Can someone tell me what pneumatics are used for in Lego? Also, what are some tips on how they can be used. I just got a bunch in a grab bag along with a M motor and a battery box.

Thanks.

They can be used in similar applications as a Linear Actuator- to convert energy into linear movement. In their case they turn air pressure into the aforementioned movement. They're good if you need brute force, but can't handle loads or stop with precision like LAs can. It is more realistic and is used more often than LAs in real applications.

Off-topic: DANG, you are VERY, VERY lucky to have found those and electrical components in a Grab Bag!

Addition: LA means Linear actuator

There just like the pneumatics, with a piston rod that extend. Except, for a linear actuator you have to turn it and the piston rod extends (circular motion transformed into linear motion), sort of like a screw. But just like TheDesuComplex said, a pneumatic cylinder uses air pressure to push the metal piston rod out while a LA needs rotation to extend the piston rod out. But, a linear actuator is more precise and is longer, while a pneumatic cylinder is shorter, stronger (I'm not 100% sure), and extends in bursts of movement(its "jerky," if you have the hand pump). But hearing as you have m-motor and most likely a mini pump, the pneumatic cylinder extends pretty smoothly so you made a good choice grabbing them bags. Does this explain with the help of TheDesuComplex?

To get a basic understanding of what pneumatics can do, I'd suggest reading Blakbird's Technicopedia, specifically the pages for the following universal sets:

• 
  8044 Pneumatic Universal Building Set (1989)
  
• 
  8042 Pneumatic Universal Building Set (1993)
  

These are fairly old sets, but helped introduce pneumatics at the time, and will give a good idea of how pneumatics can be used.

Then you might want to check out some of the other Technic sets that have pneumatics to see how they are implemented (link).

The most recent set to include pneumatics is the 8110 Mercedes-Benz Unimog U 400 from 2011, which uses a combination of a motor to drive a pneumatic compressor, and then some pneumatic cylinders to drive the crane arm on the back of the truck:

Of course you should also check out the other fantastic MOCs that other people have made. Search in this forum, on BrickShelf, MOCpages, YouTube, or Google.

Side note: It was a pneumatic set that helped bring me out of my dark ages: the

8455 Back-Hoe

from 2003. One of the best pneumatic sets

IMHO

.

Edited April 10, 201311 yr by Splat

Sometimes it can be more convenient to run a hose than a driveshaft to the location of the linear actuator or pneumatic cylinder that controls the function.

Basically you use a pump (hand driven or driven by a motor) to provide air pressure to a switch which controls which hose the air goes to. If the air goes to the bottom hole in a pneumatic cylinder than the piston will go up. If the air goes to the hole at the top, the piston will go down. Hope that helps.

tim

Thanks for the help. I think I'm going to need to buy some technic parts and experiment with pneumatics.

Here are some basic circuits:

You didn't say what type of pneumatics. The current stuff has cylinders with 2 nozzles and pumps with a single nozzle. The old stuff has cylinders (with and without the spring) with just 1 nozzle and operates differently. Both types use 3-nozzle valves. With the current system the input is connected to the middle nozzle and the 2 ends of the output cylinder are connected to the other 2 nozzles. If the valve is moved to one side, the input connects to one output and the other output leaks to the atmosphere.

The old system used a 2x4 brick with 3 nozzles - a non-return valve - on the input side and the switch valves were on the output side. You could not move 2 cylinders in opposite directions at the same time with the old system or it would lose pressure and collapse!

You can take pneumatics quite far, to build automated machines:

And yes, it is possible to make a pneumatic cylinder stop wherever you like, if you use a few tricks:

There is stiction to overcome but once the cylinder is moving, more accuracy may be achieved than was suggested by earlier posts. Also load handling is a matter of how many cylinders you use in parallel. The above system may apply to many series or parallel cylinders to handle a greater extension or a greater load, without changing the servo mechanism.

It is easier to parallel pneumatic cylinders than LAs, as TLG found with their 8043 excavator set! Pneumatics will load-share easily. Set 8455 uses them in pairs for the Backhoe's front implements. The classic crane truck set 8868 used a pair of cylinders in opposition to turn the crane's turntable. It doesn't matter that the movement of 2 cylinders is not the same throughout the range; it does matter with LAs.

More pictures & info here

Mark

Edited February 27, 201213 yr by Mark Bellis

That's really helpful!

BTW, I have 2 big cylinders, 1 little cylinder, what I'm guessing are switches, an a whole bunch of tubing.

That's really helpful!

BTW, I have 2 big cylinders, 1 little cylinder, what I'm guessing are switches, an a whole bunch of tubing.

