Casella MkII Anemometer Clean and Repair Pt.2.

Newly polished worm visible through the bearing housing aperture. This section is always hidden inside the casing for weather protection. The protected area of paint will offer a better match to the original finish if it is decided to repaint a scruffy unit.

Top journal bearing seated down inside the shaft housing and the circlip safely in place. After removal of the circlip the shaft can be simply withdrawn upwards out of the bearing housing tube. The worm will follow on the lower end of the shaft. 

The circlip must be seated properly or the complete cup rotor could lift in a gale! It doesn't need a rocket scientist to work out the damage to life and property if that should happen on a tall mast!  So don't lose that circlip or attempt a non-standard replacement. A steel circlip is very likely to rust away even if you were lucky enough to  find one of the exact, same size. 

Close-up view of the drum drive gearing and eccentric bearing bush for the countershaft. (Holding the small white gears)

Loosening the protruding screw will allow fine adjustment of the depths (overlaps) of the gear teeth between the layshaft and counter drums.

The numeral drums need some gentle cleaning. A soft toothbrush and some diluted washing up liquid suggests itself here.

The discolouration of the numerals makes them more difficult to read in normal use. Because they require the high contrast of white on black to be well seen in poor light or at a distance.

Lower housing retaining ring and its paper gasket.

A small drainage hole is provided at the lowest point of the box casing. This is to allow condensation to escape. Make sure the hole is clear. Condensation is unavoidable where metal is heated and cooled in a moist atmosphere. The mass of metal lags behind the more rapidly rising and falling air temperature. Often resulting in heavy condensation. Just being exposed to the cold night sky can cause radiant heat loss and heavy dewing. 

One cup arm was quite bent as purchased. Presumably from the fall which had badly dented the rain skirt and did rather less damage to one of the cups.

I used the ends of the grooved plywood jaws of a B&D workbench to grip the shaft without damage. The wide flat jaws of an adjustable spanner allowed precise and delicate leverage during the cup shaft straightening process. Being brass, the shafts must never be hammered! Hammering hardens brass (and bronze) making it more brittle. Even the shock of the initial bend might have hardened the cup shaft. So I was extremely careful as I "sneaked" gently towards perfect straightness.

Heating the brass shaft to redness, to soften it, would have burnt the remaining paint and spoiled the original finish too much. I used a range of tools to hammer the dent out of the copper rain skirt. The original paint had already been lost in that area. Probably too much flexure to maintain paint adhesion. Though cosmetically a little "untidy" I will not be in any hurry to make the instrument look like new again. Raised high on a post in my private, rural garden nobody is ever going to see it up close except me.

I used a tiny drop of sewing machine/bicycle oil on each counter bush and at the bottom end of the shaft before rebuilding the unit. Once reassembled the anemometer rotor now turned without any noticeable friction at all. I should have cleaned the drum numerals too but was eager to see the instrument in action. As soon as I placed it up on the pole it turned in a gentle breeze which I could hardly feel on my bare arms. A remarkable improvement over the original condition. Previously the rotor would not move even if I blew hard into each cup. Now it is hardly ever still.

Update 1: My original 1/2" BSP galvanised water pipe proved to be too thin and flexible in stronger winds. So I moved up to 3/4" BSP. This pipe size is much stiffer and the anemometer no longer rocks in the wind. I swapped the 1/2" union for a 3/4" to 1/2" reducer. I had to clean the rough end of the 1/2" thread in the lathe to allow the anemometer to screw into the reducer. The reducer makes for a neater appearance and the whole unit can be faced as desired by slackening a large, galvanised, lock nut.

Update 2: I took down my MKII anemometer due to a severe storm warning from the DMI. I took the opportunity to clean the counter window, drums and digits. The fiber wormwheel proved to be nicely polished now having run for some time with the cleaned and polished worm. Local maximum wind speeds (gusts) published by the DMI exceeded 41m/s or 90mph! Not a pleasant experience having suffered damage to our home in the Great Storm of 1999. Fortunately there was no damage this time except for some broken branches in the trees on our garden border. At least six trees were felled  by the wind within a mile of our home.

Unlike the Great Storm, there seemed to be very little obvious structural damage, this time. Apart from the usual damage to domestic greenhouses and plastic roofed carports. Many of these seem very poorly equipped to cope with high winds.

Click on any image for an enlargement.

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