Simulation
McLaren MP4/4 Gearbox Dynamics and Fatigue
Senna's 1988 Monaco qualifying lap resimulated with the full McLaren MP4/4 6-speed sequential gearbox modelled using MUTANT, computing gear transmission error, dynamic stress histories, and remaining useful lifetime through rainflow counting and Miner's rule.
Links & Resources
The Gearbox
The McLaren MP4/4 used a 6-speed sequential "constant mesh" gearbox: gears on the layshaft are machined or splined to the shaft; gears on the main shaft ride on needle bearings and engage via dog rings. Not included in the animation are the bevel gear stage to the differential and the transfer gears between engine and layshaft used to adjust overall ratios per circuit and weather condition.
FIA regulations placed no constraints on gearbox configuration or durability in 1988. Modern regulations require a gearbox to last at least six consecutive events, approximately 4000 km or 1200 Monaco laps. The contrast is relevant for interpreting the fatigue results.
Simulation
Engine torque was modelled using a 2D map expressing torque as a function of engine speed and throttle position, with target engine speed held constant at 11,000 rpm. Gear selection was added as a new control variable in the minimum lap time optimizer. Honda's 1.5-litre V6 turbocharged engine characteristics are captured at the level of detail accessible from published data.
The gears themselves were modelled using the MUTANT toolbox, bringing each gear pair down to as few as 2 degrees of freedom while retaining accurate transmission error and dynamic contact stress prediction. At F1 speeds and on a circuit as demanding as Monaco, that computational efficiency is not optional.
Remaining Useful Lifetime
Using rainflow counting of the dynamic stress history at each gear's reference tooth, combined with Miner's linear damage accumulation rule, the remaining useful lifetime of every gear pair can be tracked across the simulated qualifying lap and projected across a full race distance. Starting from a fresh gearbox every race, as was standard in Senna's era, was not a conservative margin — it was a necessity.
Second Simulation
A follow-up simulation placed Senna's 1988 qualifier alongside Leclerc's 2024 Monaco qualifier on the same track model, illustrating the evolution in vehicle and tyre performance across 36 years. Given the model fidelity, this is directional rather than quantitatively precise.