Hi,
I eat frogs so please once again excuse my english in my threads,
Two month ago i've tested a myth..
THE MYTH:
"You can reduce the vibration under at least 0.3IPS like a "dynamic balancing",
by only cloking your propeller horizontaly (3h/6h if prop mount was a clock) when 1# cylinder is at Top Dead Center"
Lot of you guy's will respond as me before testing:
"BULL****! the prop act's like a flywheel!
If balanced changing clock position can't change anything!"
I tested it anyway!
Wanting real numbers, not only "siou" feelings,
I Take my RV to a freind helicopter workshop, he have a hight dollar dynamic balncer that he use for dynamic balancing rotors. And planes sometimes.
There is a graphic chart of the vibration you can experience
in any light aircraft.
Good to look at to speak the same language:
http://www.expaircraft.com/PropBa1.gif
First value with the prop cloking on standrad position (11h / 5h) with no extra balancing. (Like lot of club airplanes).
At 2250 RPM the dynamic balancer indicates 0.7IPS... Very Rough vibration
(what they call Very Rough is not enormous, i'would better say "really feel-able vibrations, you can "see" some tiny vibrations in the cockpit during flight ")
Ok we got a reference number!
Now time to "clock the prop horizontal (9h/3h) and test it,
(i've put the N?1 blade in the front on the 1# cylinder)
Same 2250 RPM... 0.02 IPS!!!! Huuuu somthing wrong with the balancer???
"inside during the static run up I feel clearly a noticeable difference, but is the number real..?"
We checked all the sensors,mounting plates,wires etc..
And tested it again:
2250RPM... 0.03IPS...
"Whow! It seems to be true!....."
My freind to be sure of the results, putted a little scew/nut in one of the starter plate hole to unbalnce it just a bit, and check his dynamic balancer..
2250RPM... 1.2IPS..
He removed the screw/nut and try's again..
2250RPM... 0.03IPS!
"Ok so it's real! Now time to test it in flight! Cause it will not be better with a real dynamic balancing!"
The flight was a clear, "no sensor needed" response to the Myth:
Smoother engine RPMs every where, especially at 2350RPM witch delivers no vibration at all, only the smooth explosions of the o-320 in front of us,
no hight frequency vibrations anymore (they use to be feeled with my nail pick directly on the metal inside fuselage, now i feel nearly nothing, like it been divided by 2)
It feel's like the motor gain RPM faster than before, and i feel somthing like the plane is climbing better than usual but it can be the oat or somthing else..
(when you stop the engine, a prop clocked horizontal 9H/3, the prop will stops absolutely vertical like a "I" on your hood 12h/6h)
I run like that for 10h now and like it so mutch!
I'call sensenich and lycoming to be sure it's not an issue to clock the prop like that, both for prop or engine.
They both said that it is totally safe! No problem!
The lycoming guy said "between word" that they know it's gives good result with vibration but they prefers to claim 11H/5h standard cloking
to security for hand starting or proping. (anyway i will never try to start my 160hp by hand!)
A friend, after i tell him my little experiment,
try the horizontal (9h/3h) position on his airplane a kind of big "b?b? Jodel",
Same improuvments (feelings) on vibriations and smoothness!
He keep it like that, and don't want to go back to the 11h/5h standard position...
Now time to try to understand why it works so well!
I think it's due to harm force of the prop blades in that position that is avoiding the crankshaft to bend on eatch piston push, so it's limitating vibration.
In the same way the disc of the prop stop shaking allowing better efficency.
(The metal prop wheight is for sure an adventage in this explanation)
My idea to explain the feeling of little more power is that the blade is now passing by the air intake at his maximum piston delivey force..
Maybe it's helps power with a kind of blast at the valve open time?
Or somthing due to a different positioning maximum piston force delivery on the blade disk, maybe passing by the crowl?
Need the quantic phsysitians of the VAF forum to answer the "why?"
but
Even if i'm not sure to know "WYH?"
in my opinion:
"MYTH VERIFIED!"
