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MV Chetzemoka Ferry Air Vent Pipes I recently rode on the MV Chetzemoka Ferry which was running between Tacoma’s Port Defiance and Vashon Island’s Tahlequah terminal. The ship is powered by a pair of EMD 12-710 diesel engines rated at 3000 hp each at 900… Read more

Matlab’s built-in function for Butterworth filtering has stability issues. The following code snippet yields an unstable filter. The cutoff frequency is 4 Hz. The sample rate is 20000 Hz. The filter is a high pass, sixth order. fh=4;sr=20000;order=6;Wn=fh/(sr/2);[bb,aa] = butter(order,Wn,’high’);flag = isstable(bb,aa);if(flag==1)fprintf(‘\n filter is stable… Read more

The aircraft is a De Havilland Canada DHC-3 Otter, Single Engine, Seaplane. It is powered by a Pratt & Whitney R-1340 Wasp, 600 hp, air cooled, radial engine with a propeller hub speed of 2250 rpm (37.5 Hz). This aircraft is used for tours and… Read more

Teeter-Totter, Playground along Riverview Blvd, Kent, Washington State I gave the teeter-totter an initial displacement, without human riders, and recorded the damped sine oscillation with my Android smartphone accelerometer app. The natural frequency was 2.1 Hz with 0.6% damping. The frequency would decrease with riders.… Read more

My family and I recently took the Argosy Lock Cruise from Lake Union, through the Hiram M. Chittenden Locks, to the Seattle Waterfront, aboard the Goodtime III. The ship’s main engines are Caterpillar 3408’s coupled with Twin Disc MG514 reduction gears. Auxiliary power is supplied… Read more

This is my current vehicle. With the car parked, I opened the hatch door and sat down on the cargo compartment floor facing outward with my feet on the ground. I then used my legs to move my gluteus maximus up-and-down a few times while… Read more

I recently exercised on the treadmill at Rachel’s Body Shop Gym with an inclination of 3% and a speed of 3.6 mph. I measured the resulting vibration with my Android Smartphone which was mounted against the console screen. My footfall or step frequency was about… Read more

The orange block near the seat post is a Slam Stick X accelerometer. I recorded the frame vibration as I rode the bike over a gravel road adjacent to the Green River in Kent, WA at 10 mph. The time history and power spectral density… Read more

Pedestrian tunnel below Hayden Rd, Scottsdale, Arizona The tunnel is north of Indian School Rd & south of Camelback Rd. It is connected to the Indian Bend Wash which has a series of parks and a golf course along its length. The tunnel is about… Read more

This is the spectral analysis of the refrigerator in my allergist’s office that stores the allergen doses, as measured with my Smartphone. Spectral peaks occur at 60, 129, 133.5, 267, 401 & 641 Hz. The 133.5 Hz peak has integer harmonics at 267 & 401… Read more