Air/ hydraulic cylinders.

[jekjr]

Have any of you ever used a hydraulic cylinder as an air cylinder? I need a cheap air cylinder and they are hard to come by CHEAP. I can find some cheap hydraulic cylinders however. I think it ought to work if I put an inline oiler on it to keep it lubricated. An air cylinder would need an oiler as well. I do understand that an air cylinder would not be suitable to use as a hyudraulic cylinder because of the pressures involved.

I have rebuilt hyudraulic cylinders and used air to test them.

Anybody ever done this?

 

[reynoldston]

Don't know much about cylinders. I really don't know why it wouldn't work. It would be fast, jumpy, and no control either in or out.

 

[jekjr]

Don't know much about cylinders. I really don't know why it wouldn't work. It would be fast, jumpy, and no control either in or out.

Why do you say that? If I control the flow what will make it different from a reg air cylinder?

 

[mullins87]

I don't know how air cylinders are built. Hydraulic fluid will not compress, well at least not enough for us to really see it. Air on the other hand, will. I think as the air is pumped into the hydraulic cylinder, the pressure will build to the point where the pressure overcomes the stiction of the piston and it will move suddenly and could be very rapid. At work we have large demolition shears that are excavator mounted. One of my typical assignments is working with a vendor repairing those shears. Usually, he will remove a broken unit and replace it with a functional one. Then he will make neccessary repairs to that unit. Sometimes he has to actuate a cylinder for the repairs. Not having an excavator to serve as a power source, he just uses an air compressor. The compressed air works just fine, but sometimes the cylinder will jump unexpectedly. Needless to say he makes sure everyone is clear before he starts applying air pressure. If all you are interested in is full extension or retraction and control isn't an issue, then I'd say go for it.

 

[reynoldston]

Why do you say that? If I control the flow what will make it different from a reg air cylinder?

I have repacked hyd. cylinders and to take them apart I use air pressure. Like I said I am no cylinder expert but when I put air pressure to the hyd. cylinder they jump very fast to the full open to the point when the cylinder ring is removed they come apart. Now I have never regulated the air to know what will happen. Also when you get air mixed in with the hydraulic oil the cylinder gets very jumpy. I have also worked in manufacturing that used air cylinders and as I recall the were fast and were ether in or out. Air will compress as oil will not. I would say try it and see what happens???

 

[jekjr]

I found what appears to be a suitable air cylinder and a small control valve which I just ordered. Hopefully it will do the job. Thanks for the input.