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#11
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Dave Butler wrote:
Now, back to my original question (as I intended, at least): since the torsional resonance that the crankshaft counterweight vibration dampers were designed to damp is no longer present, do you remove or otherwise modify the crankshaft counterweight vibration dampers? If you remove the dampers, aren't you further changing the vibration characteristics and frequency? |
#12
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john smith wrote:
Dave Butler wrote: Now, back to my original question (as I intended, at least): since the torsional resonance that the crankshaft counterweight vibration dampers were designed to damp is no longer present, do you remove or otherwise modify the crankshaft counterweight vibration dampers? If you remove the dampers, aren't you further changing the vibration characteristics and frequency? Yes, I suppose so. Is that a good thing or a bad thing? Dave |
#13
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"Dave Butler" wrote Now, back to my original question (as I intended, at least): since the torsional resonance that the crankshaft counterweight vibration dampers were designed to damp is no longer present, do you remove or otherwise modify the crankshaft counterweight vibration dampers? Dave Hum, that would be a substantial job, since if you mess with the counterweights, you are changing the balance relationship between the piston/rod assembly, and the crank. I think you would be adding another set of vibrations into the engine. Not a job for the homebuilder, I think. It seems to me that if you added mass into the engine/prop combination, by using a heavier flywheel, or harmonic balancer, you would have a chance at fixing the problem. -- Jim in NC |
#14
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Morgans wrote:
"Dave Butler" wrote Now, back to my original question (as I intended, at least): since the torsional resonance that the crankshaft counterweight vibration dampers were designed to damp is no longer present, do you remove or otherwise modify the crankshaft counterweight vibration dampers? Dave Hum, that would be a substantial job, since if you mess with the counterweights, you are changing the balance relationship between the piston/rod assembly, and the crank. I think you would be adding another set of vibrations into the engine. Not a job for the homebuilder, I think. Sorry, I didn't realize this was crossposted to r.a.homebuilt. My point was - when you change propellers, you are already messing with the vibration characteristics. - there are specific engine parts (those dynamic crankshaft counterweights) that were presumably designed to dampen vibration with the original propeller. - someone asserted that the yellow-arc on the tachometer could be removed if one installed a 3-bladed prop. - someone else (nrp) noted that the yellow-arc was there to avoid a torsional vibration mode that occurs with the specific propeller/crankshaft comibnation. - the question was intended to address certified airplanes, and I wondered whether the STC for the propeller change addressed any other changes besides just bolting on a new propeller. - nrp seems to know a lot about torsional vibration, and I was hoping he would respond w.r.t. the effect of changing propellers and not "messing with" the vibration dampers that were installed to ameliorate the vibration with the original prop. - it was just a curiosity question. Never mind. Thanks. It seems to me that if you added mass into the engine/prop combination, by using a heavier flywheel, or harmonic balancer, you would have a chance at fixing the problem. |
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