Linear Actuators VS Pneumatics

[DrJB]

I am not sure why such 'obsession' with comparing the two. They both have their applications. To me none is better than the other. I think of them as two different tools in a toolbox, and they both serve different yet complementary functions. If you want precise positioning, then it's LA. If you want realistic models (8455) and compact builds, then it's pneumatics. Why do I have to pick a favorite?

Edited May 26, 2017 by DrJB

[Milan]

7 hours ago, Aventador2004 said:

1) if there is a topic for this, not bump it.

2) I can't find it.

1. Bump it if you have something important to add, in this case it is much better to bump than to open a new topic, for the very same thing.

2. It shows on the first page of the search results when you search for "Pneumatic" "Actuator"...

 

Merging with existing topic.

[Aventador2004]

3 hours ago, Milan said:

1. Bump it if you have something important to add, in this case it is much better to bump than to open a new topic, for the very same thing.

2. It shows on the first page of the search results when you search for "Pneumatic" "Actuator"...

 

Merging with existing topic.

Sorry, my search just have messed up, now I know next time.

[mocbuild101]

9 hours ago, DrJB said:

I am not sure why such 'obsession' with comparing the two. They both have their applications. To me none is better than the other. I think of them as two different tools in a toolbox, and they both serve different yet complementary functions. If you want precise positioning, then it's LA. If you want realistic models (8455) and compact builds, then it's pneumatics. Why do I have to pick a favorite?

Agreed!

Also, LAs are easier to use in motorised models, while pneumatics are better for manually controlled models.  

[Juxtapoisson]

I am looking to build a stationary baler.  Think cardboard, not hay.

Clearly, the pneumatic option would look more realistic and claim realism.  

But I suspect the LA might actually make the device "function" more true to life.

 

Does anyone have any suggestions in the realm of actually smooshing things to bale?  I considered using parallel pneumatics, but that would actually look sillier than the LA.

 

[Bublehead]

Two stage squisher... one overfills the second which is at 90 degrees with first... second squisher then squishes it into baler... using shredded paper as your squishing medium?

[Aris]

On 4/25/2009 at 12:25 PM, DeBriquesEtDeBlocs said:

I was wondering, why did Lego suddenly create a linear actuator when it has always been possible to make your own with existing parts ?

Yes indeed! Maybe just because linear actuators need less space than a custom one.

[Aris]

On 10/16/2010 at 12:49 PM, allanp said:

Pneumatics are faster, stronger, more reliable, far more realistic, are cooler, more authentic, more useable and just about better in every way than LAs.

The only advantages LAs have is their absolute pricise positioning (pneumatics can be positioned more than pricisely enough for most cases anyway!) and they are a bit longer (pneumatics really should be made to be about twice as long as they are now to be in scale with todays larger sets). I like that some sets have nice complicated gear trains to drive them, but you don't have to have LAs in order to have nice complicated drive trains. Besides the drive trains in the 8043 to the actuators really aren't that exciting, just a couple of gears and a bunch of UJs. The majority of the complexity of that set was in driving the tracks. When you consider how much the LA does for you (converts a fast rotary motion into a slow linear motion in one single part), it's too much to be done for you. Technic is a toy but it is more than that. It is unique in how it recreates real life mechanics and machines in a authentic way. It's not like having a toy, it's like having the real thing under the christmas tree. As a child, there was nothing cooler than that. When have you ever seen a front end loader in real life powered by LAs? I know they are not powered pneumatically either but it is a fluid under pressure moving a ram. That's just so much more real than LAs which just seem far too detatched from the real thing to give that same sence of having the real thing, just smaller.

To sum up, Pneumatics encapsulate everything that is good about technic. They work great and just like the real thing and are fun to play with. LAs on the other hand are tedious, boring and brings technic down into the realms of just another toy.

Totally agree about pneumatics. I prefer them. I very much like your philosophy. Reminds me old times.

