105 replies to this topic

[CFL Mike]

The receipe for the ceramic magnet can vary. That's why some are stronger and some are more brittle than others. That's also why some magnets if the same run can have a gauss 50 points different then others in the same batch. Which is why some of us buy 6 pair at a time while other racers buy 25-50 pair at a time. Getting very closely matched sets of magnets is an important element in motor building.

So when I got my new MegaIIIs not too long ago, I bought them and it said they were "matched" on the package, are they not really matched? Or are you talking about buying bulk magnets or something like that?

[Fast Freddie]

Matched has a different meaning to different people. Most matched magnets I have ever bought were up to 10+ gauss points different I have never had a perfect set when I purchased matched magnets. That's a good match but not perfect and usually better than unmatched sets. I have purchased unmatched magnets and found a set only 1 point apart while other sets could be as much as 30+ points apart. Thats why I buy a min of 6 sets when I buy either. There is a thinking out there that it's best to have magnets that while closely matched the negative magnet (closest to the rear motor mount) should be about 10 points less in gauss then the positive magnet. The theory being that the negative magnets gauss increases once it's soldered into the chassis thus making the magnets more equal. It is a theory with some substance yet some people also believe that the heat from soldering the motor in the chassis offsets the supposed gain in gauss keeping the magnets at a 10 point difference. Who knows? It's not rocket science or is it?

[Rick]

I am curious how one would say a perfect match, if you move the wand .005 the reading changes. What method do you use Fred to determine a matched pair?........ Do you match in or out of the can? Experts disagree on the correct method. When the magnet is installed, the change in contact area to the can will also change gauss readings.

I think you are correct it is rocket science and a lot of mojo going right.................

[Fast Freddie]

I made a jig to check the zapped magnet and tips out of the can. I match the closests pairs at this time. The wand has a dot reference and my jig allows me to move the magnet over this dot to get a maximum reading. I do the same for the tips to find the stronger tip. Then I place the magnets one at a time into their correct position in a older style PS can (the rectangular windowed one) that I've installed into an obsolete chassis and take another set of readings. I actually use the in can reading to match the magnets because the way I have it set up it seems to be much more accurate and repeatable. They do change in strength when in the can although they haven't had any heat applied to them. This might not be the best way but I'm a retired Navy Engineman so jury rigging is in my blood. By the way I have never had a perfect match just very close matches.

[Ron Hershman]

So even til today, Im assuming that Mura still makes ProSlots and Kofords magnets right?

Today.....Mura has their own magnets made, P-S has their own magnets made and Koford has their own magnets made.

Go back 10-15 years ago....P-S and Koford bought and used Mura magnets.

Today all three have their own "source" for the magnets they are selling.

[Ron Hershman]

Not necessarly. Even if Mura does make the magnets for Proslot and Koford they may want different receipes. The material in the magnets is what gives the magnets their strength. That could be why Mega II magnets or older Mura magnets even though they are longer are weaker than the newer Mega III and Koford .450 magnets. Made by the same company? Ones cornbread the others corn mush. Same stuff different receipe.

A shorter length magnet will read higher gauss than a longer magnet made from the same material. BUT...... the shorter magnet has less "energy" than the longer magnet if using the same material.

The only way to get more energy with a shorter magnet is to change the material and that can only be done if new tooling is purchased to the tune of 10's of thousands of dollars.

How so? Arent they just all ceramic wet charged magnets? I dont know a whole lot about this, but I was assuming they are made out of 100% ceramic, not leaving much room to deviate; other than size and shape.

Also what were you saying about the Mega IIs and old Muras? I dont think you finished that sentence the way you wanted lol. I actually have some old Muras (90s), but im not sure if they out date before Mura had their own wet charging process. I went through and started reading this thread, and it sounds like they have quite a rocky market history, so it maybe makes me think they werent.

The Ceramic magnets that are "molded" and used in slot racing are dry press. No wet press molded magnets... the magnet companies in Asia do not want to wet press a small arc like we use in slot racing.

Now wet press material blocks can be cut and ground and used, but they are not radially oriented like a pressed and molded magnet it.

