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Old Jan 28, 2012, 10:33 AM
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What is meant by 400 size motor.

When it says 400 or 500 size brushless motor is it relating to the wattage or model size etc?

Thanks, Rob
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Old Jan 28, 2012, 10:36 AM
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vintage1's Avatar
East Anglia, UK
Joined Sep 2002
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originally it related to the diameter of a mabuchi can brushed motor.

Now it doesn't mean much at all really.
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Old Jan 28, 2012, 10:51 AM
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Staffs, UK
Joined Nov 2003
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It refers to the old brushed motors we used to use which were called Speed 400, Speed 500 etc (the number was loosely based on the length of the motor - a 400 was 38mm long, a 600 was 56mm etc).

These days it just means the sort of size model that might have used one of those motors...so if you never used those old motors it doesn't tell you very much at all .

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Old Jan 28, 2012, 11:05 AM
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Calgary, AB, Canada
Joined Apr 2008
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A 400 size motor, is as noted, it came in a few different voltages which gave one a measure similar to today's brushless kv. Loosely the lower the voltage figure the higher the kv.

We used to run a 400 on around 10-12 amps, from a 7.2 - 9.6 Volt battery pack, and put them in planes of around the 20oz range.

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Old Jan 28, 2012, 11:38 AM
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Belfast / Dublin
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the numbers 400 were conventional and didn't seem to relate (accurately) to any dimension or characteristaic of the motor
the orig speed 400 brushed motor was 28mm in diameter and as stated above was 38mm long - a good one was good for about 100 or so watts in at 65ish % eff.

an equivalent sized quality brushless motor 2840 (28mmx40mm) will be good for maybe 3 times that power...at much better effic. maybe 80% or more

when speed 400 is specified these days it usually pertains to mounting dimensions and motor size, as power handling varies greatly from motor to motor depending on quality etc
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Old Jan 28, 2012, 04:40 PM
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Chattanooga, Tennessee, United States
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This is my understanding......what is meant by a 400-size motor these days is typically an outrunner which can cope with about the same amount of power a can Speed 400 could... namely 100W-120W. Most so-called 400-size brushless outrunners are about 56g... far lighter than the 78g for a Speed 400.
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Old Aug 13, 2012, 06:09 PM
aspiring noob
United States, CO, Denver
Joined Aug 2012
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400 size and wattage for 600g plane?

I am sorry for opening an older thread but I have a question pertaining to the "400" size motors and wattage.

I bought an eBay special 36" cap and it says on the info that the recommended motor is a 400 size or equivalent. now, most 400 size motor don't push the wattage I think I need. I hear 150w per pound and I hear 180 watts per pound for 3d aerobatics, but I can't find a 400 motor that has 200-240 watts. the instructions for the plane say its 600g flying weight if built with mini servos and a 1300-1800mah 3s

I see motors of that class but all are under powered from what the math comes out to and the last thing I want is an underpowered 3d plane!! I think a bigger motor will fit(I'm still building it up so) but should I just go 450 size or what should I use?

I want to buy all the electronics for it and I'm certain of most of what I need but the wattage of those motors has me concerned...

thanks in advance!!
~ Andy
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