how can one safely open a shock absorber?

[Arquibaldo]

I have several used shock absorbers that were replaced from my cars.

They have beautiful chrome shafts that could be used on a CNC router - at least in the
z-axis.

But, I hear they are pressurized, so I'm afraid something nasty can happen if I try to
cut them apart to remove the shafts...

Is there any danger? What would be the proper, safe procedure?

Nelson

[MadMax]

I'm assuming you're talking about airsprings which are usually also oil damped.

I've disassembled them before for a product I was working on. I was inspecting the seals to see if our suppliers were using the materials we specified.

Anyhow, one way to depressurize them is to grind a small opening into the side of the cylinder before cutting them entirely open. I like to use an abrasive wheel on a dremel rotary tool. Grind in until gas or oil starts to leak out. I prefer to hit somewhere about 1.5" from the far end from the rod. If you want, orient the rod upward so you don't get a blast of gas as soon as you pierce through. Oil will ooze out first as soon as you break out a small hole. The oil will continue to ooze out until it's depleted then you'll get a hiss of gas. You should be able to get a small pin hole with a dremel grinding wheel instead of zapping out a wide slot. If I'm working with a very high pressure cylinder, I prefer to grind a line perpendicular to the centre axis of the cylinder. Pressure vessels usually rupture on tangent to their circular cross section rather than by popping the ends off so don't grind parallel to the central axis or you'll bring the cylinder closer to rupturing condition before you put a pinhole in the cylinder. Cylinder walls are usually very over engineered. It's hard to get a bursting rupture unless you grind a long groove down the side without going through and gradually work it down the entire length. Instead grind only in one spot making as short a groove as you can.

Open up the hole further once the gas seems done to make sure it's depressurized before completely cutting open the cylinder.

Alternatively you can put a nick along the side of the rod (if this is ok) about 0.5" long and compress the cylinder so the nick interrupts the seal inside the cylinder to let the gas out. I prefer the first method because I don't have to compress the assembly, but if you're really worried about bursting the cylinder this way is pretty benign.

[Arquibaldo]

Dear MadMax:

Thanks a lot for your kind and thorough reply.

I'll use your method... of course, I'll also wear my faceshield and welder's apron and
gloves - you can never be too careful...

Nelson

[TarHeelTom]

There are many motorcycle shops around which rebuild shocks for off road bikes. Don't know their methods, but I'd bet that they would be willing to disassemble the shocks for you, maybe in exchange for the unwanted parts.

You might be able to talk them out of old shafts also.

Tom