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View Full Version : Rare Earth Magnets . . . hype?


Krabill
01-04-2003, 12:23 PM
I heard about the mod to replace the steering magnet with rare earth magnets from Radio Shack, so I thought I'd give it a try on one of my bits.

Once I got the old magnet out, it didn't seem much weaker than the rare earth one. Well . . . I've got a gauss meter at work, so I thought I'd check them out.

Stock magnet: 3,550 gauss

Rare Earth magnet: 3,700 gauss

The stock one is pretty strong already and I don't think the rare earth makes that big of a difference. I won't be wasting anymore time replacing magnets in the future.

Just my .02

Dys70pia
01-04-2003, 02:25 PM
Wow thats really interesting!

Is it possible, however, that some magnets may not be as strong as others? Maybe you got lucky and got a strong steering magnet...
Would be interesting to see other people doing the same experiment you did, and see if the stock magnets are all the same.

As for the numbers, it's been a while since I studied magnets in high school, so is that a big difference between the two numbers? What would say, a cheap fridge magnet be?

Krabill
01-04-2003, 05:42 PM
Okay, based on your questions, I went around the house with my tester and here's what I found.

Flimsy fridge magnets: about 250-300 gauss

Solid fridge magnets: about 350-400 gauss

Tool retriever magnet from my toolbox: about 1,000 gauss

Rare earth magnet that my company makes: 3,800 gauss

Rare earth from Radio shack: 3,700

Stock bit steering magnet: 3,550 (I have now tested more than one and they are all pretty close)

Going by these numbers, I'd have to say that the stock bit magnets are in fact rare earth magnets already. Probably not as good quality as Radio Shacks, but good enough to turn the little cars anyway.

Al Hounos
01-04-2003, 06:36 PM
no there aer real differences. with rem the wheels can turn at standstill on most surfaces, before it had to be moving pretty well to turn.

Dys70pia
01-04-2003, 08:07 PM
So the stock magnet is pretty stong then... I guess people are finding that the extra 150 gauss really does make a difference... I suppose the tiny changes are sorta trivial; but so are many of the antenna mods for increasing reception.
Perhaps the extra 150 gauss are somehow important when youve got the two electromagnets on either side of it... especially when the power through the magnets are boosted with a dual cell mod....
I guess everyones individual experience is more important than numbers... I'm too lazy to go through all the math anyway... =P

bill
01-04-2003, 09:44 PM
I bought a set of magnets at RS and haven't even put them on any of the cars I have. I figured that if the car is turning fine, why bother. I just put it in my box of crap just in case I would need it.

actofgod
01-05-2003, 08:13 AM
I had noticed similar results too, though I didn't have a gauss meter. I tried to see how many sheets of paper each magnet would hold to a refrigerator and found they held the same number (I forget the number of sheets).

I wonder if the improved steering that I and others have reported is in fact due to the original magnet not being properly centered? It seems like such a tiny change in actual magnetic strength wouldn't be noticeable.

I traced one improvement in steering to the fact that while changing a steering magnet I happened to swap the two micro springs installed on my steering knuckles; apparently they were slightly different lengths and after I swapped them they worked better on the other side.

Interesting findings Krabill.

Krabill
01-05-2003, 10:09 AM
Yeah, it's only about a 4% difference, which is actually an acceptable tolerance when making magnets. Anything over 3,000 gauss is incredibly strong. The magnets we make are all 1" x 2" x 2" and even the ones that only come out to about 3,200 gauss are nearly impossible to remove from a solid steel object (like the back of the forklift ;) ).

I would attribute better steering to something else, like accidently bending the spring more, or getting the magnet exactly centered, or just paying more attention when you assemble it than the original factory did.

strider_mt2k
01-05-2003, 11:56 AM
I agree, this REM stuff was probably a good idea, assuming the use of wimpy magnets being used in the first place, but the engineers behind these marvels probably pulled every trick they know (like this one) just to make them work in the first place!

johnrtse
01-05-2003, 08:22 PM
I agree that the stock magnet in my Rally Racer/Shen clone was very strong. But the steering on the car was definately not as good as my MicroSizers was.

I changed to the RS Rare Earth Magnets and it was a total night-and-day difference! The steering and control went from OK to TERRIFIC in 10 minutes time (the time it took me to change them out). Handling and steering is extremely predictable and precise now. All of my Bits/clones will get Rare Earth magnets.

