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Multi Motor Brushed to Brushless Conversion- PBY

Old 07-04-2006, 06:43 AM
  #1  
BeaverBob
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Default Multi Motor Brushed to Brushless Conversion- PBY

Working on a Multi-Engine upgrade from brushed power to brushless. Would prefer to go Outrunner direct drive vs Inrunner/Geared. Looking for motor size suggestions, recommended motors and any Motor/Esc combo ideas- know each motor requires a separate Esc.

Current flight performance is very good "scale". At a minimum want to try to maintain the same performance. Best scenario would be to gain some extra power/performance....but not looking specifically for increased flying speed. Prefer to stay in the 3S Lipo and/or 7-10 cell Nimah range for batteries.


Specs below....appreciate any comments.


PBY Flying Boat, Twin Engine----

Current power system:
2 ea Speed 400 motors
Scale 1:15.
Span 83 in.
Wing area 835 sq.in.
Length 52 in.
Weight with eight CP-1700 SCR nicads= 64 oz.
Wing loading 11 oz/sq.ft.
Two GWS geared motors E series with 3.4:1 reduction wired parallel driving APCe 9 X 6 props.
Static current is 18 amps, 9 amps to each motor, giving 26 ounces thrust. (Less thrust may be OK if pitch speed is higher, and I know there's a pay off between the two.)
Prop speed 5,200 RPM.
Average flight time is 15 minutes. (Flies 27 minutes on eight 3,000 mAH NiNH cells.
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Old 07-07-2006, 09:24 PM
  #2  
ScubaSteve
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Bob,

Two GBx doubles can replace your SP400s and let you lose that gearbox. I'll have to look up the wind count and gauge, but you'll be looking at ~ 20oz of thrust on 2s w/ a 11x4.7 GWS SF prop @ 9.5 amps, or 25oz of thrust on 3s w/ a 10x6 GWS HD prop @ 12.5 amps. Either way, you'll lose weight between the batteries as well. Motors will end up right around 42 grams a piece. AND technically if you go with the 2s setup you'll be able to run it all on a single ESC (no, each motors doesn't always have to run on its own dedicated controller if they're identical). Might have to use two tho depending on servo/bec load.

You said "static current is 18 amps, 9 to each motor for 26 oz thrust" total? This setup should net you 40-50oz of thrust and drop your weight. I know you're using 9x6s, so the bigger props may not fit with your scheme.
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Old 07-21-2006, 03:45 PM
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ScubaSteve
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Bob,

Wondering how this project is going.

steve
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