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
F = µ N
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
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
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,
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
The Normal force
from a magnet to the track rails varies as the inverse of the distance
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.
Grip tyres and weight over the driving axle are the options
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