Opposites Attract

Jameco readers share their magnetic experiences

Jameco shared Wayne Hunter's recollections of encounters with MRI magnets that field service technicians relayed when he worked at a healthcare manufacturing company. Several of our readers shared their own personal experiences with magnets, and the stories were too good not to share! We hope you find these magnetic stories as attractive as we did.

Magnetic

Gerald Johnston – When I was a preteen, I was at a friend's house when I noticed a rather large horseshoe magnet stuck to the side of my friend's father's tool box. Being an inquisitive kid, I asked my friend's dad about it. He told me that it was a magnetron magnet from an aircraft radar.

I asked him if I could look at it. He told me if I could get it off of the tool box, I could have it. Shortly after he went into the house for something and while he was gone, I attacked the magnet. Pulling it off by hand was obviously beyond me. I asked my friend to help and he said I had to get it off myself if I wanted it. I tried to slide it to the edge of the box thinking I could pull it off if I could get one leg off the box but it wouldn't slide. I finally got a piece of broom handle inside the magnet and pried one leg loose, but still could not get it off. So I got several pieces of plywood scraps and pried one leg of the magnet leg up with my broom stick and stuck a bit of plywood under the leg. Then I did the same for the other leg. On the second layer of 1/4 inch plywood, I was able to pull the magnet free.

While I was standing there holding that monster, my friend's dad came back from the house. When he saw me with it, let's just say he was surprised. The first thing he asked me was how I got it off. After I told him, he told me that he had had grown men try to get it off and fail. Then he told me that it was far too dangerous for a kid to have and that while he was sorry, he couldn't let me keep it. Profoundly disappointed, I handed it over and he stuck it to a larger tool cabinet about 6 feet from the floor.


Paul Nash – When I was a teen, in the early 60's. I read that you could magnetize aluminum and create a "rail gun" with a circle of aluminum on an iron core electromagnet.

My father said that it could not be done, so to prove him wrong I created an iron core from some bars he had and made a 2 inch square core. Then, I wound about 25,000 coils of copper wire around this core with a drill press setup and made it into a transformer by adding another low number of coiled wire around the first coil and put a 110 volt plug on it. I made a donut shaped platter from scrap aluminum about 5 inches in diameter. Then using a circuit breaker 110 outlet I fired this thing up in the basement. The coil shot up off the transformer, as the breaker opened. Now there is a 5 inch diameter compression about 1/4 inches deep in the bottom of the oak floor, which was exposed in the basement. Fortunately, I fired it from a few feet away so nothing hit me. My father's response was, "I guess I was wrong. Don't do it AGAIN!"

Now that I am "older" I would probably not do that again, but I had fun making it. Later for a class project I made a pendulum with two self-wound electro magnets and a lever snap switch to turn the moving one on as it passed the stationary one. I tuned the length so that it was once per second. I got third prize in the science fair.


Neal Naumann – In the mid to late 90's I worked for an oil field service company that developed an MRI tool (actually NMR - Nuclear Magnetic Resonance) for down hole well logging. We used permanent magnets. We shipped the sonde (magnet with an antenna) inside a thick steel tube and whenever we arrived at a drilling rig site or offshore rig, we had a safety meeting. Basically the meeting was telling folks not to get between the magnet and something metal - which isn't easy on a drilling rig. We never had an incident on a rig other than a lot of watches that permanently stopped and credit cards that were wiped clean. At the manufacturing facility, the production manager lost his thumb when two sondes were place on the floor near each other. The two started rolling towards each other and without thinking, he tried to stop one with his hand. About that time the two 500 pound sondes sucked together and chopped off his thumb. There was never another incident after that.


Bob Ursdevenicz – A number of years ago I ran a small sound contractor and install company. I received a call from a friend to help consult on a new construction Catholic Church sound system that was having interference issues.

When I arrived, the first thing I did was turn off all wireless microphone systems and thought that would be the issue. Nothing changed. I then grabbed some of the hardwired mikes and walked around. The interference noise would change depending where I was. I was perplexed on what was causing this and then had an idea. I used one of the hand held microphones as a "witching stick" and could follow a noise path on the floor. I thought this was odd but then it hit me the issue might be magnetic interference.

Dynamic microphones work by having a small magnet and voice coil to generate a small electrical voltage which is then amplified by the sound system. In this case, it seemed that the microphones voice coil was picking up interference from somewhere. I then noticed that the church's overhead lights were not at 100%, but more like 70%. I also noticed that the new dimmer system was not too far from the sound system rack. I turned the light system up to 100% and the noise went away. This was a SCR based dimmer system that chops up waveform to achieve dimming, which can create noise.

