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Crankshaft balance
R2. You need more than a scale for the rods. A rod is suspended by each end and in turn the big ends and the small ends are weighed, the C.G. is deduced. In other words the rotating and the reciprocating masses are measured. Auto guys will then make up a bobweight of nuts and bolts equal to the rotating part which they add to the crank throws and that is then spun on a dynamic balance machine /////////////////////////////////////////////////////////////// This is correct to a point. I have balanced more engines then I care to remember and I have never had a motor where I didn't weigh all the rods as is. For instance if you have 8 rods and 7 weigh in at 580 or so grams and one weighs 640, you can grind /machine /rub / pray,,, what ever you want to do there is no way you can remove from the big end or small end to get "that" heavy rod balance with the other seven. So the point I was making is one could gram out the parts at home to find out pretty darn fast is they have a bad match of stuff. Once the motor gets to a quality auto machine shop they will put the rods on a fixture and duplicate big end and small end weights. |
#2
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Crankshaft balance
"stol" wrote in message ups.com... R2. You need more than a scale for the rods. A rod is suspended by each end and in turn the big ends and the small ends are weighed, the C.G. is deduced. In other words the rotating and the reciprocating masses are measured. Auto guys will then make up a bobweight of nuts and bolts equal to the rotating part which they add to the crank throws and that is then spun on a dynamic balance machine /////////////////////////////////////////////////////////////// This is correct to a point. I have balanced more engines then I care to remember and I have never had a motor where I didn't weigh all the rods as is. For instance if you have 8 rods and 7 weigh in at 580 or so grams and one weighs 640, you can grind /machine /rub / pray,,, what ever you want to do there is no way you can remove from the big end or small end to get "that" heavy rod balance with the other seven. So the point I was making is one could gram out the parts at home to find out pretty darn fast is they have a bad match of stuff. Once the motor gets to a quality auto machine shop they will put the rods on a fixture and duplicate big end and small end weights. gee.... a fixture... What does a quality auto machine shop use? A CNC machine? Kent Felkins |
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