The rear links we observed were similar to the original Rayburn, but had some strange angl
Our goals for setup are to provide a more balanced car on tight tracks where the level of traction is high, and also one that would provide more bite on the drier surface tracks. Along with the spring layout and roll center locations, we are going to design less rear steer into this car and a little different weight distribution than many racers are used to.
In effect, this will be a CT/Bobby Clark car that will showcase critical design parameters and be used to develop a plan of attack for developing and modifying setups for changing track conditions. The overall goal is to use this car as a teaching aid. We will learn from the experience and we hope our readers will learn through our successes and failures as we go along.
Right now, with the initial evaluation completed, we see the following areas of concern and have noted where we will do some redesign. Some of the evaluation will have to wait for installation of the motor, the new rearend, and front end components. Once we have everything installed, we can weigh the car, measure rear steer characteristics, design and install ballast, and work out the spring setups. Here is a short list of items of concern:
The bumpsteer would have been severe, causing a very unstable feel for the driver as he we
1. The front moment center was not where we wanted it, nor even close to where we knew it should be. A quick measure session and entry of the data into a computer program told us that the static MC was at 0.416 inch high and 25.511 inches to the right of centerline, and at mid-turn attitude it went to 1.635 underground and 44.012 inches to the right of centerline.
This is obviously not what we want. So, with the relocation of the upper mounts, the lowering of the lower ball joints to reduce the lower arm angles, the raising of the front ride height by one inch and the changing of the upper arm lengths, we ended up with a static MC location of 2.351 high and 18.945 inches left of centerline, moving to 3.466 high and 2.531 inches left of centerline after dive and roll. This is where the MC in most Dirt Late Model cars needs to be.
I want to stray from our plan of telling you exactly what changes we made in this case because no two chassis are alike, and for you to make the same changes to your car most likely won't yield the same results. If you want your moment center to be where ours is, measure your car and do the analysis like we did. We ask you to try to learn from the process and not copy the details.
We will also do an Ackermann evaluation at the front to make sure we aren't gaining too much toe as the wheels are steered, and the steering angles must be equal for both front wheels when steering left or right for dirt.
The system that prevents and/or controls rearend wrapup is a combination of two shocks mou
2. The rearend locating design was a combination of pull bar, double shocks, and a "lift" arm with deceleration control only. We will think about this system and tweak it somewhat using a newer style pull bar and possibly removing the mostly unused lift arm.
3. Rayburn cars of this era used a Z-link system at the rear to locate the ends of the rearend. These systems are usually known for minimal rear steer and a motion ratio for the installed spring rate due to the springs being mounted on the forward links. In our case, the links were mounted at severe angles which would produce quite a bit of rear steer. We will remount these links and provide adjustment to the angles, more so than the original car had.
4. Weight distribution in this car was typical of what we see and read in literature published by some manufacturers. The car had about 58 percent rear weight distribution and 55 percent left-side weight with the driver and all gear aboard. There were no provisions to move weight around easily either.
The desired goal for weight distribution is to be able to move weight from the left to the right in the car and up and down. When running on a tacky surface, we would want more weight on the left side and lower in the car. For dry slick conditions, we would move weight to the right and higher in the car.