Voidmeter, Abtus Voidmeter c1960, used to measure the deflection of track when a train passes over it. The graduations on the scale represent units of ballast necessary to cure the deflection. Abtus voidmeter 1955-1965
Abtus Voidmeter, for measuring ballast voiding, mounted on steel stake, cast iron and brass, English, 1950-1965 Abtus Voidmeter 1950-1965
