My New Year’s thoughts related to the friction discussion thread:

 

Considering the three mentioned methods of transferring mechanical energy, namely:

1.      Tooth belt

2.      Chain-sprocket

3.      Gears

For all methods, coefficients of friction will likely change with different torque loads.

 

Interrelated effects that contribute to mechanical energy transfer, applicable to all three methods, include:

            Atmospheric gas, aerodynamic drag

                        Reduce by enclosing system in a vacuum or rarified gas.

                        Design aerodynamic pulleys/gears.  Borrow ideas from the bicycle industry which makes high-end racing wheels.

            Mechanical drag at moving contact surfaces

                        Reduce by using a lubricant and using highly polished contact surfaces, and/or using self-lubricating materials.

If materials are chosen for self-lubricating qualities, be sure hardness is not compromised, which would lead to deformation.

            Deformation of material at transfer interface (contact area), plasticity (all materials deform)

                        Reduce by using hard materials, such as hardened steel or ceramic

                        Reduce by using less force concentration over load bearing transfer area (psi).

This suggests larger diameter pulley/gears and/or thicker sprocket/gear teeth (or grooved V-belt).

Thicker sprocket/gears would lead to higher contact surface area which would increase friction,

while larger diameter would lead to higher angular velocity and distance over which friction would act.

                        Deformation would result in coefficients of friction changes between acceleration/deceleration and constant velocity due to load change.

            Axel/shaft bearing and adverse influence of directional forces on shaft bearing resistance

                        Suggests gears would be most efficient, since gears need zero belt tension.

                        Centrifugal forces on any belt will cause tension of the belt and a resulting side force on the pulley shaft.

                        Magnetic or gas bearing, though expensive, would give the best results. 

            Electrostatic forces generated from triboelectric and/or Faraday effect may contribute to observed friction.

It would be a surprise if this somehow played a role in the success of the subject device.

 

Different materials, atmospheres, physical positioning of magnets, allowable tolerance in uniformity of fields, and geometry need to be explored, once we replicate this thing.

 

--signed, The self-made Mechanical Engineer. (-: