The Eunos Roadster we are converting to our MX-5e was an automatic, so it came with a pedal box with just an accelerator and brake pedal. Whilst this is helpful, we are fitting a iBooster and this has a slightly different pattern for the mounting holes. It also has some welded spacers on the back of the pedal box mounting plate, which make it really difficult to modify. We also need a throttle/accelerator pedal that drives a hall sensor, rather than a cable driven throttle body. For these reasons, we are fabricating a custom pedal box.

The MX-5 pedal box is fairly well made but it is quite heavy (2060g) and features some things that we no longer require, such as a spring return on the brake pedal. The actual position of the pedals and pivot points is right for our MX-5e needs though, so we can reuse parts if need be.

The MX-5 brake pedal is a solid piece of steel 6mm thick and it weighs 770g on its own. The pedal pivots on a 10mm bolt with nylon bushes on a clamped tube (55mm long). This works well but we would rather use proper bearings.

To check the positioning and function of the brake pedals, we are designing and 3D printing the components of the pedal box. We started with a brake box mounting plate. We are 3D printing the spacers that sit between this plate and the bulkhead separately as the exact length of spacers required is unknown at this point. We will start with 20mm spacers though, as currently welded to the MX-5 pedal box. It's going to be pretty close to 20mm though, as we measured the distance from the mounting face to the centre of the clevis pivot and it was about 125mm in both cases.

The great thing with 3D printing is that you can design in elements to make the component lighter, stronger and stiffer. Most of these will come later, once we have the measurements correct.