Knowing the speed



Bob:"My car doesn't have a speedometer."



Rob:"Then how du you know how fast you're going?"



Bob:"Well,when i'm driving at 15 miles an hour ,the fenders rattle;



at 25 milesan hour ,the windows rattle;



and at 30 miles,the motorstarts knocking and



that's as fast as it'll go."

rattle: (车等）格格作响地行驶．

Did he create the car by himself?

the car should be send to the museum

But I understand a little!