Re: [femm] PMsquare dead end...

[Dave Squires <djsquires@xxxxxxxx>]

Stefan,
The trick is to use more than one magnetic
circuit acting at once. Think parallel magnetic
circuits and then also use the fact that force
is inversely proportional to gap spacing (distance).
Increase the gap on the exit half in the direction
of motion by using a notch. This way you can
create a force asymmetry. You need the force
patterns spaced apart and overlapped such that
the positive is enhanced and the negative partially
cancelled. Then you can get somewhere.
Otherwise you will see the usual integration of zero
net force.

Dave Squires

harti@xxxxxxxxx wrote:

> Hi All,
> thanks a lot for all your help.
> I see now, that the PMSquare as suggested
> is a "dead horse".
> It seems only to generate horizontal forces
> due to the end conditions of the stator magnets....
> It is also too complicated to be build for a real
> linear motor.
> Thus I am working now on a kind of Howard Johnson
> like linear magnet motor, where the runner magnet
> flies over a track of steel plates.
> So the difference to the Howard Johnson design is,
> that the stator track does not use any magnets but just steel
> plates. The runner magnet above it uses special core pieces
> so the magnet never locks in any position, but always
> wants to move on to the side.
> It just depends on the steel plate spacings versus air gaps
> versus runner magnet dimension.
>
> I am trying now to find the right dimensions, so that there is
> always a positive force into the x-direction.
>
> Regards, Stefan.
>
> --- In femm@xxxx, David Meeker <dmeeker@xxxx> wrote:
> >
> >
> > Dave Squires wrote:
> >
> > > David,
> > > I don't think I quite agree with your explanation.
> > > If the two magnets are locked together and held
> > > in the position shown you then have a
> > >
> > > Net force = +B*Q +(-B*Q) = 0
> > >
> > > if embedded in a uniform field. Isn't that correct?
> > >
> > > Dave Squires
> >
> > That's exactly right--there is no net force on a permanent magnet
> in a uniform
> > field.
> >
> > Dave.
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/