Technical My Model T Thinks It Is a Porpoise!

...kinda like this at hyperspeed?




My favorite "bad kids" word growing up was "Rapscallions"

 

Maurice Olley's research before WWII pointed to an ideal of the front static deflection being about 15-20% greater than the rear. This is counterintuitive, as we expect the heavier end of the car to be more stiffly sprung. The opposite appears to be desirable. This remains useful despite the advantages of heavy damping being better understood now than in Olley's day.

Unless you're very far from Olley's ballpark I'd say the condition to aim for is the softest practical pitch rate — which would conventionally imply soft wheel/spring rates — combined with damping far nearer critical than is usual.

 

this is getting into slightly more complex territory (i was trying to keep it simple) but its a good point.

there are two dynamics at work vertical and pitch, each have there own natural frequency. Ideally they would be separate if the front and rear spring rates are set as I have suggested. However, if you generate a pitching force (front wheels go over a bump) it may be advantageous to have a small differential spring rate, that way the two natural frequencies are "coupled" and could act to dampen each other out, but it only applies order very specific circumstances. most road surfaces nowadays are relatively flat so there is less pitching force generated from the surface. Mostly its an undulation that generates a mainly straight downward force that sets up a pitch if the springs are not correct. And as you say, damper technology has come along way since then.

 

That is a great illustration, if the wheel base happens to match the distance the bumps are apart.
Now if the wheel base is shorter, or longer then the spacing of the bumps, then each axle goes over the bumps separately. The front goes over and tends to rock you back, then the rear goes over and rocks you forward. If those bumps are spaced in such a way that the axles are crossing different bumps with one in between, the ride really gets wild. Space those bumps apart at just the wrong consistent distance for a few miles and you fully understand the porpoise effect.

We drive hot rods, maybe the trick is to drive fast enough the car skips over the low spots and just kind of skims across the high spots... I wonder how fast that would have to be?