As with anything, your results may vary. If I have learned one thing in this hobby it's that the construction and manufacture of these cars is very inconsistant, even within the same brand.


Just my personal observations.
John

strider_mt2k
01-06-2003, 11:13 AM
I have heard the same thing from others too.
I guess for the low price of those magnets I'd be crazy not to at least try 'em.

Namuna
01-06-2003, 12:52 PM
Thanks for the investigative work Krabill, I've added the info to the Bit FAQ.

bitbeater
01-06-2003, 03:17 PM
Are you measuring the rare earth magnets stacked together? Or is there even a difference between 1 magnet and two of them together?

Krabill
01-06-2003, 04:32 PM
When I took the reading, I had (2) of them stacked together, but I'll take the meter home again tonight and do just one for ya and post my findings later this evening.

Krabill
01-06-2003, 09:53 PM
Okay, as promised here are my findings tonight.

I have (4) bit clones from Walgreens that I opened up all for the sake of science.

Car 1 - stock magnet: 3,350 gauss

Car 2 - stock magnet: 3,550 gauss

Car 3 - stock magnet: 3,560 gauss

Car 4 - (2) r.e. from RS: 3,450 gauss

Stock magnet taken out of Car 4: 3,550 gauss (I guess I should have left it in, huh?)

Remaining r.e. from RS #1: 2,600 gauss

Remaining r.e. from RS #2: 2,600 gauss

Remaining r.e. from RS stacked together: 3,700 gauss

All stock magnets (which are in fact rare earth to begin with) are within 6% of each other. The (2) I bought from Radio Shack are more than 7% different.

This leads me to believe that the stock rare earth magnets are of better quality and a better bet to getting good steering than any magnet bought at Radio Shack since you probably don't own a gauss meter to pick the very best ones, and even if you did, a couple hundred gauss will not make a noticable difference in steering. I really don't know what to tell those of you who insist you have noticed a difference, because as you can see, it is pretty much an impossibility. :shrug:

payaso
01-07-2003, 03:21 AM
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
01-07-2003, 08:12 AM
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? :D

payaso
01-08-2003, 12:06 PM
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
01-08-2003, 12:53 PM
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 :D I'll bet you a nickel that it doesn't. ;)

johnrtse
01-08-2003, 03:01 PM
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
01-08-2003, 04:00 PM
Hmmm . . . I don't know. You might be on to something. I can smell another experiment brewing tonight. :D

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 :D

mcharles13
01-08-2003, 08:10 PM
With the coil energized won't that interfere with the reading of the actual magnet itself?

Krabill
01-08-2003, 09:42 PM
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. :D:D

BMWFanatik
01-11-2003, 02:40 AM
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
01-11-2003, 10:54 AM
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
01-14-2003, 06:10 PM
what about in a 2 cell mod? shouldt that extend the coils voltage to 2.4/3.0 instead of 1.2/1.5?

arceeguy
01-14-2003, 06:35 PM
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
01-15-2003, 12:29 AM
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
01-15-2003, 08:03 AM
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
01-16-2003, 03:12 AM
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

mbartell
01-17-2003, 02:16 PM
I tried the REM in a zip zap, and the magnets were so strong that they attracted the pins in the steering knuckles, and the car wouldn't quit going in circles.
I tried it with one magnet and it wasn't strong enough, but the magnet out of a microsizer worked very well. It's a dual cell, so that may have a little to do with it.

do you have a zip zap around that you could check too? they have them re-stocked at most radio shacks now.

I also found that sanding the steering arm helped a lot. I used a manicure set to file and polish the steering surfaces, and it made a huge diffrence. just make sure to melt the pin your steering spring is on- they fly and dissapear.

Krabill
01-17-2003, 02:35 PM
No, I haven't tested a zz yet. I don't have one :( I know the local rs that I go to most of the time doesn't have any. They have like two body sets, but no cars. Maybe I'll start checking the other ones around town to see if they have any.

If your car was going in circles, I'd bet you missed one side of the spring when you put it back together, not that the magnet was too strong.

Yes, sanding and polishing the steering arms/pins did the most for me too as far as helping steering action.

Spanky
01-23-2003, 06:08 PM
mine bit, and my ms both turn while standing still with no mods. and they constantly pick up staples in the office. which makes the steering a bit of a chore.

however would the magnets have anything to do with why my car will turn very sharp to the left and makes big sweeping turns to the right? it was doing this right outa the box, i have cleaned it out and it dosent seem to have any chunks lingering anywhere in the steering area. what do you think?

