another question about mags

[jake]

Hi
A couple people (incl paul c) have mentioned that mag performance has something to do with the type of power supply on the track. Does this mean that I should choose mags based on my track PS?

Can somebody tell me how this works?
Thanks and regards
jake

btw this new board looks great

[DDDDDDerek]

some magnets (like kelly) do not like high power tracks. I ahev seen some people set up a kelly and blow the whole motor up. Most of the racers here use Mura mags. They are really the universal magnet. This is what I know for box 12's Anything else I really cant help ya.

[GaryH]

I have three setups with Proslot SMQ magnets, and several others with Mura Blue Dots and Kelly and Proslot quad magnets. On our track using 13.5 volts of power supply power (75 amps I think) I don't see a tremendous about of difference from one motor to the next. These are x12 motors that I refer to. I do find that the ones with the blue dots work really well running 8:38-39 gears. The others perform best with 9:37-38 gears. Mostly I am comparing these with only one car on the track and driving the same lane in order to make a fair comparison. I'm sure reconditioning the arms and switching them to another setup would change everything. So I guess there is no true formula for setting these things up. It's all guesswork.

GaryH

[Doc]

Here is what I belive. Tall tips and tighter air gap for high power tracks. For c-cans, mura red dots or proslot blue dots (tall tips). If you are racing on a low power track, Kelly mags (short tips) honed to .530 or .535. The Kelly mags also have the advantage of weighing about 1.5 grams less than the red or blue dots. By the way, the Kelly mags are only legal in the kelly cans. I also believe that the Kelly mags will work on high powered tracks given the right combination of gap and arm.
Hope this helps.
Robert

[Phil I.]

:cool: Add the SMQ mags to the low power setups.:)
PHIL I.:)

[LoudCat]

A big reason the fast guys are fast is that they are very good at finding the right combination of timing, magnet strength and gearing to best suit the track power and length.

On lower power tracks, weaker magnets usually work better. On higher power tracks, stronger magnets usually work better. Either setup might work with midrange power. Many people say stronger is always better but that is definitely not true.

Gearing has to be considered when talking about magnetic strength. If the magnetic field is decreased (by using weaker magnets or a thinner can) a lower gear ratio must usually be used.

It is difficult to accurately compare the relative strengths of the different brands because they are shaped differently. Generally speaking for a C can, SMQ are the weakest and Kelly the strongest. Mura is in the middle but overlapping the others.


If you want to experiment with different magnet strengths, it is very important to use consistently measured and matched magnets. This is because magnets of the same brand vary in strength and if you don't have accurate readings there is no reference point to make comparisons.

[jake]

Thanks for all the info. I'm starting to figure some of this out.

Hey LoudCat you brought up a new question though:

"If the magnetic field is decreased (by using weaker magnets or a thinner can) ...."

Looks like what youre saying is a thicker can adds to the field strength of the mags. Is this what you mean?

Regards/jake

[LoudCat]

For example, the old ProSlot can had a stronger magnetic field than the newer thin ProSlot can. Many racers started using a stronger magnet with the new PS can to compensate.

The main reason racers adopted the thinner can is because it is lighter and most believe that taking weight off the rear end is the best thing you can do to improve handling.

[Speedshop]

Jake, LoudCat is right on this one except I don't buy the "matched magnet" theory. LoudCat, if matched magnets are so important how do you account for the success for the Pacific Northwest IMCA racers with deep magnet slots and cans cut almost in half for rear axle clearence?

[Slapshot]

Magnet matching is myth. Slot car Motor Magnetism is based on the constant fluctuation and imbalances of the eddy currents in a repetitious manner. Why match something that is meant to be unmatched.

Hey just for reading confusion sake.

Gary's Perpetual Motion Motor (http://www.geocities.com/CapeCanaveral/Lab/4810/)

[LoudCat]

Originally posted by Speedshop
Jake, LoudCat is right on this one except I don't buy the "matched magnet" theory. LoudCat, if matched magnets are so important how do you account for the success for the Pacific Northwest IMCA racers with deep magnet slots and cans cut almost in half for rear axle clearence?


Let’s get back to the original question about magnet strength. If one wants to experiment with magnet strengths, it only makes sense to measure the magnet and put a number on it indicating the strength. If one goes to the trouble of measuring the magnets, it also makes sense to put the same strengths together. Unless of course there is some evidence that mismatching the magnets leads to a performance advantage. I have not seen this but it could be true in practice. From my limited knowledge of DC motor theory, the motor should be most efficient when the resistance of the poles is equal and the magnet strength is equal.

