pneumatic switches help

[shimon]

Hello!

i have recently noticed that there are many pneumatic switches that are leaking air

40% of my switches have the same problem

i dont use to much air in them i use them very carefully

but for example i put the switch on the center and press the pump and then i hear the air leaking from the top of the switch

and theres no way to fix it

about 5 switches i own have the same problem

i cant send that much letters to TLG about replacements

is there something i can do with them ?

some of them i get broken and some are breaking after a while

anyone has the same problem?

[Jurgen Krooshoop]

I've recently uses some (10-year) old valves in two models, but they didn't give any real problems. I've noticed that (bigger) pneumatic systems aren't 100% air-proof, but no air-leaking-noise or equivelent.

Edited April 21, 2010 by Jurgen Krooshoop

[Blakbird]

I have over 100 pneumatic switches and I can't say I have ever had one leak. If the valve is not centered, it does indeed let air out but that is by design. Other than loose hoses, I'm not sure what else would cause the problem you are mentioning on multiple switches.

On the other hand, I have had quite a few pumps that leak and won't put out much pressure.

[shimon]

I have over 100 pneumatic switches and I can't say I have ever had one leak. If the valve is not centered, it does indeed let air out but that is by design. Other than loose hoses, I'm not sure what else would cause the problem you are mentioning on multiple switches.

On the other hand, I have had quite a few pumps that leak and won't put out much pressure.

the valve is centred but its like the black thing is too narrow so i see some space when i look at it from the top

it is the design alright..

theres nothing i can do i cant move it

[DLuders]

Shimon, do you have the older Pneumatic Switch #4694 (first picture below), or the newer #4694b (2nd pic)? EB member Mark Bellis would probably know best about how to troubleshoot the pneumatic components.

You many have to shell out some shakels to get some replacements from Bricklink.

[Blakbird]

the valve is centred but its like the black thing is too narrow so i see some space when i look at it from the top

it is the design alright..

theres nothing i can do i cant move it

Are you saying it is stuck?

Have you had these switches since they were new? If not, it is possible someone tried to disassemble them. If the cover is removed it could leave a space around the black part and allow air to leak out. They are not made to be taken apart and reassembled, though a couple of people have done it successfully. I would suggest putting in a little synthetic grease along the edges and see if that seals the leak. ( I use "Super Lube" as an assembly aid when building rocket motors and swear by the stuff, so I recommend that.)

[Jetro]

I've opened up a number of the old type switches (never tried the new type) and have never had a problem with leakage. I did find that the material used to keep the switch air-tight (the rubbery part that is inserted in the bottom centre of the actual switch) is made of different materials depending on when the valve was made and no amount of lubing will make the older switches work as smoothly as the newer ones.

[Brickthus]

I have opened a couple of the older switches when they leaked enough to cause problems with operation (i.e. the major leakage prevented highly-loaded cylinders moving). I don't recommend opening switches unless they are already failed to a similar extent, because this will wear the tabs that lock the two parts of the casing together and it might never be possible to squeeze the lever as well as when the switch was new.

I would recommend re-lubing of older switches, since the sealing effect of the lube must wear out eventually by being spread around and forced out of the ports. It might not be necessary to open the switch to do this, because some lube could be injected into the ports or put on the port side casing in the hole made by moving the lever. I might try getting some of that super-lube to try it out on older switches. Be sparing with the lube though.

Certainly the newer switches (with pin holes) are stiffer in operation than the older ones. This is not a bad thing because it gives them enough life (measured in lever movements). It made me wonder whether my proportional pneumatics might cause them to expire early (many operations per minute) but the cycling is not as much as for the components of a pneumatic engine.

Pneumatics are life-limited components, just like motors and anything made of rubber. The design criteria for the parts would extend only to the point where a child, who is of suitable age for a pneumatic set to begin with, might have given up on LEGO as a hobby, so components need to last only 3-5 years to satisfy that criterion. Like many products, the characteristic life of a component is set to the length of time after which the manufacturer will not see too many complaints. If a certain length of guarantee is sold in the shop (on top of the usual 1 year guarantee), you can bet the characteristic life of the product is set to be just beyond it because otherwise everyone who bought the guarantee would need a replacement. Therefore extended guarantees on most electrical products are worthless, unless you get a duff product. Just make sure the box you take away has the product in it before you are asked about the extended guarantee, so no-one can select a better or worse item on the basis of your decision! Thankfully this would not apply to LEGO products and most of them last a lot longer than electronic goods! The quality of LEGO products is one of the main reasons to recommend it.

This limit of life might be about 3 months running time for a motor, but it's measured in running time, not in real time. This means it should last 10 years or more. There is a time factor with pneumatics and rubber items though. The lube becomes less viscous with use and probably with higher temperature too. this may account for the stiffness when a valve has not been used for some time. Therefore don't bury them too deep in your MOCs so that you can cycle them a bit before running a MOC. I usually take a pneumatic MOC through all its cycle stages before running it from air pressure.

Mark

[Paul B Technic]

I have some of the older type switches that would be 15 years old at a guess and I have never had any issues with them at all.

Paul