  The concept of 'deformable arm scale' (completely different from a
traditional rigid arm balance) is theoretically introduced and experimentally
validated. The idea is not intuitive, but is the result of nonlinear
equilibrium kinematics of rods inducing configurational forces, so that
deflection of the arms becomes necessary for the equilibrium, which would be
impossible for a rigid system. In particular, the rigid arms of usual scales
are replaced by a flexible elastic lamina, free of sliding in a frictionless
and inclined sliding sleeve, which can reach a unique equilibrium configuration
when two vertical dead loads are applied. Prototypes realized to demonstrate
the feasibility of the system show a high accuracy in the measure of load
within a certain range of use. It is finally shown that the presented results
are strongly related to snaking of confined beams, with implications on
locomotion of serpents, plumbing, and smart oil drilling.
