I?m sorry to ask this question, but I forgot exactly what I?d learned in college. I?m building an increased stroke 280 Mercedes (1960s) engine, had the crankshaft offset welded, ground and balanced. I had wondered why the balancer didn?t need to know the weight of my slightly lightened piston and rod assembly, in order to remove the correct amount off the counter weights and he insisted that on an inline 6 cylinder there was no need to change the balance of the crankshaft unless I was building a high revving racing engine (I?m not/ 6500rpm). While I didn?t notice any imbalances after assembling and testing this 1st version of the modified engine, the current 2nd version has custom pistons, rings and wrist pins that weight approximately 150 grams less than the original. Does the balance now have to be adapted to achieve a smooth running engine? Ross Pistons and my crankshaft grinder (Marine crankshaft) claim ?NO??, but don?t seem to be able to back-up why...
I seem to remember that there can be several ?orders? of frequencies that occur on any engine and while it seems likely that on an inline 6 cylinder, one of those orders is inherently balanced, if their were NO imbalances at all, on an inline 6, it wouldn?t make much sense that the manufacturer added fairly sizeable counter weights opposite most of the crank shaft journals, to balance the weight of (I?m assuming), the big end journal, the pistons and the oscillating mass of the connecting rods. They even take care to fine tune, (drill) these weights to achieve the accurate balance. This is what I am trying to understand. Why would it not matter if I change the weight of the pistons and rods.?
Much thanks, in advance, Tom
I seem to remember that there can be several ?orders? of frequencies that occur on any engine and while it seems likely that on an inline 6 cylinder, one of those orders is inherently balanced, if their were NO imbalances at all, on an inline 6, it wouldn?t make much sense that the manufacturer added fairly sizeable counter weights opposite most of the crank shaft journals, to balance the weight of (I?m assuming), the big end journal, the pistons and the oscillating mass of the connecting rods. They even take care to fine tune, (drill) these weights to achieve the accurate balance. This is what I am trying to understand. Why would it not matter if I change the weight of the pistons and rods.?
Much thanks, in advance, Tom
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