# Hard drives again.....



## SapunovDmitry (Mar 11, 2008)

Guys, recently we've analyzed a magnet from an old hard drive and it showed that, it nad 33% Nd by weight. Can it be true? Maybe there are some specifications for those magnets? Kind of chemical content or something?


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## junkelly (Mar 11, 2008)

Is this what you mean? Neodymium "rare earth" magnets:

http://en.wikipedia.org/wiki/NIB_magnet

They're common enough now that they are used in toys. I've even seen them used as latches in America OnLine packages that are given away for free.

-junkelly


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## Gotrek (Mar 11, 2008)

I always thought they were all mostly Nd. It's the only thing magnetic enough to work reliably in a hard drive.

They are great to stick on your oil pan and oil filters to protect your engine.


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## starzfan0211 (Mar 11, 2008)

My neighbor is wanting me to give him some to put on the bottom of his motorcycle to help disrupt the traffic signal things in the roads. It seems his bike just isn't enough to do it and he thinks that the magnets will help.


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## Gotrek (Mar 11, 2008)

starzfan0211 said:


> My neighbor is wanting me to give him some to put on the bottom of his motorcycle to help disrupt the traffic signal things in the roads. It seems his bike just isn't enough to do it and he thinks that the magnets will help.



That won't so anything as far as I'm aware those are usually pressure switches under the slab and the weight of the vehicle is what triggers them. The other type of sensor is optical just rock the vehicle back and forth to re-trigger them.


I guesss they operate like ametal detector so lack of metal does not trigger them. So he is correct a strong magnetic field would trigger them more readily since that';s how a metal detector works (

Wiki:

More sophisticated control systems use electronic detector loops, which are sensors buried in the pavement to detect the presence of traffic waiting at the light, and thus can avoid giving the green light to an empty road while motorists on a different route are stopped. A timer is frequently used as a backup in case the sensors fail; an additional problem with sensor-based systems is that they may fail to detect vehicles such as motorcycles or bicycles and cause them to wait forever (or at least until a detectable vehicle also comes to wait for the light). The sensor loops typically work in the same fashion as metal detectors; small vehicles or those with low metal content may fail to be detected.

It is also commonplace to alter the control strategy of a traffic light based on the time of day and day of the week, or for other special circumstances (such as a major event causing unusual demand at an intersection).


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## starzfan0211 (Mar 11, 2008)

Thanks. I figure I will let him try. He works for a uniform supply company and has given me some mats and stuff that they were throwing out to put down under our work table. I am just trying to be neighborly back . 

They are some strong magnets though. We use them for picking up all the screws that we drop and I have some strategically placed on my work table to hold the bits for my drill for when I am taking things apart.


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## Anonymous (Mar 31, 2008)

hi all, not trying to but in but the magnets actually do work in tripping the light switches for motorcycles. There is a company that sells these, they are called "Green Light Trigger". I had one on my bike and yes it does trip the light without a problem...


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## pcecycle (Mar 31, 2008)

What does putting the magnets on your oil pan supposed to do?

Mike


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## Noxx (Mar 31, 2008)

To get magnetic dusts I suppose...


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## Palladium (Mar 31, 2008)

You are correct Noxx. As the engine wears things like bearing and rings wear also. After the oil drains from the top of the engine to the bottom of the engine it is picked up by the pickup tube and pumped from the pan thru the filter to the engine.

By placing a magnet on the pan it traps the fine particles and sometimes shavings before they can enter the oil pump and cause damage to the pump or clog up filters. Some newer engines actually have a magnet inside the oil pan. When i rebuilt my 92 Dodge this was the case. I had a rod cap bearing that was not tightened at the factory correct. It always was just a little low on oil pressure and had just a little tick to it. Well on day on the interstate while running about 80 the bolt finally sheared and the crank connecting arm snapped. When i took the oil pan off to see the damage there was the rod cap bearing and the inserts all stuck to the magnet.


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## viacin (Oct 22, 2008)

starzfan0211 said:


> My neighbor is wanting me to give him some to put on the bottom of his motorcycle to help disrupt the traffic signal things in the roads. It seems his bike just isn't enough to do it and he thinks that the magnets will help.



Amazingly, it does work, and here's a great video on how to do it http://www.metacafe.com/watch/828731/trigger_green_traffic_lights/

They use inductive-loop traffic detectors. The video does a good job to explain it. One note however, I use much stronger magnets than he does for better results. You can get a set of 4 with a pulling force fo 65lbs a piece for about $15.

I put some on my bike as a test and it changed everyone almost as soon as I pulled it. Not all lights use these detectors however, so pick your route wisely if you're running late.


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## Jehu (Oct 22, 2008)

From memory most HDD magnets are either made from Neodymium or Samarium-cobalt. Neodymium being the more common. 

Yes, alot of cars have magnets in the oil pans. My '95 Toyota Camry has one in the engine pan and in the auto-gearbox/differential pan. This also stops the metal filings from doing more damage to other parts of the engine like the cams, valves, bore and bearings. It's cheap, extends the life of the engine and also aids in diagnostics.


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