12S power systems ideas and options

[Enterprise]

Just for comparison the DA-60 on a pitts muffer is about 5.6 hp. With the RE2 tuned pipe we get about 7 hp. It looks like the DA-70 is getting around those same numbers as the pipe setup with more low grunt. Electric will still win in the torque contest and noise.

Looking at that chart the last combo seems to be close the DA-60/RE2 combo. I am getting h.p. numbers from the Pe Rievers spreadsheet and it shows 7 hp to get 6800 rpm on the 24x10TH. Great data.

 

[Aeroplayin]

BTW -- Red highlighted Amps are high, not low.

 

[Aeroplayin]

Also keep in mind that I calculate HP from Watts-out, not Watts-in. Unlike a gas engine, we will have a margin between the Watts the meter shows us at the source, and what power makes it to the prop shaft after part of the power is used in heat, magnetic fields, and a few more minor items. For a gas engine, we calculate power by load and RPMs, so I do the same thing with electric motors. It's not the same as using a dynamo, but it is at least extremely relative. So although the 24x10TH is producing 5130 Watts at the meter, the 6853 RPMs requires only 4500W at the shaft. The efficiency is a high 88%, but the HP is 4502 / 745.7 (6.03 HP) instead of 5130 / 745.7 (6.9 HP). You can check this by putting a scale on it and see if the thrust makes sense. Pe used a 6x HP value for thrust, but we discussed this and I included prop power absorption into the equation to fine tune the value at his recommendation... his last post on FG. It works for me, and using the simple 6x value, 38 pounds is relative to 6.3 HP, but my formula calculates it as being relative to 6.04 HP.

Tim also mentioned that he got 38 pounds when Bryan asked him, so it all works.

 

[gyro]

All those numbers come from castle data logs?

 

[Aeroplayin]

No, that's my analysis of the log output. The CSV file looks something like this:

 

[Aeroplayin]

And this is what it looks like when I'm done with it....

 

[gyro]

Let me rephrase, did all those numbers come from a 5335 powered through a castle ESC?

 

[Aeroplayin]

Yes... all from post #95

 

[Aeroplayin]

The rest of the values in the last ten columns from the chart in post #96 are calculated using typical power formulas, which I did in Excel.

 

[Aeroplayin]

Gmarsden, who has always been a behind the scenes contributor by verifying my calculations and explanations, did catch something interesting. It's not possible that the motor was swinging a 24x10TH faster than a 24x10 PJN, so I need to make sure I did not make a labeling mistake. I'll do that ASAP and let you know what happened, so the Mejzlik production may not be correct, and may actually be another prop entirely.