Analysis of the Efficiency of a Hypercar Gearbox

Abstract

The performance of a transmission is instrumental to the performance of a vehicle’s
powertrain. In the hypercar industry, where lap time performance has a larger influence on the design of vehicle components than in normal vehicles, the impact that the transmission has is further emphasized. One key parameter to understand and model is the efficiency of the transmission, which affects acceleration, cooling requirements and top speed.

This thesis analyzes the efficiency of a new Seven Clutch Transmission (SCT). With
the use of seven clutches, the compounding effect and layout of the SCT offers significant improvements in terms of packaging compared to other transmission solutions but with no compromise in shifting response time. This thesis analyzed the SCT using two tools; the CAE-tool KISSdesign and a self-developed model written in Python.

Standards for speed-and load-dependent losses for gears, bearings and seals were implemented. ISO/TR-14179-2 was used for speed-dependent gear losses and seals, the
SKF-efficiency-method was used for bearing losses and Niemanns friction estimation
was used for load-dependent losses of gears. The losses from the clutches were implemented based on previously established models by Pahlovy et al. The Python-model aimed to analyze a simplified layout of the SCT, whilst the KISSdesign-model aimed to recreate the SCT as close as possible.

The models were compared with real tests that were performed prior to the project’s
initiation. Due to some values concerning the oil flow to gears and clutches being unavailable for this project, estimations had to be done. After some scaling of the initial oil flow parameters in the two models, relatively large convergence could be found between the KISSdesign-model and tests, approximately 2-3% deviation from the test.
The Python-model indicated relatively decent convergence with tests, but, as expected, not as close as the KISSdesign-model, approximately 2-5% deviation from the test. This thesis also highlighted that further understanding of oil flow is necessary in order to more accurately predict the speed-dependent losses. The results also identified trends in terms of efficiency between the different gear speeds, which roots back to the fundamental transmission layout of the SCT

Popular Abstract

Changing gear, that’s it? No, not at all. The vehicle’s transmission does much more than that.
It plays an instrumental role in the performance of the car, especially if the car in question is a
hypercar. The hypercar industry represents the peak of road legal car performance. To reach the
highest top speed and acceleration, the transmission has to be efficient. When new transmissions
are introduced to the market, like the Seven Clutch Transmission (SCT), it’s crucial to develop tools
that can analyze the efficiency of the transmission fully. The software KISSdesign and a Pythonscript were used to predict the efficiency of the SCT in this project. The models proved to be able to
estimate the efficiency within 2-5 unit percent from reality, and also identified some very interesting
traits of the SCT.

• author: Nilsson, Ludvig
• supervisor: Rikard Hjelm
• organization: Machine Elements
• course: MMEM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• other publication id: LUTMDN/TMME—5012—SE
• language: English
• id: 9151252
• date added to LUP: 2024-05-06 13:30:25
• date last changed: 2024-05-06 13:30:25