it was for use as a vacuum generator, i think you know what i mean... I believe some suction ball grabbers did utilize it.

[Greg Needel]

yes but if you are talking about just recycling the air it will be very ineffective because every time you have power transfer you have loss. you would also need a series of 1 way valves to make this work otherwise you will be loosing air because it will spread out over as much space as it can take up. The 1 way valves would be in-between the output on the 1st cylinder and the input on the second and on the output lines going to your tee

[Billfred]

I checked out that site--if I can figure out how to make that four-cylinder engine into a three (a lego geo metro--who knew?), then I bet I'll be hot to proverbially trot.

And I don't think that there were any side loads on my small pump. I could be wrong, though.

[Alex Pelan]

Yeah...we used two cylinders to create a vacuum as well. Originally, it was going to power three suction cups on our arm so that we could handle all 3 2X balls, however, we ended up having to take our arm off due to center of gravity issues/driver inexperience with this arm. So, we were left with the vacuum only powering the shifter.

[greencactus3]

Originally Posted by Billfred

if I can figure out how to make that four-cylinder engine into a three (a lego geo metro--who knew?), then I bet I'll be hot to proverbially trot.

a 3 cylinder may be a little harder because a 90 degree angle is more often used in LEGO pieces than a 60 degree. of course there are propellers, and rotors, pulleys and wheels, angle beams and universal joints...etc,, using lego, a 4 cylinder pneumatic engine may actually be more compact than a 3 cylinder. definitly easier to make. also the timing of the valves would be a little harder. with a 2 or 4 or 8 cylinder, the valve timing just needs to be half rotation, quarter rotation, eighth rotation off. i think thats easier than a one third off.

[Billfred]

Touché. This is why I don't design engines for a living.

Anyone got a spare large cylinder? (grin)

[greencactus3]

Originally Posted by Billfred

I was thinking about the operation of the cylinders, and it hit me. If you connect two cylinders at the lower port with one extended, then push on it, the other goes up. So if I were to take, say, two cylinders, connect them at the same ports, stick t-junctions somewhere in between, and put an alternating force on both (as in one is pulled up, the other's pushed down, and it rotates between the two), then I'd have myself a Lego-grade compressor, right?

actually, no. youd need a one way valve before the "t junction" on both sides. only if you do that, you won't be able to pull the cylinder out... well, LEGO leaks so you will eventually, but...
so the easy way out is, make a double acting compressor using a cylinder.
you have one cylinder. connect it as you normally would as an actuating cylinder. now push and pull the piston while turning the valve.
sorry, bad explantion.
ok, ill try another way. have you ever built a pneumatic engine?(they are quite fun)
well, now crank on the supposedly output shaft of a pneumatic engine.
there yougo. you have a nice compressor. same as an electric motor. youcan use a motor as a generator. same principle.
you cannot create or destroy energy. the law of conservation of energy or something of the sort.

oh, heres a nice site on pneumatic lego engines
http://www.nicjasno.com/
some people have actually built radial pneumatic LEGO engines too.
cant seem to find the url though.

Originally Posted by Billfred

(On a tangent, I have found out that the small pump is quite possibly the wimpiest thing in all existence. It took about a pump and a smidge on the large pump to get a large cylinder all the way out--on the small pump, it was more like twelve.)

it may be that you have side loads on the small pump. as puny as it may be, it is a very useful piece. the small pump will leak like no other if you have side loads going on it. eg) too tight of tubing will actually hurt the pump's performance