This manual summarizes the knowledge compiled through 30 years of racing and consulting the world’s best and fastest racers and builders.

We would like to thank, especially

Craig Landry of Zap Racing Products, and 1993 World Record Holder for his thoughts on this subject and his partnership in car development.

Bob Green, previously of Mura Products, for sharing his insights in Motor design.

Joel Montague of Camen Enterprises, for the collaboration and correspondence over the years on the subject.

Csaba Zekelihidy – 1984 National Champion, for his many contributions to the sport and his technical conversations during the early days of Cobalt motor development.

Fred Hood was a devoted racer and friend for the many years of help and testing that developed my understanding of the slot car mechanism.

Tracy Chin for his testing and sharing his unique and innovative views on Eurosport car designs.

Lee Gilbert for sharing his innovations during our many after-the-race dinner talks.

Lee Roberts, builder of some of the fastest motors in modern times. For his trust and for sharing his findings in developing some of our magnet designs.

Don Perko, for his collaboration while developing the “P” magnet that launched our magnet projects.

Mike Aceves for his devotion to our company and for testing and developing the world’s fastest dragsters. This has allowed us to build our understanding of the Slot Car drag racing motor.

Dennis Kurshner for sharing his findings during his developments of some of the fastest Eurosport motors (used by the winner of the 1994, 1995, 1996, and 1997 USRA Nats).

And in memory of:

Ivan Jenkins: Who shared his many findings with us and, in his tinkering, has developed some high-speed motors.

Of course, many have shared race results, testing results, and the effects of changes they made with me. The people listed have been most influential during my long study of the Slot Car Motor design.


Magnetic Theory

What is a Magnet?

Magnet theory is a very complicated subject, which is covered in many graduate school textbooks with a great level of detail. Some important fundamentals will be covered here in common terms for slot car racing. I hope that this guide will help the average racer with motor and magnet selection and guide what to do in developing the racing program.

Only a few common magnetic materials exist: Iron, Nickel, and Chromium. Traditionally, all magnetic materials were made from alloys of these materials. In addition, Ferro-magnetic materials exist in two forms. These are soft and hard magnetic materials. A hard magnetic material can be magnetized permanently, whereas a “soft” magnetic material is magnetized in a magnetic field and then reverts to near-zero magnetic fields when the field is removed. The armature material is a perfect example of a soft magnetic material.

Another type of material is Para-magnetic material. This is typically a good electrical conductor material, which, when subjected to a fluctuating magnetic field, allows currents (Eddy Currents) to flow. Eddy Currents counter-act the electromagnetic field and act to reduce its strength. These materials include aluminum, copper, brass, and similar good conductors that are otherwise non-magnetic. A paramagnetic material acts to reduce the magnetic field strength instead of increasing it, and this is one reason why they are not used for armatures or can material.

A material becomes magnetized because polarized molecules or groups of molecules called domains become aligned in a magnetic field. These domains are little magnets themselves with a “North” and “South” Pole.
In soft magnetic material, these domains are free to move, and when a magnetic field is applied, they line up and form a magnet, but once the field is removed, the material becomes non-magnetic again. This type of material is used on motor “cans” or armature blanks, where the polarity needs to change.
The para-magnetic effects due to induced currents are the other parameters to consider in can and armature materials. As previously mentioned, non-magnetic materials decrease magnetic fields due to the good conductivity of eddy currents. This same effect will reduce the performance of a magnetic material. Adding alloys like silicon to iron alloys will increase resistivity and decrease the induced currents to improve magnetic performance and reduce heat from the induced currents in soft magnetic materials (making them better for armature blanks and cans!).

Silicon-bearing alloys are chosen for Armature laminations and sometimes for can materials to reduce the induced Eddy Currents. Another method used to reduce the Eddy Currents is using laminated armature stacks. The thin laminations act like a small diameter wire, increasing resistance to these currents.

A “hard” magnetic material is used for a permanent magnet, where these domains are trapped and not free to move. With a very strong magnetic field, these domains are rotated and trapped in an aligned orientation, so when the field is removed, the material remains magnetized.

Now you know some basics of magnetic materials and what a permanent magnet is. It’s a material with small magnetic domains, which are trapped in the material’s lattice and are aligned to form a magnet with a very strong magnetic field.

With this knowledge, we go into a more refined definition of magnets and magnetic materials:

Early magnets were no more than high carbon steel, magnetized by an electro-magnet, but with advances in material science, alloys with very strong dipoles have been designed. The first of these alloys were the Alnico magnets, where iron was heavily alloyed and cast to form a magnet with very high flux densities.

