On 14/08/2014 17:49, Chris Hogg wrote:
On Thu, 14 Aug 2014 16:08:28 +0100, "Nightjar \"cpb\"@" "insert my
surname here wrote:

On 14/08/2014 11:10, Chris Hogg wrote:
And surely only really applicable to small volumes of water supplying
isolated locations such as farms or individual houses. They used to be
fairly common in Cornwall, and no doubt elsewhere were the topography
was appropriate, for raising water from a valley bottom to, for
example, a water trough for cattle on higher ground. Can't see them
being used on anything like a large scale.


This claimed to give 50,000 litres a day with a 100ft lift:

https://www.youtube.com/watch?v=B1PlQzRYkII

Oh interesting! Thank you.

Until I found that video I hadn't realised how noisy they are.

It doesn't say where it is AFAICT, but a
set of three Green and Carter pumps were unearthed (literally) in the
valley below Heligan Manor* in Cornwall some 20+ years ago. They had a
(combined?) capacity of 9.5 gpm (~62,000 l/d), pumping against a head
of 300 ft and over a distance of 1.5 miles. They were refurbished with
G&C's help. See http://www.greenandcarter.com/main/history/case_1.htm

I like the 'guaranteed forever' on their products and the fact that they
have spares for all ram ever made on the shelf, presumably because they
have made very few changes to the design in the past couple of centuries.

But you'd still need an awful lot of them to run a decent sized tidal
generating system, and the volumetric efficiency (water pumped / water
used) is poor. See http://en.wikipedia.org/wiki/Ram_pump and scroll
down to 'Efficiency'.

Oh yes. Hydraulic rams are only useful if you can put high volumes of
water through them. In that case, if you want electricity, an
Archimedean screw generator would probably be a better option.

* 'The Lost Gardens of Heligan' http://www.heligan.com/)


--
Colin Bignell