Reference

White Metal Bearings

<a href='/node/896'>Bearing in pouring jig </a>Bearing in pouring jig


T
he Beardmore engine employs the use of “Babbitt” or “White metal” bearings; these were first patented by Isaac Babbitt in 1839 and were used in steam engines, machinery and the internal combustion engine.

Babbitt has excellent embed ability which means that a foreign matter not carried away by the engine lubricant is embedded below the surface and rendered harmless, this is due to Babbitts hard/soft composition (approx 87%Tin, 5.5%Copper, and 7.5% Antimony) this is a very important factor in these older engines as they do not incorporate the use of an oil filter unlike a modern engine.

replicating the originals

<a href='/node/897'>Line boring jig. </a>Line boring jig.
In most cases the Babbitt is poured into a bronze shell which is first overlaid with solder to help create a bond between the Babbitt and the bronze backing. The shells are held in jigs which support the bearing shell while the molten metal is poured in. In more modern practice, the crankshaft and connecting rod big end bearings are made of a replaceable steel shell, keyed to the bearing caps. The inner surface of the steel shell is plated with a coating of bronze which is in turn coated with a thin layer of Babbitt metal of only .002- .007 inches as the bearing surface. 
<a href='/node/901'>remetaled bearing prior to machining </a>remetaled bearing prior to machining
Relining the crankshaft bearings on the Beardmore engine was an interesting exercise in that the center five main bearings are of a conventional setup with caps bolted to the crankcase top half while the two end bearings are integrated into the lower half of the crankcase making it difficult to access the centre bearings with the two halves assembled . Another interesting point is that the crankshaft centre line is offset from the cylinder bores, this was apparently done in an attempt to reduce piston rattle as the engine passed over TDC .

 

<a href='/node/900'>Conrod showing oil pick up </a>Conrod showing oil pick up<a href='/node/904'>Bearings after machining </a>Bearings after machining
All the bearings were remetaled and machined to exactly replicate the originals, with before and after photos being taken. Lubrication of the main bearings is a mixture of pressure and splash feed whilst the Bigends are of the dipper type where the oil is picked up by means of a scoop on the conrod, as distinct from modern engines which have an oil pump supplying oil directly to the bearings under pressure.