Modern materials have been made for many applications.

  • Mechanical attraction-Repulsion
  • Mechanical-Electrical – Like Generators or microphones
  • Electrical- Mechanical – like motors, loudspeakers, or deflectors for charged particles
  • Mechanical to heat – like eddy-current or hysteresis torque devices.
  • Special effects – like magnetoresistance, Hall effect devices, ECR (Electron-Cyclotron Resonance Plasma sources), and Planar Magnetron Sources for metal sputtering sources, controlling target Erosion.

Modern Magnet Materials:

Since the early days, there have been many developments in magnet materials; modern materials can be summarized into five different types:

  • Neodymium-Iron-Boron
  • Samarium-Cobalt
  • Ceramic (Barium ferrite or Strontium-Ferrite)
  • Alnico (Al-Ni-Co)
  • Flexible or Plastic magnets

Neodymium and samarium-cobalt are called rare earth magnets because they contain rare earth elements, neodymium or samarium, and are the strongest magnets available. Ceramic magnets have good coercive properties and are low cost. Alnico magnets were commercialized in the 30’s and are still used today, especially in areas where very high operating temperatures are required. Plastic magnets are simply magnet powder bonded by a plastic or rubber binder. Because of the binder, the strength is never the same as a magnet made out of the powder by itself. The plastic magnet, however, is lower cost, can be made into different shapes easily, and can be made as a flexible magnet.

Magnets for Slot Car Motors

The Slot car motor requires the strongest and lightest magnet possible, so when one looks at what is needed the conclusion that the magnet needs the following:

  • High Coercive force
  • Large Energy Product ( BHmax)
  • High operating temperature
  • Small temperature coefficient

If only one of these properties is considered, like an energy product, which has received a lot of discussion among slot car racers, you could decide that the magnet to use is Neodymium-Iron-Boron. You can get these magnets with energy products in excess of 50MGO.

The problem is the maximum operating temperature is 200 degrees or below, and the temperature coefficient is around .1/degree. Compare this to Samarium Cobalt with BH less than 32MGO but with operating temperatures of 300-400 degrees and temperature coefficients of under .03/degree, which explains to a great extent why Neodymium slot car motors don’t work.

Slick 7 Samarium Cobalt magnets have the right balance of properties, making them superior for slot car applications. Our material is so stable that we have never seen a change in properties after several races in a Gr-7 motor. Therefore, the need for re-magnetizing is eliminated, and motors don’t heat up because of a loss in magnet properties during racing.

 Motor Facts

Have you ever wondered why motors have 6 or 12 clicks per revolution and why some motors feel like they have dead magnets, yet others feel super strong?
In slot car Cobalt motors, this has to do mostly with magnet geometry, tip strength, and tip position. Below is an example of a 12 “click” motor using .400″ tall magnets on a .459 diameter armature. Note the position of the stack labeled “1” during each 30-degree click.

You have the primary click whenever the face of a pole is aligned with the face of the magnet; this gives you six clicks. You have a secondary click when the pole is between tips. As you will notice, the tips cover the ends of the pole when they’re between tips, and the center web is always about 50% in the magnet face when one web is in the opposite magnet. That means you have a centering pull on the opposite poles when the primary pole is in the field.

 12 click motor - .400 tall magnets in a .459 armature.

Description: 12-click motor – .400 tall magnets in a .459 armature.

When the magnets are not so tall, then you can see that when the primary pole is aligned, the center of the web on the other two poles are further away from the tips. This means the poles are too far away for the tips to apply a strong counter pull, so the clicks are primarily due to the one pole aligned with the magnet.

Armature rotation- 30 increments .360 tall magnets on a .459 armature

Armature rotation- 30 increments .360 tall magnets on a .459 armature

When the magnets are tall, like .450 tall in the example, the tips overlap the web in the first photo, where pole one is aligned with the top magnet; this provides a very strong centering force. This causes a very strong primary “click” followed by a weaker secondary click and an armature that is hard to turn in the field due to the condition of all three webs being within the magnet at once.

.450 tall magnets with a .459 diameter armature

.450 tall magnets with a .459 diameter armature

It is believed and argued that a hard-clicking motor is “unbalanced” and makes the motor run as if it’s out of balance. This is not true, of course, because one is relating the static magnet coercive attraction to an un-charged coil to that of an operating armature where the poles attract and repel from the magnets. The operating conditions are quite different from the “feel” of a motor when turned by hand.

