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How to measure for engine offset

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How to measure for engine offset

Old 03-21-2017, 03:59 PM
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YellowBlueBird
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Default How to measure for engine offset

The instructions that came with my latest ARF purchase are very chinglish. The question is how to measure for the offset of the engine. It must be moved to the left of center so that the prop shaft will center in the opening in the cowling. This model has a lot of right thrust. The model is a Christen Eagle from Sig.

Thanks

Jerry
Old 03-22-2017, 03:47 AM
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loopdeeloop
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Flat piece of wood in place of prop. With wood facing 3 & 9 o'clock, measure between wood and firewall equal distance from crankshaft.
Old 03-22-2017, 04:45 AM
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flyinwalenda
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One you figure out the degree of firewall offset that is built-in then you can figure out how far to move the engineover by using the formula:
Engine Offset= Sine (offset degree) X Engine Length.

So if you have a firewall that has a 1.5 degree offset and your engine measures 4" from the rear of the engine to the rear of the spinner backplate then : Engine Offset = Sine 1.5 Deg X 4"

If you can't do the math then simply copy/paste Sine 1.5 Deg X 4" into google and it will do it for you .

The result for this example will be Sine 1.5 Deg x 4" = 0.1047. That is about 7/64 ".

You would move the center of the engine over to the right (as you are facing the firewall) 7/64" so the center of the prop shaft is in line with the center of the firewall.
Old 03-22-2017, 09:25 AM
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Zeeb
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Umm.... lots of work/monkey business and then you have to mark the mount holes for the engine from that measured spot on the firewall.

I guess that's okay but I prefer to just stand the fuselage on it's tail before the rudder is installed, set the engine on the firewall, put the cowl on it and move the engine until the front of the engine is centered in the cowl opening. Lift off the cowl, mark the mounting holes and you're done.

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