Ten gm extra force was required to keep the car moving around the corner (same radius
as the Victorian track) compared to along the straight, this is an extra 0.1 Newton. As we
suspected significantly below the force measured with a car having all aluminium wheels.
CAUTION: We have in the past seen problems with cars when steering systems have not
tracked straight holding the car hard onto the guide rail thus increasing drag. We have
also seen wheels that have gone into and maintained a serious shimmy type motion,
causing significant increase in wheel drag.
Remember everything you add to the car increases weight, take care that any steering
system is not too heavy.
Consider the possible problems and gains then make your own decision on steering.
10 Stability
The main form of instability is the car tending to roll over while cornering. It does not
require a complete roll over to give you trouble, as soon as the guide system becomes
disengaged the car will run out of control.
A low centre of gravity increases stability, this becomes more important as speed rises. A
light weight panel with ballast carried low down will lower the centre of gravity.
Remember the forces trying to roll your car over while cornering vary with velocity
squared; consequently if you have a high speed car take care in your design.
Wheel positioning can influence stability, with stability increasing as the wheels are
moved further out from the centre line. A wheel at each corner will be more stable than a
tricycle wheel arrangement.
As a guide, calculations indicate that a car with its centre of gravity 80mm above the
track will not roll or disengage the guides on cornering below a velocity of 9.9 metres per
second. This assumes a smooth track as a bump in the track can upset the cars stability
and initiate guide disengagement or a roll over at a lower velocity.
For comparison a car with a race time of 18.3 seconds has a final velocity of about 7.2
M/sec. Remember car mass does not influence stability (except by slowing the car down).
The height of the cars centre of gravity above the track, car velocity and the radius of
corner are the main factors that influence roll over stability.
11 Suspension
Suspension systems are not in common use in the competition, but a well designed and
constructed suspension system could be of great help in increasing stability and
making sure your drive wheel(s) are in contact with the track at all times. Is it worth the
effort and weight?
Remember any suspension must ensure the guide system remains engaged and does not
hit the track.