Very neat. I assume the bumpers will form the hexagonal sides? Very clever, and it performs the same function.
What made you opt for screw+washer and eclips to secure the shafts over circlips everywhere?
Is it just me, or are there 4 wheels on the far side and only 3 on the close side?
EDIT: Did you add any extra spacing for the chain? Apparently that's a problem according to
these tests.