Scalextric Magnatraction explained for your Scalextric cars

Magnatraction, how it works and how to adjust it for your for Scalextric cars

Introduction

Magnatraction is a made up marketing word from Scalextric (Hornby) to explain the use of a magnet to help give a scalextric car extra traction on the track. Simply put a magnet mounted to the chassis of a Scalextric car will be attracted to the steel track rails giving extra downforce and tyre grip. Hence the word Magnatraction

How does this work?

Magnets are attracted to steel and iron objects, this is well known. It is also well known that adding some weight over the rear axle of a scalextric car gives better traction. To explain this we need to take a look at a simple mathematical equation:
F = µ N
Where:
F = Force, this is equivalent to traction in our case.
µ = coefficient of friction, (pronounced mu). This is the interaction between the tyre material and the track material, tyre grip in this case.
N = Normal force, this is the force pulling the friction surfaces together.
This formula reads as:
"The traction the drive tyres give is equal to the grip of the tyre material to the track times the force the pulling the tyre to the track."
Therefore using weight over the rear axle or a magnet to attract to the track rails increases N and tyre grip is increased. Equally you can increase µ by using better, grippier tyres. That's it, maths states you can increase tyre grip by increasing µ and N.
Scalextric has selected the use of Neodymium magnets for all of their cars for some years and has become lazy over the tyre and track surfaces. They have massively increased N with the magnet and reduced µ to save time and money, lower grade tyre material and less grain on the track surface is the result.

Adjusting the grip levels

With the mathematical formula F = µ N there are only two variables to play with, µ and N. µ is all about the tyre and track surface while N is all about the downforce over the driving tyres. Lets consider µ.
µ has only a few options as you can change the track surface or the tyre material. Keeping your drive tyres clean and free of dust can be a great help and if this is not enough then MAX Grip tyres are available for all Scalextric cars. Apart from MAX Grip tyres the only other option is to change the track surface for more grip.
N, on the other hand, has lots of potential to tune the Scalextric car's performance. More magnets, stronger magnets is an easy way to give better grip. Less magnets, weaker magnets is an easy way to give less grip. One solution not always realised is the distance a magnet is from to the steel track rails controls the attractive force.
The Normal force from a magnet to the track rails varies as the inverse of the distance squared.

This means you only have to move the magnet a small amount to get a big effect. For example to reduce the Normal force from the magnet to one quarter the current value the distance between the magnet and the track rail just needs to be doubled. So, tuning the magnetic grip is relatively easy to carry out, stronger magnets for more grip and just move the magnet further away from the track for less grip.

Going "old school"

In this context "going old school" is all about removing the magnet completely and finding grip the old way. As we used to in the 1960s and 1970s before Scalextric hit on the idea of adding magnets. As F = µ N tells us, there's grippier tyres and weight to play with.
MAX Grip tyres and weight over the driving axle are the options available.

Conclusion

Magnatraction as used by Scalextric is a very easy way to give a Scalextric car significantly extra traction on the track. Strong Neodymium magnets can easily overcome poor mechanical grip from the tyres. With this feature the choice is a very personal one.
Magnatraction can be a great feature to speed up racing or it's a curse that reduces racing skill.

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