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Mill repairs 2015 day 6

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1st August 2015. Mostert's Mill. Sickles into Harps.

Article reproduced with kind permission of Andy Selfe 
Original can be found here http://compagnesdriftmill.blogspot.com/

 

We all know the Biblical expression 'Swords into Ploughshares'; today we ground Sickles into Harps! But we did plenty more besides.

Last time we were trying to raise the part of the Bedstone nearest Cape Town with various levers, but the curb was holding it back. Today I brought a 'koevoet' made by a Railwayman and a few steel plates to lever the bedstone upwards. It still was being stubborn until, while I levered the stone upwards, Paul gave the curb a good smack downwards with a 4lb hammer, with a wooden block in between, of course.

Hammering the Curb down while levering the bedstone up

This had the desired effect! We repeated the procedure three times, every time gaining a couple of millimetres. Referring as before to the drawing on page 87 of Professor Friedrich Kick's 1888 'Flour Manufacture', I drew two overlapping triangles ABC and DEF and took readings with the spirit level on top of my Staff between each as he explains.

Overlapping equilateral triangles marked on the bedstone and Kick's book

When we had reached the stage where there was one or at a stretch two millimetres difference in total we decided we wouldn't get any better. By that time there was space to tap in a wooden spacer of approximately 7mm at the place we had raised it the most.

7mm spacer under the bedstone

Thinner spacers were inserted between the stone and the blocks on each side. We tapped down the wedges around the bedsone, flush with the curb again and Paul refitted the wedges we'd removed last time holding the curb in place.

Paul refitting the washers and wedges holding the curb in place

Here are our readings:

Readings taken when levelling

For a long time there has been concern about the state of the oil, flour and dirt mix in the footstep bearing of the stone spindle. This was an ideal opportunity to pull out the stone spindle and lift out the thrust bearing with a magnet that Neville had brought and to clean everything.

Neville dismantling the footstep bearing

Neville had been unaware of the loose washer under it which also came out with the magnet.

Bol spindle bearing and spacer with Neville's drawing

The relatively small thrust surface supports the full weight of the stone spindle, runner stone, upright shaft and Lantern Pinion.

This small area supports a lot of weight, and centralises the stone spindle in the bridge tree

We were then ready to grind out the sloping edges of the Harps I marked out last time. Using a piece of wood held in place by my left hand and either Neville or Paul's foot at the other, holding the angle grinder with a diamond-impregnated face-grinding disc at about the angle shown by Kick on page 94, I ground out to the 9 to 13mm deep that he suggests.

Grinding out the sloping edges of the furrows

It was difficult to judge the depth sometimes because the remaining surface was either grinding face or furrow from the old sickles. We were always comparing with the existing pattern on the runner.

How the Journeyman meets the Master furrow on the runner

.... and making sure the bedstone was the same, for example at the inner tip of the Journeyman furrow:

..... likewise on the bedstone

I did each pair of Master furrows first, all the way around, then filled in each harp in turn.

First Harp complete

In the end, we had a pair of stones looking very similar:

All Harps done!

The stone itself is very different from the runner, being volcanic.

Detail of the bedstone's texture

Paul vacuumed the bedstone thoroughly. John and Fortune will come back and give the whole Mill a proper clean now that we've finished making a mess!

Paul vacuuming the bedstone

With both the upright shaft and the stone spindle out, it was an ideal opportunity to check the vertical alignment of the pintle bearing in the Sprattle Beam, the neck bearing in the bedstone and the footstep bearing. Paul had his plumb-bob.

Paul hanging the plumb-line through the pintle bearing to check alignment with the bedstone and footstep bearing

We found the line going through the neck-bearing about 10mm too close to the University.

About 10mm too close to the University

Likewise (looking from the other side) at the footstep bearing.

Likewise at the footstep

We then checked between the neck bearing in the bedstone and the footstep bearing and found them vertically in line.

Plumb-line held central in the neck bearing, aligned nicely with the footstep bearing

The conclusion is that a thicker shim is needed between the Sprattle beam and the Pintle bearing blocks. Now the Brake wheel and Lantern are meshing properly, this will be a good idea. It will mean the top disc of the Lantern will be slightly further from the face of the brake wheel which had to be ground away for clearance.

We could then lubricate the neck bearing in the bedstone and the corresponding surface on the stone spindle with lard, pour gear oil into the footstep bearing cavity and refit the stone spindle.

I did some grinding on the dummy cock-head for hanging the runner stone from to check the static balance, after we have turned the stone over. It was made according to Neville's drawing of the cock-head of the stone spindle and it needed very little removed to fit snugly!

Dummy cock-head in the inverted Rynd

Last week I was pleased to meet up with Gawie & Gwen Fagan. Gwen was responsible for laying out the Gardens, Gawie for ordering the removal of the unnecessary concrete lining to the Mill tower (and much more!) during the 1994 restoration. He asked whether we were being paid for our 'work'. I said no, we were happy to do this for nothing but if he had any influence at Public Works, we would appreciate him asking for a re-paint. A stitch in time saves nine!

Paint beginning to crack

Faded paint on the door

Paint cracking up on the Wind boards and varnish at the top.

We all packed up, well pleased with the part-day's progress, at around 3.30. Next steps are to turn the runner over again, hang it and balance it statically, to refit it to the stone spindle and to assemble the furniture and start Milling!

Can we go home now?

So There! 

:-) Andy

1st August 2015

Link to Day 7

 

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