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Old 01-14-2007, 10:13 PM
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tlgibson97 tlgibson97 is offline
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help with creating an engine.

I'm trying to set up a torque curve for an OS 91fx. they dont have any information except for a range of rpm's with differnet props. Is there a way to set up an engine in G3 with only this information. Meaning can I derive a torque value from the rpm with a certain prop. Any help is appreciated. Thanks
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Old 01-14-2007, 11:18 PM
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CanCanCase CanCanCase is offline
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If there's a howto on creating engines, curves, etc. I can't find it. (Adding recorded audio of the engine IRL would be great too!)

Maybe OpJose will chime in here with a few "Click me!" and "Me too!" lines to point us in the right direction? If there isn't anything handy that's relevant, maybe someone will bribe him to write up some directions to get where we want to go?

Seems engines are a hot topic this week... keep digging in the other engine related threads too. An answer may pop up in one of them soon...

-Case
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Old 01-14-2007, 11:20 PM
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Well when I lack other info here is what I do.

Look up the recommended prop and the power output in BHP of the engine.

This info is available on the standard info sheets for the engine.

You'll also find the RPM at which this output is measured and weight of the engine.

Remember that this is an expression of power on an UNLOADED engine in flight (e.g. decending in a dive).

Now I take a similiar engine in G3 and look at the torque values to determine approximately the torque figure should be at a given RPM...

e.g. 210oz/in, etc.

I then create the new engine with a 10 point curve and set this value at the highest point of the curve with everything else curving up to this point realistically.
This is saved with a new name.

I then set up G3 to have the recommended blade/prop size using my new engine.

I then fly the plane straight up and watch the power output maximums in the Navguide, both loaded and unloaded.

I then re-adjust the engine until I get about 70%-80% of the stated max bHP as a MAXIMUM instantanous power output in G3. This max should only occur briefly and only under certain conditions.

Finally I adjust the curve so that the engine cannot rev faster than the real thing.

e.g. if the O.S. 91 limits out at 13000RPM I set this to about 180oz/in and then 14000RPM to ZERO.

My numbers are no where near exact, I'm just using them to illustrate the process.

That's it. This will not be too far off!
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