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Lighweight opposite 2-stroke engines

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Niels

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Aug 15, 2019
Messages
77
Don’t the counterbalancing shaft take out those unwanted vibs?
No not completely.
A single cylinder with a counter-rotating shaft still has a lot of second order up and down forces.
For each crankshaft revolution you get two complete cycles and they are not insignificant.
On an opposite they cancel out.
 

Bille Floyd

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Joined
Sep 26, 2019
Messages
406
Don’t the counterbalancing shaft take out those unwanted vibs?
When i go to Bennett RC field, in Las Vegas ; i can tell without
looking inside the engine compartment, if it is a twin or single cylinder
by simply looking at the wing tips, when the engine is revved-Up.
The single will shake the air-frame a, (Lot) more, than a twin of
similar size . Every engine,, over 100cc, that Desert aircraft
builds, for the RC industry , is a twin or 4-cylinder ; maybe there is
a reason , for that ?

Bille
 

proppastie

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Feb 19, 2012
Messages
4,885
Location
NJ
at low rpm this vibrated really bad....course it is not fully broke in here.....3w-200
 

Bille Floyd

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Joined
Sep 26, 2019
Messages
406
...
at low rpm this vibrated really bad....course it is not fully broke in here.....3w-200
Almost like the prop was out of balance ? When ya increased rpm
at one point in went through a really bad vibe ; then got better.

Bille
 

proppastie

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Feb 19, 2012
Messages
4,885
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NJ
perhaps yes prop issues....it was lots smoother at + 2000 rpm the bad vibration was at 1000 or less...this is the first engine I ever had where both cylinders fired at the same time, they were both at TDC at the same time. With all its flaws it still is an amazing little engine.
 
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