7 vs. 1 ...

[iacob alex]

.....is simply a notice or point of likeness and differences of two machines,purposed to use the power of gravity:

       -Villard de Honnecourt's wheel (7 hammers but...a non-workable machine),intended to collect free gravity power.

       -an impact test hammer (1 hammer and it works) ,a laboratory instrument that allows the delivery of calibrated gravity impact energies on test objects.

    A hammer,usually is a tool with heavy head at end of handle,for beating,driving nails.

    A hammer can be considered a particular pendular mass (rod-mass) also,but...it depends on you his usefulness (including to imagine a gravity motor...).

        All the best! / Alex