Will magnetic tank bags wipe iPod, mp3 music?

[MsKABC]

Unfortunately I don't remember. I just remember thinking that they didn't know much about rigorous experimentation, and neither did my wife and she should know - Masters and past Lecturer in Physics.

A lot of what they do is probably fairly black and white i.e. it either works or it doesn't. But there will be some things that need more detailed investigation before any firm conclusions can be drawn.

Yeah, M.Sc here too, and I always have a bit of a giggle about mythbusters - too much drama and not enough scientific method Good for getting people (especially kids) interested in science though I guess.

[Winston001]

Sorry but your incorrect!

A Magnetic tank bag can wipe a standard magnetic plastic card.. it's got to be close to the magnet though!
As for mp3's etc etc etc, nope you'll find they are shielded enough, i.e. inside and surrounded by a case / protection so they are not affected by a normal magnetic field!

Credit cards, ATM / EFT-POS / bank cards, door entry cards, library cards that contain the dark magnetic strip commonly found on most cards have four tracks of data.
Any magnet source with some strength (a normal magnet, transformer field, speaker/s non shielded etc etc) can wipe or harm one if not all of the four magnetic tracks on a card, normally it's enough to kill it, however the most common is a partial wipe of data so it's un-readable or just contains meaningless characters / rubbish somewhere in the line on the affected track.

SMART cards: The smart chip is not affected by a magnetic field, electrons however do stuff them.

If I was you I wouldn't put any atm, eft-pos or credit card anywhere near a magnetic field.

You'd be okay to put anything in it so long as it was on your bike, but the moment the tank bag is taken off you/or it will close the magnetic flaps and if the card is close enough to them, o bugger!

Yep. Pretty simple. The black strip on the back of your credit card/EFTPOS card etc is composed of iron particles which are magnetised. The orientation of the particles provides information to a reader. If a magnetic field comes sufficently close to the strip, the particles will adjust their position and produce gibberish when next read.

Same thing with cassette tapes and video tapes.

The saving grace is that most common magnets don't produce sufficently strong magnetic fields to create problems. You'd have to place the card over the magnet but this could happen if your wallet was at the bottom of the bag and the magnets closed up under the bag.

[mister.koz]

mythbusters

They do one-time tests, i am certain that if the tests were done on a regular basis that the cards would have been wiped.

With magnetic media the damage causing part is a changing magnetic field so if something is sliding around a magnetic field it will have a greater effect. I have had credit cards wiped by being put together stripe on stripe.

Interesting fact is that the card writers that the banks use to write pin's to the cards have a magnet in them that is around about the same strength as the ones in my oxford bag.

As someone mentioned earlier the magnets have less effect on surrounding things when the bag is stuck to the tank, this is because allot of the magnetic field is consumed by the metal tank (thats how it sticks).

ANYTHING that uses magnetic storage like hard disks or mag-stripes can be effected by a magnet and some electronic equipment can be as well, power regulators using FET's or toroids can under or over-cook when they have a magnetic field applied to them. Also good to note that most ipods with hard drives have a metal case around them which should protect them.

I tend to only put my wallet and ipod in the bag once its on the bike.

I guess the problem could be avoided completely by putting a steel plate in the bottom of your bag as it would absorb the magnetic field but there's trade-off's with weight etc.

[Gubb]

mythbusters



Everyone's doing it.

[Mikkel]

With magnetic media the damage causing part is a changing magnetic field so if something is sliding around a magnetic field it will have a greater effect. I have had credit cards wiped by being put together stripe on stripe.

Indeed, it's magnetic fluctuations more than a constant field that is going to mess up magnetic storage.

Bulk erasers - for floppy disk, in a now forgotten era - worked by applying a constantly alternating magnetic field.

I guess the problem could be avoided completely by putting a steel plate in the bottom of your bag as it would absorb the magnetic field but there's trade-off's with weight etc.

Magnetic shielding is a bit more tricky than this. There are certain materials out there which are efficient magnetic shields - mu metal being one - but steel is not one of them.

[mister.koz]

Indeed, it's magnetic fluctuations more than a constant field that is going to mess up magnetic storage.

Bulk erasers - for floppy disk, in a now forgotten era - worked by applying a constantly alternating magnetic field.



Magnetic shielding is a bit more tricky than this. There are certain materials out there which are efficient magnetic shields - mu metal being one - but steel is not one of them.

Mu metal? come on dude, we aren't making an AM radio here. We could get into crazy details with mh per mm^3 but no one really cares.

Steel, tin or aluminium sheet will work as shielding, it will absorb magnetic waves to a nominal amount significantly greater than air.

[Usarka]

They do one-time tests, i am certain that if the tests were done on a regular basis that the cards would have been wiped.

I worked at a place where employees monthly tube cards were getting wiped all the time. The london underground told us it could be our magnetic security cards, we scoffed and did some tests of which no cards were wiped.

However we decided to warn everyone against carrying the two together "just in case", and shortly thereafter the problem mysteriously disappeared.

Wooooooo arthur C clarke......

[gatch]

Why do y'all need to put cards in your tank bag ?

Surely a card case with the essentials in your pocket would be better (like I do), if you bin and your tank bag parts company with your tank... it could happen.

Also why ride with an music going ? Tried it once, even with comfortable ear phones it was terrible, to block out the wind noise it had to be turned up loud, then I couldn't hear anything but the music..

Kind of like rolling in a car with the music turned right up..

