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Old Jul 31, 2009, 10:39 AM
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Power-to-weight ratio for the complete power train

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I have done a study, with interesting results, which are shown in graph 1. The motor data is taken from graph 2. The computation is shown in the table.

By "complete power train" I mean motor+prop+ESC+wiring+battery.

Please note the % no-load speed at which the best power-to-weight ratio occurs. 70%NLS for a 5 minute WOT motor run. 74%NLS for a 10 minute run. 78%NLS for a 20 minute run. 80%NLS fof a 40 minute run.

Note that peak efficiency is not a good operating point unless you are into long motor runs.

Graph 3 shows an example of how the data translates into powertrain weight for a particular application.
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Description: GRAPH 2

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Description: GRAPH 1

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Description: GRAPH 3
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Last edited by peterangus; Dec 03, 2013 at 06:08 AM.
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Old Jan 03, 2010, 03:44 PM
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Fourdan's Avatar
Antony (France)
Joined Sep 2003
2,992 Posts
Hi Peter
Good presentation
I remark that for your 70%NLS
the ratio PowerIn/motorWeight is 3W/g
(150W In for 50g motor)
It is my upper limit, generally
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