When one tests performance, motors with heavy cogs and real tall magnets may have high torque but may sacrifice top speed. On the other hand, a small magnet motor with a heavy cog may have lots of top end. The point is a heavy cog in both cases, but much different motor performance.

Commutator Timing and Magnets:

Timing affects the performance of the motor. More timing generally gives the top end and less torque. As you can see from the following picture, when the armature pole is coming into the magnet, the commutator contacts the brush and energizes it, causing it to attract to the magnet’s middle.
Bob Green always told me that the performance of the motor was based on the tips, which is why the armature is turned off when the poles get to the magnet’s middle. The real work is done when the poles are closer to the magnet tips. When the pole enters the tip of the magnet, this is the point when the commutator turns on the armature. It is seen in the drawing that the more timing a motor has, the more of the pole is out of the magnet, and the following holds true:

  1. More of the coil is out of the field, causing a lower back-EMF (Voltage countering applied voltage and limiting RPM). This causes more RPM.
  2. The Pole is further out of the magnet, causing a greater angle between the magnet field lines and the armature field lines (Slip Angle), which causes higher current flows & more heat. (Reduced with quads because the fields are better aligned.)The
  3. The Pole is further out of the magnet, reducing torque because more of the pole is out of the working area.

For these reasons, I believe higher timed armature is improved with taller magnets (More torque and less heat).

Another factor to notice is the position of the tips relative to the center webs during commutation. The thicker web armatures have more metal in the magnet and more metal to produce stronger fields; these armatures prefer magnets that are not as tall or angle-tipped. Note that armatures produced from the 1990s to today, with thin webs (27s and C-12s), are increasingly taller magnets than older armatures. The newer armatures have thinner webs! The Armatures with smaller webs can produce more torque without loss of RPM, and because they run hotter, the taller magnets improve the reliability of these armatures.

 Horizontal Vs. Vertical Brushes

In the picture below, you can see the two contact points of vertical and horizontal brushes. Which do you believe is better?

horizontal-vs-vertical-brushes

38 timed armature in .400 tall magnets, with superimposed vertical and horizontal motor brushes.


Here are some facts:

  1. There is an orientation with horizontal brushes where the poles are directly short; luckily, the contact area where the short occurs, called overlap, is small, and the motor still runs. However, this short-out condition is eliminated with vertical brushes unless the commutator gets very small.
  2. Commutation takes place sooner in the rotation with horizontal brushes, so you have the effect of more timing with horizontal brushes, which may account for why, in some conditions, the horizontal brushes give more top end.
  3. Because, for the same armature, vertical brushes produce an effect of less timing, you can expect more brakes and bottom-end torque on a vertical brushed motor.
  4. The amount of time the poles are on is less with a vertical brush; this can account for a cooler running motor and better throttle response to a motor (important in Eurosport racing)
  5. Vertical brushes have more contact area with the brush hoods.
  6. You have more wrap-around with a horizontal brush and, therefore, more contact area against the brush.

I conclude that vertical brushes should be better for open motors or motors or high-power racing, but only because you eliminate the short-out condition on the commutator. I have seen many horizontal brush motors work better, particularly in group racing, where there is more timing given and more time allowed for the coils to charge since there are a lot of turns of small wires. So horizontal brushes work best on restricted motor classes like Gr-27 and C-12 or boxstock, etc.

Wing Car Motors:

Wing car motors are the most refined for slot cars because they have developed for over 40 years. The basic requirement for the wing car motor is good power at high RPM, strong mid-range, and medium low-end torque. Other characteristics desired or enhanced are:

  • Light Weight
  • No brakes needed
  • Low operating temperature
  • High RPM
  • Optimized for qualifying or race conditions (not both)
  • Optimized for low and high power.

Gr-7 “Open” class motors:

Open-class motors are complicated but give the motor builder the most tools. The ability to change the timing, armature length, winds, and blank dimensions allows the manufacturer great flexibility in making a good motor. For the racer, the same applies to using a particular manufacturer’s armature (blank design) and selecting timing, wire size, and number of turns.

When planning your motor, you must decide what armature you will use, its diameter, can type, power conditions, and how much timing the arm has. Since I wrote this article, there have been some new developments. Introducing our 6, 8, and 10 magnet sets gives the builder new choices. One can characterize multi-mag motors as even number segments for smooth bottom end and more top end and odd number segments for more bottom end. The more segments you use, the more efficient the motor, and you get a cooler running motor and a motor less prone to power drops or voltage changes.

