QFR18 Tech: Sprocket optimisation

In motorsport, drivers, engineers and team owners all have one ambition – to be as fast as possible. Formula Student is no different and in many cases, it is the first experience students will have of this need to go faster.

Queen’s Formula Racing tasted success last year in the acceleration event but has only added fuel to the ambition of doing better in other events in 2018. A key goal for QFR in 2018 has been to build a car with a mass of 200 kg. Several components around the car have been redesigned this year to try and build a car as lightweight as possible. Final-year student, Sean Le Ng, took on one of the optimisation projects after the exam period ended.

“I optimised the drivetrain sprocket to achieve a lightweight, high stiffness and high strength component which had to withstand the driving load from engine,” explained Sean. “The function of the sprocket is to magnify the torque from the engine to the drive wheel by reducing the sprocket rotational speed in correspondence to engine speed.”

Not only does a reduction of the sprocket’s mass reduce the car’s mass but it also reduces the component’s moment of inertia while rotating at high speed, which in turn reduces the stress on the sprocket’s carrier too.


A total of 500 g was saved through the optimisation, from around 1100 g to 600 g, almost a 50% mass reduction. This optimisation was achieved using Abaqus FEA software which is taught in third and fourth year at Queen’s University Belfast.

“Input forces were required to run the FEA in Abaqus,” said Sean. “They were calculated from engine’s maximum torque during engine testing on QUB’s dyno.”

“A 20 mm restrictor was used to get a torque value at 1000 rpm intervals. Then, the maximum engine torque measured was used to calculate the torque at rear sprocket.

“Using the gearing ratio and sprocket geometries the input forces at the sprocket pinholes were found.”

Follow QFR on Facebook, Twitter and Instagram to see regular updates on the QFR18 build and test programme as more projects like this are added to the car.

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