One Gee Magnet Rule Philosophy

By Jim Cunningham, Owner, Nomad Slot Racing

Since 2002, Nomad Slot Racing has held weekly (often 3 or more per week) races on a variety of tracks for a wide variety of cars. Currently, we have 12 classes of cars and about half of our classes permit traction magnets. We attribute the health and variety of our racing program in large part to good clear rules. The cornerstone of our rules for traction magnet classes is what we call the “One Gee Rule:

This simple rule accomplishes several things at once: 

  • It provides a clear, easily tested limit on the biggest factor in magnet car performance. It’s quick and eliminates debate over picky rules. Racers can check their own car for conformance and adjust them without special equipment.
  • By equalizing the ratio of magnet to weight, a wide variety of cars can be included. Without the One Gee Rule, often the only competitive cars are a single brand and sometimes even and single model. We routinely have close races between, for example; GT cars from Scalextric, Carrera, SCX, Ninco, and Monogram. Without tuning to this rule, those cars would all run very different lap times. “One Gee” opens up the field variety letting people run what they like.
  • A common problem with magnet racing is “escalation”. If adding magnets to the cars is permitted without a limiting rule, racers will invariably add more and more magnet in search of maximum speed. This leads to cars only capable of very short races due to motor overheating. At some point, there is very little driving left to do as the cars negotiate most of the track at full throttle. When cornering limits are exceeded, there is no drift or warning, the car snaps off the track in a violent crash and car damage is common. While some enjoy sheer speed and even the violence of the crashes, we find that interest in this racing style tends to be very short lived and has lead to the dissolution of many slot racing clubs. “One Gee” caps traction at a reasonable level and has worked very well for us for almost 7 years.
  • We have found a considerable variation in magnetic downforce in a single shipment of new, “identical” cars. Manufacturing tolerances are such that some “box stock” cars will always be better than others. Being racers, there is also a chance of stronger magnet substitutions or hidden magnets added above the stock ones could affect performance as well. Since magnetic downforce is the biggest and most import variable, we use this rule to equalize it with a simple, quick concrete test. Motors also vary in performance, but if the magnetic downforce is limited, and the track is not too big, the advantage of a faster motor is less of an advantage. 
  • Use of the One Gee rule eliminates the need for most other rules that attempt to control performance though measurement or component specification.

Here’s how it works: 

Select a piece of standard straight of the same type as your racetrack. Cut a piece of ¾” MDF or similar material. We like MDF because is stable and very flat. Use hot glue, contact cement or foam double stick tape to secure the track section to the MDF base. Press down firmly with your complete Model Car Racing Magazine collection or similar weight until secure. The purpose here is to insure that this test section is and will remain flat. Use tape or paint to define a point at which the front of the car will be placed. Each raceway will have one “official test track”. You can make up duplicates for racers to test on but because there can be slight variation in rail height, check each new test track to confirm you get the same results as the “official” one.  

There are differences in the amount of magnetic attraction between track brands.  Carrera’s 1/24 track is a mild stainless that contains less iron, so magnet tuning on a Carrera Track would give too much downforce on Ninco, SCX or Scalextric track... Make your test track from whatever brand of track you are racing on.

The test:

Prior to the race, all cars must pass this test: Place the car on the test track, with its front even with the line of the track. Slowly turn the track section over. It’s best to pivot the track at the slot center line to avoid any momentum which might “help” the car off the track. Legal cars will fall off the track to your other hand. (Don’t drop them!) Cars that have too much magnet will hang upside down.

Cars that “hang” must have their traction magnet reduced or have weight added. In most cases adding adhesive-backed weight to the underside of the front of the car will do the trick. In other cases, it is best to remove the stock magnet and achieve just the right balance with tuning magnets.

Under this rule competitive cars will be right at the limit of this test. We almost never see an off the shelf car that is “One Gee ready”.  If your car drops easily when tested, it almost certainly will not be competitive. A car which has been tuned for optimum performance under this rule will often be so close to the limit that is may take a second or more before it “decides” to fall!

Until you are experienced with setting cars up for One Gee it may take numerous combinations of weight, magnets and placement to find the right balance for the car and driver. Try a set up, confirm it is “legal” then drive to confirm you have competitive lap times and that you like the car’s handling. Not quite right? Try again. We use thin lead tape and usually multiple thing magnets to get the balance just right.   

One little “cheat” to get a car very close to the limit to pass the test, is to use stiff braid and set the braid very high angle prior to the test. This will help lift the front of the car and “peel” it off the test track. To cut any advantage gained by this technique, drivers may not touch or adjust their cars after test until the race has begun. A high, stiff braid setting would then compromise a car’s handling, or require an on-the-clock pit stop to adjust.  

