After buying a rusty Geo Tracker for quite a lot more than it
was worth given its condition, Pentium set about attempting to
fix it up. One of his junkyard upgrades was a replacement gauge
cluster with a tachometer. But the new cluster's odometer was
nowhere near the mileage of his original, and they were too different
to swap. So he brought it to me to see if I could reset it. Easy!
All I needed was some Lego...

Here you can see our very complex build in progress.

By removing one of the gears in the odometer mechanism, a standard
lego gear neatly meshed with the counter. All we had to do was
slip it onto the shaft of a lego motor and apply power.
After a few minutes of racket from the lego motor, the new odometer
read the same as the old one. Although why he'd want to advertise
the fact that his Tracker had the better part of a gazillion miles
on it, I don't know.