Why even perfectly balanced machines start shaking once they warm up By Josh Iris, President, Ace Electric Motor & Pump Co. If you’ve been around rotating equipment long enough, you’ve probably seen this one. You rebuild a motor, line it up perfectly, balance the rotor to G 1.0, and it runs smooth as glass at startup. Ten minutes later, the vibration starts creeping up. You double-check everything — balance, runout, coupling, base — all good. You pull the laser out again just