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Old Aug 26, 2012, 12:02 PM
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smitty919's Avatar
manahawkin NJ
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choosing a electric motor to replace a gas motor

Is choosing a power size as simple as using the nitro size motor say a .50 and cross that over to a electric size comparing to a .50 size motor?

I want to convert a few planes to electric including this one that i plan to do first..


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Old Aug 26, 2012, 01:38 PM
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Ken Myers's Avatar
Commerce Township, MI
Joined Aug 2001
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Here is an article that might help.
"An Easy Way To Select an Electric Outrunner Motor Power System for an ARF, Kit or Plans Built Glow Powered Prop Plane "

http://www.theampeer.org/Glow2Electr...w2Electric.htm
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Old Aug 26, 2012, 02:03 PM
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Letchworth, Great Britain (UK)
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The way I did it with my first e-conversion was to aim for an electric motor with the same power as the manufacturer reported for the 4-stroke it was replacing. Maybe not the "proper" way, but it worked for me.

The 4-stroke in question was an OS48 which is quoted as 0.8hp, which is equivalent to 596 watts. The original motor was a Speed 700 with gearbox, running on a 12-cell NiMh pack. The model is now running on a much lighter AXI 2826/12 with a 5S A123 pack, is lighter than the original glow model with a full tank, and seems to have more power than when it was glow powered.

The more-usually quoted rule-of-thumb is that you need anything from 50 to 200 watts per pound of flying weight, depending on the model and your required flying style. The model in my above example (Flair Magnatilla http://www.flairmodels.co.uk/Aircraf...coutframes.htm, on wheels not floats) now weighs 4lb 15oz ready to fly, and is flying on 507 watts, giving just over 100 watts per pound.
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Old Aug 26, 2012, 02:09 PM
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Quote:
Originally Posted by abenn View Post
The way I did it with my first e-conversion was to aim for an electric motor with the same power as the manufacturer reported for the 4-stroke it was replacing. Maybe not the "proper" way, but it worked for me.

The 4-stroke in question was an OS48 which is quoted as 0.8hp, which is equivalent to 596 watts. The original motor was a Speed 700 with gearbox, running on a 12-cell NiMh pack. The model is now running on a much lighter AXI 2826/12 with a 5S A123 pack, is lighter than the original glow model with a full tank, and seems to have more power than when it was glow powered.

The more-usually quoted rule-of-thumb is that you need anything from 50 to 200 watts per pound of flying weight, depending on the model and your required flying style. The model in my above example (Flair Magnatilla http://www.flairmodels.co.uk/Aircraf...coutframes.htm, on wheels not floats) now weighs 4lb 15oz ready to fly, and is flying on 507 watts, giving just over 100 watts per pound.
Is that the weight now with the nitro motor removed and fuel tank removed????
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Old Aug 26, 2012, 03:28 PM
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Here's my conversion on an old EZ arf Dago Red: http://www.rcgroups.com/forums/showt...ht=ez+dago+red
It's about the same size as your VooDoo. I have since flown several times with a 14x12 and it's rather fast.
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Old Aug 26, 2012, 04:21 PM
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Originally Posted by tlh101 View Post
Here's my conversion on an old EZ arf Dago Red: http://www.rcgroups.com/forums/showt...ht=ez+dago+red
It's about the same size as your VooDoo. I have since flown several times with a 14x12 and it's rather fast.
Nice job the plane looks great now you really got me itching to get this done lol..
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Old Aug 27, 2012, 02:33 AM
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Originally Posted by smittyplugs View Post
Is that the weight now with the nitro motor removed and fuel tank removed????
The target watts-per-pound is ready to fly, with all the glow stuff removed, and the electric stuff installed including battery so that it's ready to fly. You have to start by first guessing a weight for the motor and battery and adding it to the bare frame weight so you can get a target flying weight and, hence, required power. Then find a motor that'll deliver the watts you need with the prop size you plan to use, and match an ESC and battery to that. Then substitute their actual quoted weights for the weight you initially guessed and, if it's not right, make the appropriate adjustments.

In practice my brushless conversions from glow have always ended up the same weight as the glow model was with about half a tank of fuel. I've never done any structural lightening to achieve this, though on a couple of occasions I've replace Solar Tex with a lighter covering.
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