Wet press molded magnets would have higher gauss and higher energy than dry pressed magnets due to better materials and better orientation when pressing wet.

[Ron Hershman]

. Who knows? It's not rocket science or is it?

It is not Rocket Science. First matching magnets by gauss alone is not good. Better than nothing but you are not checking the "energy" of the magnet and that is more important than gauss readings.

The magnet companies will tell you that two magnets within 10% of gauss is a match..... not really.... if you have a magnet that reads 900 on gauss...that means a magnet that read 810 would be match to them. Sorry..... magnets matched by guass numbers as close as you can get them will run better than a 90 point spread.

So you buy 100 pairs of magnets and match them all identical into pairs...... when a pair that reads 850 run better than a pair that reads 920..... that's "energy" working...not gauss.

The best and only way to match magnets the way we slot racers do and using the meters we have access to...... is by sliding the magnets into a can and taking the readings in the can.

When magnets oppose one another and are surrounded by a "flux path" numbers change drastically. You can not match magnets on a bench out of a can with any success. They have to be matched in the can where they will live.

Take one pair of matched magnets and use that same pair in 10 different cans and you will find changing numbers due to the steel differences in motor cans.

Steel..... like magnets vary on numbers even when coming out of the same batch of material.

[Gator Bob]

Jeez Ron, you know a lot about this stuff and not just "kicking the 'can' down the road".
On those 1990 purchased Champion Yellow dots I posted - could they be Koford's repackaged?

what I was saying there was a 'run' on them because the 'fear' incited that "they can not produce these any more, the tooling broke" I was running them with Super Wasp and Challenger II arms. They worked good, better then the stock mura mags that came in the S Wasp.

I bought the 4pr left and they didn't restock those...

[Ron Hershman]

Jeez Ron, you know alot about this stuff and not just "kicking the 'can' down the road".
On those 1990 purchased Champion Yellow dots I posted - could they be Koford's repackaged?

Nope...... they are Mura Super Magnum X Plus mags.

Koford didn't buy or use Mura mags until the very late 90's or early 00's as they didn't produce a complete X-12 motor until then.

[havlicek]

It is not Rocket Science.

No it isn't Ron...it's actually more complicated than rocket science, and there are still many aspects of magnetism that are not well understood.

First matching magnets by gauss alone is not good. Better than nothing but you are not checking the "energy" of the magnet and that is more important than gauss readings.

Matching by Gauss is really all that racers can do...so it is good and perfectly useful. There are several ways of looking at the strength of magnets that I know of...but this term "energy" you're using is unfamiliar and vague.

-john

[Rick]

John, think of it like a tiny button neo will gauss like 1700 but would be almost useless to power a slotcar. What Ron calls "energy" is the real strength of the magnet not the gauss reading..............

[Zippity]

which is the more important - the leading or the trailing edge/rim??

which one do you want to match for the best result?

[havlicek]

John, think of it like a tiny button neo will gauss like 1700 but would be almost useless to power a slotcar. What Ron calls "energy" is the real strength of the magnet not the gauss reading..............

That would be more like the shape and size of the field AND the gauss....since a large magnet that measures 300 gauss would also be useless, they used to call them "Mabuchis" The term "energy" as Ron is using it isn't used in physics, but measuring the gauss IS good and perfectly useful for slot cars.

-john

[Ron Hershman]

No it isn't Ron...it's actually more complicated than rocket science, and there are still many aspects of magnetism that are not well understood.



Matching by Gauss is really all that racers can do...so it is good and perfectly useful. There are several ways of looking at the strength of magnets that I know of...but this term "energy" you're using is unfamiliar and vague.

-john

No it's not rocket science if you have the equipment to measure the "energy" of the magnet. Being I have done this before as well as every single magnet MFG..... it's not rocket science.

Of course the "term "energy" you're using is unfamiliar and vague" to you...... have you ever sat down and discussed magnets and magnet manufacturing with a company such as Hitachi, TDK, Arnold??? I have..... I know this term and this term is used frequently in the magnet "world".

