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Old Aug 01, 2012, 10:55 AM
azflyingguy is offline
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Gilbert AZ
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Twin Motors Do I really want to deal with this.


Ok First Twim motor setup. These are the motors.

http://www.headsuprc.com/servlet/the...h-04%29/Detail

I have seen countless times pilots that fly Glow powered twins are always fussing with RPMs, and tuning their motors to get the RPMS the same. Seems like a lot of fuss to me.

Should I expect the Watts, Amps, and RPMS to be Identical for each motor?

What if they are slightly off?

Should I stop worrying about the what if's and get everything hook up?

Thanks.
Last edited by azflyingguy; Aug 01, 2012 at 11:25 AM.
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Old Aug 01, 2012, 02:04 PM
eflightray is online now
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An itch?. Scratch build.
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As long as the rpm difference, (the only thing to worry about), is not too far out, multi motor planes are no problem, I have 3 twins, 2 fours.

I can't remember the figures I got, but I wouldn't worry at 200rpm difference at say 7000rpm.

The rudder trim should be able to hold any greater difference, and you wont know what the difference will be like until flying as the prop rpm can change when flying.

It is possible to set up differential throttle and mix it with rudder, I use that on my Sunderland mainly for better water steering, then switch it out for flying, but it could be used when flying if set at a small percentage.

Just beg, borrow, buy a tacho for rpm, and of course you already have a wattmeter
Old Aug 01, 2012, 02:26 PM
azflyingguy is offline
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Thanks for the comments Eflight. I haven't worried about RPM Before. I think if the Watts, amps are close I wouldn't worry about it to much.

If it matters and I do believe it does a bunch is I'm using a single 6s Battery so the volts will be the same.
Old Aug 01, 2012, 02:28 PM
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Wake up, feel pulse, be happy!
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If it was me and they were severely out of whack, I'd run one of the motors on its own channel mixed to throttle and use subtrims to get them running as close as possible.

It probably won't be possible or practical to get them 100% matched at all points on the throttle range, but "close enough" should do it.
Old Aug 01, 2012, 02:57 PM
azflyingguy is offline
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Interesting concept C4. Thanks for the Ideas.
Old Aug 02, 2012, 05:22 AM
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Quote:
Originally Posted by azflyingguy View Post
Thanks for the comments Eflight. I haven't worried about RPM Before. I think if the Watts, amps are close I wouldn't worry about it to much.

If it matters and I do believe it does a bunch is I'm using a single 6s Battery so the volts will be the same.
It's not the watts, amps, or motors that make the plane fly, but the right prop(s) doing the right rpm.
You could have electric one side and a steam engine the other, but as long as the prop rpm was similar, (and the plane balanced), it would fly.

The only worry with a twin is one motor failing, (asymmetric thrust), and if you are quick enough on the throttle, and high enough, even that is not a major problem.
Old Aug 02, 2012, 05:36 AM
MagnusEl is offline
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If you start with a throttle calibration on both controlers, they should be very close to each other in terms of linearity. See your ESC:s manual for how it is done.
Old Aug 02, 2012, 05:57 AM
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just get two identical speed controls and use one battery - with identical motors the difference will be minimal and you can ignore it
Old Aug 02, 2012, 10:18 AM
azflyingguy is offline
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Thanks for the Comments. Yes the ESC and Motors are Identical.
Not sure if a should get a Tach but I'm sure someone has one at the mostly Glow Field I fly at.
Old Aug 02, 2012, 01:30 PM
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How about some pictures of the plane, must be a fair size with two 5065-04's.

I'm using a pair of 2826 motors to fly this -
Old Aug 02, 2012, 01:51 PM
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Nice!! are the props counter rotating?
Old Aug 02, 2012, 03:31 PM
azflyingguy is offline
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No Picts of Airplane to Share yet. Scratch building it. When I get the motors mounted I will share picts.

The airplane should be around 12lbs.
Old Aug 02, 2012, 03:33 PM
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Originally Posted by zeroback View Post
Nice!! are the props counter rotating?
No, there is no need to. Though they did start out counter, (19 years ago), but a later motor and prop change ended up with both anti-clock, no trim change, no flight difference.
Old Aug 02, 2012, 07:17 PM
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That's interesting, I have heard that repeatedly from RC twin pilots. It's counter (haha) intuitive, with boats two same direction props is very noticeable. The hull crabs thru the water , it's going the direction it's pointed just a little crooked. So I've always been convinced that if I build a twin airplane I would go with CR. The other thing we play with which dose have performance effects is which direction the vortex is spinning, into each other or away from each other. I would imagine on a twin airplane spinning them in so the prop wash makes it to the tale even if one shuts down. More evidence that's not the case.


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