The Ford GTs of Robertson Racing


Speaking of the engine being at the back on the Ford GT, you would think that the front would then be the convenient and logical place to mount the fuel tank. You would be partially correct, as what you see here is only the filling port. On these cars, the fuel cell is actually located in the center and at the bottom of the chassis and runs almost the entire length of the car. Mounted low and in the middle, this helps to ensure that the center of gravity and the polar moment of inertia stays almost the same no matter what the fuel load is. When carrying a maximum of 108L of fuel (28.6 gal), the change in fuel weight from full to empty is almost 200lbs! When the team first started, they ran E100, but later switched to E85. Why the change? Engineering and gaming the rules.
ALMS and the FIA have very, very specific rules for not only fuel capacity but also things like what size restrictor goes in the fueling rig and how high the fueling rig can be off the ground – and all of these factors are dependent on fuel type. For example, when running E85 the Robertson Racing team was allowed to mount their fueling rig's tank 400mm higher off the ground (~16in). To most sprint racers that don't refuel, that is meaningless. But when you make several pit stops per 12- or 24-hour race, fuel economy and refueling time is a massive concern. After lots of calculations and rulebook spelunking, H and the Robertson team determined that E85 actually gave the GTs a competitive advantage, so they switched. Now? The vintage rules aren't as particular, so they just run every-day C16.
Getting into the suspension, things are relatively simple. Öhlins 4-way (!) adjustable shocks are mounted with Eibach race springs at all four corners with a double-A arm. A humongous 1 3/4” (45mm!) tubular anti-sway bar is also employed. Remember that sway bar stiffness goes as the cubic power of diameter – that's pretty big! Every suspension arm is a custom piece, and all connections are made with spherical bearings / rod ends. The wheels are attached via a single lug nut and you can see the carbon brake duct as well. The spare chassis is actually mounted on a rotisserie, which makes it extremely easy to flip the entire thing upside down or perpendicular to the floor for easy access to just about every nook and cranny.
The brakes, too, are relatively simple. Approximately 15” front and 14” rear rotors are sandwiched between massive 6- and 4-pot Brembo calipers, respectively. With approximately 110mm of space between the pistons, each brake pad is almost 30mm (1.18”) thick. During the 24-hour LeMans race, the team only changed the pads once. You might be wondering what the paint stripes on the top of the rotor are for. Each paint color will turn white at a specific temperature, which helps the team quickly know if the rotors may have been overstressed. In order, green, orange and red will change colors at 458C, 550C and 630C, respectively. Not bad for “simple” paint!

Leave a Reply

Your email address will not be published. Required fields are marked *