Development

Second Prototype

For our second test vehicle we decided to build a Sacli suspension system that has double a-arm suspension both for dive and roll suspensions.  This way we were able to better control roll center locations, roll center migrations and camber curves for both roll and dive suspensions.

Based on what we learned from our first prototype testing we located the roll centers for both roll and dive suspensions about the same distance from the CG of the vehicle.  This was a safe approach since it made it easier to predict the reaction of the suspension.  We also set the dive suspension geometry like conventional double a-arm car.  This allowed more camber recovery at dive suspension at a penalty of camber change during jounce.

2nd prototypeThe second prototype suspension system was also fitted to an existing FSAE car.  We used the original uprights since we were using double a-arm design for the dive suspension, much like the original suspension that was on the car.  The steering and rear stabilizer tie rod linkages were made as two stage links to minimize the toe change during roll and jounce, even if the wheels are leaning into the turn.  The steering linkage had to connect the rack & pinion on the bottom of the frame to the pitman arm on its original high location on the upright.  This lead to large angle of transfer between the links and increased the deflection in the system. 

The rear suspension stabilizer bar linkage didn’t face such problems since the original rear upright design had its connecting point at the bottom.  On the other hand the rear dive suspension shocks had some packaging issues and had to be shifted from its ideal location which caused some deflection in the system.

Our second prototype required a lot of welding for the 16 a-arms and 4 center uprights.  On the other hand, four new bell cranks were the only parts that needed machining other than spacers and etc.  The car weighed just over 500 lbs and had about 45/55 front to rear weight distribution.

2nd prototype rearview