Tuesday, 17 March 2020

Mothballing the mill for the pandemic

We hoped it wouldn't come to it, but we have been told that all volunteering activity is suspended until further notice. A number of us had turned out for a meeting with the manager, so we spent a couple of hours cleaning out  the tun, hoovering the stones and putting it all back together in a hopefully rodent-proof state.

 Cleaning the stones                                                       and filling the groove

Because our stones are on a mezzanine floor, and the French burrs extend under the upper floor, we had to build the tun so that it separates around its middle - otherwise we could never lift it clear of the stones. We built it from tongue and groove boards and never thought to fill the remaining groove at the bottom of the top half. It proved an excellent hidey hole for mill moth.

So, while we had it apart, we took the opportunity to put some wood filler in in the groove.

Wednesday, 5 February 2020

Improving the mesh of the gears

Recently, when milling, we had noticed that the machine tended to slow down once per revolution of the waterwheel and pit wheel. Initial investigation showed that this was because the pit wheel was moving into closer contact with the wallower, to the extent that the beam carrying the top end of the upright shaft was moving.
A millwright we spoke to suggested that the pit wheel, which is cast in 2 halves, might be oval due to casting shrinkage. If so, it will always have been like that, so something else must have changed.  Once we shut down for the winter, we carried out some detailed measurements. These showed that, while there was some movement, it was nowhere more than 15mm - really no more than you can expect from these castings.
We tried a range of possible solutions to improve the mesh. Re-centring the pit wheel on the main shaft proved to be very difficult - the wedges that hold it in place were put in dry and had since swollen and were very tight.  Readjusting them would be a huge job, and removing and refitting the pit wheel was ruled out for the same reason.
We then tried to tilt the pit wheel slightly on the shaft. Our measurements had shown that there was a slight tilt as well as eccentricity. Again the tight fit made this very difficult.
Eventually we decided that the simplest solution would be to raise the wallower by a few millimetres. We achieved this by lifting the whole upright shaft out of its bearing and inserting a steel plate under the bearing before reassembly. A trial running (but not milling) under water power suggested that there had been considerable improvement.
Time will tell!
Bill and Neil working on the wallower

Thursday, 19 December 2019

Our value as Millwrights

Back in 2011, when we had first got the mill to produce flour again, we submitted an application for the Marsh Heritage Award.  History (including this blog) shows that we actually won the award.

Part of our successful submission was the statement "By their efforts they have re-established a tradition of milling and millwrighting at Acorn Bank."  Since then we have continued to develop our skills and increase our experience.

I was therefore very interested recently to discover the Heritage Crafts Association (President HRH The Prince of Wales) which publishes lists of endangered crafts.  Millwrighting is listed as Critically Endangered (see https://heritagecrafts.org.uk/millwrighting/) as there are so few practitioners.

That means, as far as I can see, that we old volunteer millwrights are ourselves suitable subjects for preservation by the National Trust!

Monday, 27 May 2019

Hunting for the cause of the hunting

We had been noticing that when water, and therefore power, is short the mill speed varies, slowing down once per revolution of the waterwheel.

Eventually, careful observation showed that the problem was that the angled gear teeth on the pit wheel, which shares its axle with the waterwheel (visible at the left of the upper picture and just seen over Neil's right shoulder in the lower) were not engaging at a constant height with the matching angled teeth on the wallower (showing just over the beam in the upper picture and half visible at centre right of the lower picture).

With the wallower higher, the coupling is slack.  When the wallower meets the pinwheel lower, there is considerable pressure exerted due to the angled gear faces.  The top of the wallower appears to move from 1cm below the top of the pinwheel to 2cm above.

Clearly something has run a bit out of alignment.  We made an attempt to help matters by twisting the pinwheel slightly on its axle and repacking the wedges.

This weekend there has still been some hunting, but we've had a bit more water so it has been less of a problem, so not sure if we have really improved it.

Work on the third pair of stones

The third runner stone lifted
 While we are waiting for the go-ahead to restore the second waterwheel, we decided to overhaul the moving parts of the drive for the third pair of stones (out of 4).

This involved the usual process of lifting and supporting the runner and removing the bearing (strips of wood) from the cast iron fitment in the bedstone.

This time we go on from there and remove the drive shaft, take the bottom bearing out and take out the wooden tentering beam.  This is mounted in a cast iron box set into the wall, and that was in a scruffy condition, so that had to come out too.  Here is Dave Freak cleaning it up with a wire brush prior to giving it a coating of Waxoyl.

The box was then fixed back in the wall with lime mortar, and the beam re-inserted and hung from the tentering bar.  The final picture shows Richard and Peter fixing the box.

Thursday, 4 April 2019

Continuing work on the second waterwheel

The second wheel in 1981
 As can be seen from the 1981 picture, the waterwheels suffered considerable damage when the mill was neglected before that date.  Some of the cast iron sections of the shrouds fractured when the spokes rotted and collapsed.

When the building was restored in 1990 the first (upstream) waterwheel (seen in the background of the picture) was repaired and restored, but the shroud sections of the second wheel were removed and stored.

Since the mill was upgraded from a Grade 2 to a Grade 2* listed building last year, work on reconstructing the second wheel has been restricted to conserving the shroud sections and ensuring they will fit together.  We need Listed Building Consent to continue with the restoration.

However, it now looks as if we may have found the means to begin the application for permission, under the auspices of a historic building consultant, Paul Lewis.

In the interim period, one of the sections has been lost, so we have set about designing jigs and templates to allow a new one to be fabricated.  The first picture shows the template for the main piece of the shroud, the others show the use of an existing section to construct a jig so that the various channels which hold the boards can be tack welded accurately in position.

Tuesday, 21 August 2018

The model wheel to encourage coin donations!

Today I finally completed the model waterwheel, which is designed to encourage kids to pester their parents for coins to drop in.

The wheel is very free on its bearings, and even a 5p coin will turn it. The whole is protected by a perspex cover - I had a lot of fun cementing that together. The coins fall in and strike a bell, so there is a very satisfactory series of clunks followed by a "ding"!