A brief guide to the restoration of our water wheel at Roch Mill, Pembs.

According to local recollections the water wheel last turned about 50 years ago. Since then it has rested on its rims in the slowly silting wheel pit. All that remains of its bearings are two half shells. The 12 foot axle and, crucially, its journals are heavily pitted with rust and need extensive restoration.

With a lot of help from our friends we took the old wheel apart over a busy weekend in 2006 and we had hoped to re-use the various bits after a bit of restoration and a coat of paint.

Dan and Kevin Harrison dismantling the old wheel 

However, during the dismantling it became clear that one of the hubs (pictured below) was beyond repair and also that several of the rim segments were so badly corroded, and in some cases damaged, that a new wheel was going to be needed. 

 Thanks to the Internet we found Paul McCairn who helped us create a copy of the old wheel. Paul runs Bri-Mac Engineering in the Black Country and he supplied new bearings and wheel castings at an affordable price. We created engineering drawings of the old wheel components and had new wooden patterns made.

 New rim pattern, painted with red varnish, ready for sand mould and casting.

The hubs and rims were cast by a traditional foundry in the Black Country and machined and (initial) assembly at Bri-Mac prior to transportation down to Pembrokeshire. 

One of the new hubs

One of 12 rim segments

For a while we toyed with the idea to re-use the original axle. However, after several failed attempts to restore the journals (in-situ) we decided on a new axle as well. In fact, to ease assembly and avoid bearing alignment difficulties we decided to replace the long three-bearing axle, with two shorter axles, joined with a "flexible" coupling. However, it did add the new problem of having to separate the pit wheel from the old axle. It weighs half a ton and was nicely rusted on - fast!

 Rusted axle journal in original bearing housing and bronze shell

 Another important material is the wood for each of the wheel's buckets. No doubt they originally used elm as this apparently copes well with the wet but isn't so good if you allow it to keep drying out. Sadly, elm is not as plentiful as it was 100 years ago but unbelievably George, the owner of a wonderful timber yard in Carmarthenshire, recently found a tree in the middle of his wood. It was just big enough to supply wood for all the buckets, so he cut it up for us and it's now seasoning by our barn.

  Elm log (centre) ready to go!

Elm log in the sawmill

The existing leat (mill race) was pretty silted up but, because it lies along a spring-line and because it collects extensive run-off from the local hills, it has retained a flow despite 50 years of neglect. The primary flow was originally tapped off from the Brandybrook river about 600m upstream. Unfortunately, about half of this now crosses a neighbour's land and is no longer accessible to the Mill. Also, the weir has completely disappeared (or may never have existed). However, with the springs and run-off there is enough residual flow to generate up to about 1kW, at least during the winter months . To reduce maintenance in one difficult-to-get-at-section we chose to duct the water through a culvert.

 New sluice gates have been made by Kevin Harrison at his engineering company (Stowfledge) near Loughborough and we've started their installation in the leat.

 First sluice gate in position

Actually, none of the above tasks is as straightforward as it sounds and the grand re-opening of Roch Water Wheel has yet to happen - but it's getting close now.

One day we may try to harness the power to drive a ground-source heat pump. This will supply our underfloor heating in the house. But that's another project, possibly next year's, but don't hold your breath!

In removing the old wheel we fully exposed the end wall of the mill, which was is in serious need of re-pointing. After hundreds of years of getting pretty wet it is not surprising I suppose, but it's a job I could have done without. We have used traditional lime mortar for this, so that moisture can escape from the walls and also to help absorb the stresses and vibrations when the wheel is turning again.

In Spring 2008 another engineering friend, Terry, very kindly came along to cut the old axle in two. The cut was made close to the pit wheel so that I could drill out the old iron wedges and release the remaining axle stub. Once that was done I could set about rebuilding the bearing supports and aligning the bearings - but it proved to be a real pig of a job!. In all it took 18 months of effort, mostly mine but Kevin and Terry played a big part too. We wore out two electric drills and a heap of drill bits.

Terry using an angle grinder to cut through the 150 yr old 4inch axle

Success. But drilling out the wedges was no mean task.

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With heroic efforts by Terry, Kevin and myself and more than a year of toil we finally drilled out the axle core from the pit wheel

A Champagne moment!

New wheel - final machining at the factory

The completed wheel parts were delivered to Roch Mill in Spring 2009 and were treated with a primer coat (picture) before a rubberised top coat or two.

Wheel components after primer coat

Martyn squaring off the steel wedges

First part of hub assembly completed

And in position

Under construction - with lots of help from our friends (Denise helping me install the cross struts)

Metal components assembled. All it needs now is the drum and wooden buckets - all 36 of them!

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