Originally Posted by John St.Amant
I've been doing this for almost 30 years now and changing the ratio of the length or the upper arm and lower arms including the angle of the upper arm effects the ROLL CENTER. What ever effect you may have described is in fact a ROLL CENTER change. Raising the roll center make the wheel camber gain and lowering it does the opposite. And I AM John St.Amant thank you.
I may resemble your remark, but concidering the source....
remember some values are absolute and usually refered to as positive when it is actually and commonly not refered as a negative value.
First let me apologize for my remark, Mr. John St Amant. That was very immature of me to drop to that childish level. For two individuals to successfully communicate, one has to remain in the adult mode for successful communication.(Deltac Customer Relations) With that being said... The following is a quote from a Circle Track magazine article on roll centers and an interactive software that determines the roll center they where reviewing. I will not publish the whole article here on this forum as it is quite lengthily but I will attach the link so you can read the entire article at your leisure. Instead, I will only post the section about measuring the suspension points and what effect changing those points have on changing the roll center.
"It's important to look at the control-arm angles which will determine the roll center location height and width (both static and dynamic). To reposition the roll centers, we must change these control-arm angles. For example, if we increase the right upper control-arm angle and/or decrease the left upper control-arm angle, we will move the roll center to the right from its original position. If we increase both the upper control-arm angles, we increase the roll center height.
The program calculates the tire camber angles after the chassis dives and rolls, and the kingpin angles of our spindles. Making changes to the upper control-arm lengths affects the amount of tire camber change when the chassis dives and rolls.
As I said in my original post, changing the length of the upper control arm does not change the roll center. It only changes the camber gain. To change the roll centers you must change the angles of the control arms relative to a horizontal flat plain such as the ground or in the case of pan cars, the chassis.
Additionally, since we are sharing experiences, I started racing radio controlled cars in 1979 with an Associated 12E. From 1976 to 1981 in addition to racing RC cars, I was also a part of a Mazda race team. In 1978 we won the SCCA national championships in B sedan at Road Atlanta. Because of that win, Mazda gave us a full factory ride for 1979 and 1980 and gave us two new, full tube chassis RX7’s that where fabricated by Huffaker Engineering. We campaigned these cars in both C production in SCCA and selected IMSA endurance races in GTU (Daytona 24hrs, Sebring, Riverside Times Grand Prix, etc.). My main responsibilities on the team, among others, where for the drive train and rear suspension. I also did fabrication and the fuel catch can for long races.
Mr. Cochran says that the movement of the suspension on a 1/12th car is so little, we common racers would probably not feel the difference of a roll center change. He is correct and I have been told many times by fellow racers that the real world does not apply to toy cars but… I still say that basic geometry and physics apply across all worlds.
So being that we both have considerable knowledge about race cars, we should be able to have adult discussions about said subject. I look forward to future discussions with you.