The BARMERE
Work Continues on the Winch: Repair to the Gearwheel

The main gearwheel on the winch is 24 inches in diameter. It is attached to one end of the anchor chain roller; is made of cast iron and has four spokes. Major corrosion had been suffered during the boat's fifty-year life; in places the scale was a quarter of an inch thick. The rim of the wheel was found to be cracked in two places. One crack had penetrated completely through the thickness of the rim; the other only part way through. The effect of scale building up within the second crack was to force it open, thus levering out the section of wheel rim between the two cracks and leaving it hanging out slightly from the rest of the rim. Known in technical circles as scale jacking, this resulted in a quarter segment being out of line with the rest of the gearwheel.

One possible means of repair was to weld. The cracks would be first ground out to remove all traces of scale in the cracks and provide vee shaped grooves for welding. The out-of-line segment would be pushed back into position and clamped while weld metal was deposited to fill the cracks. The whole wheel would require heating in a furnace before welding and the cooled down process afterwards would have to be over an extended period of time. This is to ensure that the whole wheel cools at a uniform rate. Otherwise there is a high risk that further cracks might develop. Cast iron is a very brittle material and liable to crack if one part of the wheel shrinks faster than another due to uneven cooling. Guaranteeing a successful weld was impossible.

Facilities were not readily available for welding, so a simpler repair method was adopted. A strip of steel plate was attached to either side of the wheel; the out-of-line rim segment being clamped into place between the two pieces of plate. Although the final appearance of the wheel may not be as good as a welding job might have been, the segment is correctly repositioned; and the anchor chain roller can be rotated by the gears. The chosen repair method was much more readily manageable and enables the winch to operate.

The cracks were first ground out to remove rust scale; a clamp was made up to surround the whole gearwheel rim and allow the displaced segment to be pushed back into position. Two pieces of plate were cut to the required shape and held in position; one either side of the rim segment. Holes were drilled all the way through the plates and the wheel rim and bolts inserted and tightened up. The surrounding clamp was finally removed. To resist further corrosion, coats of anti-rust paint were applied; "Kurust" followed by "Hammerite". The assistance of Duncan Brocklehurst of Arley with the drilling was very much appreciated.

George Bruce

The repair carried out on the BARMERE's winch gearwheel

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