Originally Posted by
terry.sc
The answer is simple, they are found the cars are faster that way. Chassis used to be very stiff, some of the old touring cars had absolutely solid chassis. The chassis development these days means the drivers are given a range of chassis of width and flex, then test them to find out what's faster. It doesn't matter what either full size or small scale setup theory says, if the car laps quicker that's the chassis that will be on it.
Just look at chassis layout, the early touring cars had the electrics down the centre with perfect side to side weight balance, by it this meant a layshaft up above the motor. Now most of the cars have the heavy motor tucked into the left rear corner of the chassis with the battery a lot further forward on the other side. This is totally against any dynamic theory, but as they are faster because the layshaft is around 25mm lower that's what we use.
Thank you for the response. I am still looking for the engineering reason why the cars are faster with a flexible chassis. If it's because it lowers the roll stiffness of the front or rear, then why not run a super stiff chassis and then just lower the roll stiffness by softer springs and/or softer ARB's? I can understand that, I just don't understand why you want to decrease the roll stiffness using the chassis. I understand it on a kart because they don't have suspension, but we have a darn good suspension on our RC touring cars. I would love to do some testing with a top notch driver that can run consistent laps using his best setup with a flexible chassis. Then stiffen the heck out of the chassis and re-adjust the springs/ARB's to obtain the same results. Maybe it's not possible, but I'm betting that it is. I'm only skeptical because of all the tribal knowledge that seems to exist in RC racing. It reminds me of the guy at one of our local dirt tracks that showed up with helium in his sprint car's wing. He was the fastest driver and by the next week everyone was running helium in their wing. At least it was good for helium sales that week. But nobody went as fast as the same guy because that guy was the best driver. The helium was just noise. The other issue we run into is determining what is a real gain and what is just natural variance. I liked Mark Donohue's book, The Unfair Advantage. Mark said if you make a change, make a large change so you can tell the real difference.