Mostert’s Mill

+27 (0)82 771 6480
Rhodes Ave, Mowbray, Cape Town

Mill Repairs 2015 - Day 3

– 11th April 2015. Mostert’s Mill again, assembled!
After leaving Mostert’s Mill last visit, I realised that it would be good to have the Pintle Bearing bored true, now that the pintle itself is set firm and vertical in the Vertical Shaft. I asked Neville to collect the two halves from the mill, he gave them to Pieter, who brought them all the way to Compagnes Drift Mill in Bot River two weeks ago, and I dropped them off at Orbit Engineering with specific instructions as follows:
1 Mark 1 and 2 permanently in blocks (we had marked them with chalk. There are two X’s to show how they go together, but the 1 and 2 show the top and which way around we removed them).
2 Measure the full length of the two blocks together.
3 (Having established that they had 3mm steel plate) Machine off 3mm from each side of both of the mating faces of the bearing halves.
4 Make and attach 2 steel shims 3mm thick to the mating faces of one of the blocks.
5 Clamp the two together, align, and bore to 43mm. (It would not matter if this didn’t remove all the hour-glass wear. In fact it did).
6 Make a 3mm shim the full size of the end of the block.
7 Check the assembled length, it must be the same as 2 above.
 The same team assembled today, 11th April, thanks to all of you before I forget! We decided to use the opportunity, while the Vertical  Shaft was not engaged on the Rynd to observe how the Runner Stone turns while the stones are separated. We know there are problems with the Bedstone which is not flat, but it would be good to know if there was any wobble on the Runner, at least at slow speed, especially as the Rynd is tight in the Runner and tight on the tapered Cock-Head of the Stone Spindle.
The Vertical Shaft was resting on a block of wood on the Stones, so we rigged the chain block from a strap over the Wind Shaft, lifted the shaft clear and carefully lowered it on to wooden blocks to one side of the Stones. Here Paul is attaching a safety-rope to ensure that the strap couldn’t slip upwards on the shaft, which tapers slightly towards the top:
Paul tying a safety rope on the straps on the Vertical Shaft
The results, using nothing more scientific than my finger as a ‘feeler’ were very satisfying. However, with the runner well clear of the Bedstone, it’s very clear there are problems with the latter! Here one can see that the Runner is rubbing on the Bedstone (which, technically, it shouldn’t even touch):
Signs of the Runner rubbing on the Bedstone
…. while in this area there is partly milled meal from last Milling Day:
In this section there is a gap where the meal is only partly milled
We also decided that, because we will have to remove a considerable amount of material to get the Bedstone flat, we will dress it with Harps like the Runner. The stones are not a pair, the Runner has Harps, the Bedstone is Sickle-dressed. No doubt we would have experienced resistance to this decision from the traditionalists, but to sacrifice proper Milling to sentiment is not an issue.
This is how the Bedstone is set up, according to Professor Kick (in 1888):
Professor Kick’s advice on levelling a Bedstone, in 1888!
All this was in preparation for some day in the future when we tackle the Dressing. Today we had decided to reassemble the top of the Vertical Shaft and the Lantern Pinion, so that we can test the Milling with all the problems at the top corrected. This is how we left it last time, with duct tape to hold any Steenvas from oozing out of the sides:
The top end of the Vertical Shaft with duct tape to hold the Steenvas in place
With the tape pulled off, it left a smooth finish on the Steenvas:
Duct tape removed, leaving a smooth surface on the Steenvas, now very hard
This picture makes me realise that we didn’t nip-up the nuts on all the through-bolts. This will have to be done before the next Milling Day, to give the Steenvas the best opportunity to work. But first, we had to re-step the Vertical Shaft on the Rynd. There was some discussion as to whether or not to build up wear we could see has occurred on the fork (or in fact to grind it flat as worn), and which way around it should go. There are (fading) blobs of paint on each, which is how it has been assembled all along, but we found an X on one side of the fork and another X on the Rynd, which would mean we were 180° out. Then someone found another X on the other side of the Rynd! In the end we decided to stick with the paint marks.
I lifted with the chain block while Morne took charge of the top end……..
Morne guiding the top end of the Vertical Shaft
….. and the others guided the bottom into place:
Neville, Pieter and Paul guiding the fork back on to the Rynd
