We started out with a team project of Sudoku.
Each would give a proof of why a block would be correctly placed and
all would check.
Finished quickly.
Then we searched on LEGO Links of Linda Hamilton lesson plans
for egg beater
to get picture ideas.
Two crown gears back to back can mesh with 8 tooth gears at right angles.
Use that idea to make egg beaters.
Have a 40 tooth gear drive an 8 tooth gear on the axle with the crown
gears to make a FAST egg beater.