[allanp]

7 minutes ago, Aris said:

Totally agree about pneumatics. I prefer them. I very much like your philosophy. Reminds me old times.

I forgot I wrote that, but I agree with you agreeing with past me 100% 

[Aris]

On 7/30/2012 at 5:43 PM, daniele said:

I prefer pneumatics BUT with this, you don't have a precise control. I think pneumatics need a more precise valve.

Of course you don't have a precise control with pneumatics. But in case you create a specific structure near the cylinders (for example with rubbers) you can fix their precision a lot. It's about creativity. For me, the air precision is not solved by air switch, even if it's manually operated or motorized .

[Aris]

On 9/4/2012 at 9:10 PM, ShaydDeGrai said:

I used to teach a robots class where we'd often prototype things in LEGO parts before heading to the machine shop. We had brick built linear actuators at that time (no official part available yet) and the new parts are clearly stronger and smaller than the ones we used to build, but for the types of models I was assigning, it was pretty clear that you needed both. Pneumatics did some things very, very well. LA had other fortes. Sometimes the mechanism itself was less important that the form factor and we just went with what was easier to fit/mount.

LA had the advantage of smooth starts and stops, controllable velocity and precision placement down to the size of gear tooth; Pneumatics, not as good on these fronts.

Pneumatics fit into tight places, faster to react, faster to reach max/min extension, controllable strength (via air pressure in the reserve), lighter (results in less torque at the base when articulating multiple joints) and more vibration tolerant.

LA's need either embedded motors or a drive transmission to move them. This adds bulk, weight and complexity to the design. In the case of LEGO models it also raises the question of batteries and snaking power cables.

Pneumatics need pressurized air, this means a reserve, hoses and some way to recharge the reserve dynamically (we used to use geared motors to drive a brick built compressor for our tanks, giving us the worst of both worlds: hoses, wires, tanks, motors, drive chain _and_ batteries...)

LA can lock their position solely by the force of friction through a worm gear. This can be both a blessing and a curse. If you want a model to hold a pose without draining batteries or bleeding off air pressure, it's a big win. If your model is subject to external forces (possible large ones) it's a good way for things to break off or even snap.

Pneumatics need active pressure to hold a pose, but can also be bled off quickly if need be. If a pivot point is over torqued, safety valves can trip, bleeding off the air and allowing the model to move with the external force in a timely fashion rather than fight against it and risk breaking something.

And finally, for the true geeks out there, pneumatic valve networks can be configured into the mechanic equivalent of NAND gates and PLAs so with enough valves, tubing and air pressure you don't even need a NXT brick to control things. I suppose I could probably build an actuator-based relay-like system with the addition of a few non-LEGO conductors, but it would never be as compact as the valve based implementation.

Excellent survey. Thank you for mentioning these.

[Bricktrain]

amazing, it was almost two years since this thread was posted in.

[allanp]

1 minute ago, Bricktrain said:

amazing, it was almost two years since this thread was posted in.

Yeah but to be fair if someone starts a new topic people complain that there's already a topic about it, so what's a guy or gal to do?

[Aris]

Hi all,

In 2016 I did some interesting experiments with large pneumatic cylinders and LA, considering 2 very important factors : distance and torque.

However, not in a straight distance, but multiple directions. As for pneumatics, air flow depends on the pump used (large or mini) and the use of air tank as well.

All pneumatic functions had 1-2 large cylinders and their air switch.

Pneumatic cases :

a) 1 manually operated or motorized switch, 1 meter away from air compressor.

b) a system with 10 manually operated or motorized switches, 1 meter away from the same air compressor.

c) 10 manually operated or motorized switches, 1 meter away from 10 different air compressors (1 for each air switch).

LA case :

a) 1 motorized LA, 1 meter away from the pf motor, including a structure with diagonal paths and gearing.

 

So if you are interested in this survey, you may mention your personal experiences if there are any.

The question that arises here, is which case is delivering the highest torque and which the lowest. I would very much like to see your opinions.

Edited May 11, 2020 by Aris