Deon Roux, the builder we have approached to work on the tail-race, solved a mystery! We knew his father had carried out the restoration of the building in 1989, but the bomb-shell he dropped was that he himself collected all the loose parts we'd found in the attic! He also informed us that they came from an already dismantled Mill in Cradock, almost 800 km away from La Cotte. He knew that the (rather flimsy) Hurstings and remains of a water-wheel were badly worm/beetle-eaten. The remaining parts seem remarkably free of damage.
The Pit-wheel didn't look too impressive when we found it lying in the attic, although interesting in that it has four spokes and five cants.
It was one of the first parts which Jon took away to his workshop in Maitland. He cleaned it up, made three new cogs, copying one of the better ones, and discovered the cants are lovely honey-coloured Yellowwood! It seems expertly made and surrounded by a heavy wrought-iron band.
The disappointment was that the Lantern pinion I photographed in 2010 was missing. All we had to work on was this photo, taken from a gap in the attic floor. Already at that stage, the balance-Rynd was missing from the Runner stone:
We reckoned there were nine rungs, and by measuring it and the Bed-stone on the photo I arrived at a diameter of the discs and the pitch circle diameter (PCD). I made up a mock-up of half of the lantern, along with a wooden rod for it to rotate on and a pivot to clamp to the middle of the assembled spokes.
The PCD was too big. The rungs, I could see would never enter and exit the cogs comfortably. I rather made several measurements cog-to-cog, which maybe I should have done in the first place. I plotted that distance on the drawing I'd made and marked out the first set of rungs from.
The measurement came out on a smaller PCD. I sawed off the nine rungs, turned nine more rungs, drilled new holes on the new PCD, between the old rung positions and fitted them.
At this stage we had to hang the Pit-wheel loosely over the Axle-tree and from then on I had to work sitting on the edge of the pit with the wheel hanging from a chain-block. I worked with the mock-up half-pinion and a 'Power-file', a very narrow belt-sander. After every few cogs, the most about eight, I had to lower the wheel, sling it again a few cogs further around, then pick it up again with the chain-block and work on the next few cogs.
I marked the cogs I was happy with, then moved on....
Once I'd gone full circle, I tested some of the first I'd done and was satisfied. Next job is to make a full Lantern pinion with top and bottom discs, and the same rung diameter, which is 1" (25.4mm). I will use the same drawing to mark out both discs. This time the holes will be square, so the rungs can be turned four times in their life.
Originally the Stone spindle would have been square and the top and bottom discs of the Lantern pinion would have had square holes to match. However, Mark wants the water-wheel to run often during the day, and I don't like the idea of the Millstones turning unattended. That left two possibilities, one to have a series of about four rungs of the pinion removable, which are called 'Slip-cogs' ('schietstaven' in Dutch). I wasn't happy with this, so I decided to fit bearings in the top and bottom which will run on a round shaft. The shaft will have a key-way cut in it and flanges above and below the Lantern with pegs which engage with the discs when we do want the Stones to turn.
Jon laminated two pairs of square wood, glued together at right angles and nine square bars for the rungs made of Ironwood. I marked the outside diameter, the pitch circle of the rungs and divided those up into nine equal divisions, also the diameter of the bearing outer race.
After some dismantling on the lathe to fit the remaining piece, it was possible to turn the rough edges of the disc round.
After setting the now round disc a little distance from the face-plate, I could bore a hole for the bearings, first with a 50mm Forstner bit.
When the second disc was machined and ready for its bearings, I tapped the first pair a bit further through so one protruded about half its width, and linked the two up, then took a light cut to true the outer diameters exactly the same.
Then the face which would be on the machine bed when the holes are made had to be trued up as well, otherwise the holes wouldn't be square to the discs.
The circles and squares were drawn according to 30mm square rungs Jon had supplied, made of Ironwood, but as the round parts of the rungs will be 1" (25.4mm), and because it's easier to make the hole first and to fit the rung to it, I decided to go for a smaller square.
With this job in mind, I was watching advertisements and found a Multico chisel mortiser for sale not far away at a reasonable price. I'm sure I'll wonder in future how I managed without it!
With 18 holes to make (or nine pairs), it made sense to set the machine up with limit stops. It's supposed to have longitudinal stops built-in, but those were missing. No problem to re-cut a metric thread over a UNC one and install a 12mm Redibolt through the top slide with double nuts at each end. Fore-and-aft was a different matter! I drilled and tapped two holes and attached a plate to the front left of the saddle and drilled two 12mm holes, one in line with the bed-way, the other to just miss it. In the first, a piece of Redibolt with two locking nuts engages with the front of the bed-way. A long one reaches to the back with a washer pinched between two nuts which engages the back of the bed-way.
To locate the discs centrally every time, I cut a half-moon of scrap wood and clamped that to the table against the back fence, and drew a register arrow exactly in line with the chisel in the middle of its longitudinal travel. This register could then be aligned with each of the 40 degree radial lines for the holes on the discs.
After all this preparation and with no little trepidation, I started the first hole. The wood is Hard Pear and (I had been warned!) there was smoke, particularly making the first hole. I started back left of the square each time, working a little way into the wood, then withdrew and shifted across half a chisel-width and worked a bit deeper and so on. The depth stop was set to finish in a piece of wood under the discs, so that the drill/chisel didn't touch the table and also that the chisel would exit cleanly.
The actual machining took an hour and a half; the setting up had been a different matter altogether! I recorded the process on video https://youtu.be/DyG3e8jRDYw
I was concerned that the wood might crack outwards, and normally a Lantern Pinion has a metal band around the discs. It was Christmas time and the engineering shops were closed, so I looked around in the shed and found a cast-iron pulley with diameters which could work. I cut a slice off it wide enough for both rings and again dismantling the 'gap' of the lathe bed, and using the biggest 4-jaw chuck, it just fitted!
The inside diameter of the first half cleaned up exactly on the right size, and I could force it over the lower disc:
The second one for the top disc is slightly thicker, the pulley was 'crowned' and there was no need to continue machining off material unnecessarily.
I started on the first rung as an experiment, sawing from the 30mm square to 27mm, then sanded it down to very close to the final size. It was then necessary to fettle the square holes a bit with a sharp chisel. One end had to be marked for its exact centre and drilled with a centre-drill to hold it centrally in the lathe at the right hand side:
I turned the first rung to 1" (25.4mm) when I was happy that the top and bottom would fit snugly into each disc.
Then tapped the rung into the first hole in the bottom disc.
The same process was repeated eight more times, gradually filling up the lower disc.
With more fettling of the holes to allow the rungs to align with the top disc, it was possible to tap the two discs together. The pinion is tight as an assembly! This shows the rungs partly inserted in each disc.
It remained to press them together, with a spray of 'Woodslide' on all surfaces.
There must still be some way of driving from this which will be driven at all times that the water-wheel turns, to the round Stone-spindle which will have a keyway cut along its length, for when it's required that the Millstones must turn.
To be continued.....
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