Here's the full version of TRE's video of this tarmac rally car on their 7 Post shaker rig:
TRE Dynamics are technical partners with Ohlins DTC, Germany.
You can see in the video, the shaker rig forcing vibrations in the suspension. About half way through, they show you a "track replay". The actual suspension movements from the track are reproduced.
Best dynamic grip comes from minimizing the tyre load variation, minimizing disturbance, minimizing vibration at the tyre contact patch. (Note the difference in shaker rig testing for road cars. The required set-up will be a compromise between ride quality - least disturbance for the driver and passengers - and best grip - least disturbance at the tyre contact patch.)
To minimize disturbance at the tyre contact patch, you need the required "natural suspension frequency" or "suspension frequency", as we regularly call it.
The "natural suspension frequency" is the vibration of the suspension...
Weight Transfer Part 3: How Does the Driver Control the Race Car?
This is the final part in our “Weight Transfer” series. See Part 1 and 2 home page /blog
Summarizing what we discussed in Parts 1 & 2:
Nowadays, “weight transfer” thinking is commonly used to describe what the racing driver is doing. The driver is said to manage or control the weight transfer. The “rate of weight transfer” is considered important. And as discussed in Weight Transfer Part 2, the driving coach Rob Wilson talks weight transfer almost exclusively when he describes what he is teaching to drivers.
Talking “weight transfer” with respect to race driving is a fairly recent phenomenon. Most of the authors of books on handling don’t talk about weight transfer in the context of the driver controlling the car.
My major sticking point with weight transfer thinking is that drivers cannot feel...
What do these three F1 racing drivers have in common? Kimi Räikkönen, Valtteri Bottas and a young Nico Rosberg (when he drove for Williams in 2006).
They’ve all been coached by Rob Wilson – “the F1 drivers coach”. He’s also coached many other professional drivers, racing in just about every pro racing series around the world.
Rob knows weight transfer. Most times, when he is talking about driving, he’s talking about weight transfer. He says that “the rate at which you transfer weight”, is just about the most important thing you do in a race car.
For a quick look at what he does, check out this video with Formula E driver, Karen Chandok. It shows Rob's great sense of humor as well:
https://www.youtube.com/watch?v=r3uBhntzrtU
2017 Belgium - Rob Wilson Driving School
Rob is teaching smooth introduction of the steering brake and throttle so as to maintain maximum grip. From that...
Racing drivers often talk about weight transfer – weight transferring forward under brakes, rearward under acceleration and from inside wheels to outside wheels when cornering.
Weight transfer concepts are hugely important in suspension set-up. Weight transfer across the car in cornering, is the basis of the most important tool we have in suspension set-up – using weight transfer distribution between the front and rear axles to adjust the balance of the car. But the driver is unaware of the weight transfer distribution itself - only the feel of the car resulting from the balance adjustment.
Weight transfer is the result of acceleration, braking or cornering. If you accelerate, brake or corner harder, you transfer more weight.
For weight transfer to be useful to the driver in controlling the car, the driver would need to feel the weight transfer, or something related to it.
Weight transfer in pitch and roll is just weight transfer coming off...
The "Virtual Model" of the car is built in software known as Multi-Body Systems Software (MBS). In my view, the success of MBS modelling, and particularly the driver in the loop simulator, is affirmation that the nature of handling and the driver's task can be best understood with the application of some basic vehicle dynamics principles.
The motion and feel of the vehicle is governed by the forces generated between the tyres and the road. So, in order to "drive" the virtual model, engineers have developed mathematical models, the so-called "equations of motion". Tyre forces are calculated in cornering through an estimation of the vehicle sideslip angle and a related tyre model for the vehicle in question.
First up, we should highlight the difference between the algorithms used in high end racing computer games and...
These simulators use software based on the mathematics of Classical Vehicle Dynamics.
The "Virtual Model" of the car is built in software known as Multi-Body Systems Software (MBS). In my view, the success of MBS modelling, and particularly the driver in the loop simulator, is affirmation that the nature of handling and the driver's task can be best understood with the application of some basic vehicle dynamics principles.
First up, we should highlight the difference between the algorithms used in high end racing computer games and virtual prototyping of real cars. The racing game only needs a life-like experience for the driver within the racing game. The virtual prototype represents the build and response of the real car. The driving experience in the simulator must transfer to the real car, for the virtual prototype...
What Car Would You Choose to Drive? For me, I’d like to drive Andrew’s superb Triumph TR3A Group SA historic production sports car.
In historic production car racing, it’s all about the cars. That’s where the passion comes from.
But they’re not only there to look good. The cars have to go fast, and race pretty hard as well.
Pictured is Andrew Gibson’s Triumph TR3A Group SA Historic Sports Car. He’s raced at race meetings throughout NSW and Victoria for almost twenty years now - always immaculately presented, just like you see here. On a bright sunny race day, in the pits, it’s a magnet for lookers and photographers alike.
It’s Australia’s fastest ever side-screen TR in historic racing.
We started working with Andrew in the year 2000. The car was hugely responsive to suspension set-up improvements and by 2001, he was getting class and overall race wins in Group Sa and combined...
What’s wrong with taking the car out and seeing what it can do?
Problem is, you probably won’t learn anything. If it’s fast or slow, you won’t know why. You won’t know how to address any of the handling issues you experience with the car.
Most times, testing the car straight off is sure to disappoint.
Much better to do your homework first. Just like James has done, and delivered such staggering results last weekend.
In the 60's and 70s, we had no idea. We'd give the car a wheel alignment and that's it. We'd drive the car as it was given to us by the factory or previous owner.
Today it is very, very different. We can engineer the changes to the car, and have the performance unfold before our eyes. I can't tell you how stark the difference is, in my experience.
One thing hasn't changed however:
Never...
What do we do most times when buying aftermarket springs for our race or road performance car? We depend on advice from our supplier or our car builder. Or we might talk to our competitors, maybe check out the forums, to see what others with our brand of car are using.
There are so many different views. Some may feel it doesn’t matter that much, what springs you use. Others may think softer springs are better; “I’ll settle for the 8kg/mm spring rather than the 10kg/mm for XYZ...
In Part 1, we established how we might select springs and anti-roll bars using the Racing Car Technology Weight Transfer Worksheet™ (WTW). We can choose the springs and anti-roll bars by trying different spring rates and anti-roll bar diameters in the spreadsheet, to come up with the Suspension Frequency, Balance and "Roll rate" we want.
In Part 2, we'll look at some of the finer points of selecting anti-roll bars.
As long as the car was balanced, stiffer ARB’s would always be better for grip, wouldn’t they?
In terms of roll stiffness, yes. In principle, we can never have too much roll stiffness, as long as the car is balanced' (See Selecting Springs and Anti-Roll Bars - Part 1)
The problem is, with very stiffer ARBs, the stiffness difference between front and rear of the car is dissipated in the torsional twist of the chassis. We could make a change to the anti-roll bars, and nothing...