Chuck's Jaguar D Type Build

Shift Knob

Some details set off a reproduction more than others. Like the shifter knob. The original had a simple turned aluminum knob screwed onto a steel shaft.

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Reproduction D Type shifter knobs are available from several British suppliers. We got ours from Moss Motors. Part # 37-0311. https://mossmotors.com/shift-knob-replacement-for-any-thread-on It set us back about $100.

The knob requires 5/16”, 18 TPI, on a 7/16” steel rod. Therein lies the problem. Unable to find a proper shifter rod we put the lathe to use and learned how to make threads. After couple of less than perfect results to start with, the last was spot on and came out great. We now know how to cut threads. (Ryan is a great teacher).

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The bottom of the shifter rod will be welded to a flat plate bolted to the stub on the top of the transmission, but determining the exact length will need to wait until work on the interior moves forward.

Now back to the Carbon Cub project.
 
Oversteer. Oversteer occurs when the rear end swings out farther than intended as rounding a corner.

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Current design practices incorporate aerodynamics that generate substantial down force and wide rear tires to minimize the effects of oversteer. That technology was not yet developed when the Jaguar D Type was winning Lemans in the 1950s. Indeed, the D Type suspension sets high and resembles an airfoil which aggravates the issue.

The D Type’s vertical stabilizer may provide directional stability at high speeds similar to what virtually every airplane uses. The issue for consideration is whether that fin can also be utilized to provide improved tracking on high-speed turns.

When landing an airplane in a cross wind the pilot turns the ailerons into the wind causing it to track with the runway at an angle, called ‘crabbing.’ To align the airplane with the center line opposite rudder is applied, called ‘cross controlling.’ The same concepts can be applied to the D Type.

The plan is to add a rudder to the vertical stabilizer which would be integrated with the steering. Note, however, that when going around a corner the rudder would turn in the opposite direction of the turn, the same as a pilot cross controlling to maintain directional control. The addition of the rudder would counteract the oversteer tendencies permitting higher cornering speeds.

The rudder (tinted red) would ideally be extended downward to match the contour of the rear, but doing so would interfere with the function of the boot door.

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The rudder will be fabricated from fiberglass laid over a foam core following standard practices. Aircraft style control surface hinges can be used. Control horns at the base of the rudder will connect to 3/32” cables extended into the rear clip. The control cables will be connected to a Garmin autopilot servo. A sensor connected to the steering wheel shaft will provide the input to the servo. Alternatively, a yaw sensor, common on aircraft, could be used but this would require more complex programming. Once these components are sorted the actual installation will be straight forward. Indeed, the servo could be programmed to control the amount of rudder application based on the steering wheel angle to optimize the anti-over steer for a specific radius turn.

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There are a few details remaining to be sorted. We will post updates as research and development progresses. These images capture the overall effect.

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