Fan-Mount Bracket & Modal Analysis, Raghav Singh

A ceiling-mounted fan was raised out of an elevator car roof to cut cabin noise, which meant designing the sheet-metal bracket that carries it. Because the bracket holds a running fan, the design question was not only whether it is strong enough but whether the fan can shake it, so I checked it against the fan's own excitation frequency.

Design & analysis data
Part	Sheet-metal fan-lift bracket, 50 mm and 100 mm variants
Excitation	Fan at 2,050 RPM, about 35 Hz
1st mode	2,310 Hz (50 mm) · 1,230 Hz (100 mm)
Separation	>35× above excitation, no resonance risk
Analysis	Modal, 4 modes, 3-hole constraint · Creo Simulate
DoE	Taguchi orthogonal arrays + improved Latin-hypercube sampling; ~70% fewer test runs
Output	Production drawings + flat-pattern DXF for fabrication

Engineering decisions

The real risk was resonance, not static strength. A bracket carrying a running fan can be shaken apart at a fraction of its yield load if a natural frequency sits near the drive frequency. That made modal analysis the governing check, not a stress plot.
The result is a frequency margin. First mode at 2,310 Hz against about 35 Hz excitation is more than 35× of separation, so the fan cannot drive the bracket into resonance. The 100 mm variant, longer and more flexible, still clears it at 1,230 Hz.
Stiffness added where it counts. Flange walls along the bends raise out-of-plane stiffness, the direction that sets the first mode, without adding a heavier gauge across the whole part.
Designed to be built. Every bracket left as a production drawing and a flat-pattern DXF, ready for sheet-metal cutting and bending, with a DoE that cut the validation test matrix by roughly 70%.