There was an order from Zest Catering for 18kg of meal for each of the forthcoming Open Gardens Weekends, so I decided to do both batches together. I have been looking for an opportunity to put bigger volumes of grain through the elevator.

But first, there was a surprise! The rotary sieve bought at least a year ago from Joos Solms in Champagne Valley, Natal had arrived! We heard about the availability of the machine through Joos’ involvement in the Reichenau Mill project.

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The machine needs attention to the outside woodwork at the bran end particularly, and it must be connected up to be driven from the shaft above, to run at a speed of 280 to 300 RPM. Also, the frames of the screens don’t seem to fit quite correctly and one has no screen, another is torn, so some work is needed there. Later in the day I found the handle for the left hand flap inside the machine and glued and screwed that back on.

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I haven’t wanted to add any other machinery to the Mill house, but I feel sure there was such a machine and there are marks in the concrete floor next to the Stamford Mill, where some kind of machine was bolted down. Putting a machine there would be too much in the way, so this corner is ideal, under the line shafting. It can be driven, through a lay-shaft, from the unused pulley above.

While the water wheel was running at 6 RPM, I measured the speed of the line-shafting at 50 RPM. Theoretically, the pinion shaft running off the pit wheel should be running at 6 RPM times 88 (cogs on the pit-wheel) divided by 11 (Teeth on the pinion) = 48 RPM. It has a pulley of 610mm diameter and that drives a pulley on the line shaft of 500mm diameter, which should make the line-shaft turn at 58.56 RPM. The ‘spare’ pulley above (but not in line with) the sieve input pulley has a diameter of 600 and that on the sieve is 225mm. If we work on the theoretical speed of 58.56 RPM, and if these two were to be directly coupled, the sieve would turn at 58.56 RPM multiplied by 600mm divided by 225mm = 156 RPM; about half speed. So any lay-shaft must have an input pulley half the diameter of the output. Somehow it must be possible to set the tension of both belts. There is a bracket on the top of the machine which can be used, where an electric motor was previously mounted.

The tests with the elevator weren’t entirely without a problem! I was pouring grain into the hopper, it was being lifted and thrown out at the top, despite the water wheel turning at only 5 RPM, yet the quantities didn’t seem to tally! There could only be one reason, a ‘leak’ at the base of the elevator. I raised the crawl-space cover, and not entirely surprisingly, found a big pile of grain on the floor!

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Also interesting was the ‘crop’ of sprouted wheat from previous spills, growing entirely in the dark, looking like strands of yellow plastic! Luckily, I had vacuumed this space out recently and it was possible to scoop most of it out. The last batch which needed sweeping together, went into the sieve I use for the meal to let the dust fall through to waste.

The problem I had overlooked when I made and attached the base about two years ago is that grain flows like water. Any gap, even if it faces upwards, will ‘leak’ grain. A handy wedge was lying around which was just right for the main gap, and after some more tests showing that the corners leaked, I mixed up some epoxy putty and filled them.

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Once this problem was corrected, the elevator worked well, and for the first time, it could fill the Vitruvian Mill’s hopper faster than it was emptying.

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There are losses from this delivery chute, some grains jump over the sides, so I measured for ‘greedy-boards’ to be made of light galvanised sheet to raise the sides.

Another test I did while the wheel was running at 6 RPM was to check the speed of the Stamford Mill. It was running at 300 RPM exactly. The now unfortunately torn and lost instructions stated it should run at 450 RPM. This would require the water wheel to run at 9 RPM which is out of the question! By about 7 RPM the whole Mill-house starts to shake uncomfortably. This now requires a major re-think. Either the driving pulley, which at 910mm in diameter is the biggest in the Mill, would have to be increased to 1365mm, or the already very small driven pulley on the Mill would have to lose 2/3 of its diameter. If so, then the engine will run it too fast!

When all the grain was used up, 38kg had been milled during the day, and a total of 1½kg out of this bag could not be accounted for. There is normally a small loss out of any 50kg bag, so considering the losses incurred while the elevator has been tested, that’s not bad!

Just before leaving (I had to wait until the water stopped flowing!), I fitted the hand rail to the wall above the launder. It’s easy enough to walk in the launder when it’s dry, but walking on the edges when the water is flowing is like tight-rope walking over a turning water-wheel!

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I showed five groups of visitors around during the day. They all seemed to leave suitably impressed seeing the Mill in full swing!

Andy Selfe

24th October 2010