[Ron Hershman]

That would be more like the shape and size of the field AND the gauss....since a large magnet that measures 300 gauss would also be useless, they used to call them "Mabuchis" The term "energy" as Ron is using it isn't used in physics, but measuring the gauss IS good and perfectly useful for slot cars.

-john

The grade of a magnet directly refers to the Maximum Energy Product of the material that composes the magnet. It in no way refers to the physical properties of the magnet. Simplistically, grade is generally used to describe how "strong" a permanent magnet material is. The energy product is specified in the units Gauss Oersted. One MGOe is 1,000,000 Gauss Oersted. A grade forty (N40) would have a Maximum Energy Product of 40 MGOe. The higher the grade the “stronger” the magnet.

[Ron Hershman]

which is the more important - the leading or the trailing edge/rim??

which one do you want to match for the best result?

Leading edge is the most important when it comes to the highest strength. The hardest part of matching tips in a ceramic magnet either molded or machined is the tips on both sides being the same and also all the pieces being the same after machining.

All molded ceramic magnets are "machined" after sintering or as it is called in industry...."qualifying". The magnets after sintering have rough edges that have to be ground to knock off flash and to fit to finished dimensions. If you seen how this was done...you would laugh at how they do it...nothing precision about it..... the make a "fence" on the grinding table and usually push the magnets past the grinding wheel...... there is deflection and if a magnet has a "high side" on the edge up against the fence.... it takes off less material on the tip than a magnet with a lower side on it.

It's not very accurate nor precision and therefore you get un equal tips and tip dimensions among the batch of magnets.

Machined from block material magnets can have the same problems and seen this a zillion times at RJR when I worked there.

So if you have a magnet with a thicker tip than a magnet with a thinner tip.... you will find two different gauss reading/numbers.

Why you want the leading edge to be the stronger tip......... when the armature comes into the field ( this also has to do with magnet height, timing, air gap, wind just to name a few factors ) the leading edge of the arm laminations start to fire and you want to fire or charge the coil as the tips intersect. If you fire past this point or before this point....... loss of performance. You also do not want the arm firing or charging with the leading tip of the lams at the center point of the magnet either.... that's almost too late.

This is why certain arms with certain timing work with a certain magnet. There is a "sweet" spot for the firing/charging and over the years we have all figured out that a X-12 arm with 38 to 42 degrees is raceable versus a 50 degree X-12 arm. Sure you can use the 50 degree arm for drag racing or qualifying as it won't be ran long and get excessively hot and then fail.

Generally speaking.... the lower or shorter height of a magnet.... one has to reduce or retard the timing..... the taller the magnet more advance can be used.

But again this varies based on turns and wire size as well as air gap and magnet strength and energy.

Perfect example is the RJR Big Diameter 16-D arms.... being the tip width across the crown was reduced and a smaller width.... timing had to be reduced as the arms with 38 degrees and higher were firing way before the leading edge of the tip got to the leading edge of the magnets..... this caused heat and no RPM or torque. We reduced the timing to 32 and 36 degress and had a totally different animal and one that changed 16-D racing in a hurry.

So you always want the leading edge of the magnet tip to be the strongest. The "push pull" guys had it all wrong a few years back.

[havlicek]

No it's not rocket science if you have the equipment to measure the "energy" of the magnet. Being I have done this before as well as every single magnet MFG..... it's not rocket science.

I beg to differ. I understand that you have worked for and with magnet manufacturers, but the theorey behind magnets, especially in a dynamic system like a motor with interacting fields of both the permanent magnets and the electromagnetic fields of the spinning armature is way beyond "rocket science" which is basically ballistics and Newton's laws of motion. What's going on here is still not well understood in some ways by physicists...certainly no one here and DEFINITELY not me! In a sense, it's not rocket science...it's black magic.

The grade of a magnet directly refers to the Maximum Energy Product of the material that composes the magnet. It in no way refers to the physical properties of the magnet. Simplistically, grade is generally used to describe how "strong" a permanent magnet material is. The energy product is specified in the units Gauss Oersted.

"Simplistically", I understand what grade means and refers to as I'm sure many here do as well. We're not talking about where the magnet's strength comes from, but rather how to accurately (enough) measure that field in a useful way. Saying that "measuring Gauss is not good" really has no meaning when it's all a slot racer can do.

