When the engine ran under idle conditions, the
frequency of 29.08 Hz the second unbalanced inertia
force of the engine producing caused handle vibrating
violently; when the engine ran under medium speed
condition, the frequency of 19.16 Hz the combustion
exciting force of the engine producing was the reason
why handle vibrates violently; when the engine ran at
high speed, the frequency of 43.05 Hz the first order
unbalanced inertia force the engine producing was the
main reason which caused handle vibrating violently.