Rare Earth Magnets . . . hype?

[payaso]

Is there any other form of testing magnets? Or maybe a different gadget to use? This is weird. Can you explain what the mumbo jumbo is printed on the back of the rem package?

Thanks


silla

[Krabill]

First . . . no, there is no other way to test a magnet's usefull power. Our company manufactures very high quality ceramic magnets and our testing equipment is calibrated and very accurate.

As for the mumbo jumbo . . . well . . . that's really all it is.

Peak Energy Density: The point on the demagnetization curve where the product of B and H is a maximum and the required volume of magnet material required to project a given energy into its surroundings is a minimum.

Residual Induction: This is the point at which the hysteresis loop crosses the B axis at zero magnetizing force, and represents the maximum flux output from the given magnet material. By definition, this point occurs at zero air gap, and therefore cannot be seen in practical use of magnet materials.

Coercive Force: The demagnetizing force, measured in Oersteds, necessary to reduce observed induction, B, to Zero after the magnet has previously been brought to saturation.

Intrinsic Coercive Force: Measured in Oerseds in the cgs system, this is a measure of the material's inherent ability to resist demagnetization. It is the demagnetization force corresponding to zero intrinsic induction in the magnetic material after saturation. Practical consequences of high Hci values are seen in greater temperature stability for a given class of material, and greater stability in dynamic operating conditions.

Magnetizing force: The magnetomotive force per unit length at any point in a magnetic circut.

As you can see, the numbers on the back of the package are either immeasurable, or inconsequential to the actual usable force of the magnet. That is measured with a gauss meter as I have done.

If you want to do a simple test yourself, try holding sheets of paper to the refridgerator with the stock magnets and r.e. ones the way that actofgod did. He came up with both of them being able to hold about the same amount = same amount of magnetized force.

Clear as mud, huh?

[payaso]

So the gauss on the rem is not 10,800 like the package says. Why doesn't the package give the gauss reading that you came up with? Is this the RS way of marketing?lol



silla

[Krabill]

No, it isn't 10,800. If you read the definition of Residual Induction in my previous post, it is an immeasurable number, which means it has no real life value. Yes . . . it is just for marketing.

Try the "how many sheets of paper will each one hold to the refridgerator" test and you tell me if the RS magnet can hold 3 times as many sheets as the stock magnet does I'll bet you a nickel that it doesn't.

[johnrtse]

Does the gauss reading of a steering magnet change when the steering coils are energized?

Could there be a difference between their electro-magnetic strengths or characteristics?

Just a thought,
John

[Krabill]

Hmmm . . . I don't know. You might be on to something. I can smell another experiment brewing tonight.

Now I'm going to have to take a couple of them apart again and test them w/ a coil energized.

I'll do one w/ a stock magnet & the one I have the RS magnet in and report back what I find out. Who would've thought these little bitty cars would be this much work

[mcharles13]

With the coil energized won't that interfere with the reading of the actual magnet itself?

[Krabill]

No, it won't interfere . . . it would only add to it if there is a difference.

However, here are the latest findings from Krabill's house of magnetic research :

The coils have absolutely no effect on the strength of either the stock magnets or the RS magnets. So . . . no . . . there is no difference as far as the electromagnets are concerned.

A little trivia for ya though - the coils only make about 40 gauss.

Yes, I typed that correctly -40-

My little tiny micro screwdriver shows about 140 gauss and it will barely hold onto the little screw that holds the front cover down if that gives you any indication of how weak the electromagnets are. All of the steering power comes from the extreme strength of the rare earth magnet and has very little to do with the coils' strength.

Anyway . . . there you have it. My complete findings on the mythical "Radio Shack Rare Earth Magnet" mod.

[BMWFanatik]

Ok, so the Rare earth magnets (RS or stock) are in the 3500 range...and the coils are pushing 40. It would lead you to believe that if we can increase the coils pull intensity, we'd be seeing even better results.

The question is...is it possible to do that? And if so...how??

[Krabill]

Okay, say the magnet has a pull of 3500, and the coil has a pull of 40.

3500 + 40 = 3540

Even is you could double the coil by wrapping it around a metal rod (which won't work anyway because the metal rod would continue to be magnetic after the coil was turned off, but that is a whole other discussion), that would give it a pull of 80 gauss.

3500 + 80 = 3580

3580 / 3540 = 1.0113

Which is a 1.1% difference in combined pulling power. I highly doubt 1.1% would make a noticable difference in the cars ability to turn.

Bottom line is, they designed these little suckers pretty good and I can't think of any way to increase there steering. I'm open to ideas, but none of them mentioned so far seem to make any difference.

The one car that I have noticed the biggest difference in, I sanded the steering arm so everything that moved was nice and smooth. That did seem to help. Messing with the magnets is futile from what I can see.

[Need4Speed210]

what about in a 2 cell mod? shouldt that extend the coils voltage to 2.4/3.0 instead of 1.2/1.5?

Thanks for the extensive scientific testing!
I bought some RS rare earth magnets, and I was disappointed in the difference that they made. IMO, there was a *little* bit of difference because the wheels would move (a little) from a dead stop - but they didn't do that before. The original magnet is on my fridge doing a great job of holding up some take out menus!

[johnrtse]

Outstanding work Krabill!

But, I will say again that I saw a DEFINATE difference in the steering on the (3) MicroSizers & Bit clones I've converted- They went from ok steering to "flip when you turn" with just this mod.

The only thing I can attribute this to would be variations in magnet strength & quality between the various micro RC manufacturers.

Your investigative abilities are definately an asset here!!!!

HEY MODERATORS- This thread is a MUST for the "Bit Science" section!

John

[Krabill]

Originally posted by Need4Speed210
what about in a 2 cell mod? shouldt that extend the coils voltage to 2.4/3.0 instead of 1.2/1.5?

If you read my previous post, even by doubling or tripling the power of the coil, it is so insignificant that you would only increase the total strength by 1 to 1 1/2%. I highly doubt this would make a noticable difference in a high performance machine like a bit

Thanks for the thanks everybody I'm an engineer, and I love tinkering with these little things. I mostly deal with large structural steel stuff, but we also manufacture eddie current rotors here, and I just happen to have access to a gauss meter. After I did the r.e. mod myself and noticed that both magnets were about the same strength just by playing with them, I thought I'd start checking stuff out by the numbers. Strange what you can find out if you dig deep enough.

[JTM]

when i put the REM into my clone, i could now move the front tires from a dead standstill full, but before id di it i coudlnt turnthem unless i was moving.. my scientific study took alot less time and effort, and i know i have stronger steering, also it holds turns with high speed sbetter.. its a really good thing to be able to turn when your stopped when you play table soccer