john smith wrote:

Forgot to add that
- the detection boxes were single channel
- the transducers were moved to each axis and the data collected
- the detection boxes had a built in strobe circuit to independently
measure RPM

Ben Jackson wrote:
In article ,
Jim Weir wrote:

I've come across a marvelously cheap vibration sensor that I want to convert
into an engine vibration instrument for a Kitplanes article.


If you really wanted to try to diagnose problems with it you should try
to couple it to RPM. Then you could measure vibration in terms of the
order relative to the moving parts. If you could include the phase of the
crankshaft you could probably spit out enough information to do a dynamic
prop balance on a serial port.

Alternatively you might be able to infer RPM by doing an FFT on the raw
data. That would be a neat party trick.

As far as mounting it seems like getting it as far forward as possible
(where you should see the largest magnitudes) would be good. And if you
only get 2 axes then I'd go with your idea and ignore push/pull and keep
side/side and up/down.

Weeel--kinda depends on whether you got a heavy metal prop, or a piece'o tree
mounted in the prop flange---the gyroscopic inertia of that 40# hunka 'luminum
kinda resists vibrating--I think the assend of the engine would kinda describe a
jitterbug motion around the nose of the crank.--If the prop is balanced, then a
"new" vibration introduced into the system would probably be detected easier
with a rear mounted pickup...'Course a wood prop & a front cylinder goin bad
might change the scenario somewhat. Y'all run a test & let me know!!