Hard Disk Drive Magnets For Wind Turbines

Obtain super strong magnets from old hard disk drives to use in wind turbine alternators

The most expensive parts of a wind turbine alternator (1) are the magnets (2) and the enamelled magnet wire (3). In a previous article we have introduced cheap and easy to make PVC wind turbine blades (4). Here you will learn how to obtain magnets for free.

Hard Disk Drive Magnets

50% of the world's neodymium magnets (5) are currently used in computer hard disk drives (HDD) with each HDD typically containing two magnets. The magnets are used in the actuator - a device which moves the actuator arm on the tip of which is the head which reads and writes data to/from the ultra-delicate platters. Driving the arm using magnets means that mechanical wear and tear is not an issue - unlike old-fashioned stepper motor powered hard drives.

View inside a hard disk drive showing the location of the neodymium magnets

Removing the magnets from an old hard drive is very easy - usually just a cross-head (phillips) screwdriver is required. Click here to view a 77 second video from metacafe on extracting magnets from an HDD (6).

When you remove a magnet from a hard drive it will still be attached to a steel backing plate (see below) which should be removed.

Hard disk drive magnet still attached to backing plate

This can be difficult, however the easiest way is to put one corner of the backing plate into a bench vice and bend the other corner of the plate using a pair of vice grips.

Bending the backing plate away from the magnet

WARNING! Sometimes the magnet will break instead of coming away from the backing plate. Ensure that any pieces of broken magnet are kept well out of the reach of children since a couple of swallowed pieces of magnet sticking together in the intestine could be fatal.

Neodmium Magnets in Hard Disk Drives

The magnets used in hard disk drives are very strong neodymium (rare earth) magnets. Typically a magnet will have a north pole on one face, and a south pole on the other face. Hard drive magnets differ in that they act like two magnets stuck together side by side. On one face there is a north pole on the left and a south pole on the right, on the other face there is a south pole on the left and a north pole on the right.

This is shown in the image below with the white labels pointing to the top face of the magnet, and the yellow labels pointing to the (hidden) bottom face of the magnet.

Looking side-on the polarity of the magnet can also be represented as follows:

NORTH	SOUTH
SOUTH	NORTH

Therefore, in using these magnets to make a wind turbine alternator you have two choices. The first is to cut each hard disk magnets in half (using a non-magnetic cutting disk) to make two standard magnets with one entire face a north pole and one entire face a south pole. Alternatively they can be used as is, but the coils in the alternator must be sized to straddle just one pole at a time.

5 hard disk drive magnets stuck together to make one very powerful magnet

However you decide to use them, the power of the magnets can be increased by sticking them together (as shown in the photograph above). Three magnets stuck together for example should give somewhere between 2 and 3 times the magnetic power of just one magnet.

Web Link References

(1) http://www.reuk.co.uk/Wind-Turbine-Alternator-Basics.htm
(2) http://www.reuk.co.uk/Neodymium-Magnets.htm
(3) http://www.reuk.co.uk/Enamelled-Magnet-Wire.htm
(4) http://www.reuk.co.uk/PVC-Wind-Turbine-Blades.htm
(5) http://www.reuk.co.uk/Neodymium-Magnets.htm
(6) http://www.metacafe.com/watch/486981/strong_magnets_from_your_hdd/

Article from REUK.co.uk:
http://www.reuk.co.uk/Hard-Disk-Drive-Magnets-For-Wind-Turbines.htm
Published: 14th April 2007
© REUK 2009