Qualifying

Motors for qualifying need to be built for lightweight and top-end power. In qualifying, there will typically be a lot of glue and power, so you don’t want to overpower the car with low-end torque or draw too much current to arc the braid.

The magnets to pick for qualifying Gr-7 will usually be Multi-magnet types:

Traditional .459 qualifiers

For .459, armatures were picked in order of heavier, more mid-range, and bottom-end torque:

S7-360 – .400 tall x .360Long x .073 thick flat tip quads
S7-352 – .400 tall x .380 long x .073 thick flat tip quads
S7-304 – .430 tall x .380 long x .072 angle tip magnets
S7-306 – .430 tall x .380 long x .072 thick – flat tip magnets (Proslots like these)

For .480, Armatures pick in order of heavier and more mid-range and bottom-end torque:

S7-360 – .400 tall x .360 long x .073 thick – is so light they work for qualifying.
S7-352 – .400 tall x .380 long x .073 thick flat tip quads
S7-303 – .450 tall x .380 long x .073 thick angle tips
S7-306 – .430 tall x .380 long x .072 thick, flat tips – Will give more top end than 305’s

New .480 arm qualifiers

For .480 arms, you have to kill their brutal bottom end to hook up your car for qualifying; now, you do this with our introduction of 8 magnet motors. Eight magnets give you a smoother bottom end and more top end.

Use .360 long 8 mags for high power qualifying – S7-500 with S7-482 center segments for a .450 tall 8 mag.

There are many combinations you can do; if you use S7-503 – 10 mag outer segments and S7-479 center segments, you can make a wicked .480 tall 8 mag

Use .360 long 6 mag for high power qualifying – use S7-360 and S7-482 center segment.

Other combinations are S7-500 and S7-479 center segment for a .420 tall six mag qualifying motor – light and Fast!

Gr-7 Racing

You must consider reliability, operating temperature, and crash resistance for racing. Quads are best for reducing operating temperature and high power racing, whereas singles have the advantage in that they are more durable, and run best in low power, specially low volts operation.

Quad Magnets for .459 armatures:

S7-352 – .400T x .380L x .073T. Flat Tips
S7-365 – .400T x .400L x .073T Flat Tips
S7-304 – .430T x .380L x .073 T -Angle tips
S7-380 – .400T x .440L x .073 T -Flat Tips
S7-306 – .430T x .385L x .073T Flat Tips

Single magnets for .459’s:

S7-366 – .400T x .400L x .073T Flat Tips
S7-312 – .430T x .380L x .073 T angle Tip
S7-314 – .430T x .380L x .073T Flat Tips
S7-317 – .400T x .440L x .073 Angle Tips (creates impressive horsepower!)

Quad Magnets for .480 Motors:

S7-303 – .450T x .380L x .073T Angle Tips. (Works best with Camen and PK arms)
S7-365 – .400Tall x .400L x .073T flat tips, this is a popular size for both .459 and .480’s
S7-380 – .400T x .440L x .073 Flat Tip Quads

Single Magnets for .480’s

S7-311 – .450T x .380L x.073T Angle Tip
S7-313 – .450T x .380L x .073 flat tips
S7-427 – .450T x .360L x .065 These magnets work well on low-power open racing with big air gaps
S7-429 – .480T x .360L x .073 These are good single mags, plenty thick for all open motor applications and high-power racing.

Newer Models:

Six Magnets Sets:

S7-350 and S7-407 center – Makes a ..450T x .380L x .073T 6-mag, The original six mag. configuration, use this as the baseline.

S7-350 and S7-480 center – Makes a .470T x .380L x .073T – 6mag. These were developed during the 2000 Nats and provide more bottom end and reliability than the thin center segment 6 mag configuration. Better on high-power tracks, and more reliable.

S7-304 and S7-407 center – Gives a big .490T x .380L x .073T 6-mag – Really big horsepower, and rpm from angle tips!

S7-360 and s7-407 center – makes a .450 tall x .360L x .073 6-mag – good on med to low power shorter magnet gets more RPM and is lighter than using the .380L sets.

S7-360 and S7-480center – Makes a .470T x .360L x .073T – 6mag. These are lighter than the .380L brothers but are more prone to heat. so they will be better for med to low-power tracks. The shorter magnets will also give you more RPM.

Eight Magnets Sets:

Eight magnet sets are characterized by more RPM, less Bottom end, and Cooler running motors.

