wrote:
> Meredith,
> What you've done is VERY interesting. Am I correct in assuming that
> your latest test (1.5 lbs
> oscillating 50 minutes) was with the aluminum rod hanging down and
> swinging from the stationary steel plate,
> with the 1.5 lb weight at the bottom? If so, how far below the axis was
> the weight. The moment of inertia is an
> important issue in the decay time, so I would really like to know this
> number to try and assess the
> relative importance of air damping compared to the internal friction
> associated with your axis.
>
> Randall
>
Hi Randall and all,
Yes, I put the steel block upside down and clamped it to the edge of a table; with of
course the magnets underneath the steel block (and moved the magnets to accomodate
a clamp). I put up a third picture and text at the web site in relation to this. See:
The distance between the center of the pivot and the center of (another steel block) is
~17.625", with a natural period of ~1.34s. The web page distance number is not correct.
Of course the surface hardness of the gold plated neo magnets and the surface of the unhardened
steel rod are not very good. One could rightly say the whole thing is kind of a curio type
experiment, and of little long term operational value...which it is presently. It might be
possible to "adapt" some kind of cutoff small section of harder magnetic steel pipe that fits the outer
contact portion diameter of the neo magnets to provide a harder contact surface there....while
also getting a harder pivot rod.
If one compares say a "standard" crossed rod that simply gravitational rests atop the rods, and this
magnetic attachment; the standard crossed rods can freely oscillate up to about ~ 4 times
longer (per past home brew experiments). However, the magnetic centering aspect of
this present unit is of great interest as it can roughly ~"positon zero" itself, whereas the
standard non-magnetic crossed rod/cylinder unit can't self adjust, without perhaps resorting to
again configuring some kind of magnetic attraction/repulsion system on the "standard"
configuration. Obviously I'am interested in the crossed rod pivot approach even though it
has its problems of positional zeroing use.
I note that per the first web site picture, where the boom goes up, it could also go down
through the steel block hole; with the mass hanging underneath. I suppose that route
would be even better to manipulate any mechanical or magnetic centering aspects.
I've not yet tried any kind of vertical with any kind of spring add on. Can only roughly
surmise the mass weight would need to "whatever" the spring and pivot can take of
course.
If one stands the 1-2-3" block on its 2x1" thick side per the first view (with a base
plate slight tilt)....then you can likely get another horizontal sensing route; but likely
the mass weight would again be alot less than 2 pounds of course. Yes...there is
a variety of possiblities of a number of pivot orientation routes with this....but whether
they are proven practical (with improvements) remains to be seen.
Meredith Lamb
On Nov 10, 2007 9:14 AM, Randall Peters <
PETERS_RD@..........> wrote:
Meredith,
What you've done is VERY interesting. Am I correct in assuming that your latest test (
1.5 lbs
oscillating 50 minutes) was with the aluminum rod hanging down and swinging from the stationary steel plate,
with the 1.5 lb weight at the bottom? If so, how far below the axis was the weight. The moment of inertia is an
important issue in the decay time, so I would really like to know this number to try and assess the
relative importance of air damping compared to the internal friction associated with your axis.
Randall