piston within a piston water pump?

[Aquarius21]

Hi, while visiting an ill gentleman in hospital today he spoke of seeing years ago a low power water pump
which had a piston within a piston perhaps made in Scotland. He could provide no more details.
Anyone every heard of such a creature? thanks, Quincy

 

[Henk]

I am not sure whether this answers the question, but there is at least an example of a steam engine with concentric steam cylinders. It was used to pump out polders. I guess it is not low power, but at least relatively low pressure (3 - 4.5 bar). But then again the piston diameter is 3.5 m. The outer ring is used with expansion. So in essence (if I remember correctly from visiting it say 15 years ago) the inner piston is the high pressure one, and the combination of inner piston and outer ring is used for the low pressure cycle.

You can have a quick look :
http://www.cruquiusmuseum.nl/englishsite/steamcycle.html

Animation of the steam cycle: http://www.cruquiusmuseum.nl/englishsite/flashanimation/CruquiusEN.html

Even if it did not answer your question, you may like having a look around.

Henk

 

[Aquarius21]

My thanks, Henk, and a joyfull Christmas to all reading, Quincy