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Here a rear lower arm is being welded up in this simple jig. All of the A-arms are made from this elliptical cross section extruded steel tube. This is super cool open wheel car stuff.
The completed lower arm attached to a Ginetta upright for mock up purposes. Using Ginetta uprights is an example of how the designers were resourceful and kept the costs “low”. Designing and machining uprights from scratch would have been far more expensive than using off the shelf parts and making them work.
Another cool feature about these uprights (and most other race car uprights) is that shims are used for camber adjustment. While not its intended purpose, the scrub radius can even be finely adjusted with a combination of spacers at the front within the limit of the CV joint extension of course.
In this shot of the front suspension, the section where the OEM sheet metal was cut out is clearly visible. The sheet metal that makes up the wheel well was boxed in and tied into the cage with tubes. There was extensive work done to the OEM frame rails to prepare them to have A-arms mounted in them. Notice that caster can be easily adjusted with swapping washers from the left to the right of the rod end spacers. Where there were arms from the factory (i.e. lower arms in the front), the pick up points for these new A-arms are within 1″ of factory. Since there are no upper arms at the front of an EVO on McPherson struts, the new upper A-arm pick up points were optimally placed.
That large cylindrical puck at the top of the damper is a load cell that was borrowed from a grain silo application. Rather than using shock travel sensors that produce no further data once the suspension is on the bump stops, load cells were used to record an actual force measurement at the top of the shock. Then by using math channels in Motec's I2 Pro software calculated by the suspension's movement ratios and the spring rate, both the amount of theoretical suspension travel can be displayed in I2 as well as the amount of aerodynamic downforce at any speed.
