The set up

The set up
5.46mm jet delivering 0.68 l/s to the pelton which is rotating at 900 rpm and generating 135 watts into the grid.

Monday, 7 August 2017

Peltons past and present.

I've recently acquired a new pelton wheel, - only it isn't new, - it was made in 1905 by an engineer who, at that time of his life, lived and worked from a small town about 40 miles from here. His name was Percy Pitman and here is an article he wrote for the October edition of 'The Engineer' in 1905. I guess it's probably him in the picture:

It's worth remembering that 1905 was only 25 years after Lester Pelton, living in Ohio, USA, filed his patent for an impulse turbine having cups with a splitter ridge, so that the cups effectively became two cups side by side. Prior to this, cups were more like a single bucket and the water entering them had to bounce back rather than be streamed outwards to each side.  Pelton's design made the wheel significantly more efficient.

The wheel that has come to me was for sale in a farm auction.  Where I live, when a farmer retires, it is usual for him to have a sale of his old equipment, - everything from tractors to scrap wood and steel. The farmer who was retiring had bought the pelton at a similar farm auction some years before, but had never done anything with it. By the look of it, the lack of wear on the buckets indicated it had NEVER done any real work:

Back home, shot-blasted, painted and mounted on a frame which I picked up from another farm auction, the wheel is beginning to look presentable.  I'm intending to put it close to my Powerspout so people passing can understand what a pelton wheel is.  I'm amazed at how many people have never heard of the word !  Here's how it looks now with a Powerspout pelton next to it to give an idea of size:

Life sometimes throws up odd coincidences !  A few weeks after getting my pelton, a friend drew my attention to an advertisement for the sale of ANOTHER pelton wheel, almost certainly by Percy Pitman because of having identical construction and being located in the vicinity of Bosbury where he lived, but this time a more complete example than mine:

To have TWO historic pelton wheels become available within weeks of each other is a truly unusual event.  And to learn that one hundred years ago, in this part of Wales, there was a man making his name by the manufacture of such wheels gives a nice historical dimension to my Powerspout operating today.  

There's one curiosity that remains with me though: - my pelton is NOT well made; the cups are steel castings bolted to a circular steel plate, but they have not been attached around the circumference in a way that makes them equi-distant from each other, - at one side they are crowded together and at the opposite side spaced more apart.  The effect is that the wheel is badly un-balanced and a rather crude effort was made to balance it by bolting on a strip of steel. I have removed it because it was rusting badly and the rust was eating into the circular steel plate, but where it was attached can just be seen by the presence of two bolt holes at the wheel's 12 o'clock position.

Perhaps Percy Pitman was not the meticulous engineer he advertised himself to be ! Certainly he quickly left behind the manufacture of 'industrial' pelton wheels to pursue the manufacture of "hydraulic equipment for educational establishments".  But judging by the progressively more prosperous houses he occupied in London he must have died a well-to-do gentleman and a far cry from his humble beginnings in Bosbury, Herefordshire where he started out.

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