Cars may also be checked at any time during a race to insure that no added magnets have mysteriously appeared between heats. Failing a mid race test earns the car a black flag.

Here are tips for how to tune your cars for the One Gee rule:

In stock form on Carrera track, we find most cars except for some Scalextric can have a little added magnet. On other brands, most cars need magnet reduction or weight added.

Although the MCR charts or Magnet Marshal readings may show weight and magnetic downforce that suggest certain cars will or will not pass the test in stock form, we have not found the charts to be an accurate guide. One reason is that the placement of the magnet is as important as its strength. For example; a front-motor car with much of its mass forward can have more downforce magnet just ahead of the rear axle than the weight of the car. The heavy front will “lever” the magnet away as it falls. More magnet can be used at rear of a car than at its center for the same reason. 

For best lap times, the best place for traction magnets is just in front of the rear axle. For sidewinder cars and some in-lines, we often remove plastic, (if any) under the motor and stick the traction magnets to the motor casing on their own power. We have not seen any effect on motor performance from doing this. This is very convenient for testing different magnet combinations and even allows the magnets to be easily removed for subsequent no-traction-magnet races. In other cases, a drop of glue can hold the magnets in place. Be careful to allow clearance so that magnets do not touch the rails and cause a short. For some low-slung cars, magnets must only be placed inside the chassis. (Plastic has no effect on magnetic fields.) Magnetic attraction climbs dramatically with proximity so the higher the magnet is in the car the stronger it must be. Stacking magnets on top of each other greatly increases their strength. 

Since magnet distance to rails strongly affects downforce, tire diameter affects performance significantly. Unlike HO where there are a few standard wheel sizes and multiple tire sizes to tune with, the huge variety of tire and wheel sizes in 1/32 makes this impractical. You can fit cars with aftermarket wheels that have multiple tire diameters, but often at the loss of scale appearance and increased cost. At Nomad, most of our classes specify stock wheels and tires. We true our tires and use a rubber softener called Frog Spit to increase stock tire performance.

At Nomad, we stock weight tape and a wide variety of magnets for One Gee magnet tuning. Most useful are the small 1/32” thick neodymium magnets because they can be added until just the right balance is found. Magnet tuning supplies are available from Nomadslotracingestore and you can even send your cars in for tuning by our experts.  

These cars are all tuned to meet the “One Gee” rule. There are many configurations that work! Drivers often have preferences. Some like the magnets set wide, to increase as the car drifts and “catch” the car, some like the magnets directly over the rails to prevent drift. Others like the forgiving nature of magnets placed further forward... Some like cars heavy or light... Dips and banked turns will also affect optimal placement.


Cars tuned for Carrera track: LtoR Fly BMW - 1/2" by 1/32" disk added directly over stock magnet. Carrera Vintage NASCAR - front magnet removed, small bar on motor casing,  large bar replacing stock rear magnet.  Slot it Porsche 962, Stock magnet removed, four thin 3/8" by 1/32" buttons added.   Monogram NSU, Large block of lead at front, 1/8" by 1/8" by 1" bar middle and rear, plus stock magnet, plus two 1/4" x 1/32" thin disks and two 1/4 by 1/8" by 1/32" bars!

Scalextric Seat with stock magnet plus two small bars on motor casing and two small disks set wide.   38 grams of lead tape up front.  Scalextric Jim Hall Camaro - Stock magnet removed, no added weight and 3/8" by 3/4" x 1/16" bar on motor casing.  Fly Marcos with stock magnet plus two 3/4" x 1/2" x 1/32” bars.

Vintage sport cars with magnets restricted within to 1.5" of front of guide blade.  LtoR Monogram Ferrari with stock rear magnet removed and stacked on front magnet.  No added weight.  Fly Porsche 906 with rear magnet removed, 30 Grams of lead tape and two 3/4" x 1/2" x 1/32” bars.    

We have added a variation to our rule for our Vintage Sports Car class. We thought that vintage sports cars should drift in the turns and be slower than modern cars, so our normal ruled made the cars too aggressive. On the other hand, it took too much tuning and modification to get some of the cars to be competitive with no traction magnets. So, we added the stipulation that no traction magnet may be placed further than 1.5” from the front of the guide blade, to the One Gee Rule. This creates a class midway between magnet and no magnet cars. The cars are evenly matched and easy to set up. And they drift and slide that way an early sports car should!   The further forward the magnet is, the “looser”, more forgiving the handling is. If you find the unstipulated rule makes the cars too aggressive for your tastes, you can back

off the magnetic effect by stipulating a more forward magnet position... Maybe a different one for each class... 

 Experimentation is the key. The “One Gee" rule has provided the framework for years of Fast Fun at Nomad Slot racing. Let us know how it works for you!