Using old HD Magnets
to boost fuel efficiency and
by Bernd Nurnberger
Once out of service, hard disks are taken to have a remaining value similar to that of a
brick. If you have one disk that you can take apart, you may salvage some powerful
magnets. Here is how
and what you can do with them. Would you have thought your magnets
can do work similar to a $90 fuel-saver or a $300 device sold for water treatment? With
surplus magnets, such experimentation costs very little, but if you invest into the
devices, you may be biased to justify the expense.
How many broken things do we trash because we have no idea of uses for their parts, and no
space to keep them as collector's items (dust collector's ;-) The junkyards make a living
on knowing Parts, Use and Value of. They help keep prices lower while we the customers
appreciate re-usable products.
While cars and consumer products are said to have obsolescence built in (quite so in
fashion products, computers and their parts rather become obsolete by rapid appearance of
much improved (ahem?)products. Faster, bigger and cheaper, recently more networked, and
for the life of it dependent on occasionally costly upgrades and giving away your privacy
by registration and other nagware features. But I digress.
Inside a hard disk are usually three electromagnetic devices. The weakest one is the
read/write head that lays magnetic tracks on a fast-spinning platter to represent the bits
we want to read later. No strong magnet here - it would erase the data. A little stronger
are disk motor magnets, but recovery would not make much sense. The real strong magnets
are in the head actuator.
They are the brute force that makes the heads jump from track to tack in a few
If you want to save all this disassembly work outlined below, simply order some surplus
magnets for a few dollars at
If you want to look at what's inside your trusted hard disk, read on.
This is not a complete manual, just the bare necessities for a curious mind and
mechanically skilled hands.
The hard disk inside is an airtight container, assembled in a clean room because tiny bits
of dust would jam the air gap the magnetic read-write head needs to float above the
spinning platter. The result is known as a forceful contact between head and data surface,
often resulting in the permanent lathing away of the platter magnetic track surface,
including the data.
Therefore the seal "Warranty Void when Broken" on the ominous gap in the disk housing
enclosure. If you have determined the brick-like status of the disk (do you really value
the magnet more than the data on the disk?) you may as well ignore this warning and
proceed to locate the four or more screws that hold the shells together.
Special head shapes not matching any of the screwdrivers you own are a temporary obstacle
until you find a small but strong flat blade (called "minus" in Japan) to engage in the
recess and transmit the necessary torque. Short of buying a set of matching bits for this
recovery job, you may try a chisel or drill on the screw heads. Be inventive, but know
that brute force in untrained hands may have injurious side effects.
Once laid open, the hard disk bares its spin platter; one of the read/write heads is above
it and at the end of the head's pivoting arm is a drive mechanism which contains our
valued pair of magnets. Loosen screws as necessary to get them out.
These magnets are so strong that they can hold several pages of newspaper to the fridge.
The downside is, if you allow them to touch the surface directly or with too few pages
between, you may not be able to pull the magnets off; and in sliding them along, you mar
Various devices are sold on the automotive aftermarket that claim to save fuel. When I saw
the magnetic clamps to put on the fuel line, my engineering mind was at its wit's end.
While any saving device would recover its price in the long run, and there must be
customers for such a device, I figured I'd have to save an awful lot to break even on the
purchase price of about $90. The blurb was honest "mileage gains may vary", and not
knowing whether my vehicle would gain any, I tried with my surplus magnets.
First on the motorbike, a 400cc water-cooled 1993 Kawasaki ZRX-II, where the fuel line is
fairly accessible. With the magnets--they held by themselves due to the strong attraction
even across the separation by the fuel hose--I just secured them with a bit of wire.
Watched the mileage for a few tankfuls but within the variation inherent in weather and
driving conditions, I noticed no improvement. Checked with commercial products and on the
Internet. Seems the magnets are not set for attraction but for repulsion. I pulled some
brackets out of my grab box and attached the magnets repulsing each other. From the start,
I noticed a stronger throttle response. I narrowed it down to being able to push back the
choke immediately after the engine started. No more hesitation, which had been common
without choke during the first 5-10 minutes.
In cooler weather, following a colleague's advice (he is an automotive inspector), I
removed the magnets to be sure nothing else had changed. No, the improved cold response
went and came back with these repulsing magnets on the fuel line. Within my margin of
error, I noticed no power gain or fuel saving, but off the cold start, driving is more
fun, safer, and a little less polluting.
Tried a similar repulsing arrangement of HDD magnets on the car, a 1994 Toyota Caldina 2.0
L wagon. No noticeable effect. I did have a power gain when I switched to a higher
efficiency ignition, but that is another story.
Various sources from Internet shops to Tokyu Hands claim magnets on water pipes reduce
limestone deposits. They sell devices in the price range of hundreds of dollars. Some are
mighty magnets, held with an ingenious contraption to the faucet; some are small, some
electromagnetic. University research reports range from believable findings supported by
electron microscope photos to sites who claim it is all quackery, and from many of which I
retain the impression they operate on an unscientific paradigm like "it cannot be true
because we can't understand it (or: it affects our undisclosed business interest)".
This public debate was invitation for me to find out for myself, and with surplus HDD
magnets at my disposal, the investment risk was negligible. Said and done in winter 1999.
We moved to the current house in summer 1999, and just like the one before in the same
area, it took about 6 months for the bathroom faucets and other wetted parts to succumb
their original luster to whitish deposits of limestone. While removing them with citric
acid (available in granular form in the drugstore) works well, and intervals can be
prolonged by coating the chrome with car wax or silicon oil, it is just that: work, that
I'd rather avoid or postpone.
In came the magnets on the main water pipe and - were forgotten. Half a year later, same
story: limestone deposits, citric acid cleaning. I remembered what I had learned on the
fuel devices and turned one magnet around so they were now repelling each other. Only this
summer, after another year, I looked at the faucets and other wetted parts and noticed
they were rather good looking, without having been through a citric acid treatment since.
Inquired with the family, if anyone had voluntarily cleaned... no.
So this is the effect of the magnets. In repulsive configuration they do reduce the
tendency of the calcium in the water to form hard deposits. It says so on some of the
research sites, and the debunkers are herewith rebuked.
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October , 2002
The Newsletter of the
Tokyo PC Users Group
Tokyo PC Users Group,
Post Office Box 103,
Shibuya-Ku, Tokyo 150-8691, JAPAN