But how much difference does it make? It all depends. For fast bank track racing, the boxstock guys who are into doing everything possible to squeeze the last .001 out of the motor swear by matched magnets. In that kind of racing if you don’t have a very fast motor, you are gonna loose. I think people can get overly fanatical about matched magnets but on track result have shown that it matters to some degree in that form of racing.

This month I’ll be racing GT12 on two tracks that could not be more different. First is the high powered swoopy king track at Buena Park and the next is on a low powered road course at the Flat Track Worlds. One is a two and a half blip horsepower track and the other is a six turn driver’s track. At BP the emphasis will be on getting the most out of the motor: high timing, strong matched magnets and high gearing. At AFTW, if I need to cut into the mag for a better mesh with a 7t pinion or to get the motor farther back for more speed off the corner I’m certainly going to do it.

Many years ago I asked a top builder (initials LG) why his cars were so fast. He said one word, “balance.” I took this to mean that the racer needs to look at the total package. Sometimes we have to give something up in one area to gain in another.

[Gary NJ]

LoudCat - I think you accounted for the success of the NW racers very well - good post!

Gary NJ

[LoudCat]

Originally posted by Slapshot
Magnet matching is myth. Slot car Motor Magnetism is based on the constant fluctuation and imbalances of the eddy currents in a repetitious manner. Why match something that is meant to be unmatched.



I'm not knowledgeable enough in motor theory to argue about eddy currents and such. Instead, I’ll cite some results from the 2002 Div II Nats held in a few months ago in South Carolina.

An OWH sponsor, Best O’ the West, had several racers using BOW matched magnets at the pro Nats. They were, just to name a few, the winners in GT12 and 4 inch NASCAR; first, second and third in 4 ½ NASCAR; second, third, fourth, fifth and sixth in GT1 and second, fourth, seventh and eighth in GTP.

I’m certain a lot of other racers, including the GT1 and GTP winners, matched their own magnets or got them from another motor blueprinter. The 2001 Nats was pretty much the same story.

[Speedshop]

LoudCat, there is only one way to settle this "Matched Magnet" deal. Next time we are at the same race where there is a banked speedway, say West Coat Champs, let's take one of your "Matched" setups, not a race motor just a pratice motor, and put it in a car and run some laps for times. Then pull it out and I'll cut the car and magnets like we do for the PNW IMCA. We will put it back in in the same position and run some more timed laps. That should tell us what we want to know.

[jake]

Thanks for the feedback everybody. Recall my original question was regarding the relationship between mag strength and track power supply type. This came up after PaulC suggested that my choice of mags should depend on the track's PS type...

So I ran a little somewhat controlled test based on the theory that stronger mags perform better on higher powered tracks (ie battery) and/or stronger mags give more torque and less speed and vice versa. The track is an Oglivie hillclimb 155(?) using power supplies.

I took a Parma 502 S-16d and replaced the mags with Rotor mags (more powerful according to Paul C) and set it up in a new TFlex w/ nascar body. My 8-28 setup ran awful (8-26 was a little better). It sems that the more powerful mags were a real drag on the top end but the tork seemed to be there.

Then, using the exact same setup/chassis etc (8-28), I replaced the rotor mags with the std 502 mags (noticeably weaker) and this was much better--turned 5.7s, not bad for a new setup. This would seem to support the torque vs speed thing when using a power supply.

My raceway has another track (origin unknown...) that uses batteries and I want to continue the test there. So this starts to make some sense, I guess.....
Thanks again for the input.

Regards/jake

[eap9]

Good topic and discussion guys! Now my question is what arm timing and magnet strength combo will work best for either a low or high powered track? I am talking of Box 12 racing.

[pbj59]

It makes it difficult to have any consistancy between tracks in different locations ( even same raceway! ) when everyone is running different levels of power on the tracks. Maybe some like it that way but wouldnt it be better if there was a fairly strict standard voltage and amperage to use? Seems like it can vary from 10 to 14 volts? Thats a pretty wide range. I think .2 volt should be max otherwise fix your PS. There are easy ways to stabilize voltage. More battery capacity, leave PS on all the time and use a good regulator among others.
Put a voltmeter on my Pinto alternater and it reads 13.2 volts every time. Simple.
Then you could set up your motors etc at your home track and only have to work on handling when you visit a different raceway.
Some people like the varying power but it adds another complication when there might be better things to spend time and money on than different sets of mags and arms just to adapt to a wide range of voltage.