Bug report: difference in reported engine speeds

td9cowboy

td9cowboy

New member
If you look at the max rpm of a motor in the editor compared to the shown rpm in the Nav guides there is a substantial difference. Example: DA 50 editor shows 7940, Nav guide shows 10,300 What's the scoop? Which is correct?
 
OK....I get that. So maybe this isn't a bug. That does seem like a lot of gain though. Maybe I just need some advice to get me into the ball park RPM wise on this DA50. From my research it looks like the engine peaks at 7900 rpm. I'm assuming that I might expect that there might be some damage to the motor, if it was real, if I exceed that rpm substantially. Since the static rpm with a recommended prop is in the ballpark, should I adjust the throttle curve down in the radio to a point that it doesn't exceed the recommended rpm in level flight reported in the Nav Guide? Will that give me a reasonable performance level for this motor assuming that the aircraft weights and drags are correct? You can probably tell, I'm an electric guy.
 
Doesn't sound like a bug to me!

We're modeling a complex dynamic system. It's hard to prove the system wrong with simple observations because, well, we've already worked through all those!

I don't have the sim in front of me as I type this but if you look at the torque curve of the DA50 I'm guessing you'll see that at these RPMs we're on the down slope of the curve.

Jim
 
td9cowboy said:
OK....I get that. So maybe this isn't a bug. That does seem like a lot of gain though. Maybe I just need some advice to get me into the ball park RPM wise on this DA50. From my research it looks like the engine peaks at 7900 rpm. I'm assuming that I might expect that there might be some damage to the motor, if it was real, if I exceed that rpm substantially.
Click to expand...

I frequently static tach my gassers with spec'd props to determine if they actually produce the Horsepower the manufacturers say they do.

The DA 50 will produce around 7800-7900 peak sitting on the ground in a static test.

In the air it can get up to about 9200 RPM, but I've never seen it hit 10K. I imagine it COULD but at that point the engine would be producing very little power as the performance curve drops off precipitously in that range.

There is no "damage" to the motor at these speeds as this is not that far out of normal operating range, but there is also little power being produced at that high of an RPM...

I find that the motor curves in all versions of Realflight do not drop off steeply enough to emulate that, so to mimic the DA 50's true performance I'l have the curve hit ZERO torque at 10K, and very very low figures above 9200 RPM.

I'll also tone down the Realflight curves above spec'd RPM's too.

Try doing the same and you'll get far more accurate results.

BTW: this has been there all along in all versions.
 
jbourke said:
Doesn't sound like a bug to me!

We're modeling a complex dynamic system. It's hard to prove the system wrong with simple observations because, well, we've already worked through all those!

I don't have the sim in front of me as I type this but if you look at the torque curve of the DA50 I'm guessing you'll see that at these RPMs we're on the down slope of the curve.

Jim
Click to expand...

Jim as I wrote in my e-mail to him, I've always found the gas/glow engine torque curves to be too optimistic to the right of the motor torque peaks.

While it is easy to adjust this, it would be nice if the default curves pulled back a bit on the right of the peak to avoid seemingly overpowered engines....

I don't see this as a huge problem though.
 
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