MH's ideal coil and voltage question

[allcanadian]

@MH

I am not going to look anything up, but I think in some engines they simply change the length of the exhaust expansion chamber to match the engine RPM.  That's to ensure a synchronicity between the piston pulse rate to empty the exhaust gasses and the tuned expansion chamber helping suck the exhaust gasses out of the cylinder, but it is not resonance.  It might be called a tuned exhaust port or a variable tuned exhaust port or something like that but it is not resonance.

Actually it is resonance MH just like a Helmholtz resonator and it is not designed to suck anything in a two stroke engine but rather push any excess fuel/air back into the cylinder also pressurizing the cylinder. Here is a pretty cool animation of the process, https://en.wikibooks.org/wiki/Engineering_Acoustics/Sonic_Supercharging_of_2_Stroke_Engines

We should also note it is more like a turbo charger than a supercharger as it is the reclaimed energy in the exhaust gas which aids the process.

AC

[MileHigh]

Thanks for the link and it was a very interesting read.   Note that the "straight pipe" helps draw out gases with a reflected negative pressure wave, and the "tune pipe" is essentially a "leaky" version of what appears to be a Helmholtz resonator but in fact it is not.  The "tune pipe" returns a reflected positive pressure wave as shown in the animation.  That is not what a Helmholtz resonator does, although I will agree that it is similar in function.

I suspected that there was no resonance operating on the exhaust side of the engine, it is more of a fixed time delay event that promotes better engine operation at a certain RPM.  So we are back at something that helps the engine run better with a synchronous event to the engine RPM with a fixed time delay, but it is not resonance.  And like I said before, if it is called "resonance" in the world of motor shop talk, that's fine, but on this thread and the Joule Thief 101 thread we are discussing resonance in the true scientific and engineering sense of the word.

MileHigh

[minnie]

  When I was in my two stroke days we called it Kadenacy.
  I've got an LC 350 and it's just so much better than the
  air cooled I had previously.
  This whole thing just goes to prove that when you've dug
  yourself in to a hole-stop digging.
         John.

[MileHigh]

For resonance there are no "cross discipline differences."  That point has been made many times with references.  An LC resonator and a mass and spring resonator or a swinging pendulum resonator are the same thing with respect to resonance.

[tinman]

Thanks for the link and it was a very interesting read.   Note that the "straight pipe" helps draw out gases with a reflected negative pressure wave, and the "tune pipe" is essentially a "leaky" version of what appears to be a Helmholtz resonator but in fact it is not.   That is not what a Helmholtz resonator does, although I will agree that it is similar in function.

  So we are back at something that helps the engine run better with a synchronous event to the engine RPM with a fixed time delay, but it is not resonance.  And like I said before, if it is called "resonance" in the world of motor shop talk, that's fine, but on this thread and the Joule Thief 101 thread we are discussing resonance in the true scientific and engineering sense of the word.

MileHigh

I suspected that there was no resonance operating on the exhaust side of the engine, it is more of a fixed time delay event that promotes better engine operation at a certain RPM.

And as usual,you have got it all wrong again.
You obviously took no notice at all at the animation showing the precise timing needed in order for the returning pressure wave to re-inject the gas mix back into the cylinder at the correct position of the piston. When this timing between piston position and reverse gas flow is correct,the system is in resonance,and at this particular frequency(RPM) engine power and efficiency is at a maximum.

This is resonance in the purest sense,where maximum amplitude(maximum explosive force)is reached at the systems natural resonant frequency.
And do not get this mixed up with turbo charging or super charging of a 4 stroke engine,as they are not the same. The only thing they have in common,is that they all increase engine power.

This (in the animation)is the very same way your tuning fork work's,but where as maximum amplitude can be maintained in the two stroke resonant system,meaning it remains in resonance,while the tuning fork just ring's down-amplitude decreases the instant it has been struck-->Quote: In physics, resonance describes when a vibrating system or external force drives another system to oscillate with greater amplitude at a specific preferential frequency. Increase of amplitude as damping decreases and frequency approaches resonant frequency of a driven damped simple harmonic oscillator.

The "tune pipe" returns a reflected positive pressure wave as shown in the animation.

Just as i tried to tell you earlier on in this thread--but you knew better-once again-->hey MH
Like i told you,if you want to discus ICEs with me,then you need to brush up on how they work,as im simply not going to waste my time talking or arguing with some one that has no idea as to what they are talking about.


Brad