Speed 400 to outrunner conversion  
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All Forums >> Electric Aircraft Universe >> Brushed/Brushless motors, speed controls, gear drives >> Speed 400 to outrunner conversion
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Speed 400 to outrunner conversion - 6/26/2008 4:41:10 PM   
vmsguy


 

Posts: 474
Joined: 4/4/2007
From: Woodville, WI, USA
Status: offline 		Hello all,

I just ordered a Dare B-17 kit. I'm looking forward to building it. And someday flying.. (I'm not ready to fly that type of bird yet)

Anyway... Dare's website recommends a power system consiting off Speed 400 motors, gear drives, and (as best as I can tell) 9x4.7 in props.

I don't have a clue as to the plane's weight, or the size of the engine nacelles, or anything like that... But I'm thinking I should be able to swap out the speed 400 & gear box.

From what I've found... Here are the specs on the motor...
Diameter: 1.1"
Length: 1.5"
Weight: 2.5 oz
Shaft Dia.: 2.3 mm
# of cells: 6-8
Max Amp: 10
Model weight: 28 oz.

Here is what I believe to be the specs on the gearbox
Gear Ratio: 2.5
Weight: 3.3 oz
Shaft Dia: 4mm 6mm prop adapter
Prop: 7x6 - 10x7

From those specs, one could infer the maximum weight of the model would be less than 112 oz (28 x 4)

So... Any thoughts/ideas on a brushless outrunner to replace this??? What reasoning would one go thru to determine an outrunner replacement...?

I'm thinking.. Find a motor that uses a similar prop range and is for a similar weight plane...

The first motor I came up with is the Rimfire 28-26-1600: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWT4&P=SM

Anyway... I know thisn't much to go on.. And more than a little premature.. But I thought I'd start looking and researching...



Thanks in advance...

Lyndon


_____________________________

“It is possible to fly without motors, but not without knowledge and skill." - Wilbur Wright
       Post #: 1

RE: Speed 400 to outrunner conversion - 7/16/2008 6:01:02 PM   
mikekosatka


 

Posts: 186
Joined: 6/26/2004
From: houston, TX, USA
Status: offline 		I'm not following your math. If the model weight is 28 oz (1.75 lbs.) how do you come up with 112 oz (7 lbs.!!)for the weight of the plane? You are on the right track as far as how to find a replacement ( prop size/ thrust per pound of plane weight) but your math logic is off.

Mike

(in reply to vmsguy)
       Post #: 2

RE: Speed 400 to outrunner conversion - 8/2/2008 5:15:45 PM   
Dr Kiwi


 

Posts: 1146
Joined: 12/4/2002
From: Chattanooga, TN, USA
Status: offline 		He is assuming that if one geared 400 motor can fly a 28oz model, then four geared 400's can fly a 112oz model.

You really need to find out the estimated AUW then select four motors which would collectively get you ~100W/lb to get a decent amount of power into the B-17.

http://www.rcgroups.com/forums/showthread.php?t=384181

http://www.darehobby.com/modelers/images/bhunt-b17-01.jpg

Apparently the beast can be flown with four stock 400's so that is only about 300-350W. I'd put four brushless motors in, of at least 150W each, to get you 600W total. Two or three-blade 9x5 GWS HD's on a <1000Kv 70g motor might be good.

< Message edited by Dr Kiwi -- 8/4/2008 2:20:54 AM >

_____________________________

Dr Phil Millener, Chattanooga, TN

(in reply to mikekosatka)
       Post #: 3

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All Forums >> Electric Aircraft Universe >> Brushed/Brushless motors, speed controls, gear drives >> Speed 400 to outrunner conversion
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