I'm thinking of good vibrations...

**weed_eater_guy** · 01-20-05, 04:48 PM

I was sitting on a bus the other day, and noticed something funny. Or maybe I'd noticed it before and noticed it again, I don't know, but anyway, a bus with a diesel engine will vibrate when it's still. Put your head against the window and you can feel the vibrating sizzle through your skull, very wierd, no good for headaches. But the real mystery is when the bus moves foreward: it stops vibrating! Bouncing on the road doesn't count, the engine vibration isn't felt anymore! Why is this?!?!

Damn, I must be pretty bored if I just wrote this, lol

**one_raven** · 01-20-05, 05:14 PM

Gas engined busses too.
Resonance.

**bbcboy** · 01-20-05, 05:35 PM

You felt it in your head?
God what a waste!!

**Fraggle Rocker** · 01-21-05, 05:32 PM

Any really large internal combusion engine that is not perfectly counterbalanced (e.g., the perfectly spaced rotary configuration pistons on an airplane engine, or even the opposed four cylinders of a Honda Gold Wing) will develop a rocking couple at a very slow idle. At that speed it invokes the resonant frequencies of the larger pieces of sheet metal and other potential vibrators. At higher engine speeds the only parts of the vehicle that will resonate with it at 4,000 hz are pretty small, things rolling around in the dashboard, seat springs, that kind of stuff. It will drive you crazy in a different way. Mostly you hear it. But you get the large metal plates that make up a vehicle vibrating at 200 or 300 hz, the idle speed of a gigantic engine, you don't just hear it, you feel it.