Just for fun, a sample (may not exist) crankshaft and its harmonic orders. Natural frequency: 250 Hz. The orders are located at: RPM = Hz × 60 ÷ N, where N is the order number.
Ranked by severity (magnitude of damage from sustained use), worst on top:
#3 5,000 RPM
#2-1/2 (yes, it's there) 6,000 RPM
#2 7,500 RPM
#6 2,500 RPM
#9 1,667 RPM (pretty weak)
#12 1,250 RPM (almost harmless)
#1 15,000 RPM (pretty strong, but out of reach)
#4, 5, 7, 8, 10, 11 = harmless in an L6
A V8, L4 etc. will have the same orders (if the Hz matches) but which ones are important will be pretty different.
Is that a specific order (damaging frequency harmonic orders) for any straight 6, or just your hypothetical?
I can do the math easily enough (the formula you posted is simple enough) but I was curious for the 4200 (OT engine for this thread maybe, but still harmonics).
the story seems to be they have a
really bad harmonic somewhere between 6700 and 7300 (some say 7200).
It's a bit more difficult to find since I don't know which order, or the crank's natural frequency.
Hence my question, is that "safe" to call it 3rd order?
