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Old pneumatic cylinders leaking


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#1 sqiddster

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Posted 15 April 2012 - 04:19 PM

Hello everyone,

I am one of the ones fortunate enough to have purchased the amazing lego pneumatic backhoe all those years ago.
Recently I have set about building a pneumatic MOC. However I am distraught to find that the rubber seals in my old pneumatic cylinders have partially failed, and air is leaking out the top whenever the cylinder contraction encounters a small force.
I certainly do not want to pay the huge price for new cylinders, especially when I have perfectly good ones (apart from the seals).
I contacted Lego customer service, but they are not being very helpful.

Does anyone have any experience on repairs, modifications, or replacements I could make to stop this air leakage? I am prepared to dismantle the cylinders and/or purchase replacement rubber seals.

Many thanks,
sqiddster

#2 allanp

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Posted 15 April 2012 - 04:48 PM

You could try a silicone based lubricant. Sometimes that works, just make sure it's one that won't corrode the seals as most lubricants will.
Even the best can be made better, but most important is to be excellent to each other and party on dudes!!!!!!

#3 sqiddster

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Posted 15 April 2012 - 05:08 PM

View Postallanp, on 15 April 2012 - 04:48 PM, said:

You could try a silicone based lubricant. Sometimes that works, just make sure it's one that won't corrode the seals as most lubricants will.

I don't see how lubricant would stop the air from leaking out of the seal. I would be delighted to be wrong about this, however. I wonder how long it would last...

#4 allanp

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Posted 16 April 2012 - 04:50 PM

I'm not completely sure why it works either, but sometimes it does, sometimes it doesn't. If you have a suitable lubricant lying around it's worth a try. I don't think the newer cylinders have this problem, not one of my newer style cylinders have leaked.

Edited by allanp, 16 April 2012 - 04:52 PM.

Even the best can be made better, but most important is to be excellent to each other and party on dudes!!!!!!

#5 sqiddster

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Posted 16 April 2012 - 09:38 PM

View Postallanp, on 16 April 2012 - 04:50 PM, said:

I'm not completely sure why it works either, but sometimes it does, sometimes it doesn't. If you have a suitable lubricant lying around it's worth a try. I don't think the newer cylinders have this problem, not one of my newer style cylinders have leaked.

OK, I am going to give it a try. I have access to a workshop, perhaps they will have some silicon based grease.
What do you mean by 'sometimes it does, sometimes it doesn't'? Have you had experience with trying this method?
Yeah, my newer cylinders from the Unimog don't leak, but who knows what will happen in 10 years...

#6 allanp

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Posted 17 April 2012 - 04:27 PM

View Postsqiddster, on 16 April 2012 - 09:38 PM, said:

OK, I am going to give it a try. I have access to a workshop, perhaps they will have some silicon based grease.
What do you mean by 'sometimes it does, sometimes it doesn't'? Have you had experience with trying this method?
Yeah, my newer cylinders from the Unimog don't leak, but who knows what will happen in 10 years...

It depends on how badly they are leaking. I have tried it before in the past, it seems the thicker the lubricant the better for stopping minor leaks.
Even the best can be made better, but most important is to be excellent to each other and party on dudes!!!!!!

#7 DarkShadow73

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Posted 18 April 2012 - 07:15 AM

On my first built 8455 Backhoe Loader, the cylinders have started to corrode, no leaking seals though that I have noticed.  Good question, maybe a bit off your topic, but i have one:  How do you clean up partially corroded cylinder rams that were left exposed to air?  I thought about a very fine sandpaper (kind of like the finish coat sandpaper you use on real car for final paint imperfections and blending, but am a bit unsure about that, might end up with leaking cylinders like sqiddster had if I took even a minute amount of metal off of the rams.  Any ideas?

View Postsqiddster, on 15 April 2012 - 04:19 PM, said:

Hello everyone,

I am one of the ones fortunate enough to have purchased the amazing lego pneumatic backhoe all those years ago.
Recently I have set about building a pneumatic MOC. However I am distraught to find that the rubber seals in my old pneumatic cylinders have partially failed, and air is leaking out the top whenever the cylinder contraction encounters a small force.
I certainly do not want to pay the huge price for new cylinders, especially when I have perfectly good ones (apart from the seals).
I contacted Lego customer service, but they are not being very helpful.

Does anyone have any experience on repairs, modifications, or replacements I could make to stop this air leakage? I am prepared to dismantle the cylinders and/or purchase replacement rubber seals.

Many thanks,
sqiddster

Edited by TechnicFreak, 18 April 2012 - 07:17 AM.


#8 Blakbird

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Posted 18 April 2012 - 06:34 PM

View PostTechnicFreak, on 18 April 2012 - 07:15 AM, said:

On my first built 8455 Backhoe Loader, the cylinders have started to corrode, no leaking seals though that I have noticed. Good question, maybe a bit off your topic, but i have one: How do you clean up partially corroded cylinder rams that were left exposed to air? I thought about a very fine sandpaper (kind of like the finish coat sandpaper you use on real car for final paint imperfections and blending, but am a bit unsure about that, might end up with leaking cylinders like sqiddster had if I took even a minute amount of metal off of the rams. Any ideas?

If you want to clean off corrosion, I'd recommend steel wool. Use the finest type (#0000) and it will give you a polished surface.
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