I was looking after a lot of the brakes and cockpit components that year, and we fancied taking a look at the pedal arrangement. In F1 you have a funny situation of spending a lot of time designing parts to be a few grams lighter than the year before, and the same or better stiffness. Every year you believe that you have pushed it to the boundary of what is possible and yet the very next year you some how manage to rearrange things to pinch another few grams. In order to really make a sizeable weight saving you have to take chances and go to the extreme. At the time no one on the grid was prepared to take the chance and use carbon for the brake pedal. It's hard to explain why really when most of the rest of the car is made from the stuff.
The pedals on all of our cars had always been fabricated Titanium pieces. If you read my last blog you'll know the processes involved in making fabrications from Titanium. It's very labour intensive and tricky stuff to work with. Carbon provides you with a lot of ways of putting material exactly where you need it, without having to carry around material where you don't need it. You can vary the thickness through the part, you can orientate it differently to get different characteristics, and you can use different cloths and resin systems to get different material properties. The base fibres and resins are also stiff and very light, so ideal for making lightweight high stiffness parts so long as you can design the shape in such away as to physically make it in a mould(s).
Each driver has the cockpit laid out to their preference. So for each driver the pedals were different, shapes, positioned differently in the cockpit, so had side fences on to trap the foot in the pedal, others had a fence on one side but not the other, or like Alesi (picture above) no side fences. In this era the two pedal arrangement was just becoming popular, with the clutch on the steering wheel. Alesi preferred the three pedal arrangement pictured above, and so the brake pedal has no side fences because he needed to move his foot from one pedal to the next. Most other drivers on the grid used left foot braking and so there feet were held into the pedals to prevent them slipping off.
For the spare car you needed to be able to quickly change the cockpit to suit which ever driver was about to jump into it, so we had removable pedal pads that could be swapped over. At Prost the money was an issue and so in the later years we had a lot of different drivers paying for their seat, and each driver needed a new design of pedal arrangement, which drove me mad.
Mid season we decided to experiment and make a carbon brake pedal to retro fit into the car if it was successful. So the pedal set you see in the picture was born. The brake pedal is made in two halves, with a split line in the middle of the front and back faces. The pedal pad was a bolt on arrangement. The layup was varied to give a strong/stiff pedal face and basic neck of the pedal, and thinner in the less well loaded parts. The bottom was solid carbon, which we then machined and sleeved with Titanium, into which the pivot bearings were fitted. There was also a Titanium plate and insert where the master cylinder push rods attached either side. The two halves of the pedal were made so they socketed together and were bonded together.
Like all Carbon parts, you have a lot of things to make before you get to make your final component. You have first to make a pattern, which in this case the two halves of the pedal shape made in aluminium. Then these patterns get laid up with a tooling Carbon fibre pre-preg material, and "cooked" in an autoclave to produce the moulds. Now aluminium expands a fair amount with the heat of the curing process so the patterns have to be made smaller by the exact amount that they will expand. The contraction after curing does help release the patterns from the moulds. One you have the carbon mould tools, you can then make your final brake pedal, by laying up the carbon pre-preg in the moulds, and curing them in the autoclave. These mouldings then go to be machined which often meant making mould shaped jigs so they component could be held correctly whilst being machined. The final part of assembly is then to bond in the Titanium fittings and the two halves together.
Once we'd made the first one and tested it by applying loads to the pad face with an enormous hydraulic test rig we had, we knew that it was both considerably lighter and very much stiffer than the previous Titanium one. On subsequent pedals we were a lot less cautious with our layup reducing weight further. The unnerving thing about Carbon in these applications is that when you first apply the considerable load, the component makes large cracking sounds, as the fibres start to align with the direction of the load. You think it's going to snap, but, after repeated loading cycles it goes quiet. McLaren at the time had very sophisticated sonic measuring equipment and kept track of these noises on all components, and they used it to "life" each part.
Below is a picture of a Coulthard pedal that we went on to design and make for that years McLaren. David was very unsure about using a Carbon brake pedal and apparently took a lot of convincing. Like all things these have become a bog standard item now. In the picture below the two recesses in the pad face take gripper tape, which is essentially like a sticky backed sand paper to give the driver added grip.
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