ok - a rocket sled, a clay pidgoen launcher and a catherine wheel should just do it
mount turtle on launcher, mount launcher on sled and attach catherine whell to turtle -
right ----- launch rocket sledge, 2 or 3 stage rockets if needed, at the end of the track there needs to be 2 devices, 1 to start the clay pidgeon launcher just as the sledge hits the buffers,2 another device to tap (smartly) the shell of the turtle so he retracts his head, arms and legs for the rotation providing pidgeon launcher
with a few test runs a timed fuse can be added to the catherine wheel so it will ignite at the maximun rotaional velocity that the clay pidgeon launchers provides and maintain this force as the turtle flys and then skims across the water, and by cahnce if there is any powder left in the catherine wheel the water will put it out thefore not endangering the turtle - puke bucket to be provided only if the turtle requests one !
Never buy a stupid dwarf - Its not big and its not clever