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Using old HD Magnets
to boost fuel efficiency and
clean water? 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.

Hard Drive Magnet before 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.

... and after placement 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 milliseconds.

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 the paint.

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.

© Algorithmica Japonica Copyright Notice: Copyright of material rests with the individual author. Articles may be reprinted by other user groups if the author and original publication are credited. Any other reproduction or use of material herein is prohibited without prior written permission from TPC. The mention of names of products without indication of Trademark or Registered Trademark status in no way implies that these products are not so protected by law.

Algorithmica Japonica

October , 2002

The Newsletter of the Tokyo PC Users Group

Submissions : Editor

Tokyo PC Users Group, Post Office Box 103, Shibuya-Ku, Tokyo 150-8691, JAPAN