S7-445 (S7-439 and 2 sets of S7-407) These are our original 8 mag sets, .450T x .380L x .073T- These are super reliable, have smooth bottom end, and lots of top end! Good on any power.

S7-500 and 2 sets of S7-407- .450 T x .360L x .073T – Makes a high revving motor, perfect for qualifying or really hot power!

S7-504 and 2 sets of S7-478 – .480T x .380L x .073T – Makes for a real animal! More bottom end than the .450 T motors, just what the 8mag needs.

S7-503 ad 2 sets of S7-479 – .480T x .360L x .073T – Lightweight and more bottom end, makes a very good, light motor for all types of power.

Ten Magnets Sets:

Then magnet sets are characterized as stronger bottom end than 8 mag, the motor will run more like a 6 mag motor with more reliability. Because of the improved efficiency, the motor will usually have more top end than a 6 mag motor as well.

S7-504 and (3) S7-407 – .450T x .380L x .073 – 10 mag – The baseline 10 mag motor.

S7-504 and (1) S7-478 and (2) S7-407 – .470T x .380L x .073 – More bottom end.

S7-504 and (2) S7-478 and (1) S7-407 – .490T x .380L x .073 – More bottom end and top end.

S7-503 and (3) S7-482 – .450T x .360L x .073T – Lighter and more top end than baseline

S7-503 and (1) S7-479 and (2) S7-482 – .470T x .360L x .073 – More bottom end but about the same weight as the baseline

S7-503 and (2) s7-479 and (1) S7-482 – .490T x .380L x .073 – This is the preferred configuration for a .490 tall 10 mag, a magnet this tall needs to be short to save on weight.

There are more configurations to make up; here are the guidelines to decide on your motor:

Dimension: Effects:
Height Higher means more bottom end and cooler running motor.
Length Shorter means less weight, less bottom, more top end, and a hotter running motor.
Center segment The presence or wider center segment means more bottom end. Center segment also makes the motor more immune to power changes, motor does not tend to slow down when the power drops during the heat.
Number of segments The more segments, the more efficient and cooler the running motor.
Air Gap A tighter air gap, means more torque, less RPM, and a cooler motor
Angle of tips More angle means more RPM, less bottom end.
Thickness of magnet Effects the strength Gauss readings change dramatically with magnet thickness, thicker magnets make the motor run cooler with more bottom end.
Combining angle and flat tips Give an effect like changing timing; using an angled tip on the leading edge and a flat tip on the trailing edge provides more RPM.
Can thickness The thicker the can, the stronger the field. The effect is that a thicker can has more torque and cooler running, while a thin can give more RPM and less weight.

Newer Models:

Gr-27 Class Wing Car Motors:

Restricted class motors are tricky because you have fewer parameters to change. Therefore, you can only pick magnets for different arm brands and power conditions.

Qualifying:

S7-306 – .430T x .385L x .073T Flat Tips – High power qualifying
S7-366 – .400T x .400L x .073T Singles – Med-High power qual.
S7-307 – .400T x .440L x .068 T Singles – Baseline magnet, works everywhere
S7-381 – .400T x .400L x .064 angle tips quads for .480 arms in big .459 set-ups
S7-382 – .400T x .400L x .073 angle tips quads for .459 arms or .480 arms in .480 set-ups
S7-365 – .400T x .400L x .073T- Quads For high power qualifying
S7-415 – .430T x .400L x .073T – Improved qualifying magnet for .490 arms
S7-471 – .430T x .440L x .065T – Great qualifying Singles for .490 arms.
For multi-magnets – see the Gr-27 multi-mag section below.

Race Magnets:

S7-366/367 .400t x .400L x .073 for 366 and .064T for 367. Use #s7-367 for the lowest power conditions depending on the set-up and arm diameter.
S7-307 .400t x .440L x .068T flat tip magnet – A very popular Gr-27 magnet for med-high power.
S7-381 – .400T x .400L x .064T angle tip quads for .480 arms in .459 set-ups, a thin magnet.
S7-382 – .400T x .400L x .073T angle tip quads for high-power racing
S7-317 .400t x .440L x .073 Flat tip single magnet. Lots of torque with this one.
S7-321 – .450T x .440L x .073 angle tip single – Big magnet,. But the motor runs cool! works well on low power.
S7-380 – .400T x .440L x .073 flat tip quad for real high power conditions

Newer Magnets:

S7-415 .430T x .400L x .073T – One of my favorites for high-power racing or qualifying
S7-471 .430T x .440L x .065T – Single mag. designed for .490 arms – fast!