I eat frogs so please once again excuse my english in my threads,
Two month ago i've tested a myth..
THE MYTH:
"You can reduce the vibration under at least 0.3IPS like a "dynamic balancing",
by only cloking your propeller horizontaly (3h/6h if prop mount was a clock) when 1# cylinder is at Top Dead Center"
Lot of you guy's will respond as me before testing:
"BULL****! the prop act's like a flywheel!
If balanced changing clock position can't change anything!"
I tested it anyway!
Wanting real numbers, not only "siou" feelings,
I Take my RV to a freind helicopter workshop, he have a hight dollar dynamic balncer that he use for dynamic balancing rotors. And planes sometimes.
There is a graphic chart of the vibration you can experience
in any light aircraft.
Good to look at to speak the same language:
http://www.expaircraft.com/PropBa1.gif
First value with the prop cloking on standrad position (11h / 5h) with no extra balancing. (Like lot of club airplanes).
At 2250 RPM the dynamic balancer indicates 0.7IPS... Very Rough vibration
(what they call Very Rough is not enormous, i'would better say "really feel-able vibrations, you can "see" some tiny vibrations in the cockpit during flight ")
Ok we got a reference number!
Now time to "clock the prop horizontal (9h/3h) and test it,
(i've put the N?1 blade in the front on the 1# cylinder)
Same 2250 RPM... 0.02 IPS!!!! Huuuu somthing wrong with the balancer???
"inside during the static run up I feel clearly a noticeable difference, but is the number real..?"
We checked all the sensors,mounting plates,wires etc..
And tested it again:
2250RPM... 0.03IPS...
"Whow! It seems to be true!....."
My freind to be sure of the results, putted a little scew/nut in one of the starter plate hole to unbalnce it just a bit, and check his dynamic balancer..
2250RPM... 1.2IPS..
He removed the screw/nut and try's again..
2250RPM... 0.03IPS!
"Ok so it's real! Now time to test it in flight! Cause it will not be better with a real dynamic balancing!"
The flight was a clear, "no sensor needed" response to the Myth:
Smoother engine RPMs every where, especially at 2350RPM witch delivers no vibration at all, only the smooth explosions of the o-320 in front of us,
no hight frequency vibrations anymore (they use to be feeled with my nail pick directly on the metal inside fuselage, now i feel nearly nothing, like it been divided by 2)
It feel's like the motor gain RPM faster than before, and i feel somthing like the plane is climbing better than usual but it can be the oat or somthing else..
(when you stop the engine, a prop clocked horizontal 9H/3, the prop will stops absolutely vertical like a "I" on your hood 12h/6h)
I run like that for 10h now and like it so mutch!
I'call sensenich and lycoming to be sure it's not an issue to clock the prop like that, both for prop or engine.
They both said that it is totally safe! No problem!
The lycoming guy said "between word" that they know it's gives good result with vibration but they prefers to claim 11H/5h standard cloking
to security for hand starting or proping. (anyway i will never try to start my 160hp by hand!)
A friend, after i tell him my little experiment,
try the horizontal (9h/3h) position on his airplane a kind of big "b?b? Jodel",
Same improuvments (feelings) on vibriations and smoothness!
He keep it like that, and don't want to go back to the 11h/5h standard position...
Now time to try to understand why it works so well!
I think it's due to harm force of the prop blades in that position that is avoiding the crankshaft to bend on eatch piston push, so it's limitating vibration.
In the same way the disc of the prop stop shaking allowing better efficency.
(The metal prop wheight is for sure an adventage in this explanation)
My idea to explain the feeling of little more power is that the blade is now passing by the air intake at his maximum piston delivey force..
Maybe it's helps power with a kind of blast at the valve open time?
Or somthing due to a different positioning maximum piston force delivery on the blade disk, maybe passing by the crowl?
Need the quantic phsysitians of the VAF forum to answer the "why?"
but
Even if i'm not sure to know "WYH?"
in my opinion:
"MYTH VERIFIED!"
Last edited: