The Grasshopper Escapement
Harrison developed his first grasshopper escapement in the early 1720’s as a redesign of the original Brocklesby Park clock anchor escapement. Problems with lubrication was causing the clock to stop, so Harrison’s solution was ingenious, by pivoting the pallets to the original pallet frame, he overcame sliding friction, eliminated drop and the associated loss of impulse, and produced an escapement that required no lubrication. Brilliant! It is still a recoil escapement, where the recoil is used release the pallet after impulse. The geometry of the Grasshopper also lends itself to a variety of configurations which can provide either a constant impulse to the pendulum, or an impulse of variable force. It also proved to be a versatile escapement in that it was used both on his land regulators and sea going clocks, H1, H2 and H3.
The constant force escapement mock up is on the left, and a co-axial variable force escapement on the right.
The final configuration of the constant force grasshopper. The pallets are made from a naturally oily wood, lignum vitae, also used by Harrison.