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Author Topic: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet  (Read 24813 times)

sm0ky2

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some years ago, while experimenting with rotating magnetic fields, I came across a strange phenomena.
This set-up used a normal, small DC motor (6-12v) coupled to the magnet and shield plate from an old-school 5 1/4" Floppy Drive.

this shows the magnet w/ shield plate and its' properties.
http://hackedgadgets.com/2007/05/10/magnetic-viewing-paper/


This magnet was attached directly to the gear-head of the motor, and when pulsed (1/4sec - 1/2sec) from a 9v battery (no resistance)
the motor would self-sustain operation for 70-90 seconds.
This seemed extremely 'odd' to say the least, and had me playing with it for endless hours... The motor would operate 'as if' it still had current running through it.
Not simply the "flywheel" effect.

This is what I discovered:

When attached to a fly-wheel of similar weight to the magnet-shield combination, the motor would not behave this way. The fly-wheel effect would keep it spinning for just a few seconds, as the motor slowed to a halt. I believe this was due to the induction through the coils from the permanent magnets in the motor housing, causing a back-EMF, fighting the rotation.

When attached to an axially-magnetized magnet (from a microwave oven), it performed similar to the fly-wheel.

When the battery was connected in reverse, while the 'event' was occurring, it took some time, and energy drain to slow the motor, and reverse the direction of rotation.

--------------------------------------------------------

my conclusions at the time were that, the magnet, being magnetized in a sectional manner, induced a current-flow through the motor coils, which helped sustain the rotation / operation of the motor.
Lots of giggles and amazement from the device...
Eventually, I put the thing down, because after all, it was not completely self-sustaining, as it did eventually come to a stop. (70-90 secs)
But, recent studies into magnetic theory have led me to begin thinking about this again, so I figured I'd place this in here to share.
This may have some use, or lead to further discoveries.

The floppy drives are becoming more and more rare, as it is an obsolete, and outdated technology...
semi-hard to get ahold of, so I don't have the materials to replicate another one at this time. but I will attempt to gather one.
Other than that, its very simple to assemble this set-up.

below is my (attempt at) drawing of the device. It is just a motor, with the magnet and shield plate attached.
(note: the shaft in the drawing is elongated, the real device had the mount very near the motor housing)




gyulasun

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #1 on: March 04, 2015, 10:27:44 PM »
Hi sm0ky2,


If I get you correctly, you intermittently switch on the motor with a 9V battery,  by pulsing it for 1/4 to 1/2 second (by your hand I suppose) and you find the motor maintain rotation of the magnet for 70-90 seconds, much longer than with an flywheel which has an equivalent mass to the (floppy) magnet.

The strange thing is that the motor has a closed circuit for the brief 1/4 to 1/2 second time you attach the battery and for the rest of the run down time, 70-90 secs the motor has an open circuit.  At least this is what I think: your normal DC motor has brushes and the rotor coil becomes an open circuit whenever you remove the battery (and the stator of the DC motor has permanent magnets I suppose).

If this is correct, then the rotating magnet you attached to the shaft of the motor could not induce current in the rotor coil but a voltage only, right?  (and the induced voltage could be measured across the connecting pins of the motor) 
And I assume further that you did not connect the battery during the run down time of the 70-90 seconds but let the rotor slow down to zero rpm, right?

Is it possible you connected the battery for the indicated short time while the rotor was still spinning from a previous run and you got the long spin down time in that case only? Or you started the motor with the battery from a stand still and removed the battery after the 1/4 or 1/2 second, and you got the long run down time?

Anyway, a possible explanation for the long run down time could be the presence of the extra magnetic field the floppy magnet provides, participating in the operation of the motor at the very moment of the connection of the battery. 
You surely found already that the rpm of a normal DC motor could be influenced (either positively or negatively) by placing a permanent magnet near to or directly onto the outside of the motor stator body, this is how I mean the effect of the floppy magnet on the operation time in your case. Of course there could be other factors present.

Maybe you could adjust the distance between the floppy magnet and the front part of the motor to see how it may influence the run down time?  Also, if you happen to have a diametrically magnetized ring magnet, you could also test it (making sure for adding some extra weight to it to make for any mass difference between the floppy magnet and that ring magnet.
What is the diameter of the DC motor and that of the floppy magnet, just curious.

Thanks for sharing this puzzle.

