Pneumatics General Discussion

[allanp]

First check your routing of hoses for kinks and hoses connected to the wrong ports. If this all checks out time to check for worn out parts.

Hold a retracted piston in one hand and block the top port. Now with the other hand, try to pull the rod out. It will move quite far as the air compresses but if the seals are good it shouldn't be able to move all the way out. If you can fully extend it without too much difficulty the seals are probably old and worn out. A small amount of silicone base oil will put some life back into the seals. Do not use petroleum based like 3 in 1 oil or WD40 as they will corrode the seals.

If your cylinders are ok then check your pump to see if it is making any pressure. All pumps in good condition generate over 30 psi, most over 40 psi.

If cylinders and pumps are sound check the valve for leaks. You can do this by submerging them in water whist pressurised. However, do not connect you piston to the valve otherwise there is a slight chance of it sending water to your piston and you may confuse exhaust bubbles for leak bubbles. Instead block the ports and pressurise the valve as you would in normal use. With the ports blocked and the valve pressurised there should only be bubbles when switching from one valve position to the other. There maybe a few small bubbles, that's fine but a big burst of bubbles every pump means a knackered valve.

Keeps us posted.

[Milan]

Pneumatic cylinder's performance degrades over time. You cant do much about it. Try to push and pull them with your hand few times before using them. And try to check if the seals inside the cylinders are leaking (block one inlet and push/pull the cylinder)

[lcvisser]

When I got the cylinders out of the box of the 42043 MB Arocs, I noticed the metal part of one of them was damaged: there is a small ring-like scratch around it. Has anyone seen something like his before? Can it hurt?

I'm not very good a macro shots, as you can see. The scratch is about 1.5cm from the right.

[Alasdair Ryan]

I don't think it will matter as the top of the piston is sealed from the cylinder.

There is a rubber seal at the end of the piston.

Edited August 11, 2015 by Alasdair Ryan

[lcvisser]

The cylinder indeed seems to work fine. I was more worried about rust or something. If it's solid aluminum it should be good, but if it's coated or something, it might deteriorate.

In any case, I asked LEGO the same question. I'll post when they answer.

[gmshades]

Anyone else confused on calling the new pneumatics "v2"? Should be "v4" in my opinion. First we had the square bottom 1 port cylinders. Then the square bottom 2 port. Then the 2 stud wide round bottom 2 port. Now we have 1 stud wide round bottom 2 port.

[9v system]

regarding gbc and pneumatics can anyone tell me how to make a double negative feedback loop?

[LennyRhys]

Anyone else confused on calling the new pneumatics "v2"? Should be "v4" in my opinion. First we had the square bottom 1 port cylinders. Then the square bottom 2 port. Then the 2 stud wide round bottom 2 port. Now we have 1 stud wide round bottom 2 port.

I don't think the version relates to the shape of the cylinders or number of ports, but rather the family of pneumatic parts - until now the pneumatic cylinders have been the same size (with the exception of the old long cylinder, which didn't really last). These 11L cylinders are brand new and all being released at the same time, hence the V2 designation. And also the shape of the ports has changed, which may be a minor thing, but it's part of the V2 family I think.

[Blakbird]

Anyone else confused on calling the new pneumatics "v2"? Should be "v4" in my opinion. First we had the square bottom 1 port cylinders. Then the square bottom 2 port. Then the 2 stud wide round bottom 2 port. Now we have 1 stud wide round bottom 2 port.

I was also confused by V2, although I would say they should be V3. The original pneumatics were single acting and required a distribution block. V2 were dual acting and worked totally differently, so were clearly a new generation. I'd put both the square and round bottomed versions in this new category. The newest pneumatics are not really a new version, they are just expanding the existing series with new lengths. The fittings are slightly modified and so are the rod ends.

[allanp]

Well, I guess they are v2. V1 was single acting, v2 was double acting and had some different sizes and colours. So I guess pneumatics have been v2 since the late 80's, it's only now that they have started calling them v2.

[9v system]

Does anyone know how to make a feedback loop?

