Pneumatic cylinders single and double outlet

[Chilly]

I've been looking to buy some pneumatic pumps that don't have the spring, so I can make a compressor.

I mistakenly thought that some items on ebay were pumps because they only had one outlet, like the sprung-loaded pumps I already have, but having bought them, it seems they are cylinders!

So, my question is: why and where would you use a single outlet cylinder. ( I have two sets that came with pneumatics, the 8462 Tow Truck and the 8455 Backhoe Loader, and although they have different style cylinders, they all have two outlets.)

[sogel]

The cylinder you're referring to are from the old pneumatic system from the 80's. For example the set 8851 - excavator uses this system (I still have one from my childhood days). On blakbirds technicopedia the functions of these two different pneumatic systems are explained.

Greetings, Henry

[kieran]

Yep, you have one of the old style cylinders, they also come in 2 sizes for info.

[Jetro]

The old cylinders work fine as pumps, they simply lack the valve that avoids you sucking the air back in again. If you use them together with a valve block they do a great job.