{HEAD ~ Bicycle drive unit} capable of backward movement and {TAIL ~ naughtrotation} and forward movement traveling when rectitude or reverse pedaling 
capable of
{ HEAD ~ Bicycle drive unit } capable of backward movement and { TAIL ~ naughtrotation } and forward movement traveling when rectitude or reverse pedaling
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH