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Old 08-18-2012, 04:39 PM
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Why would there be a difference in reading from one taken at the hub compared to the tip? 2000 rpm is still 2000 rpm, no matter where it is measured on the prop. You are measuring revolutions not angular velocity.

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Originally Posted by Theflyinglineman View Post
Hey guys I have a question when u are using you tach where do you test. At the hub the middle or the tips of the prop. I would guess the difference in reading could be significant.

Thanks

Adam
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Old 08-18-2012, 04:49 PM
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Question
When will my DLE 111 stop putting out black stuff I have prob run 4 gallons of fuel waiting for the day I don't have to clean it up reminds me a little of my glow days

Thanks

Adam
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Old 08-18-2012, 04:52 PM
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Quote:
Originally Posted by notruthless View Post
Why would there be a difference in reading from one taken at the hub compared to the tip? 2000 rpm is still 2000 rpm, no matter where it is measured on the prop. You are measuring revolutions not angular velocity.
I am thinking the tips are traveling slower than the hub. I know when I set up my speedometer on my bike I had to put the sensor a certain distance from the hub so it would show the correct speed. Maybe it's different on a prop
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Old 08-18-2012, 05:09 PM
Ohio AV8TOR is offline
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Quote:
Originally Posted by Theflyinglineman View Post
Hey guys I have a question when u are using you tach where do you test. At the hub the middle or the tips of the prop. I would guess the difference in reading could be significant.

Thanks

Adam
No it is not measuring speed of the physical prop it is measuring light pulses between the blade passing through ambient light. It is just a light pulse counter. Circumference has nothing to do with it.
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Old 08-18-2012, 05:14 PM
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Quote:
Originally Posted by Ohio AV8TOR View Post
No it is not measuring speed of the physical prop it is measuring light pulses between the blade passing through ambient light. It is just a light pulse counter. Circumference has nothing to do with it.
You will have to forgive me sometimes I am a little slow. If the prop is moving faster at the hub will not there be less of an opportunity for the light to pass not sure if I am making sence

Thanks

Adam
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Old 08-18-2012, 05:24 PM
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Quote:
Originally Posted by Theflyinglineman View Post
You will have to forgive me sometimes I am a little slow. If the prop is moving faster at the hub will not there be less of an opportunity for the light to pass not sure if I am making sence

Thanks

Adam
It is just a two blade prop, in one 360 of revolution there is just "TWO" pulses of light. That is what it reads not speed. That is why there is a setting on the tach for what blade prop you are using so it applies the correct math, is it dividing by 2-3 or 4 to the counted number of pulses/minute.

And not to confuse you more but the tips of the prop are traveling a faster mph that the hub due to a larger circumference but both are traveling the same rpm's.
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Old 08-18-2012, 05:34 PM
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Quote:
Originally Posted by Ohio AV8TOR View Post
It is just a two blade prop, in one 360 of revolution there is just "TWO" pulses of light. That is what it reads not speed. That is why there is a setting on the tach for what blade prop you are using so it applies the correct math, is it dividing by 2-3 or 4 to the counted number of pulses/minute.

And not to confuse you more but the tips of the prop are traveling a faster mph that the hub due to a larger circumference but both are traveling the same rpm's.
Thanks
Had a brain fart about thetip speed I don't like when I have to tell myself to engage my brain
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Old 08-18-2012, 05:36 PM
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[QUOTE=Theflyinglineman;1800900]Question
When will my DLE 111 stop putting out black stuff I have prob run 4 gallons of fuel waiting for the day I don't have to clean it up reminds me a little of my glow days

Thanks

Adam
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Old 08-18-2012, 07:09 PM
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[quote=Theflyinglineman;1800922]
Quote:
Originally Posted by Theflyinglineman View Post
Question
When will my DLE 111 stop putting out black stuff I have prob run 4 gallons of fuel waiting for the day I don't have to clean it up reminds me a little of my glow days

Thanks

Adam
You won't have to wait much longer. The exhaust will clear up this coming Thursday.
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Old 08-18-2012, 08:24 PM
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OK who makes a Good tech? The one I have does not seem to read half of the time.
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Old 08-19-2012, 04:51 AM
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What makes you think the prop is moving faster at the hub??????????
Angular velocity (degrees movement) is the same all over the prop. Real SPEED (velocity) is largest at the tips, because there the measuring RADIUS is largest.
Our rpm meters measure light pulses, regardless of prop diameter measuring location. They also include rustling leaf light pulses, and sunlight reflections, so you have to be careful to get good readings.
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Old 08-19-2012, 05:58 AM
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have a Question what causes an engine to run fine when plane is in upright flight but when put inverted engine goes burble rich engine is mounted cylinder down in aircraft any help on this would be great.
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Old 08-19-2012, 06:21 AM
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Quote:
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have a Question what causes an engine to run fine when plane is in upright flight but when put inverted engine goes burble rich engine is mounted cylinder down in aircraft any help on this would be great.
That's interesting because I have a dle 30 that leans out just a little inverted.

Jeff
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Old 08-19-2012, 06:38 AM
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just wondering if it could be the metering side of carb going from bottom to top because in upright flight metering is on bottom when i go inverted it is now on top so fuel flows down easier oh forgot to say this happens at lower throttle settings above around 5/8 it seems ok and i did use the tuning method from the start of this thread
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Old 08-19-2012, 07:20 AM
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Quote: Originally Posted by Ohio AV8TOR

It is just a two blade prop, in one 360 of revolution there is just "TWO" pulses of light. That is what it reads not speed. That is why there is a setting on the tach for what blade prop you are using so it applies the correct math, is it dividing by 2-3 or 4 to the counted number of pulses/minute.

And not to confuse you more but the tips of the prop are traveling a faster mph that the hub due to a larger circumference but both are traveling the same rpm's.
Thanks
Had a brain fart about thetip speed I don't like when I have to tell myself to engage my brain

What makes you think the prop is moving faster at the hub??????????
Angular velocity (degrees movement) is the same all over the prop. Real SPEED (velocity) is largest at the tips, because there the measuring RADIUS is largest.
Our rpm meters measure light pulses, regardless of prop diameter measuring location. They also include rustling leaf light pulses, and sunlight reflections, so you have to be careful to get good readings.
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