The design of grommets is critical to the acoustic performance of any partition such as engine bay bulkhead.
- Design Guidelines
- Grommets should be of soft material (natural rubber recommended by a supplier though may not be suitable for high temperature areas) to ensure consistent fit.
- Maximise grommet thickness.
- High contact area to hose/harness, usually involves a sleeve.
- High contact area to panel.
- Grommet should be bonded to hose/harness to ensure good contact.
- Hose/harness should be stress-free in area of grommet (i.e., is not at an angle or forced to one side of the grommet).
- Overlaps acoustic treatment ensuring that no metal is visible.
- For large areas, e.g., heater gaskets, do not use open cell foam, closed cell material provides a much better barrier.
- Minimise size of hole in panel.
- Put form in the panel around the grommet (i.e., a recess) to ensure a flat panel condition.
- Ensure that the holes in the panel are remote from seam sealer, underseal and spot welds.
- Harnesses - Wires bonded together under the grommet
Subjects: Noise & Vibration