[TheForge] Re: magnets as latches

[Roger Olsen]

Let me try asking the question this way________do any of you have actual
experience using magnets for a closing system on firedoors?  I am not asking
those of you who have guesses or assumptions or opinions, only those of you who
have actually used them and what you found______did the doors latch the same
two years from day one or did they loose a lot if not all of their magnetic
qualities.

Thanks,
R Olsen
__________________________

Steve Smith wrote:

> I don't have a clue, Roger. I did find a list of Curie point
> temperatures for different materials. Here are a few (in degrees
> Kelvin--subtract 273 and you have Centigrade):
> Iron 1043
> Cobalt 1388
> Nickle 627
> source: http://www.nationmaster.com/encyclopedia/ferromagnetism
>
> etc. So your question is good, how soon do you see effects? It also
> looks like you have a huge effect in the actual temp by what alloy
> you're magnet is made of. I don't think this helps, just more info.
>
> Steve Smith
>
> Roger Olsen wrote:
>
> > So I assume the higher the heat the faster the magnetic loss but when does
> > the affect kick in?  100 degrees________300 degrees_________500
> > degrees________700 degress?
> >
> > Does anyone know the answer to this?
> >
> > R. Olsen
> > _______________________
> >
> > Bruce Freeman wrote:
> >
> >
> >>Clearly, when steel goes non-magnetic, if the steel WERE a magnet it
> >>wouldn't be afterwards.
> >>
> >>However, any heating or hammering will reduce or destroy the magnetic
> >>properties of a steel magnet.
> >>
> >>If using a magnet as part of a door latch:
> >>
> >>First, be aware that those rare earth magnets can be VERY strong.
> >>Think pinch-points when using them in a design.
> >>
> >>Second, you may want to move the magnet itself away from the heat.
> >>Imagine, for example, using a horseshoe magnet as the handle on a hot
> >>door.  The cooler handle will be less likely to lose its magnetic
> >>properties.  But if constructed correctly, this remote handle could be
> >>an effective latch for the door, since the magnetic forces will follow
> >>the path of the steel.  (Constructed incorrectly, there would be no
> >>magnetism to latch the door, however.   Avoid a complete loop.  Think:
> >>"horseshoe" shape.)
> >>
> >>Bruce
> >>NJ
> >>
> >>
> >>>>>erik at methow.com 5/13/2004 12:22:50 PM >>>
> >>
> >>Hey Andy,
> >>
> >>Ask your friend one other thing about magnets.  I wonder about heat, at
> >>what
> >>point does it drain a magnet of its magic affects?   I have never used
> >>them on
> >>fire doors but I know many have.  I have considered using them in the
> >>past and
> >>I am sure I will again in the future.
> >>
> >>If I did I would use the 'Rare Earth Magnets' sold by Lee Valley and
> >>others as
> >>well.  They seem to be about 10 times stronger than the radio shack
> >>type
> >>magnets.
> >>
> >>Roger Olsen
> >>__________________________________
> >>
> >>Gladish Family wrote:
> >>
> >>
> >>>>1. I have a number of assorted magnets used for set-ups, mock ups
> >>
> >>and
> >>
> >>>>the like...should they be stored separately, carefully aligned
> >>>>north/south, to retain max  pull ( suck?) or is it not a problem
> >>
> >>just to
> >>
> >>>>toss them in a box with their friends?
> >>>
> >>>My understanding is that magnets are manufactured by applying
> >>
> >>overwhelming
> >>
> >>>magnetic fields (i.e. really really huge!) to a previously neutral
> >>
> >>chunk of
> >>
> >>>metal, and that heat or overwhelming magnetic force are the only ways
> >>
> >>that
> >>
> >>>magnets lose their pull, other than physical deterioration.
> >>>I have a friend who sells magnets for a living- I'll ask him.
> >>>Andy G.
> >>>
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