Multi-Segment Newer Magnets:

Multi-segment magnets are characterized by having good power, even when the power dips. The magnets used are 6 and 10 mag configurations. 8 mag configurations give more RPM, but in Gr-27 you need torque.

S7-382 + S7-483 – .450T x .400L x .073 – The first of our 6 mags for 27’s produces great bottom end, and is immune to power drop during the race.
S7-381 + S7-483 – .450T x .400L x .064T – Same as above, but for .490 arm. You don’t have to hone as much.
S7-382 + S7-480 – .470T x .400L x .073T – Taller six mag for more torque and higher power tracks.
S7-505 + (3) S7-483 – .450T x .400L x .073T – Makes awsome 10 mags
S7-505 + (2) S7-483 + (1) S7-480 – .480T x .400L x .073 – Makes the secret 10 mags used by Beuf.
S7-506 + (3) S7-484 – .450T x .440L x .073T – 10 mags for lower power tracks.

C-12 Wing Car Motors:

Because these armatures have many turns of small gage wire, we need a magnet that does not overpower the arm, and allows it to rev. A tall, short magnet can accomplish this.

S7-350 – .400T x .285L x .064 thick singles for C-12 set-ups – very light
S7-351 – .400T x .285L x .071T flat tip singles for C-12 arms, more magnet for more power.
S7-427 – .450T x .360L x .065T – Designed for C-12 racing, this is the baseline magnet for C-12
S7-429 – .480T x .360L x .073T – Gives improved bottom end over S7-427
S7-468 – .430T x .360L x .065T – Code name “AL” magnets (Al Chuck built a motor with S7-314 magnets that were cut to .360 by mistake) These magnets were responsible for several world records!
S7-411 – .430T x .360L x .063T – Quad versions of “AL” magnets, holder of several world records. Good for qualifying and high power racing.
S7-500 + S7-479 – .430T x .360L x .073T – The 6 mags Benny Justice used to blow everybody away at the 2001 Nats
S7-503 + (3) S7-482 – .450T x .360L x .073T – Killer 10-mag C-12 motor, lot’s of bottom end, and runs cool!

Drag Racing Motors:

Dragster Motors:

Just as Eurosports are the finesse motor in slot cars, Drag motors are the brutes in the sport. The drag motor requires a strong, but not overpowering, bottom-end torque, but a HUGE one! Mid-range, the Dragster motor operates most of the time within the middle RPM range of the motor and does not need to have the high top-end RPM performance of a Wing Car Motor. This is because the dragster is at the top end for a very short time and spends most of the time getting off the line and up to 60ft speeds.

The important attributes to consider on a drag motor are:

  • Mid Range horsepower
  • Low rotating mass (small arm. Diameter)
  • High Gauss reading magnets, especially at the tips.
  • Lightweight

Dragster Gr-7 Motors Magnet Selection:

The objective in drag racing is low-end and mid-range power; the motor operates at the top end so quickly that the top end does not seem to matter as much. The key here is a small diameter arm for low inertia, a milder bottom end, and then boosting the bottom end with a magnet and can.

S7-303 -.450T x .380L x .073T angle tip quads These are useful for medium power tracks, of which there are many. for bigger arms in small cans.

S7-305 – .450T x .380L x .083 T – The main drag magnet – In a .459 can, you can run a .450 arm with these, and you will get a light motor with good bottom end and mid-range. If you use a larger .480 can, you need a .465 diameter arm. We have set many world records with these.

S7-350 + S7-478 – .450T x .80L x .073T High power 6-mag motor for more bottom end in a small diameter can

Drag Racing Gr-27 Motors:

S7-318 – .450T x .440L x .075T – angle tip quads – For larger diameter arms on low power tracks
S7-319 – .450T x .440L x .085T – These are the main Gr-27 drag magnets – hard to beat!
S7-382 + S7-481 – .450T x .440L x .073T – Big 6-mag configuration for small diameter cans or big diameter arms. great on lower power configurations.

