Now we have to square the car up on the DCMS. Once the car is square and at ride heights w
D.Rear steer. Another very detrimental effect of chassis dive and roll is rear steer. We can usually tolerate small amounts of rear steer, but larger amounts will cause unstable handling that can't be corrected with normal setup changes such as spring rates, weight distribution, and moment center changes. Rear alignment is very important.
E.Camber change. The fixture can measure static and dynamic cambers and provides a view of the change in increments. It's widely accepted that there should be minimal camber change in order to provide the most stable grip characteristics. Modern soft spring setups yield high amounts of camber change and we need to know where the cambers end up at mid-turn.
F.Caster split. The caster for each front wheel can be measured and tracked through dive and roll to where it ends up at mid-turn. With teams using Anti and Pro dive in the frontends, each will cause caster changes and we need to know where each side is going in order to end up with the caster split needed to suit the tracks we are running.
How It All Started The DCMS took 18 months of engineering and creative thinking to dream up. The idea originated with Sonny. "I first had the thought to do it, but I was just over matched mechanically," he says.
The DCMS takes data from a multitude of different locations. You have the plate mounted on
He then turned to the company's systems design engineer Paul Dionne. Paul used his mechanical engineering background to design the machine. They use 18 linear variable differential transducers (LVDT or potentiometers) to measure the various points that make up the frontend geometry. These transducers measure accurately to 10 microns. To give you an idea to how accurate that is, this dot (.) is approximately 1/64-inch wide and equals 615 microns. Now think how accurate your caster, camber, Ackermann, bumpsteer, and moment center could be if you knew the technology you were using was accurate to 10 microns.
From there, the other owner of CCI, Sonny's sister Denise, wrote the software that uses the points that the LVDTs produce and converts the data into the readouts for all of the aspects of frontend geometry.
The DCMS accomplishes this by measuring and recording the location of the upper and lower ball joints and the chassis connections for the control arms. The process starts with measuring the points when the car is at ride height. Then the program moves the front suspension from ride height down through a range of motions to full compression. This will allow you to be able to see exactly how your front geometry changes throughout your travel.
Gathering data for the right front upper ball joint involves taking three measurement poin
One of the most valuable pieces of information is defining where your moment center is located. The moment center's location is crucial to how well your car handles. It does all of this without having to remove the engine from the car. This makes the time you can spend on the DCMS extremely valuable. Don't confuse this process with the normal pull-down rig. A pull-down rig will bring the chassis down and show you how the car is traveling. This process will move the chassis using hydraulic actuators. This allows them to stop at precise positions to retake the measurements.
The DCMS will also show you what your camber curves are. You can see from our final run on the DCMS, that our camber curve on the right front actually gains a ton of camber when it reaches full compression. We always knew that we were gaining a few degrees but we never knew we were getting close to 10 degrees of camber at full compression.
The idea is to show up at the racetrack with a car that is as close to perfect as it could be, since normal Saturday night races give less than an hour of practice. Races are not won during race day, they are won with the preparations leading up to the race. The better you can show up at the racetrack, the less you will have to tune on the car to make it handle. You should be fine-tuning your setup at the racetrack, not making wholesale changes.
The DCMS software program calculates all of the frontend geometry settings based off X, Y
Here is our first chassis report off of the DCMS. We noticed right off the bat that our ca
Now we need to fix our problems. The caster split we can fix by moving our caster slugs in