JTM
01-23-2003, 06:19 PM
i think you got a defective bit if it doesnt turn right very good.. wrtie MS about it, they may send you a new chassis or parts to repair it @ least...

Krabill
01-23-2003, 09:42 PM
It's not really defective, per say. The magnet is just not centered in it's holder. This can happen by dropping it, or running it off the side of the table, or as seems to be in your case, they just come that way.

Very easy fix:

1. remove body

2. carefully remove the pcb cover

3. carefully lift pcb just enough to allow access to the little screw in the front.

4. remove tiny screw

5. lift off front cover *be sure not to lose the centering spring* It's a tiny little sucker.

6. You will notice that the magnet is not centered in it's holder, or one of the coils is in the way not allowing full steering action. If it is the magnet, break it loose (the stock glue isn't very strong in and it is easily removed), center it, and use some 5 minute epoxy to glue the magnet back into the exact center of it's holder. Epoxy will also work on the coils if they are the problem.

7. carefully put everything back where you found it, making sure to get the centering spring in the right place.

Hope that helps. Let me know if you need some pics.

Spanky
02-12-2003, 06:41 PM
it would be nice to see how some clones magnets rate with the bits that youve tested.

Zephyranthes
02-19-2003, 11:21 PM
The REM helped the steering on my dual cell, but now centering is too week. Need to put 2 steering srpings on to increase pullback to center strength and speed.

Krabill
02-24-2003, 11:09 AM
Originally posted by Spanky
it would be nice to see how some clones magnets rate with the bits that youve tested.

Actually, all of the cars I have are clones, so that is all I've tested.

btlmr
02-24-2003, 11:25 AM
Can you measure the power of the coils with 2.4 or 3.6 volts?

Cheers,

btlmr
02-24-2003, 11:26 AM
Ignore me, read the 2nd page of the thread again.

Squishy
02-24-2003, 06:48 PM
what do you sand on the arm? i have taken my car apart just to gaze wonderingly at the super tiny parts, but I haven't fiddled with anything. My car veirs so-so slightly to the left, and it's not that bad, but its anoying on the race track straitaways.

Lord_Nick_D
03-11-2003, 05:22 PM
to the person who did the tests is it possible to increase the power of the steering by making new electromagnets I know a little about them and I thought If you change the wire guage that they are made of wouldent that help

Zephyranthes
03-12-2003, 12:09 AM
I think you could. There was a discussion on how you could make it stronger by using thinner wires thus more coils meaning more power.

Lord_Nick_D
03-12-2003, 07:15 PM
yeah because then you could make a kick butt monster truck who's tires could turn at a standstill on carpet
that would be amazing

Squishy
03-21-2003, 11:39 AM
I think you are seeing so little a difference because ZZs come with better magnets then bits, so if you upgrade a bit, you will defantly see the difference.
Originally posted by Krabill
Actually, all of the cars I have are clones, so that is all I've tested.

got BITS?
03-22-2003, 10:18 PM
Originally posted by bill
I bought a set of magnets at RS and haven't even put them on any of the cars I have. I figured that if the car is turning fine, why bother. I just put it in my box of crap just in case I would need it.

Do you mind sending a few to me?

got BITS?
03-22-2003, 11:28 PM
Originally posted on Quest For Madness Website Here (http://tinyrc.com/qfm/racing/mod_09.htm#31)
This mod replaces the stock magnet with a neodymium-iron-boron magnet more commonly known as a rare-earth magnet. The replacement magnet is the same diameter as the stock magnet, but half the height. Combining two of these magnets gives the proper dimensions necessary for replacement. Magnets are often measured in units called gauss and these rare-earth magnets offer a combined measure of 21,600 gauss vs. only 2250 from a similar sized ceramic magnet.

mpbiv
03-23-2003, 12:20 AM
Originally posted by Krabill
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 ;)
What about increasing the current through the coils? I forgot all the things we learned in physics about magnetic fields but would this increase the strength of the field?

Spanky
03-30-2003, 05:59 PM
well i just got my REM. 1.99 at radio shack. i am quite disapointed. the rem can barely turn the wheels, when im holding it off the ground. and does nothing for it when on the ground. i have tried repositionig the magnet.. everything. what a waste of 1.99