One of the main differences between the old system of pumping and the new was that the bucket pump is a lifting pump and thus work on the inboard ie power stroke of the engine. The later system pumping is done by plunger pumps which are in fact force pumps and work on the outboard stroke, not powered. on a normal Cornish cycle single acting engine. The weight of the rods doing the work, the engine actually lifting the rods at the end of the pumping stroke. The bottom lift was usually a bucket pump even in later configurations as this was easier to extend during shaft sinking.
Both types tended to be made of cast iron, although brass was sometimes used. The obvious physical difference visually was that the spur of the pump rod powering a bucket lift went right down the centre of the rising main of that lift to the bucket of the pump at the bottom, with the later type of pump (plunger) the spur of the pump rod only left the main rod just above the H piece of the plunger pump (near the bottom of the rising main for that particular pump). Forcing or plunger lifts can be much longer than bucket lifts thus less of them are needed in a deep shaft, working on the weight of the main rods in the shaft they tended to be gentler on the steam engine itself, giving less shock load a the beginning of the steam (power) stroke.
Thus the main visual difference in the two types of pitwork is the length of the pumping spur which leaves the main rod and how it reachs the actual pump, in the old system as mentioned it travels the whole distance to the pump down the inside of the rising main from that pump, whereas with the plunger it is much shorter and leaves the main rod just above the pump body itself, with the rising main towering above it.
The bucket lift also looks like one straight pipe, whereas the plunger lift as what looks like a letter H at the bottom with the actual pump body at the side of the rising main.
Many pictures of the later system are available, if they show the bottom lift of pumps it will generally be a bucket lift (pump spur disappearing into top of rising main) To picture the old/early system, just imagine the bottom lift repeated the whole length of the shaft!!
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