Does a diaphragm sit still or move vigorously in high speed operation?

MattG · Jan 5, 2018

Chainsaw Jim said:
Most carbs have a little casting mark to pinpoint where to drill the hole if the carb is designated for an intake block set up. Here's a WJ39 from a husqvarna 394, and a WJ48 from a stihl 066.
View attachment 104930

You say the carb you pictured has a problem. You will likely need to drill a hole in the location pointed out to complete the impulse passage.View attachment 104934

Hi Jim,
The carb came out of the factory with that outer port blanked - and it ran fine for years like it.

I assume Zama must have designed this particular carb that way. Note this is a S126B, and I've not found anyone yet here with a genuine similar carb. I chatted to Lone Wolf the 200T guy, and he had only S126A - which have the hole drilled as expected. I'm assuming that the S126B is more a european thing than a US one?

Chainsaw Jim · Jan 5, 2018

MattG said:
Hi Jim,
The carb came out of the factory with that outer port blanked - and it ran fine for years like it.

I assume Zama must have designed this particular carb that way. Note this is a S126B, and I've not found anyone yet here with a genuine similar carb. I chatted to Lone Wolf the 200T guy, and he had only S126A - which have the hole drilled as expected. I'm assuming that the S126B is more a european thing than a US one?

Does your intake boot look like this?

With this hole circled in pic?

Mag Craft · Jan 5, 2018

chy_farm said:
The structure of the detecting unit is like this below, the tri-ped post for the detector is made from copper wire, holding this blue detecting terminal in the center. View attachment 104753

Looks like a transducer.

nohoff · Jan 5, 2018

A saw with clogged airfilter has enough vacuum to pull the fuel through the carb without a pulse line.

srcarr52 · Jan 5, 2018

nohoff said:
A saw with clogged airfilter has enough vacuum to pull the fuel through the carb without a pulse line.

I had an 066 with a clogged impulse, it would start and run on the choke and die 15 seconds after shutting the choke off.

chy_farm · Jan 5, 2018

nohoff said:
A saw with clogged airfilter has enough vacuum to pull the fuel through the carb without a pulse line.

Yep, seems this happens to my other saws.

chy_farm · Jan 5, 2018

[Voltage divider]

I wrote;

chy_farm said:
--------
I wound the wire 150 times, which gives nearly the half of the primary current as you see in a oscillo view above, which is a little too much. Less than 35-turns is enough now I suppose. Chy

A simple comparison tells that this 150-turn-pulser coil generates 150 volts when the primary coil generates e.g. 300 volts for its primary current for a spin at running speed.
So this means 1.5-turn is enough for 1.5 volts.

Now what I need is a voltage divider to this 'too-high-voltage' pulse signal.
The dividing ratio can be 1/100, but as a security purposes I optimized the pulse signal to 1/3000.

chy_farm · Jan 6, 2018

[Results of the vibration record of a standard aluminum plate on a diaphragm]

Now showing how I did this first operation;

Data from the diaphragm-vibration-detector is shown in the lower column, which looks like an orange straight line, while the one from the pulser coil which is colored in blue in the upper column.

[Optimizing the data]
A digital cut-off filter was applied to the data from diaphragm-vibration-detector, periodic/frequencial noise, e.g. 50Hz-noise given by the commercial power lines in our environment was cut off.

Vertical yellow lines with number from 00 - 05 show the points we are going to see deeply on this time-domain wave forms of the vibration.

Chy

MattG · Jan 7, 2018

Chainsaw Jim said:
Does your intake boot look like this?

I'll get to you on that Jim - sorry I've not checked for a couple days. I'm gonna drill the impulse outer port through next week to see what difference it makes....

Chainsaw Jim · Jan 7, 2018

MattG said:
I'll get to you on that Jim - sorry I've not checked for a couple days. I'm gonna drill the impulse outer port through next week to see what difference it makes....

I shouldn't have asked as if I needed to know. Lol
I should have just said if your intake boot has the the impulse hole in the flange as pictured, you'll need to drill the passage in the carb to match.

MattG · Jan 7, 2018

Chainsaw Jim said:
I shouldn't have asked as if I needed to know. Lol
I should have just said if your intake boot has the the impulse hole in the flange as pictured, you'll need to drill the passage in the carb to match.

Lol back

Don't worry I've followed the passage of the pulse signal from the line back to the carb many times! Got a couple of other carbs too, with the expected drilling through the outer body to the pump chamber. This carb is just one of those mysteries, I have to say...

Chainsaw Jim · Jan 7, 2018

MattG said:
Lol back

Don't worry I've followed the passage of the pulse signal from the line back to the carb many times! Got a couple of other carbs too, with the expected drilling through the outer body to the pump chamber. This carb is just one of those mysteries, I have to say...

I'd say they missed it at the factory.

MattG · Jan 7, 2018

Chainsaw Jim said:
I'd say they missed it at the factory.

They are all saying that

But this is how it used to run a few years back before the carb started to dies, in my first 200T when I'd just finished the rebuild. Exactly the same carb.

It used to work just fine, in all parts of the operating range, then.

chy_farm · Jan 8, 2018

[Wave Forms of the diaphragm in operation]

Previously I posted a series of wave forms of the diaphragm in operation, this is the one;

Now I am showing the magnified views of the each points numbered from #00 - #05.

#00 shows the starting point, its magnified view is;

The orange line sitting in the lower column tells diaphragm movement.

Let's see other views too.
#01

Magnified view of #00 wave here;

Magnified a little more;

Spark noises are given to the signal from the diaphragm, they come in a very short period of time, so they do show up as a short vertically straight bar in the graph.
These straight lines tell how the spark timing are.

Now we understand that the diaphragm sinks before sparks, and rises after sparks. This mean when the wave goes up the negative impulse comes.

Chy

chy_farm · Jan 9, 2018

[Wave Forms of the diaphragm in operation - 2]

After #1 point above I tried to minimize the distance between the diaphragm and this detector. Then motor stopped on its way of adjustment, that told me of a possibility that the distance was a little too small to keep operation.

So I widened it again a bit.

#2 at 1940rpm;

#4 at 4057rpm;

#5 at 7472rpm;

#5 magnified view;

Now we see the spark timing comes nearly at the peak of the negative impulse, or in other words another hypotheses can be possible, that is the negative impulse delayed to reach the diaphragm at high speed spin.

Chy

Marshy · Mar 17, 2018

Did the pulse continue to occur at 1x running speed?

chy_farm · Mar 18, 2018

Marshy said:
Did the pulse continue to occur at 1x running speed?

As far this experiment tells YES, if this '1x' means '1000rpm'. The last pic above tells the pulse comes and works at 7000rpm too.

Mastermind · Mar 21, 2018

Very interesting stuff from you Chy. I love the way your mind works.

chy_farm · Mar 22, 2018

Mastermind said:
Very interesting stuff from you Chy. I love the way your mind works.

Glad you like the way I go, thanks Mastermind.
Chy

shorthunter · Mar 25, 2018

Chainsaw Jim said:
The pump flaps move as fast as the piston moves, which is why you'll see different performance grades on pump side diaphragms...the blue plastic, black rubber, and the tan woven.

Rubber allow the most flow, blue plastic the least?

Does a diaphragm sit still or move vigorously in high speed operation?

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