Gyula

conradelektro

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #2 on: March 05, 2015, 08:50:05 AM »
some years ago, while experimenting with rotating magnetic fields, I came across a strange phenomena.
This set-up used a normal, small DC motor (6-12v) coupled to the magnet and shield plate from an old-school 5 1/4" Floppy Drive.
.............................

This reminds me of Harold D. Aspden and his "virtual inertia":

http://de.scribd.com/doc/76567187/1995-Harold-Aspden-Discovery-of-Virtual-Inertia#scribd

--- citation from that page --------------
Imagine an electric machine having no electrical input itself and which, when started on no load by a drive motor and brought up to speed  (3250 rpm), thereafter runs steadily at that  speed  with the  motor  drawing a little extra input  power  with a time  decay  rate of  about  two minutes.  The machine rotor has a  mass  of 800 gm and at that  speed  its inertial kinetic  energy  together with that of the drive  motor  is no more than 15 joules [to overcome friction], contrasting with the  excess  energy of 300 joules needed to satisfy the  anomalous  power  surge [to spin up from rest.] Imagine further that when the motor, after running five minutes or more, is switched off and the machine  is stopped,  you can restart  it in  the same or opposite direction  and find that it  now  has a  memory  in  the  sense  that it will not  now ask  for that 300 joules of excess input, 30 joules will suffice provided  the  time lapse between starting and restarting is no  more than a minute or so.
-------------------------------------------------

I could not find out whether one has to spin a magnet or just mass in order to see that "memory effect".

Greetings, Conrad

sm0ky2

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #3 on: March 05, 2015, 11:41:04 AM »

If this is correct, then the rotating magnet you attached to the shaft of the motor could not induce current in the rotor coil but a voltage only, right?  (and the induced voltage could be measured across the connecting pins of the motor) 
And I assume further that you did not connect the battery during the run down time of the 70-90 seconds but let the rotor slow down to zero rpm, right?

This was my thoughts as well. there was a detectable voltage occurring at the terminals (A/C?) and shorting the terminals seemed to shorten the time that the motor would continue to operate.
however, there was the quite noticeable electric 'hum'.  That's why I said it was 'as if' the motor was still running.
I couldn't get my meter at the time to show a current, but I think that's because of the way the slip-ring switches back and forth, its not a real rectification. and I did not have an a/c current meter.

the only diametrically magnetized ring I had at the time was too large to produce any testable results, so I didn't go down that road.
 
Quote
Is it possible you connected the battery for the indicated short time while the rotor was still spinning from a previous run and you got the long spin down time in that case only? Or you started the motor with the battery from a stand still and removed the battery after the 1/4 or 1/2 second, and you got the long run down time?

The second case - motor was pulse-started from a standstill, by hand via touching the 9v to the terminals directly.

And yes, I did perform some tests with sticking other magnets to the side of the motor housing, while there were some minor effects, nothing as substantial as the one described here.

motor size - it was relatively small DC motor, about the diameter of a US quarter. maybe 1&1/4" - 1&1/2" long.
rated at 6-12v I think


pomodoro

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #4 on: March 05, 2015, 04:00:14 PM »
I wonder if the motor is necessary? Spinning by hand and having the shaft vertical hanging by a cotton thread could be a good test. I've got a few of these drives as well as 3.5 inch ones stashed up somewhere. Might give it a go .

sm0ky2

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #5 on: March 05, 2015, 06:40:43 PM »
I wonder if the motor is necessary? Spinning by hand and having the shaft vertical hanging by a cotton thread could be a good test. I've got a few of these drives as well as 3.5 inch ones stashed up somewhere. Might give it a go .

The shaft in my illustration is drawn way too long,. there wasn't much of a shaft to speak of in the actual build,
   the magnet was mounted directly to the gear-head on the motor shaft. It was the motor itself that caused the effect.
somewhere in the combination of the motor coils, its' own internal magnets, and the sectional magnet from the Drive.
I did try spinning it by hand, and I couldn't seem to get up enough RPM to cause the effect that way....
im not sure if the electric field has anything to do with it, or just RPM of the spinning magnetic field.


I'm not sure if the shield-plate is necessary, or what effect that had on the whole thing, I left it on there out of convenience.
   it gave a nice hole to mount it with, and the magnets are kind of hard to separate from the shield-plate without breaking them.

I didn't try with the 3.5 inch, not sure what the magnets from those are like... but it might be something to look into as well.

Low-Q

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #6 on: March 05, 2015, 07:16:12 PM »
Maybe an old harddrive will be just as suitable for this experiment - in case you cannot find another floppy drive.