Putting the pieces together, I found that the feeder cable that feeds AC power to the dimmer system went right under the area where the microphones where having issues. I suggested to them that they either leave the lights at 100%, or use condenser type microphones that don't use a magnet and a voice coil. The sound gear itself was mid pro level gear and not really at fault, but how it was used was.


Brian Laine – My bad experience happened when I mail-ordered some strong magnets for a project. The box came, but it was empty, and I noticed a slit ripped in the corner of the box. I've since wondered what postal machine received those magnets, and how much damage occurred as a result.


Thomas Kesler –I was an MRI field service engineer at GE Medical. Once, an MRI tech in Arlington Heights, IL. called to report that the images were distorted. The service engineer would arrive at site and find no issue. This went on for a week or two and nobody could find the source of the problem. This particular service engineer smoked so when he went outside to smoke, he noticed an ambulance pulled up to the ambulance bay which happened to be next to the wall of the MRI machine. The wall was not insulated and the metal truck caused the magnetic field to distort. Once the wall was properly insulated the problem was fixed. Who knew smoking could fix problems. I also worked on CT scanners. A GE worker forgot to tighten the screws on the newly installed x-ray tube so when the unit was at full speed, the tube flew out! Luckily no one was on the table.

When a patient is scheduled for a MRI they usually do an x-ray to see if there is any metal in the body. One patient was laying on the MRI table and the tech misread the x-ray and thought the patient had metal in his eyes. The tech panicked and pushed the emergency quench button on the wall.

On top of the MRI there is a ceramic disk, when the pressure inside the MRI builds up to a certain level the disk breaks and the liquid hydrogen or liquid nitrogen rush out turning from liquid to gas and going through a pipe to the outside. This action is caused by heater wires inside the MRI, which is activated when you push the quench button. In this instance, the pipe had not been installed correctly and it fell down during the quench of the magnet, so the gas filled the room up and the tech had to crawl on her knees to the patient and lead him out the room. A scary moment for sure.


Robert Kern – The company I worked for had a couple mainframe computers with a number of tape and hard drives. The hard drives were old and stood along one wall like a row of refrigerators. I think the hard disk platters were 14 inches in diameter and the heads were moved by a voice-coil magnetic positioner. There was a head (and magnet) on opposite sides of the drive, which permitted a head on either side of the drive to read or write data. Each magnet had a 1.5-inch hole through the center of it to drive the piston to which the disk head was connected.

One day I was walking out of the data center after a technician had been working on the hard drives, and saw two voice coil magnets in the trash. There was a sticker on each of the magnets which said, "Danger. Strong magnetic field." I picked one up and estimated it weighed about 30 pounds. I thought to myself, "These are much too valuable to throw away. We can have some fun with them."

I used one as a doorstop and placed the other one under my desk. A couple friends came by and asked about my new doorstop. One of them put an 8-inch screwdriver near the magnet and it pulled it out of his hand. When he tried to remove the screwdriver from the magnet, he bent the screwdriver shaft. The next day, someone brought in some steel ball bearings. Any ball bearing within two feet of the magnet was attracted to it with a ‘tink.’ Removing the ball bearings from the magnet wasn't easy, but it was possible to get them off - probably because the contact area was small compared to the screwdriver.

Someone had the bright idea to put the flat sides of both magnets together. When one magnet was within a foot of the other, it wasn't possible to keep them apart. If anyone had their fingers between the magnets, they surely would have been smashed. After the magnets were joined, we couldn't get them apart. Three of us pulled and tugged at the magnets, even bending the shaft of a heavy duty screwdriver attempting to separate them, but to no avail.

Over a six-month period I amazed people showing them the attractive force of the two magnets. If anyone tossed a paper clip within three feet of the magnets, it would be dragged toward the magnets like a star being pulled into a black hole. One day a friend asked if he could have one of the magnets. I said, "If you can get them apart, you can have one of them." The joined magnets sat in my doorway for a couple more months, but then one day I discovered only one remaining.

I tracked down my friend and asked how he had separated them. He said that he had gone to the building engineer's work area where they had a massive vise. He and two of the building engineers used a crowbar and the vise to pry the two magnets apart. My friend said his son was working on a science fair project and the magnet was going to be a part of it. Eventually, we moved to a different building and the remaining magnet really was thrown in the trash this time, but we had a lot of fun demonstrating the power of a strong magnet.