TECHNOLOGY – SIMULATION
Figure 1: a typical Sportscar overlay Above all else, take your time.
It might annoy team managers and mechanics, but the good ones will readily assist. When I am measuring suspension geometry, I use the sheet illustrated in figure 2. Using this, you will have everything you need to measure right there in front of you. You can also easily extend this to deal with bell cranks and damper locations, too. Always measure across the chassis to minimise measurement error, and run the numbers straight through your geometry package to ensure they make sense. It will take you longer, but it will be worthwhile.
The other thing I would
like to highlight here is the measurement of motion ratios. Even though suspension geometry programmes will happily calculate this for you, I strongly advocate measuring it yourself. The reason for this is it is such an important parameter and it can ruin your day if you get it wrong. So, to this end, I always advocate measuring damper / bar vs wheel displacement. When you have done all this, you should wind up with something like that shown in figure 3. The key thing to note as you
Figure 2: suspension geometry measurement sheet
are measuring this up is to have something like Excel open and to plot it as you go. What you want to avoid is any inconsistencies or sudden spikes in the measured data. If you find you have any, this is your cue to re-measure the motion ratio. Another matter I want to
touch on is the situation when you have incomplete engine data. This is a bugbear, but one there are a few simple workarounds for:
• Put the car on a rolling road dynamometer
• If you have only peak power and torque values, talk to an engine builder / tuner. I can speak from direct personal experience that they are very susceptible to flattery and nice wine / beer
Fig-3 – Plotting motion ratios. 70
www.racecar-engineering.com • February 2012
The key is to obtain something representative. While it is not
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