BrianW
Well-Known Member
For several years, I owned a C-150 formerly used by Spartan - Tulsa for training.
The overhaul engine in it had chrome cylinders and was remarked on for its smoothness.
I supposed that Spartan would have used vibration analysis in the course of training A&Ps.
I needed to smooth minor prop chips once or twice over the period of ownership.
I noticed that Vibrometers go for $150 - $2000 so I looked for a homebrew.
As it turns out, 3 axis accelerometers with analog outputs are now available at attractive prices.
ADXL335 ~ $15
So far so good. Next was the question, how to display the vibrations in X, Y, Z ?
I settled on a chinezium toy oscilloscope a DSO150 ~ $28
This device displayed the orthogonal accelerations in units of g as desired but lacked a most important facility - a second channel to display a trigger pulse, which I envisioned as a laser pointer and a phototransistor with a ruby colored plastic filter. Although I did not consider the extra cost of a two channel display was warranted for this test, I see that triggering on a sensor trained on a prop blade and adjusting the display speed suitably would indicate the crank angle for maximal amplitude. (I omit the details of connecting the accelerometer to an ethernet socket, so that a regular enet cable can be arranged to remote the sensor into the cockpit, etc.)
The overhaul engine in it had chrome cylinders and was remarked on for its smoothness.
I supposed that Spartan would have used vibration analysis in the course of training A&Ps.
I needed to smooth minor prop chips once or twice over the period of ownership.
I noticed that Vibrometers go for $150 - $2000 so I looked for a homebrew.
As it turns out, 3 axis accelerometers with analog outputs are now available at attractive prices.
ADXL335 ~ $15
So far so good. Next was the question, how to display the vibrations in X, Y, Z ?
I settled on a chinezium toy oscilloscope a DSO150 ~ $28
This device displayed the orthogonal accelerations in units of g as desired but lacked a most important facility - a second channel to display a trigger pulse, which I envisioned as a laser pointer and a phototransistor with a ruby colored plastic filter. Although I did not consider the extra cost of a two channel display was warranted for this test, I see that triggering on a sensor trained on a prop blade and adjusting the display speed suitably would indicate the crank angle for maximal amplitude. (I omit the details of connecting the accelerometer to an ethernet socket, so that a regular enet cable can be arranged to remote the sensor into the cockpit, etc.)