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remagnetising old magnets

N

NumanR

Jan 1, 1970
0
I would like some help on increasing the magnetic strength of some
magnets in some d.c motors. The motors are small 540 size,
approximately two inches long and inch and a quarter in diameter with
two half moon magnets inside approx 4mm thick. How can I increase
their strength? As far as I know they are ferrite? magnets, I know
they are definately not rare earth magnets.
 
B

Bill

Jan 1, 1970
0
I would like some help on increasing the magnetic strength of some
magnets in some d.c motors. The motors are small 540 size,
approximately two inches long and inch and a quarter in diameter with
two half moon magnets inside approx 4mm thick. How can I increase
their strength? As far as I know they are ferrite? magnets, I know
they are definately not rare earth magnets.

I believe the usual method is to take a large DC electromagnet,
build a pole structure on it to focus the field where you want
it, and whack it with a big pulse of current.
 
A

Aslaner

Jan 1, 1970
0
I don't think that you can do much, it is all pre configured at the
manufacture with the metal itself the density of the particles etc, sure
you make it look like is holding a charge for a little period of time but it
is about all, it will return to its original magnetism.
There is saturation point after which you will be wasting your time.
The smaller/stronger one are made that way not just charged that way. It
took years of development to get to that point.


I believe so anyway, I could be slightly wrong but not that far.
 
F

Fred McKenzie

Jan 1, 1970
0
<< There is saturation point after which you will be wasting your time.
The smaller/stronger one are made that way not just charged that way. >>

Aslaner, Bill & NumanR-

I believe you are correct that there is a saturation point, but the alloys are
not naturally magnetized. They are "charged" in a machine that works about the
way Bill described.

The question is whether or not the magnets were magnetized to a point beyond
their saturation point. If so, then the field would have eventually ended up
at some maximum stable value. However, they may not have been magnetized to
saturation, or there may have been some condition such as mechanical shock,
that caused the field to be reduced. In either case, it may be possible to
increase the magnet's strength using the magnetization process.

One thing that might go wrong, is a field reversal caused by the magnetizing
field (or current) being backwards. You have a 50-50 chance of getting it
right!

Fred
 
N

NumanR

Jan 1, 1970
0
The motors are used for racing r/c cars, now please take this
seriously as there is a tool on the market which costs £600 which
appears to be just a high strength magnet.(This is used before each
race by the top racers) What I want is a cheaper alternative, or an
idea to help me build wht i need. The magnets are subjected to heat
and I think this effects the magnets. I cannot stop the heat but if I
could top up the magnets each time then this would help. Thanks for
your ideas.
 
P

PaPaPeng

Jan 1, 1970
0
The motors are used for racing r/c cars, now please take this
seriously as there is a tool on the market which costs £600 which
appears to be just a high strength magnet.(This is used before each
race by the top racers) What I want is a cheaper alternative, or an
idea to help me build wht i need. The magnets are subjected to heat
and I think this effects the magnets. I cannot stop the heat but if I
could top up the magnets each time then this would help. Thanks for
your ideas.


Is it possible to strap rare earth magnets on the motor casing to
boost the strength of the motor's magnet?
 
S

Sam Goldwasser

Jan 1, 1970
0
What I had already suggested via email is to try using the rare earth
magnets from a high performance harddrive to see if this is possible.

Experiment with a pair of magnets from a dead motor - one to test and
the other as the "control".

Of course, if you can affect the magnetizism at all, it would be possible
to reverse the field or magnetize the megnet along any arbitrary direction
so you'll have to figure out where the polse are on the motor magnets and
disk drive magnets and orient them accordingly.
Is it possible to strap rare earth magnets on the motor casing to
boost the strength of the motor's magnet?

I have a feeling this is against the rules.

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traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
C

Chuck Harris

Jan 1, 1970
0
PaPaPeng said:
Is it possible to strap rare earth magnets on the motor casing to
boost the strength of the motor's magnet?

Boosting the strength of the field magnets doesn't necessarily do
what you think it might. For instance, once a motor has started,
and is up to speed, weakening the field magnets will cause the motor
to speed up..drastically!

Conversely, strong field magnets will give you high, lowspeed torque,
but will limit the maximum speed of the motor.

-Chuck Harris
 
N

NSM

Jan 1, 1970
0
| The motors are used for racing r/c cars, now please take this
| seriously as there is a tool on the market which costs £600 which
| appears to be just a high strength magnet (this is used before each
| race by the top racers) What I want is a cheaper alternative, or an
| idea to help me build what I need. The magnets are subjected to heat
| and I think this effects the magnets. I cannot stop the heat but if I
| could top up the magnets each time then this would help. Thanks for
| your ideas.

