# UFO & G60

Dan Cordon cord4530 at uidaho.edu
Tue Feb 1 18:50:37 EST 2005

```Bernie Benz wrote:

>>However, in the last two years, it's seen frequent trips down a few
>>miles of washboarded gravel roads. That's got to be like 10 years of
>>potholes right?
>
> Dan,  Here's a topic for your thesis.  A formula for the optimum speed at
> which to transverse pot holes of varying diameters and depths.  When is
> flying across better than dropping in?

<snip>

A simple mathematical model wouldn't be too bad (just a mass, spring,
damper system). Of course, to make it hard, we could incorporate the
non-linear damping, and how compression and rebound damp differently.
Then the suspension geometry and relative mass-in-motion would have to
come in to play. Chances are the rear suspension likes a speed that's
different from the front, so we'd have to consider the MSD system of the
car's unit body in all its vibrational modes. And of course there's
sensitivity issues...how sensitive is the model to wear in the
components. Don't forget the statistical analysis to determine average
washboard dimensions...which could be a thesis in itself.

Maybe I should do another thesis. It wasn't *that* bad the first time :o)

Oh, my bad. I read 'washboard' when you clearly typed 'potholes.' This
is looking more and more like a dissertation. <grin>

As much as I hate to admit it, I really like driving my Land Cruiser
over washboards. The dimensions created by average car/truck tires
aren't even noticeable with the 39" tires on the Cruiser. Of course, it
stinks to drive anywhere else :o)

For the washboards here, and my worn shocks/bushings, 25-30 mph seems to
be the worst. Anything over 55 and you can't even tell the difference
between the road bumps and a passenger passing gas. I guess eventually
you'd smell one case....but you get the idea.

--
Dan Cordon
Mechanical Engineer - Engine Research Facility
University of Idaho

```