[Epic Technic]

Does anyone know the best crankshaft configuration for a V6 LPE?

[1974]

I was also confused by ...

.. another thing : The first official pneumatic compressor

No, it wasn't the 8868 in '92, it was the 8843 (very nice, imho) forklift's C-model (with 8700) in '84 :

But yeah, it worked like crap (even with a removed spring and a more powerfull motor)

I do love pneumatics V1 and use it a lot. Airtanks and motorized pumping is no good though. Manual strokes with the 64mms works like a charm as long as it's the strokes, not retraction, that's important! (<-- that sounds dirty, I know)

Cheers,

Ole

Edited October 23, 2015 by 1974

[9v system]

.. another thing : The first official pneumatic compressor

No, it wasn't the 8868 in '92, it was the 8843 (very nice, imho) forklift's C-model (with 8700) in '84 :

But yeah, it worked like crap (even with a removed spring and a more powerfull motor)

I do love pneumatics V1 and use it a lot. Airtanks and motorized pumping is no good though. Manual strokes with the 64mms works like a charm as long as it's the strokes, not retraction, that's important! (<-- that sounds dirty, I know)

Cheers,

Ole

I might have to try that, would it work better with a gear reduction block?

[slopemodified]

Thanks allanp and Milan for your pneumatic troubleshooting help from July 31. Apologies for the delay in replying. Past few months have been busy. The pneumatics have been working fine so far with very few problems. If it's not working, I just push or pull the piston and then it works. I'll take note of your suggestions for the future.

[aeh5040]

Does anyone know how to make a feedback loop?

Here is a schematic of the simplest feedback loop from Mark Bellis' brickshelf. (This system actually appeared in the B-model of 8868). Depending on what you want to achieve, things can also be much more complicated...

[parngon]

While I was googling for pneumatic sets I came across this video:

Mind you this video is not Lego related, but I think it contains some very good basic information about pneumatic system in real life. It helps me a lot in understanding different terms and mechanics about pneumatic and I think it would be great for anyone getting into MOC with pneumatic components.

(Moderators: please let me know if it is inappropriate to post this video link here...)

Talking about pneumatic sets, my eyes are always on the 8868 and 8455. I think I will definitely get a used 8455, but for 8868 I am looking at the "studless" version of it (http://www.eurobrick...howtopic=43444) because it is easier to get PF components than a 9V motor (especially in Hong Kong). Has anyone compiled a part list for this studless version?

Thanks in advance!

[Jim]

Hi,

I think it's very interesting!

However, it probably doesn't need a separate topic. I will merge it with the General Discussion topic:

http://www.eurobricks.com/forum/index.php?showtopic=111891

[Epic Technic]

Hey guys, I am having a bit of a struggle trying to make my LPE more efficient.

I need to find a better method to get the rotation from the crankshaft up to the switches, without using that many gears. This is the space that I have to work with (i have to get the rotation from the blue circle to the red circle):

Any suggestions will be dearly appreciated. :)

[DK-Brickfan]

How about a chain, like a real engine? Or the small tracks with 2 gears on each axel?

[Epic Technic]

How about a chain, like a real engine? Or the small tracks with 2 gears on each axel?

I tried the chains but it not strong enough, they just separate. Thanks anyways :)

[doug72]

Try a 12T double bevel gear on the red and blue axles and a 36Tdouble bevel gear on the centre hole.

That should fit within your space limits.

An 8T/40T/8T gearing might also fit.

Edited November 13, 2015 by Doug72

[MSc Shobaki]

20t double bevel gear on top shaft, 24t gear on center shaft, 20t double bevel gear on bottom shaft will turn out fine :)

Edited November 13, 2015 by MSc Shobaki

[allanp]

20t double bevel gear on top shaft, 24t gear on center shaft, 20t double bevel gear on bottom shaft will turn out fine :)

Yup, that's probably the most efficient way. Or you could have 24t top and bottom with a 20t idler.

[MSc Shobaki]

That's the most efficient way since the balance shaft (center) is better to spin with higher torque rather than speed. Its purpose is to maintain an even distribution of rotation.