I had a tour of the dam internal chambers and straining tower at Llyn Vyrnwy some years ago. There's a hydraulic engine in situ at the top of the tower, which was in constant use from installation in the 1880' till the 1980's, it didn't break down, they just decided to use an electric motor instead. Unfortunately I can't find the photo's, but it might be worth looking on the web. Oh, I can't remember who made it.