It's possible to have a mixture of stroke lengths from one engine. At Wheal
Trewavas in Cornwall the 45-inch engine had a 9-foot stroke indoors but a
mixture of 4, 7 and 8-foot strokes outdoors. This particular arrangement
used horizontal or inclined rods, moved by angle or V bobs, to alter the
length of the stroke at each pump. I have no idea as to why this system was
necessary.
Pete Joseph
In cases where pumps were worked by flat rods underground often these were required for limited periods, for instance sinking on a rich shoot of ore where water inflow was too much for manual labour but the area would eventually be drained by a deeper level from the engine shaft. To install pumps at the same stroke as the main engine would require perhaps unneccesary work to excavate an angle bob chamber. This was probably the case with the 4ft stroke pumps at Trewavas. The 7ft stroke pumps were probably on the South Lode and were eventually replaced by the 70in engine on that lode; perhaps the 8ft stroke just represents what pumps were available on the mine or purchased second hand. These pumpd details were presumably taken from Lean, the figures may not be altogether accurate.
The stroke in pumps worked by flat rods should not in general be in any way indicative of the outdoor stroke of the engine.
Alasdair Neill.
On Wednesday, 9 April 2014, 10:49, SMITH PAUL <[log in to unmask]> wrote:
Finally had my question more or less answered, I have received a inventory
list for Snailbeach, dated December 1884, thanks to Steve Holding for this.
The engine is indeed
recorded as having an unequal beam, having a stroke of
10ft in the Cylinder and 9ft in the shaft (pumps), pump size was in general
stated as 9 inch, although the top two lifts were were 8.5 inch, almost
certainly for a supply to the engines at Lordshill. The bottom 9 inch lift
was a bucket lift. The pump rods were 12inch square at the surface,
reducing to 9 inch, lower down the shaft the mains rods extended fom the
surface to 342 yards below adit or day level.
Thanks for everyone's help on this, I will be down to Snailbeach again soon
to take proper measurements, and draw a plan.
Still hoping to find a manufacturer of this equipment if possible!
Thanks again,
Paul
On 6 April 2014
14:11, Paul Smith <[log in to unmask]> wrote:
> During a visit last year, I downloaded an article on a surface tour of the
> above mine.
>
> On reading I was particularly interested in the description of the
> Lordshill 60 inch pumping engine, which gave a stroke in the pumps of 9ft
> and in the engine of 6ft, this seemed strange to me for two reasons:
>
> The engine stroke is very short for a 60 inch engine
> Pump stokes are usually equal to or shorter than the engine stroke.
>
> Not having measuring equipment with me I decided to do a rough measurement
> of the beam lengths to ascertain the
approximate stroke in the engine and
> pumps, pacing out the distance from centre of the bob wall to the centre of
> the cylinder and the centre of the bob wall to the balance slot at the
> shaft. These distances were approximately equal, giving equal stroke in
> pumps and engine, (in fact if anything the distance to the balance slot
> from bob wall was the shorter which gives a shorter stroke in the pump).
> This confirmed my suspicion that information I read might be incorrect.
>
> I have since read and article in a PDMHS bulletin on lead mining at
> Pontesford which mentions this engine and gives a stroke in the engine of
> 10ft and in the pumps of 9ft which would tend to confirm that I am right.
>
> I am now
looking forward to another visit to the Shropshire lead mines
> this year with equipment to measure the engine house properly and have a
> wander around as many more sites as I can in a week!!
>
> A couple of other points about this pumping engine is the size of the
> pumps which at 6 inches seem rather small for a mine of this size and
> indeed this engine, (in fact the are quoted as 9.5 inch bore pumps in the
> PDMHS article), the other is the cylinder size which is sometimes quoted
> as 60 inch and other times 61 inch. If the size was indeed 61 inch, then
> the engine is almost certainly a rebored second hand engine.
>
> If anyone as plans of this engine house I would love a copy to study, I
> would also be very happy if
someone had information on the origins of this
> engine (foundry, where it worked before Snailbeach etc) and also more
> information on engine and pump stroke.
>
> Thanks in anticipation.
>
> Paul
>
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