1-1/2 HP Bates & Edmonds Bull Dog restoration, Part 2

A Bull Dog gets its bark back


| December/January 2008



rooke2

The poured bearing, the rounded edges being visible.

Peter Rooke

Editor’s note: The following is Part 2 of a four-part series on Peter Rooke’s restoration of a 1-1/2 HP Bates & Edmonds Bull Dog.

Pouring the bearings

Before starting to pour the bearings, all bearing areas on the main casting were brushed and cleaned with emery cloth to remove all traces of rust, in order to improve adhesion. In particular, the recesses were cleaned out to keep the bearings in position. Fortunately, I possessed some formers from another bearing repair that would fit this job. They consisted of a central core (some 0.100 inch smaller than the crankshaft diameter) and two recessed end caps. These end caps had supports to keep the caps aligned in the bearing recess.

The formers were coated in oil to prevent the white metal from sticking to them then clamped in position. When white metal cools it forms a curved rather than level surface, which can drop below the required line at the edges. To prevent this, a small dam was built using babbitt putty, thus increasing the height of the white metal poured. It was also necessary to seal the gaps between the edge of the formers and the engine casting to prevent the poured metal from leaking out. (If you use fire clay rather than babbitt putty, it is essential to ensure it is fully dried when pre-heating the casting or else you will run the risk of the molten metal spitting back if it hits any moisture).

On a cautionary note, adequate safety precautions are always essential when heating white metal: safety glasses, trousers, long-sleeve shirts, preferably an apron and leather gloves. The white metal was heated in a pot, stirring from the bottom with a thin pine stick to keep the alloy fully mixed. With a low tin, white metal is at pouring temperature when the pine stick starts to singe after being held in the metal for 3 or 4 seconds. When the metal reached pouring temperature, the mold and casting were heated with a gas torch to preheat it and stop the white metal from cooling too quickly and cracking when it hits a cooler casting.