Little off topic: First time you open a harddrive, just take a moment to look at the mirror polished disc. It is the cleanest place on earth. No specs, no dirt, finger prints, nothing. But try to close your eyes and imagine a mirror polished surface without specs or marks on it. It's impossible :-)


Vidar

Pirate88179

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #7 on: March 05, 2015, 07:44:48 PM »
Maybe an old harddrive will be just as suitable for this experiment - in case you cannot find another floppy drive.


Little off topic: First time you open a harddrive, just take a moment to look at the mirror polished disc. It is the cleanest place on earth. No specs, no dirt, finger prints, nothing. But try to close your eyes and imagine a mirror polished surface without specs or marks on it. It's impossible :-)


Vidar

I opened a failed hard drive a few months ago and the polished disk had ketchup and mustard all over it.  Of course, I was eating a cheeseburger at the time and it might have come from me...ha ha.

Good point though, those are assembled in clean rooms that use positive air pressure to keep dirt and dust out of the area.  A very cool technology especially when you remember that the first hard drives had hardly any memory capacity and were huge!  We have come a long way in a short time.

Bill

sm0ky2

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #8 on: March 06, 2015, 01:03:33 AM »
Maybe an old harddrive will be just as suitable for this experiment - in case you cannot find another floppy drive.


Little off topic: First time you open a harddrive, just take a moment to look at the mirror polished disc. It is the cleanest place on earth. No specs, no dirt, finger prints, nothing. But try to close your eyes and imagine a mirror polished surface without specs or marks on it. It's impossible :-)


Vidar


maybe you have something else in mind, as I've opened hundreds of these, and there are pieces inside that can be recycled,..
   magnets, polished disks, stepper motors, etc..  but nothing that resembles the sectional magnet found in the old 5 1/4" floppy drives.
http://hackedgadgets.com/2007/05/10/magnetic-viewing-paper/

this is the magnet, & shielding plate, notice how it is magnetized in sections. I didn't find much on how these are actually made, or pieced together, what have you. but I believe it is this arrangement that has the most to do with the effect.

shylo

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #9 on: March 06, 2015, 11:06:55 AM »
Hi smokey, In that link it says that the white lines are the separations between fields.
So the outer rim is a saw tooth pattern?
Other than that you would just need a steel plate with alternating magnets placed evenly around?
How many poles are there on your disc?
Interesting , wish I had one of those to test, maybe it has to do with that saw tooth pattern.
artv

sm0ky2

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #10 on: March 06, 2015, 02:43:52 PM »
yes the white lines are separations. It looks like, from the video in the provided link, that there are 12 sections.
This is probably standard for those drives, so they should all be about the same.

the saw-tooth pattern that is on the outer edge, is probably from a cutting procedure that makes it a round disk.
At least that is my speculation..  But the changes in the field around this rim are very small, detectable by a tiny compass needle,
and the magnetic viewing paper, but otherwise insignificant towards any affect on bulk matter.

The sections themselves are more likely to have an affect. What I do not know is:
    whether these sections are magnetized N<->S in the horizontal plane, or if they are alternating N and S faces.
That is something I never was able to determine when I examined the disk magnet.


gyulasun

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #11 on: March 07, 2015, 06:03:14 PM »
Hi sm0ky2,

I would like to understand the followings:

You wrote that "The motor would operate 'as if' it still had current running through it" and you also wrote "however, there was the quite noticeable electric 'hum'  that's why I said it was 'as if' the motor was still running."

(I assume on the electric 'hum' you mean the usual noise such a DC motor produces when runs from a battery, right?)

So my question is: did you hear the (similar to normal running) electric 'hum' when you short circuited the motor pins by a piece of wire or you heard the electric 'hum' when the battery was removed and the motor started to spin down (with no shorting wire) for the 70 to 90 second long time?

IT is okay that a DC motor can work as a generator and produces mainly AC voltage difference across the brushes whenever it spins down and this voltage can drive current in the rotor coil if you short circuit the motor pins with a piece of wire (or a low resistance load) what you did do and the motor stopped within a shorter than the 70-90 sec spin down time, obviously due to normal Lenz effect.

You wrote the followings:

Quote
I'm not sure if the shield-plate is necessary, or what effect that had on the whole thing, I left it on there out of convenience, it gave a nice hole to mount it with, and the magnets are kind of hard to separate from the shield-plate without breaking them.   

