TECHNOLOGY SIMULATION
Missing links Why mathematical reasoning is more important than ever now for racecar engineers
XPB
By DANNY NOWLAN
The latest simulation software packages are incredibly powerful resources, but they shouldn’t be viewed as a replacement for hands-on learning, first principles and basic mathematical reasoning
O
ver the last couple of months, I have been working with a number of junior engineers at senior undergraduate level and junior post graduate level. While their enthusiasm has never been in question, I am shocked by the lack of basic skills I am seeing. The two biggest areas of concerns are their inability to do hand calculations, and a complete lack of ability to reason mathematically. The first area of concern motivated an article I wrote a couple of months ago on the joy of hand calculations. The purpose of this article is to deal with the second concern. If you are serious about being a capable engineer in any discipline, the ability to reason mathematically is a must-have skill. I am noting with increasing alarm how when junior engineers are given a problem, their fist instinct now is to plug the numbers into something like SolidWorks or ChassisSim and hit a button, hoping it solves their problem for them. Don’t get me wrong, these are very powerful pieces of software but, used blindly and with no idea of the underlying
principles, they can easily lead you to the wrong conclusion very quickly. I can give countless examples of engineering disasters that could well have been averted if the time had been taken to have a proper think about the problem in the first place.
Conversion rates To illustrate this, let’s consider our first example, which is the conversion of anti-roll bar rates from moment per degree to a spring rate. At first, this might seem a little mundane, bordering on the trivial, but it serves as an excellent first example. The problem we need to solve here is how do we convert a bar rate quoted in Nm/deg to an equivalent spring rate in N/m? The answer is not as hard as you think. Our first port of call is to calculate the moments generated by the bar for a given spring rate and a roll angle. The force given by the bar can be expressed as equation 1.
Where, F b k b t q M R
= force on the anti-roll bar = bar rate in N/m = track width in m = roll angle in radians = bar motion ratio (bar movement / wheel)
To keep this discussion simple, let’s assume the bar rate and motion ratios are linear. The next step is to calculate the moments being generated by the bar. We have two forces providing moments in equal and opposite directions so, assuming the c of g is in the middle of the car, we may write equation 2.
(2) (1)
Where, M = rolling moment (N/m)
Countless… engineering disasters could well have been averted if the time had been taken to have a proper think about the problem in the first place 74 www.racecar-engineering.com SEPTEMBER 2022
