Carburetor Diaphragm Movement Detector and its system

[chy_farm]

As you gents may know there are several types of carburetors, diaphragm type, gravity fed type, and injection type(perhaps this may not be classified to the carburetors though). I used to have a lot of discussion at a forum where we tinker small engines of saws, on a theme that how a diaphragm acts in operation. Does it move constantly along with the movement of piston that goes up and down in every cycle of the shaft sits in the middle of mechanism ?, or it keeps moving until it comes to a certain spinning speed and stays/sits still in higher speed than this?

So I made this system to see how it acts in operation from lower spinning speed when it idles to some higher speed like 7000rpm.

The total system looks like this;

at the left you see a saw sitting with some attachments on the top cover, which is a displacement detector unit also shown below.

Within the small blue plastic cylinder there are a couple of coils,


and this coil emits magnetic force from the black part outward.


Showing a illustration to the way detecting the movement.




(to be continued...)

Chy

[chy_farm]

It's always fun to know some hidden truth coming out unveiled, a diaphragm has been keeping moving even in high spinning!!!

For each graph the upper column shows the timing signal from the motor, every high peeks in the blue curve means voltage peeks given by the pulser coil I have given to the main coil unit.
The orange curve in the lower column shows the movement of a diaphragm.

Illustration_03_1991rpm


Illustration_04_4056rpm


Illustration_05_7472rpm


Chy

[chy_farm]

Showing each part below,

this detector set on the motor,


signal amplifier upper in the middle,
voltage divider lower left, which is used to optimize the voltage from the pulser coil. (to be frank, I reeled the wire a little too much for this pulser coil, better less than 10 times perhaps.)




analog-digital converter lower left, like the one you might have used for electric guitars.


Winding wire to make a pulser coil.


Setting the pulser coil done.


How it works;


Illustration added to show how the detector/sensor works;


Chy

[tonyfoale]

Chy_farm,

Great job. You must have had a lot of fun doing this. I have also made a multitude of simple test instruments for measuring the things that go on in engines which most people don't bother with. I expect that you have several more ideas to show us.

I have one question. How did you attach the metal plate for the sensor to the diaphram? Was it already a part of the diaphram or did you have to add it? If you had to attach it then it would have affected the results.

[chy_farm]

Chy_farm,

Great job. You must have had a lot of fun doing this. I have also made a multitude of simple test instruments for measuring the things that go on in engines which most people don't bother with. I expect that you have several more ideas to show us.

I have one question. How did you attach the metal plate for the sensor to the diaphram? Was it already a part of the diaphram or did you have to add it? If you had to attach it then it would have affected the results.

Good afternoon Tony, and thank you for your comment. Glad to know you have a lot of knowledge and experience on this thing.
It's amazing that you have such a deep insight about that point Tony, definitely Yes.

When I put another iron round plate on the same place where the original aluminium plate has been sitting, namely I replace the original plate(they call it a metering plate, if I remember correctly), the result was a tad different to the one I posted above.
I think you may be looking at one feature these graphs show, that is the wave form shown in orange in each of these lower column.
They are nearly sine curbs.
This means that the metering plate was moving in one single movement, or in the basic frequency that the motor-spinning speed permits.
And this also means that this metering plate has been made to have the center position/hole for the metering pin sit right in the center of the round shape of this metering plate. Perhaps this might sound funny that I mention this thing to be some special thing, but it must be one of the very important points about the carburetor setting thing.
(to be continued...)

[tonyfoale]

Understood. I have had little experience with diaphram or pumper carbs and I had forgotten about the metering plate and pin.

You might be interested in some carb experiments that I did a while back to get a visualisation of the mixing. Here are a couple of videos;

[owen moore]

chy_farm,
That is a very interesting and noteworthy experiment. Was your sensor a LVDT?

[chy_farm]

chy_farm,
That is a very interesting and noteworthy experiment. Was your sensor a LVDT?

Good morning Owen, thank you for your comment. It seems like it is, but I did no know this word LVDT though, lol.
Chy

[owen moore]

chy,
What I was referring to was a linear variable differential transformer. Sorry for the confusion and the nomenclature. I like what you have done.
Best Wishes
Owen Moore

[tonyfoale]

chy,
What I was referring to was a linear variable differential transformer. Sorry for the confusion and the nomenclature. I like what you have done.
Best Wishes
Owen Moore

Owen,

I think that Chy's sensor could more accurately be considered analogous to an old style magnetic telephone ear piece or microphone.