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Old Feb 19, 2013, 04:16 PM
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Joined Feb 2013
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2m mfa high sierra wing & motor question

I have a 2m MFA High Sierra @ am wanting to put a motor in the nose with a folding prop.

Please could anybody provide information re what motor to use? I only have brushed equipment & want to stick with what I've got. I have a 20 amp esc (would this power a 540 motor)

Motors:
standard 540 motor
540 size car race can(a 16 triple I believe)
Speed400 Direct drive
Speed400 with a 3.6:1 gearbox. (BB megax gearbox, not planetary.)

Batteries:
Sub C's nicads:
x2 7.2v 1800mah scr's
x2 8.4v's, a 1700mah & a 3000mah so am hoping these will be suffucient.
I also have AA nimh's: 7.2v 2600mah & 12v 2200mah.

What battery/motor combination do you reccomend? I also need to know what prop to use, it will have to be a folding prop. I was thinking of adding a 9x6 to my 540 or would the 9x6 go with 3.6:1 geared 400?

Also, just to complicate matters, On a previous collision, The wings were forced forward bending the steel wing rods forward in the brass holders (Which I believe is a common problem) One of the steel rods has a slight bend in it but I can repair this without too much of an issue. The plastic wing root pieces also came off with the wing but I'm sure I can repair these easily enough.

Please could you reccomend which motor & prop combo would be best (Please refrain from recommending brushless scenarios as I want to use the brushed motors I have at hand.

Also if possible, any upgrade ideas for the wing joiners would be welcome as the stock ones leave much to be desired.

I appreciate any help you can give me regarding this. Thanks, Ian.
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Last edited by Ian2140; Feb 19, 2013 at 05:01 PM.
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Old Feb 19, 2013, 09:04 PM
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United States, MA, Waltham
Joined Dec 2001
7,106 Posts
You may find the following useful for figuring out what prop, etc:
http://brantuas.com/ezcalc/dma1.asp
If you're going to go with brushed and nimh, don't get too greedy for power or things will get to heavy. 75 watts per pound will be more than enough unless you are competing in ALES, and in that case I recommend you bite the bullet and go brushless.

I suspect the geared speed 400 won't be enough unless you go to lipos to keep things light, though I could be wrong. How much current does a speed 400 take? One of the 540 motors would probably work, but would be better if geared down, swinging a larger prop. If it seems you will have to buy a few things to get these to work, it may not cost much more to go brushless. Lighter is better.

What diameter are the joiners? If 7/32 or 1/4", they are easily replaced with music wire cut using a Dremel abrasive cutoff wheel. Good music wire is VERY strong, but hard to find in larger than 1/4 inh sizes. If smaller than those sizes, they're probably too small.
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Old Feb 19, 2013, 09:30 PM
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United States, AL, Mobile
Joined Dec 2007
1,655 Posts
High Sierra! Haven't seen one of those since I worked at Hobby Lobby! We sold a lot (most) of em to guys out west who had really big slopes. I was used to gasbag type planes and just couldn't understand how something that heavy could fly, but folks loved em.
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