Saturday 24 April 2010

Another Crankshaft Failure

Yes, it failed again. This time it twisted slightly which meant the pistons didn't reach top dead centre at the same time, and the central crank web was rotating eccentrically in the crank case. This also meant the valve timing had slipped and the pistons were just hitting the valves of one cylinder. Luckily no damage was done, and now I've decided to manufacture a one piece crankshaft and the material arrived this week. Its a good job I made the crank case with a bulge in both sides as I'm going to need that internal volume for the much larger two-part big ends of the conrods. The material is an alloy steel, EN16T which is a tough steel, good with torsional strength. The down side of all this is that (as I mentioned earlier) I have to make two new conrods with a split big end and a split bearing. This bearing is made by soft soldering two pieces of phosphor bronze together and turning the bearing as one piece, then heating it up to melt the solder to form the two big end shells.
To give you an idea of the size, the cutter in the photo is 6.0mm diameter.

Crankshaft during remanufacture


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