Why dont you post a photo, then we could tell you exactly what you have and maybe some hints on how to use them .

tim

Sounds like you got a grab bag from a Unimog, which is really quite lucky as I've never found any Technic at all in any grab bags I've got before. Do you also have the pump though?

What's a grab bag? They sound fantastic!

They're basically the bags taken from sets and put into a sealed plastic bag with some branding on it. From what I gather they're from sets that have been returned for whatever reason. I've only ever seen them in the Lego store at that Disney thingamajig in Florida, I once got a bag of parts from that Star Wars MTT which had loads of studded Technic beams, very useful as I've only really got studless parts

They're also pretty good value, they were about $9 if I recall correctly.

The grab bag was 8 dollars. Unfortunately, I think I didn't get a pump. That's the one with the spring, right?

That would be a pump, though as it sounds like the grab bag contains Unimog parts, it might have one of these, which is also a pump, and one that can be motorized at that.

If you don't have either of those, you'll need to get one in order to use pneumatics.

That's a good grab bag. Pneumatic cylinders can start at around $5 each on BrickLink.

That would be a pump, though as it sounds like the grab bag contains Unimog parts, it might have one of these, which is also a pump, and one that can be motorized at that.

If you don't have either of those, you'll need to get one in order to use pneumatics.

Alright, I guess I need a pump.

I won't be able to get any pictures up because there is something wrong with my camera.

Edited February 29, 201212 yr by Legoroni

Would it be possible to run pneumatic pumps and cylinders with water instead of air. I think it would work and might even be less bouncy.

Would it be possible to run pneumatic pumps and cylinders with water instead of air. I think it would work and might even be less bouncy.

No, sorry.

It's not possibile, since lego pneumatcs use an open circuit:

1) The Air goes from the pump to the piston chamber you select with the switch, but the air in the second chamber is discharged by the same switch to open air.

2) the pump is a single effect one, meaning it suck air from above (around the stick) and pushes it to the circuit.

Should you use air, you wuold have to use the pump submerged and you would spread water all around!

Edited February 29, 201212 yr by Rikus

I wasn't intending to use it for anything just that it might be more realistic.

There is a topic around here on using water/fluid.

http://www.eurobricks.com/forum/index.php?showtopic=51439

Seems it is possible and some people have done it, but the idea needs more refining to make it more practicle. When I start MOCing again tho one of the things on my to build list is a hydraulic excavator.

Using LEGO pneumatic parts with water is generally a bad idea. The pressure gets too high. Take a note from Robot Wars - the rules say 1000psi pneumatics or 3000 or 5000psi hydraulics - 3x or 5x the pressure.

Years ago I tried it with an old style non-return valve and ruined it - it can't stand the pressure. I had hoped it would be an easy way to make a fire engine - input end in the tank, output to the hose, pump in the middle. I think some of the old studded 2-way valves also degraded because of overpressure.

The pneumatic parts rely on grease inside them to keep the piston and valve seals. Water would wash it away. Also the seal at the top of a cylinder is not brilliant - some leak. The test is to extend the cylinder, put your thumb over the top nozzle, squeeze the cylinder fully with the other hand and let go. If it doesn't spring back at least half way, you have a leaky top seal. It usually leaks in the inlet direction more than the outlet direction, so it should be OK for light duty. I use the worst leaky cylinders for push applications only, such as rail points or the 8421 crane jib raise function.

This is the way to get precise positioning of cylinders, nearer to what real-world hydraulics achieve.

Mark

There is a topic around here on using water/fluid.

http://www.eurobricks.com/forum/index.php?showtopic=51439

Seems it is possible and some people have done it, but the idea needs more refining to make it more practicle. When I start MOCing again tho one of the things on my to build list is a hydraulic excavator.

water is possible, you wil need the old pumps, wich use a closed circuit. i made a waterpump on a trailer, it is hard to get things strong enough if you want some good pumping power tough, but it wil work. the old cylinders do tend to leak easily, so buy some good ones.

i also thought about using a lpe engine, turned by an xl, when the cylinders expand you can get water in, when the cylinder comes down, the lpe will use a switch to let the water go trough another hose. i hope someone understands this :s i would like to know if it works, but havent got the time at the moment.

niels

In case of the lubricant washing away, it was suggest in the other topic I linked to that you could use silicon oil, so it would be self lubricating without corroding the seals. As of pumps, it was also shown in the topic I linked to that you can use the new pumps and how to retrieve the water from the valves to create a kinda closed circuit. As I am trying to not hijack threads (taking them too far off topic) I should kindly ask that any more posts on this subject be made in that topic, and please read all of it first

Edited March 1, 201212 yr by allanp

How do the switches work?