I did add a 2nd Lipo and measured straight speed with 7.5V.
Single stepping youtube video shows 9 frames per second.
Here you can see that caterpillar robot does more than 2 tiles in 2 frames.
This shows that robot speed is greater than 2.8m/s or 10km/h:
$ bc -ql
sqrt(2^2+(1/8)^2)*0.315/(2/9)
2.84053171257711009556
sqrt(2^2+(1/8)^2)*0.315/(2/9)*3.6
10.22591416527759634401
The wall crash less than a second later should make me rethink whether to do more of these ...
Hermann.
P.S:
Doing 640x480@90fps slowmo video with Raspberry camera would reveal more details.