Eurosport Motors:

Eurosport motors are the finesse motors for slot racing; these motors are selected totally by power curve. The Eurosport motor has to come on smooth, have good throttle control in the mid-range of the RPM curve, and have a strong top end with brakes. Magnets for Eurosport motors are typically short to kill bottom-end torque and tall to provide the broad power curve desired. Weight has been an attribute that has received a lot of attention lately among racers. The fact is, weight is not as nearly as important as a good power curve, too short of a motor will have poor mid range properties, and lack brakes. Extensive testing at Slick 7 using armatures with stack lengths as short as .125″ and magnets as short as .120″ showed that stacks shorter than .200 lose throttle control in the mid-range. Also, it causes the motor to turn on abruptly during the negotiation of esses, where power changes during partial throttle. Magnets shorter than .280″ affect the brakes significantly on a Eurosport motor, and lower than .400 affect the drivability.

Magnet Selection for Eurosport:

Motors for Eurosports are almost always .480 or bigger diameter armatures; the popular sizes are:

S7-310 – .400T x .330L x .064T for .480 arm in .459 set-ups – The popular mag. for the Speed Inc. cars by Lee Gilbert
S7-308 – .380T x .330L x .068T lower bottom end than #310
S7-485 – .320T x .400L x .065T – Magnet for long arms for smooth bottom end 1/24 scale Eurosport cars
S7-486 – .320T x .380L x .065T – Magnet for regular and short arms for smooth bottom end 1/24 scale Eurosport cars
S7-485 – .320T x .330L x .065T – Magnet for 1/32 scale Eurosport cars

There are many combinations possible for multi-mag motors, but racers have not tried them; I would suggest:

S7-503 + (2) S7-482 – .420T x .360L x .073T – 8 mag motor that should give smooth low end plus lots of top ends for today’s 6-46 geared motors – I think the first guy to try this will have a big advantage!

 

Magnet Selection Chart:

