Escapement eventually became the escapement of choice for turret clocks, because their wheel trains are subjected to large variations in drive force caused by the large exterior hands, with their varying wind, snow, and ice loads. Since in a gravity escapement the drive force from the wheel train does not itself impel the pendulum but merely resets the weights that provide the impulse, the escapement is not affected by variations in drive force. The 'Double Three-legged Gravity Escapement' shown here is a form of escapement first devised by a barrister named Bloxam and later improved by Lord Grimthorpe. It is the
Anchor escapement to a fork pushed by the pendulum, so the anchor swings back and forth, with the pallets alternately catching and releasing an escape wheel tooth on each side. Each time one pallet moves away from the escape wheel, releasing a tooth, the wheel turns and a tooth on the other side catches on the other pallet, which is moving toward the wheel. The momentum of the pendulum continues to move the second pallet toward the wheel, pushing the escape wheel backwards for a distance, until the pendulum reverses direction and the pallet begins to move away from the wheel, with