Bicycle Mobility
Light weight, feeling solid, nimble, what other sensation would you like your bicycle to exhibit? Perhaps silence would be welcome too when cruising in nature; the absence of whines, rattles and tones. There is quite some effort behind achieving such qualities. Detailed numerical models and elaborate testing are required to be able present a mobility product with a sense of quality. Qsources is supporting the process of developing and controlling refinement with sound sound sources and shakers which allow both accurate and efficient measurements.
Today we see a variety of light weight mobility devices; scooters, one wheeler’s, cargo bicycles, and speed pedelec’s. All balancing costs, light weight and quality. The Qsources shakers and sound sources help refine these products.
Some applications
Electro-motor integration
Even with refined motors there is not just residual noise radiation directly from the motor. The wheel, the frame and the gear set are all well coupled to the motor. Unfortunately the rear of the bicycle frame is light and flexible. Depending on their frequency and the direction of the interface forces, the vibrations are easily transferred into the frame. But even crank integrated motors make the frame vibrate slightly, possibly enough to let the light weight frame radiate noise.
Contribution analysis on the airborne effects (ASQ) and on the structure borne effects (TPA) can diagnose the situation, show which parts are radiating mostly. But it can also provide meaningful requirements for the motor, the bearings, the wheels, the frame…. Furthermore the loads and measured transfer data can be used to improve the numerical models.
Some shakers for TPA type of measurements on bicycles :
Some volume sound sources for contributions analysis on bicycles and motors:
Resonances and stiffness
The frame and wheels and cranks and seat and other components all have stiffness requirements. Mostly analyzed based on numerical (FE) models. These are best verified in order to improve them. Especially as for example the seat pin to frame interface is involved. Or if, for example, the carbon lamination process in production has to be controlled.
Beside the static measurements, experimental modal analysis (EMA) will help to assure model quality or assure effective stiffness of the components. Either combined with laser scanning of the surface vibrations or combined with small accelerometers.
Depending on size and weight of the components the following shakers provide a solution for accurate and efficient measurements:
Demonstration (Link to video)
Electro-motor direct airborne noise
To determine the sound power emission is best done on a test-bed, with a well controlled load and very high structural impedance supports of the motor to prevent secondary noises.
Such a set-up will not resemble a acoustic free-field, nor a reverberation room. So using sound pressure will not provide a good measure of the actual noise emission of the motor. The small Qmir sound power reference source presents the most practical way to measure the sound power emission on a motor test-bed.
All described measurements also require software and sensors, of which several are available in the market. Depending on the exact application our partners,
Polytec, Siemens, Head acoustics
All propose leading full chain solution including the Qsources excitation sources and shakers