We then slid the Lantern Pinion loosely over the top of the Vertical Shaft until it rested on the two brackets, as we wouldn’t have an opportunity later, and clamped the two halves of the reconditioned Pintle Bearing together and tested it on the Pintle. We all decided that the fit was slightly too tight. Pieter’s own Mill caught fire from heat generated from a Pintle Bearing with too little play. We discussed methods of shimming the mating faces a bit, including cutting strips off one of the existing shims from the ends, which are interesting in themselves:
Interesting shims cut from an old oil tin
Remember the Standard Vacuum Oil Company or ‘Stanvac’ which became Mobil in 1962? Well the Standard Oil Company of New York (Socony) merged with the Vacuum Oil Company in 1931 to form Socony-Vacuum, so this tin must be older than that! Could they have been cut by Mr Bremer snr during the 1935 restoration?
In the end we decided that cardboard would work adequately, so cut two shims and tried assembling like that. Of course, with the two halves in the recess in the Sprattle Beam, there wasn’t enough clamping force to hold the cardboard shims in place anyway. They fell out, so we left them out and tested the assembly with one thin shim at the end omitted. We were all very happy with the (little) play.
Pintle in the two halves of the bearing in the recess of the Sprattle Beam
When we stripped, all the shims were on the right hand side. Today we decided to fit the new 3mm shim on the left and the remainder on the right. It doesn’t matter that the mating faces of the bearing halves aren’t tight against one another. Besides the pair are tightly clamped from the side by the bearing cap which also has a corresponding recess in it. Here the cap is fitted loosely over the bearing….. (those are not our hammer marks!)
Bearing cap loosely over bearing halves
……. and here, the tie-bolts are pulled through, new washers, 5 on each side, with the wedges nicely half-way down.
New washers, five a side, and wedges half-way in
Shipshape? But I forgot to mention lubrication: we had applied a liberal application of lard when we assembled the bearing. The two 3mm shims on the mating faces can be seen in this picture, held in place by wood-screws, as well as the cleanly bored hole. In future, as the hole wears, thinner shims can be fitted to the faces and corresponding shims fitted at the ends to apply more clamping force:
Lard applied to the Pintle for lubrication
I had hoped we could turn the Vertical Shaft on its own at this stage with the Lantern Pinion still loose, but there wasn’t enough clearance even with the wedges out, so we set about refitting the wedges and setting the Lantern to run true. We found that we had done ourselves an enormous favour by marking the Lantern according to the Vertical Shaft, as well as every wedge, as we removed them. Further, by refitting them to more or less to where the marks showed they had worked before, the Lantern was nearly running true before we started checking! Here, Morne is refitting the wedges and the marks on the wedges can be seen:
Morne refitting wedges to the Lantern
I then set up a register, clamped to the Sprattle Beam, set vertical with Neville’s spirit level. From this I could measure to the top and bottom bands of the Lantern, singing out the readings to Secretary Steve with the clip-board.
Measuring from the vertical register clamped to the Sprattle Beam to the top and bottom rings on the Lantern Pinion
It only needed fine-tuning the last few millimetres and for Pieter to tap in the wedges to an even tension. We discussed whether the Keepers should be replaced at this stage, to hold the wedges from slipping out. I was for trying it out for a while without, but was easily persuaded that it would be better to refit them, even temporarily with nails protruding for easy extraction. The consequences of a wedge or a pair of wedges falling out would not bear consideration! The top set do not need them as they work themselves in by their own weight, besides there’s the steel band on the top of the Vertical  Shaft so there’s no way they could be nailed in. We also refitted the Keepers in the Wind Shaft. Here Neville is cutting new Keepers:
Neville cutting wooden strips for Keepers
We were then ready to test the meshing. In fact we had planned to Mill, but there wasn’t even the 2 m/sec that Yr.No had predicted, so John and Paul turned the sails by hand while we watched the meshing carefully.
John turning the sails by muscle power

Here is a short clip showing the meshing

As I say on the video, I’m very happy with the results! 

Morne did another from the side

We plan to Mill in four weeks time and to observe very carefully the interaction between Runner and Bedstone and the fork on the Rynd. At some time in the future, we will open up the Stones and sort them out for good!

Article reproduced with kind permission of Andy Selfe
Original can be found here