[Mikkel]

Mu metal? come on dude, we aren't making an AM radio here. We could get into crazy details with mh per mm^3 but no one really cares.

Steel, tin or aluminium sheet will work as shielding, it will absorb magnetic waves to a nominal amount significantly greater than air.

Well, I suppose you are right about that - an enclosed container made from those materials would provide some shielding, a flat sheet on the other hand, I'm not so sure.
To me it would just never appear necessary to achieve a low level of magnetic shielding. Either magnetic fields are of importance (e.g. noise in some experimental setups and harddrives) and you implement proper shielding or it is insignificant and you don't bother at all (e.g. mp3 players and credit cards in tankbags with magnetic bases).

As for mH/mm^3 - I don't see how inductance is relevant when considering magnetic storage media. And I really do care.

[samgab]

Also why ride with an music going ? Tried it once, even with comfortable ear phones it was terrible, to block out the wind noise it had to be turned up loud, then I couldn't hear anything but the music..

Kind of like rolling in a car with the music turned right up..

Try a pair of noise isolating earphones. I've got a pair of Shure earphones, they block out as much external noise as the best quality ear plugs (-30--37dB noise attenuation vs -29dB for standard foam ear plugs). So then you have the music on quietly, and you hear it crystal clear. No wind noise, motor noise, car horns, screeching brakes, crunching metal...

[mister.koz]

Why do y'all need to put cards in your tank bag ?

Surely a card case with the essentials in your pocket would be better (like I do), if you bin and your tank bag parts company with your tank... it could happen.

Also why ride with an music going ? Tried it once, even with comfortable ear phones it was terrible, to block out the wind noise it had to be turned up loud, then I couldn't hear anything but the music..

Kind of like rolling in a car with the music turned right up..

Good point with the cards.

A guy on here has earplugs that have earphones in them, reckons the earplugs cut out almost all the wind noise so the music doesn't have to be loud plugs 4 lugs? sells them.

Well, I suppose you are right about that - an enclosed container made from those materials would provide some shielding, a flat sheet on the other hand, I'm not so sure.
To me it would just never appear necessary to achieve a low level of magnetic shielding. Either magnetic fields are of importance (e.g. noise in some experimental setups and harddrives) and you implement proper shielding or it is insignificant and you don't bother at all (e.g. mp3 players and credit cards in tankbags with magnetic bases).

As for mH/mm^3 - I don't see how inductance is relevant when considering magnetic storage media. And I really do care.

Its relevant because the effectiveness of radio shielding is calculable from the inductance of the shield material per cubic area.

[samgab]

http://store.shure.com/store/shure/e...ctID.105460100

Sound is A-

Freakin'-

Mazing!

[sunhuntin]

Why do y'all need to put cards in your tank bag ?

Surely a card case with the essentials in your pocket would be better (like I do), if you bin and your tank bag parts company with your tank... it could happen.

Also why ride with an music going ? Tried it once, even with comfortable ear phones it was terrible, to block out the wind noise it had to be turned up loud, then I couldn't hear anything but the music..

Kind of like rolling in a car with the music turned right up..

i put my wallet in the tank bag [strap on... didnt trust the magnets to stay on at high speeds] cos if its in my pants, it digs in, in my jacket i cant get it out without basically undressing, lol. in the tank bag, its a case of take it and my topbox keys out and dump the lot in my helmet.

i ride with music too... need some decent 'phones though. i find certain music relaxes me and makes the ride more enjoyable.

[motorbyclist]

your ipods etc should all be shielded

that said, a strong enough magnet may still damage them

as a general rule, keep cards away from strong magnets. if you leave your wallet on top of your fridge that's fine, but i wouldn't pin it to the door

and remember there are other fields at play too: some may notice that large electric motors (like a starter motor) and even the HT lead/coils can cause enough interference by electromagnetic fields to effect some devices... not to worry though your tank should shield your tank bag from the motor

Nope. I think you'd need a pretty strong magnet to affect Hard Disks. I frequently place my laptop on top of my (unshielded) sub and have never lost any data.

Also a lot of the newer MP3 players use flash memory which is different to harddrives, and magnets can not harm them in any way.

you will find your laptop HDD is sheilded

if an electro/magnetic field induces a current you can say bye-bye to flash memory

How about a magnetic security card? I used to keep my credit card in my wallet beside one of these until it completely stopped working. I'm only assuming it was the magnet as there was nothing else anywhere near it except leather, cash and other cards.

i have had my eftpos card next to my security card for 24 months with no ill effect

I've watched one or two of the Mythbuster episodes and, while a lot of what they do is probably scientifically sound, there were one or two experiments they did that were full of holes.

most if not all of them are full of holes and poor reasoning. it's very frustrating to watch. explosions make it all better though

often though the answer is so obvious that we can forgive them

[quickbuck]

... didnt trust the magnets to stay on at high speeds

Come on now.... How fast do you intend to go on the virago?

My tank bag has been tested to over 220 km/hr.
There is naff all wind trying to blow it off, and there is also stuff all acceleration forces at that speed either.

If the worst was to happen, then it would slide back into my lap.

It actually sits on my NS1 at 100k, and that has a plastic lid (that looks like a tank).

Now, why do I need to put my wallet in there?
Well, so the gate guard can see my ID I put it in the window.
Well away from the magnets.
Also, this prevents my backside getting pressure on one side when riding.

As an aside, office workers should take their wallets out of their back pockets and put them in a draw. This prevents a crooked back.