Quote
but nothing that resembles the sectional magnet found in the old 5 1/4" floppy drives.
http://hackedgadgets.com/2007/05/10/magnetic-viewing-paper/
this is the magnet, & shielding plate, notice how it is magnetized in sections. I didn't find much on how these are actually made, or pieced together, what have you. but I believe it is this arrangement that has the most to do with the effect.

Quote
The sections themselves are more likely to have an affect. What I do not know is: whether these sections are magnetized N<->S in the horizontal plane, or if they are alternating N and S faces.
That is something I never was able to determine when I examined the disk magnet.   

Well, on your first quote, I think the shield plate in the floppy drive is intended to enhance the magnetic field strength of the (magnetic pole segmented) ring magnet facing the coils. This field enhancement happens because the back plate (the shield) is able to close the adjacent segment poles of the ring magnet on the back side so the poles on the front side can become stronger.
This is exactly the same when you try to use both poles of magnet to do a job: recall a door magnet for instance in which a normal rectangular magnet which is magnetized thickness wise is sandwiched between two soft iron plates, so both poles appear on the edges of the plates and when you attach these two plates to a third soft iron piece the total magnet flux is able to close across the third plate and this attraction is much stronger than when you attach the third plate to one of the plates only.

On your 2nd and 3rd quotes above, to make it easier to understand, I made a picture on the pole orientation of magnets used in hard disk drives because they have exactly similar segmented poles on their both sides and they also have a back plate i.e. a shield to enhance the front poles strength (and indeed shield the back part of the magnet from the rest of the HD drive circuits).
You can see two poles on front and two poles on the back of such magnet, this means also that you have normal opposing poles across the thickness of the magnets and also opposing poles on both the front side and on the back side.
And the magnetic segments on your floppy ring magnet have exactly the same pole distribution, say NS, but they alternate all around on both the top side and the rear side of the ring. Obviously, when there is a N pole on top side then there is an S pole right beneath it on the rear side. And the soft iron plate on the back of the ring magnet closes all the neighbouring poles on the back of the ring magnet, thus enhancing the field of the poles on the front side.

For a Neo hard disk magnet the two poles on the front and the two poles on the rear side distribution mean that you could cut such magnet into half to get two separate magnets which would still be magnetized thickness wise but they would not have two poles any more (but only one) on their front or rear sides, here is a how to link to such deed: http://www.fieldlines.com/index.php?topic=139517.0

I attached one of the magnetic viewing paper pictures (from the link you gave in the first post) to show possible poles next to each other on the top side of the ring magnet from the floppy drive.   Sorry for the long rambling...   :)

Gyula

sm0ky2

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #12 on: March 07, 2015, 09:38:13 PM »
Hi sm0ky2,

I would like to understand the followings:

You wrote that "The motor would operate 'as if' it still had current running through it" and you also wrote "however, there was the quite noticeable electric 'hum'  that's why I said it was 'as if' the motor was still running."

(I assume on the electric 'hum' you mean the usual noise such a DC motor produces when runs from a battery, right?)

So my question is: did you hear the (similar to normal running) electric 'hum' when you short circuited the motor pins by a piece of wire or you heard the electric 'hum' when the battery was removed and the motor started to spin down (with no shorting wire) for the 70 to 90 second long time?


Gyula

the 'hum' would occur with battery removed, and no shorting, Both terminals were open, and it would continue long enough for me to walk outside and show my neighbor: " hey, look this motor is running itself!!"
of course, he did not know what to think of the phenomena any more than I did, and as I had no practical use for it at the time, it seemed not much more than a novelty trick...

after reading about back-EMF cancelling, and other such ingenuities concerning DC motors, I couldn't help but think this subject was of some importance after all.

   

mikemongo

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #13 on: March 07, 2015, 10:51:30 PM »
It might be worth trying to short with a diode.

If the magnet is inducing the motor coil, a diode would stop a reversal of current on the motor windings.

Magluvin

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Re: Self-sustaining DC Motor, using old 5 1/4" Floppy Drive Magnet
« Reply #14 on: March 07, 2015, 11:08:45 PM »
lol. Wouldnt it be odd if the magnet and shield plate rotating were all that is needed? Just thinking. If someone has that particular mag and the same kind of shield disk, might as well try to eliminate possibilities. Say use a longer shaft between the motor and mag/shield. get the mag/shield goin, then remove the motor from the shaft. Err, something like that.

Mags