Author Topic: My Ordinary Little Hit & Miss Engine  (Read 20818 times)

Offline Kim

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Re: My Ordinary Little Hit & Miss Engine
« Reply #105 on: October 15, 2015, 02:22:45 AM »
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

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #106 on: October 15, 2015, 07:25:53 AM »
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


Offline RayW

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Re: My Ordinary Little Hit & Miss Engine
« Reply #107 on: October 15, 2015, 11:09:48 AM »
Beautiful work Rudy and what a super little engine. Congratulations on a great job.
Ray

Offline Kim

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Re: My Ordinary Little Hit & Miss Engine
« Reply #108 on: October 15, 2015, 03:55:48 PM »
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

Offline NickG

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Re: My Ordinary Little Hit & Miss Engine
« Reply #109 on: October 15, 2015, 08:28:18 PM »
Great stuff Rudy, many thanks.

Offline Bearcar1

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Re: My Ordinary Little Hit & Miss Engine
« Reply #110 on: October 16, 2015, 12:38:36 AM »
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!

Offline b.lindsey

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Re: My Ordinary Little Hit & Miss Engine
« Reply #111 on: October 16, 2015, 12:43:25 AM »
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

Offline Hugh Currin

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Re: My Ordinary Little Hit & Miss Engine
« Reply #112 on: October 16, 2015, 01:46:34 AM »
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
Hugh

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #113 on: October 16, 2015, 07:50:24 AM »
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