Does this tool connect to a source of power, AC or DC? I have the gravest
doubts that this 'tool' works better than a chicken bone. Faith may not be
able to move mountains, but it sure moves money, usually from someone else's
wallet!

N
 
N

NumanR

Jan 1, 1970
0
Ok we are not allowed to use rare earth magnets in any form, there are
two machines which i know about one is an electro magnet using 12v dc
feed and presumably a capacitor, and the other is a box which is not
powered which presumably has a high strength magnet inside. I have not
been able to see inside these tools but vouch that they do work, on a
recent test it made a second a lap difference (on a 18 second lap). It
is not the speed of the motor but the power and torque I am after so
strengthening the magnets is a major tuning aid. Every other way of
making the motors powerful is already done and we are restricted on
voltage allowed on board the cars. Thanks for your suggestions so far.
 
N

NSM

Jan 1, 1970
0
| Ok we are not allowed to use rare earth magnets in any form, there are
| two machines which i know about one is an electro magnet using 12v dc
| feed and presumably a capacitor, and the other is a box which is not
| powered which presumably has a high strength magnet inside. I have not
| been able to see inside these tools but vouch that they do work, on a
| recent test it made a second a lap difference (on a 18 second lap). It
| is not the speed of the motor but the power and torque I am after so
| strengthening the magnets is a major tuning aid. Every other way of
| making the motors powerful is already done and we are restricted on
| voltage allowed on board the cars. Thanks for your suggestions so far.

There have been a number of books published in the UK which might help. Look
for books on measuring instruments or speakers, both of which use magnets.
Those published in the '60's are probably most useful. I recall sections on
'charging' magnets in these.

Avoid 'magic' thinking, i.e. assuming there is some magic trick known to
few. In most cases, whatever you try will help and if it doesn't, figure out
HOW to figure out WHY. That's how most items are 'designed' anyway.

N
 
A

Asimov

Jan 1, 1970
0
"Fred McKenzie" bravely wrote to "All" (09 Oct 04 15:36:00)
--- on the heady topic of "Re: remagnetising old magnets"

FM> From: [email protected] (Fred McKenzie)

FM> << There is saturation point after which you will be wasting your
FM> time. The smaller/stronger one are made that way not just charged that
way. >>
FM> Aslaner, Bill & NumanR-

FM> I believe you are correct that there is a saturation point, but the
FM> alloys are not naturally magnetized. They are "charged" in a machine
FM> that works about the way Bill described.

FM> The question is whether or not the magnets were magnetized to a point
FM> beyond their saturation point. If so, then the field would have
FM> eventually ended up at some maximum stable value. However, they may
FM> not have been magnetized to saturation, or there may have been some
FM> condition such as mechanical shock, that caused the field to be
FM> reduced. In either case, it may be possible to increase the magnet's
FM> strength using the magnetization process.
FM> One thing that might go wrong, is a field reversal caused by the
FM> magnetizing field (or current) being backwards. You have a 50-50
FM> chance of getting it right!

It is a little hard to identify magnetic polarity of a magnet. I'm not
sure but the Earth's own North Pole is actually a magnet south and
will attract a magnet negative. So using a "magnetic compass" actually
finds the south on a magnet. Is this right?

A*s*i*m*o*v

.... Reactance: your imaginary friend.
 
W

WEBPA

Jan 1, 1970
0
One means of improving the performance of pm and universal motors has not yet
been mentioned. That is: Altering the phase relationship between the brushes
and the field magnets. This was (still is?) a common control method for
traction motors in street cars/trolleys/buses. Was also used for elevators and
motor-generator (dynamotors) sets (welding, arc lamps, etc.)

Exactly how this might be applied to slot cars seems to offer lots of room for
creative engineering.
webpa
 
F

Fred McKenzie

Jan 1, 1970
0
<< Ok we are not allowed to use rare earth magnets in any form, there are
two machines which i know about one is an electro magnet using 12v dc
feed and presumably a capacitor, and the other is a box which is not
powered which presumably has a high strength magnet inside. >>

NumanR-

I can see where either method would top-off the magnets.

It may not be worth mentioning, but I wonder if adding a coil of wire around
the magnet, wired in series with the battery, would increase the motor's torque
at slow speed? At slower speed I would expect current to be higher, which
would aid the magnet if polarity was correct.

Would such a modification be legal?

Fred
 
J

Jim Adney

Jan 1, 1970
0
It is a little hard to identify magnetic polarity of a magnet. I'm not
sure but the Earth's own North Pole is actually a magnet south and
will attract a magnet negative. So using a "magnetic compass" actually
finds the south on a magnet. Is this right?

Yes, that's right. The North pole on a magnet is the one that points
north, so the pole that's near the Earth's north geographic pole is
actually a South pole.

-
 
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