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Old 08-19-2019, 08:37 AM
ron_van_sommeren is offline
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uomo ludens modellesticus
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near Nijmegen, Netherlands
Joined Apr 2009
105 Posts
How did the change effect current at full throttle? From? To?
Current drawn is proportional to pitch¹ and diameter⁴.
(And proportional to voltage squared and Kv cubed. In a perfect world, assuming no voltage losses in battery, wires, controller and motor.)
This would give a change in current by factor (20/19)⁴ × (8/10) = 0,98. Slightly lower current, by 2%.

Vriendelijke groeten Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
e-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC
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Last edited by ron_van_sommeren; 08-19-2019 at 12:36 PM.
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Old 08-20-2019, 04:53 AM
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No Balsa Withstands my Wrath
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United States, SC, Fort Mill
Joined Jan 2009
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Quote:
Originally Posted by ron_van_sommeren View Post
How did the change effect current at full throttle? From? To?
Current drawn is proportional to pitch¹ and diameter⁴.
(And proportional to voltage squared and Kv cubed. In a perfect world, assuming no voltage losses in battery, wires, controller and motor.)
This would give a change in current by factor (20/19)⁴ × (8/10) = 0,98. Slightly lower current, by 2%.

Vriendelijke groeten Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
• e-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •
While i dont have a watt meter i can definitely say efficiency went up. I got 6 flights in with the new prop and all used an average of around 300 mah less than with the xoar 19x10. Motor temps were around 115°f after landing and taxiing to the pits.
Only downside is speed i would like it to be somewhere between what i get with 19x10 and 20x8. The last 10% of my throttle doesnt really do anything with the 20x8
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Old 08-20-2019, 12:26 PM
ron_van_sommeren is offline
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uomo ludens modellesticus
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near Nijmegen, Netherlands
Joined Apr 2009
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Originally Posted by scooby61 View Post
... i can definitely say efficiency went up. ...
Also due to larger prop diameter.

Quote:
Originally Posted by scooby61 View Post
While i dont have a watt meter ...
That always scares me a bit Scoob (EE).

Without (the use of) a watt-meter you are in the dark.
Until something starts to glow
Vriendelijke groeten Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
e-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC
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Old 08-20-2019, 03:43 PM
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No Balsa Withstands my Wrath
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United States, SC, Fort Mill
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Quote:
Originally Posted by ron_van_sommeren View Post
Also due to larger prop diameter.

That always scares me a bit Scoob (EE).

Without (the use of) a watt-meter you are in the dark.
Until something starts to glow
Vriendelijke groeten Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
• e-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •
Since i never go for absolute peak power i have never had an issue using temperature and batt usage to confirm my calculations. I calculate and then setup for no more than 80% of those calculations usually start near 60% and adjust up incrementally. I agree a watt meter is the only fully accurate way but as long as i stay well to the co servative side of max output never had any kind of meltdown.
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