I decided to build a test rig for the grasshopper escapement in order to adjust the composer arms and balance before attempting assembly in the clock. The test rig is designed to enable measurement of pendulum swing and amount of driving force required for successful operation.
A second reason for a test rig is to evaluate two patterns of grasshopper escapement. I have built two types, the first a copy of the original Harrison regulator escapement and a second one to a design by Peter Hastings. Both can operate on the same escapement wheel, and my intention is to analyse the performance of each.
The Harrison pattern escapement is asymmetrical, having different length of legs, producing unequal torque with one leg pushing and one pulling. The Peter Hastings twin pivot design uses two identical legs with equal torque characteristics.
The Harrison pallet assembly is balanced, but the Peter Hastings platform will require a separate counterbalance.
The pendulum swing is measured against a calibrated scale on the rear of the test rig.
Driving force for the escapement wheel is generated by a simple pulley and weight drive adjusted with addition or removal of nuts.
All rotating arbors are running on miniature ball races with no lubrication.
The pallet assembly runs on the knife edge bearings of the arbor and is mounted on hardened steel pads. The suspension assemblies are those to be used on the clock.
This page will be updated when both escapements have been fully tested and the results evaluated.