Thin Center segment for multi-magnet motorsP/N Height Long Thick Type Wing Cars Scale cars Dragsters
S7-303 .450″ .385L .073″ Angle tip Quads Gr-7 .480 arms qualifying & racing NO – Too much torque Low power tracks, more top-end
S7-304 .430″ 385L 073″ Angle tip Quad Gr-7 .459 arms NO – Too much torque It may lack bottom end
S7-305 .450″ 385L 083″ Flat Tip Quad Not used No Way!! World record holder!!!
S7-306 0.43 385L 073″ Flat Tip Quad Gr-7 .459 arms NO – Too much torque It may work well, not tried it yet
S7-307 .400″ .440L .068″ Flat tip single The baseline Gr-27 magnet is very popular! Long arms produce good power Too soft for drag racing
S7-308 .380T .330L 0.065 Flat Tip Singles For C-12 and  Spray glue open racing not used Too soft for drag racing
S7-309 .450T .330L 0.07 Flat Tip Singles For C-12 and C-15, low power For .459 arms in .459 set-ups Too soft for drag racing
S7-310 .400T .330L 0.063 Flat Tip Singles For C-12 and C-15, Used in 1/24 Eurosport- a preferred magnet of Lee Gilbert’s Speed Inc. cars Too soft for drag racing
S7-311 .450T .385L 0.073 Angle tip singles For Gr-27 and Gr-7 – .480 arms Typically, too much magnet Too soft for Drag racing
S7-312 .430T .385L 73 Angle tip Singles For Gr-27 and .459 Gr-7 Typically, too much magnet Too soft for Drag racing
S7-313 .450T .385L 73 Flat Tip Singles For Gr-27 and .480 Gr-7 Proslot Arms Typically, too much magnet Too soft for Drag racing
S7-314 .430T .385L 73 Flat Tip Singles For Gr-27 and .459 Gr-7, likes Proslot Arms Typically, too much magnet Too soft for Drag racing
S7-315 .450T .440L 068″ Angle tip Singles Large mags for .490 arms Gr-27 motors Typically, too much magnet Too soft for Drag racing
S7-316 .450T .385L .063″ Angle tip Singles For C-12 and Gr-27, low power! It may work, but it is not popular. Too soft for Drag racing
S7-317 .400T .440L 73 Flat Tip Singles The equivalent of 307’s for .480 set-ups or .459 Gr-27 arms. Not Used Too soft for Drag racing
S7-318 .450T .440L 73 Angle tip Quads Heavy, good for high-power Gr-27 racing Way too much magnet Killer Drag magnets for high RPM
S7-319 .450T .440L 73 Flat tip Quads Not Used Way too much magnet Main Gr-27 drag magnet
S7-321 .450T .440L 73 Angle Tip Singles Gr-27  in .490 set-ups. For Low power tracks Way too much magnet Not enough torque for drag racing
S7-350 .400T .285L 64 Flat Tip Singles For C-12 racing For short Euro .480 arms in .459 set-ups Not enough torque for drag racing
S7-351 .400T .285L 71 Flat Tip Singles For C-12 racing For  Euro arms, .459 in .459 set-ups or .480 in .480 set-ups Not enough torque for drag racing
S7-352 .400T .385L 73 Flat tip Quads Qualifying or Med. Power Gr-7 or High power Gr-27 Too much torque Light, For low power conditions
S7-360 .400T .360L 73 Flat tip Quads Gr-7 Qualifying Too much torque Light, For low power conditions
S7-365 .400T .400T 73 Flat tip Quads Gr-7 racing magnets for, 1997 Nat’s winner Too much torque For low-med. Power conditions
S7-366 .400T .400T 73 Flat Tip Singles Med-low Gr-27 – .459 arms For big arms, thick version of winner 1997 World’s and Nats Not enough torque
S7-367 .400T .400T 64 Flat Tip Singles Med-Low power Gr-27 .480 arms For big arms, winner 1997 World’s and Nats Not enough torque
S7-380 .400T .440L 73 Flat tip Quads High power Gr-27 racing, a bit heavy Too much torque Not enough torque
S7-381 .400T .400L 64 Angle tip quads Gr-27 med-high power racing, Too much torque Not enough torque
S7-382 .400T .400L 73 Angle tip quads Gr-27 high power racing, Too much torque For low power and Gr-27
S7-386 0.4 0.4 0.073 Angle tip quads Gr-27 high power racing,
S7-388 0.45 0.36 0.073 Angle tip quads Gr-7  Qualifying,
S7-397 0.45 0.38 0.073 Angle tip V-6 Gr-7  racing
S7-407 0.06 0.38 0.073 Center segment Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors
S7-411 0.43 0.36 0.065 Flat Tip quad C-12 Qualifying
S7-413 0.4 0.44 0.073 Angle tip quads Gr-27 Racing – high power
S7-415 0.43 0.4 0.073 Angle tip quads Gr-27 racing General use
S7-427 0.45 0.36 0.065 Angle tip C-12 Racing
S7-429 0.48 0.36 0.073 Angle tip Gr-7 and C-12 Racing
S7-439 0.34 0.38 0.073 quads for V-8’s To make multi-segment magnet motors
S7-445 0.45 0.38 0.073 V-8 Mags To make 8 segment magnet motors for G-7 racing
S7-468 0.43 0.36 0.065 Flat Tip singles C-12 Racing
S7-471 0.43 0.44 0.066 Flat Tip singles Gr-27 Racing
S7-478 0.089 0.38 0.073 Thick center segment Thick Center segment for multi- magnet motors
S7-479 0.089 0.36 0.073 Thick center segment Thick Center segment for multi- magnet motors
S7-480 0.089 0.4 0.073 Thick center segment Thick Center segment for multi- magnet motors
S7-481 0.089 0.44 0.073 Thick center segment Thick Center segment for multi- magnet motors
S7-482 0.06 0.36 0.073 Thick center segment Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors
S7-483 0.06 0.4 0.073 Center segment Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors
S7-484 0.06 0.44 0.073 Center segment Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors Thin Center segment for multi- magnet motors
S7-485 0.32 0.4 0.066 Flat tip singles Smooth low-end power – 1/24 Eurosport
S7-486 0.32 0.38 0.066 Flat tip singles Soft bottom end 1/24 scale motor or high H.P 1/32 scale motor
S7-487 0.32 0.33 0.066 Flat tip singles for 1/32 scale motors
S7-500 0.34 0.36 0.073 quads for V-8’s To make multi-segment magnet motors for G7 & C-12 To make multi-segment magnet motors
S7-501 0.34 0.4 0.073 quads for V-8’s To make multi-segment magnet motors for
Gr-27
S7-502 0.34 0.44 0.073 quads for V-8’s To make multi-segment magnet motors for
Gr-27
S7-503 0.3 0.36 0.073 quads for V-10’s To make multi-segment magnet motors for G7 & C-12 To make multi-segment magnet motors
S7-504 0.3 0.38 0.073 quads for V-10’s To make multi-segment magnet motors for G7 & Gr-27 To make multi-segment magnet motors
S7-505 0.3 0.4 0.073 quads for V-10’s To make multi-segment magnet motors for Gr-27 To make multi-segment magnet motors
S7-506 0.3 0.44 0.073 quads for V-10’s To make multi-segment magnet motors for
Gr-27