Of course the "term "energy" you're using is unfamiliar and vague" to you...... have you ever sat down and discussed magnets and magnet manufacturing with a company such as Hitachi, TDK, Arnold??? I have..... I know this term and this term is used frequently in the magnet "world".

Again, in the physics of magnetics, the term energy is vague/general and when "we" set out to measure a magnet's field strength we deal with "Gauss". No, I have not sat down to discuss magnets with a manufacturer, but even if I had...I still wouldn't probably understand what's going on here. I do have a generally pretty good understanding of physics though. You and I get to these points sometimes where you seem to take offense at being questioned about such things. I am not questioning what you have done in the past...why would I? What I am questioning is a couple of particular statements about measuring magnets. This term "energy", other than it's general meaning, has no real meaning here. You may have used it before and even have heard it used by manufacturers, but if you can't define it or say how it is measured because "measuring Gauss is not good" (other than by a magnetometer or "Gaussmeter"...hall effect transducer), than what's the point?

-john

[Fast Freddie]

Ron
If the .450 magnets make less energy than the .500 magnets why have so many trended to the .450 magnets? Is it just for the weight savings? Is that worth the loss in power? I think the biggest problem in motor building is finding the right arm for the setup. Many times I've built setups as identical as I possibly could but put arm A into setup A and it runs OK. Now put arm A into setup B and it runs so much better or worse. I've come to realize over the years that in slotcar motor building all else being equal nothing is the same. It takes time and patience and alot of trial and error. As far as tip orentation I use the push method like the late Monty Ohren he was a very good motor builder and racer. To each his own. I use to win more races when I didn't even match magnets, but then again I was 20 years younger and Gp12s were 1 second slower than they are today.

[Mark Johnson]

I'm a push guy also , I run .450 mags on x-12 and swasp , long mags on s16c and contender .

[CFL Mike]

A shorter length magnet will read higher gauss than a longer magnet made from the same material. BUT...... the shorter magnet has less "energy" than the longer magnet if using the same material.

The only way to get more energy with a shorter magnet is to change the material and that can only be done if new tooling is purchased to the tune of 10's of thousands of dollars.



The Ceramic magnets that are "molded" and used in slot racing are dry press. No wet press molded magnets... the magnet companies in Asia do not want to wet press a small arc like we use in slot racing.

Now wet press material blocks can be cut and ground and used, but they are not radially oriented like a pressed and molded magnet it.

Wet press molded magnets would have higher gauss and higher energy than dry pressed magnets due to better materials and better orientation when pressing wet.

Maybe I said that wrong, arent Muras "Wet Charged" then? The guy who runs my local track is the one who told me this, he said thats why everyone used to use Muras mags. He was also the one that told me Koford and ProSlots where made by Mura, and thats why it doesnt matter much better the 3s magnets.

[Rick]

first off, why are you debating with Hershman who knows this information, first hand? He says they are dry press, take it to the bank, I think the old Champions were wet press type?

On to the push/pull debate. That has been going on as long as motor builders have been building motors. Now this is only my opinion but I think it doesn't matter if its push or pull, as long as the strong tips are oriented correctly. I think it is a wash of which is superior.

Its mojo, not rocket science, LMAO. As Fred says, you can build two identical motors and one will run better than the other? WHY?..........................MOJO!

[Ron Hershman]

Maybe I said that wrong, arent Muras "Wet Charged" then? The guy who runs my local track is the one who told me this, he said thats why everyone used to use Muras mags. He was also the one that told me Koford and ProSlots where made by Mura, and thats why it doesnt matter much better the 3s magnets.

Mura magnets were NEVER Wet Press. They have always been Dry pressed.

Koford, P-S, etc once bought them OEM from Mura because they were the best performing Ceramic C can magnets at the time when these other companies used to purchase and use them in their production motors.

, I think the old Champions were wet press type?

The only "old Champion" magnet was the Blue Dots and the material had water added to the Powder to create a "slurry" before pressing into the mold.

All other Champion magnets were Dry press.

[Gator Bob]

Ceramic is the binding agent ... no?

