My Ordinary Little Hit & Miss Engine

[Kim]

That is some pretty cool data, I have to agree!
So how'd you instrument your engine to collect all this fascinating data? 
Thanks for sharing,
Kim

[rudydubya]

Kim, nothing unique, but a fun exercise.  Stick a magnet on the flywheel and a Hall sensor with a pull-up resistor close by and record the running data on an inexpensive PC-based oscilloscope.  Then use the recorded waveform to measure the time between revolutions and calculate RPM.  I automated the process with a crude computer program and display.

Regards,
Rudy

[RayW]

Beautiful work Rudy and what a super little engine. Congratulations on a great job.

[Kim]

Thanks Rudy,
Simple yes, but interesting.

You said you had a 1ms sampling rate, but I'd assume your O-scope had a higher sample rate?  Otherwise you wouldn't even have been able to capture the >1Khz signal out of the hall sensor at the higher RPMs. At least not according to Nyquist

Kim

[NickG]

Great stuff Rudy, many thanks.

[Bearcar1]

Well done Rudy! BRAVO! I applaud you for having the gumption to hack together a method to get data measurements. I like it, you did just fine. Sure, there are most certainly more "high-tech" ways of doing so, but to what end? You did well, thank you!

[b.lindsey]

I certainly agree with what has been said Rudy. Seldom do we get to see such a good analysis of engines we have build. I think you may have started a new trend

Bill

[Hugh Currin]

Rudy:

I just caught up on your build, just in time. Marvelous little engine which runs extremely well. I'm surprised you can get that good a coast, particularly using an O-ring. And some instrumentation is just icing on the cake.

Thanks for taking the time to document the build, a very nice write-up. I've enjoyed reading it.

Hugh

[rudydubya]

Thanks everyone, I'm glad you found it interesting.  I've always been intrigued with their operation.

Kim, I didn't have to worry about aliasing.  The one millisecond sampling interval was shorter than the pulse width from the Hall sensor circuit up to about 2500 RPM.  Speed was never that high, so I was always able to detect the sensor pulse during each flywheel revolution.

Regards,
Rudy