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Big scale- Motor power question

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Old 07-18-2005, 12:05 AM
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Opcod
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Default Big scale- Motor power question

Hi

I will start to build a Dornier Do-335 from Al Master plan : http://www.wingsontheweb.com/do335/plans.html
So They say that the electric one can be use with 2 Astro 15G . But it's appear to me, if i got more weight or not.. i will be short of power, when i look at the spec.

So does a Astro Cobalt 40 Gear can be more powerfull and more suitable for this project ? Or maybe, there is also other motor and maybe cheaper ?....

Thanks for the help.
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Old 07-23-2005, 02:43 PM
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Default RE: Big scale- Motor power question

The general rule of thumb for electrics is 75 watts per pound for sport flying, 100 watts per pound for highly aerobatic planes.

Check out these to motors - both produce between 700-1000 watts of power depending on the amount of cells you use.


http://www.hobby-lobby.com/brushless-axi4130.htm
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Old 07-23-2005, 03:22 PM
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Default RE: Big scale- Motor power question

Opcod

Just looked at the plan info from your link, I assume this is rather an old plan as I don't think anyone would use 28 1400mAh cells in a 70" span model these days.

If the model was originally designed for IC power, it may require some thought on changes for electric power.

Also the weight at 10 lbs seems rather high. You should be able to build an electric model of that size a lot lighter, even with a reasonable amount of scale detail.

Might be worth doing a search on twins of a similar size, and see what motors people use and what weights they achieve.

My old B25 originally ran 28 cells, at 93" span, (motors and cells in series), now with the higher capacity cells, its on 14 cell, (motors in parallel), one hell of a weight saving.

Good luck with your build.
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Old 07-25-2005, 10:35 AM
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Matt Kirsch
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Default RE: Big scale- Motor power question

That's seriously "old school" technology... With the prices of some of these brushless outrunners these days, it really doesn't make much sense to go with brushed motors, their maintenance needs, and limited lifespan. You can only replace the brushes and turn the commutator down so many times on an Astro Cobalt.
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