What is the iron to ceramic ratio?

BTW: I don't know Jack Shirt about magnets. >corrected<

Off topic...maybe... I saw that neo mags can be used on incoming domestic well water pipes to 'remove' iron and 'soften' water .... anyone know about this?

[Ron Hershman]

Ron
1.If the .450 magnets make less energy than the .500 magnets why have so many trended to the .450 magnets? Is it just for the weight savings? Is that worth the loss in power?

2.I use the push method like the late Monty Ohren he was a very good motor builder and racer. To each his own.

1. Because of weight mainly...... sometimes a power "reduction" can be a good thing depending on the type of car and track. Maybe be easier to hook up with a bit less power.

2. Yes to each his own.... I have never matched magnet "tips" in the 30 years I have raced slot cars. Never knew about it for many years, once I found out about it..... I could never see much difference in readings and then never could see any difference on the track. Like I said earlier...... the tip profiles can be sanded/ground to get a better match, but in most classes this would be illegal to do so.... so why waste the time to do it if it's not legal to do so?

More on Push/Pull......... most everyone has it WRONG on this theory...even Monty.

Again like I said in a earlier post...... you want the leading edge of the magnet tip to be the strongest so when the leading edge of the arm is at the leading tip of the magnet...this is when it fires/charges..... once the arm fires/charges..... it needs to get out or leave the rest of the magnet field quickly.

If the trailing tip of the magnet is stronger than the leading edge.... you will have a magnetically "bound up" motor as the arm does not want to release as quickly due to the stronger trailing tip resisting a quick release. After the arm fires/charges it needs to get out and go to the other magnet on the opposite of the motor.

If the push method "really" worked the cobalt guys would still be doing it.... they aren't...why??? Because they had it all back wards.

Here is a test I did many years ago to prove to myself and others how push/pull doesn't work.

I took two pairs Mura Ceramic magnet and ground one tip flat or flush with the ID on both magnets.

I built two set-ups.......... same can.... same strength magnets.

I built a set-up with the un ground and stock tip as the leading tip and the ground tip as the trailing edge. Pull/Push

I built the second set-up with the ground tip as the leading ledge and the trailing edge stock tip. Push/Pull

Then I had two set-ups that would use the same endbell, arm, brushes, springs on both.

Went to the track and the stock tip leading edge set-up was a ballistic missile rocket ship.

Then switched to the ground leading edge set-up and this was a complete turd even with many gearing changes to try and regain the lost Torque, RPM's and overall power.

Of course this would not be legal to do in most D or C can classes so it's not very applicable to do. It can be done in Int 15 and the cobalt classes, but not the Box 12 or scale ceramic classes.

Now all of you think back to the different magnet profiles we have seen in the last 20 years..... Champion Force magnets with their ground back tips top and bottom.....RJR...same as the Force magnets and then the Pro-Slot SMQ's.....none of those worked very well when compared to "full" tip Mura magnets.

Why didn't Force magnets work? Not long enough tips.

Why didn't RJR magnets work?? Not long enough tips and not radially oriented. Very Very good material.

Why didn't SMQ magnets work??? The big notch in the back reduced the energy of the magnet too much to be effective.

So Ron.....why was the magnet you describe never made?? Production issues and magnet retention inside the can. Would be/work great if the magnets were epoxied in place in production motors but can't be done for cost reasons.

Yes any company making ceramic magnets could have one tip ground back on their production magnets and offer them, but this is costly to have the grinding done as second operation.

Yes they could be molded but no one has ever wanted to "flip" the tooling costs to do so plus there could be a "orientation" problem with two different tip dimensions in a molded magnet. I never talked to a magnet engineer about this, but I am sure it would lead to problems when orienting the magnets in production.

[Ron Hershman]

Ceramic is the binding agent ... no?

What is the iron to ceramic ratio?

Yes ceramic is part of the "binding agent.

What is the ratio of ceramic to iron? Depends on the "grade" of the material and other materials used other than ceramic and iron.

A good primer here for those not knowing "Jack" about Ceramic Magnets..... http://en.wikipedia....Ferrite_(magnet)