Redesign of the Test Bed for the SISU 420 DWRIE Diesel Engine A study on structural redesign, safety, and vibration control of an educational engine test bed using static and dynamic analysis
Royes Molto, Irene (2025)
2025
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https://urn.fi/URN:NBN:fi:amk-2025061222720
https://urn.fi/URN:NBN:fi:amk-2025061222720
Tiivistelmä
This project is focused on the redesign and structural analysis of the SISU 420 DWRIE diesel engine test bed, located in the Technobothnia laboratory in Vaasa, Finland. The main goal was to improve the test bed’s mechanical stability, safety, and vibration isolation to ensure better engine testing conditions.
Using CAD tools, a 3D model of the current setup was developed, followed by static and dynamic simulations. The static study confirmed that the current structure is strong, with a Factor of Safety (FOS) of 7,2, well above the minimum accepted value of 1,5, showing that the structure is robust and over dimensioned. However, vibration tests revealed poor isolation performance, especially in the transverse direction, where values as low as 6,21% were recorded at the mounting point MP4-Y.
Further analysis identified dominant excitation frequencies at 15 Hz and 30 Hz, corresponding to the engine’s first and second orders. Rubber mounts with limited static deflection (around 5 mm) proved insufficient for isolating low-speed vibrations. As an improvement, AMC Mecanocaucho 125 spring mounts were selected based on their favourable properties (17 mm deflection and 96,1% isolation). Although not yet installed, the technical and economic feasibility of the solution was evaluated, with an estimated total cost of 183,09€, including materials and labour.
Fatigue analysis of the welded joint between the upper and vertical beams confirmed a low dynamic bending stress (0,466 MPa), placing the structure in the infinite life range under current conditions. This indicates no significant risk of fatigue failure.
In summary, the proposed redesign offers a low-cost and effective way that could lead to more accurate measurements and improved test reliability. This work provides a step-by-step methodology that can be adapted to other engine test beds. Future work should include installing the new mounts, performing real-condition tests, and completing a torsional vibration analysis once more engine data becomes available.
Using CAD tools, a 3D model of the current setup was developed, followed by static and dynamic simulations. The static study confirmed that the current structure is strong, with a Factor of Safety (FOS) of 7,2, well above the minimum accepted value of 1,5, showing that the structure is robust and over dimensioned. However, vibration tests revealed poor isolation performance, especially in the transverse direction, where values as low as 6,21% were recorded at the mounting point MP4-Y.
Further analysis identified dominant excitation frequencies at 15 Hz and 30 Hz, corresponding to the engine’s first and second orders. Rubber mounts with limited static deflection (around 5 mm) proved insufficient for isolating low-speed vibrations. As an improvement, AMC Mecanocaucho 125 spring mounts were selected based on their favourable properties (17 mm deflection and 96,1% isolation). Although not yet installed, the technical and economic feasibility of the solution was evaluated, with an estimated total cost of 183,09€, including materials and labour.
Fatigue analysis of the welded joint between the upper and vertical beams confirmed a low dynamic bending stress (0,466 MPa), placing the structure in the infinite life range under current conditions. This indicates no significant risk of fatigue failure.
In summary, the proposed redesign offers a low-cost and effective way that could lead to more accurate measurements and improved test reliability. This work provides a step-by-step methodology that can be adapted to other engine test beds. Future work should include installing the new mounts, performing real-condition tests, and completing a torsional vibration analysis once more engine data becomes available.