On Mon, Aug 28, 2017 at 04:41:51PM -0700,  (via tml list) wrote:
> On 25 Aug 2017 at 12:37, C. Berry wrote:
>
> > Similarly, show me a CG technology that requires constant power input
> > in a given g-field, and I will happily use it to create a free-energy
> > generator using a classic perpetual motion "unbalanced wheel" that
> > actually works.
>
> Depends on *how* you apply the CG.
>
> If it "supports" the ship against gravity with a constant power
> input, your perpetual motion idea won't work.

Yes, it will work.  Divide the power requirement by the weight
supported, giving a figure with the units of speed.  While the device
is operating, move it upward with speed greater than that figure
(e.g. on the rim of a large spinning wheel).  Then turn the device off
at the top and let the mass fall (e.g. on the downward part of the
wheel's turn).

Example: suppose a certain contragrav device costs 10 MW to run, and
can cancel about 100 tons of weight (1 MN).  Put two such devices and
associated weights on the rim of a wheel with radius 100 m, rotating
once per 20 seconds.  Each half-turn, one device consumes 100 MJ of
energy (10 MW x 10 seconds).  The other is not operating, and the
associated 100-ton weight falls through 200 metres, converting 200 MJ
of gravitational potential energy (mass x gravity x height) into
electrical energy via a generator at the wheel's axle.  100 MJ of this
is used to power the ascending device, while the other 100 MJ is free
to be used for anything.

- Tim