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Old May 02, 2010, 01:38 AM
SVX
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Wiring 4 motors?

Can someone point me in the direction of a diagram or an article that can help me wire and
choose a power system for a 4 motor setup?

My plan is to blow up a Guillows B-24 plan to 60" and build it as light as possible. I am just
starting to search for a power system but know this, I want to throw three blade props, and I am
hoping to build as light as possible i.e. stringers and tissue so I think I can do better than 40-48 oz
TFW. Maybe a geared IPS on 1 ESC....or brushless?

Any help is appreciated.
Dust
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Old May 02, 2010, 03:36 AM
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Letchworth, Great Britain (UK)
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I've seen a few threads on this subject, but can't find them using the search facility

If you're talking about brushless motors, basically you just Y-lead all the 4 ESCs' receiver connections together into the throttle channel on your receiver, and Y-lead all the ESCs' battery connections together to one large battery (or two or more batteries in parallel).

In practice I've read of some people who've had problems with four ESCs connected to the throttle channel, even though it works okay with two; so a work-around for that is to Y-lead two of the ESCs into an auxiliary channel and mix it to the throttle channel in your transmitter.

Also, with the batteries it's ideal to have all four ESCs running of the same source so that they'll get exactly the same voltage and therefore run at as-near-as-you-can-get-it the same speed. But if it's more convenient you could run the two inboard motors off one battery and the two outboard ones off another. That way, even if there is some difference in the voltages, you won't get any differential thrust.

If you're talking about brushed motors, things get much simpler You can wire any number of brushed motors to a single ESC, provided the size of the ESC is enough to handle the combined amps of all four motors. Again, in practice I've read of people using one ESC for two inboard motors and another for the two outboard motors, and Y-leading them to the receiver's throttle channel.

In all cases, where using more than one ESC with built-in BECs, you should disable the BECs in all but one of the ESCs unless the manufacturer has confirmed that they can be run together. You do this by pulling the red wire from the 3-pin receiver plug.
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Old May 02, 2010, 05:35 AM
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Blackpool, Great Britain (UK)
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Some advice here.
http://www.peterangus.pwp.blueyonder...b'less.htm

http://www.rcgroups.com/forums/showt...=785049&page=3 post #35
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Old May 02, 2010, 08:33 AM
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Brighton Ont. Canada
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While we live in the brushless era there's still a lot to be said for powering a multi with brushed motors. One of the projects I'm currently working on is a (semi) profile 1/36 C130 Herc that has a 44" ws. It will be powered with 4 EDP 50 (IPS) motors with 3.5 x2 (cut down 4 x 2) GWS props wired in parallel, a 10A brushed ESC, and a 750maH 20C 2s lipo.
Bench testing this system showed 56W with the bat HOC. Since the projected AUW of the airframe is ~12oz. it gives the Herc a power rating of 75W/lb which is more than ample for scale-like flight.
There's a lot to be said for simplicity!
Hope this helps.
D,
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Old May 02, 2010, 08:42 AM
An itch?. Scratch build.
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South Wales U.K.
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If you can, try to find some brushless ESC's that 'beep' quietly. My B-17 sounds like a room full of of darn phones going off when armed. Can be a bit embarrassing at the flying field.

Please, would an ESC manufacturer include a 'mute' button.


Edit, Agree with Dave, I wish I hadn't converted it from brushed to brushless, purely on the noise.
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Old May 02, 2010, 08:59 AM
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You could run these 4 motors off one esc if this was brushed motors. In this case I would wire two in series and then those two in parallel. Then I would split the parallel so that if one motor burned out, the other one wired in series would be on the opposite side of the plane, so you would have reduced power by having only two running, but not both on one side, which would make it very difficult to control.

If you ran "rocket 400" 4.8 volt motors, two in series would need 9.6 volts, but as a practical matter a 3 cell lipo would probably work fine, since pylon planes used to run these on 7 or 8 cells each. Then parallel the two pairs, doubling the ampere draw, so probably a 30 amp esc would do.

I would not try to run these at the upper limits for current and voltage. The motors will last longer and be more efficient if you don't.

I think it's gonna be increasingly hard to find brushed motors, as everyone runs brushless these days. I have heard of people running matched brushless motors off one esc, but generally it is one esc for each motor.

For a guillows 60" scale, the speed 300 may be the better size. I think 400 motors weigh a couple of ounces. Most ESC's weigh .75 oz. anyway. Think about two inboard motors powered and the two outer ones just a shaft and prop that spins in the breeze, with them wired parallel or series. In series one smokes and the other will stop too. Parallel the other motor will still run but a least it won't be way out on the end of the wing.

You don't want to make the project too complicated or it won't work reliably. Reliability is what has let the aviation industry flourish. Reliability lets you have more than one flight for al your work building and setting the plane up.
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Old May 02, 2010, 10:01 PM
SVX
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Thanks for the great leads. That Sunderland was just put on my future projects list.

So from what I can gather, the best way to wire this up is to run two inboard motors in series, two
outboard motors in series, then wire them together parallel.

What do you guy's think of this combo?
\
http://www.rchotdeals.com/Products/r...18A_combo.html
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Old May 03, 2010, 03:36 AM
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I have no experience of that motor, but I can tell you that you can't run two of them in series

Two identical brushed motors can be run in series off one brushed ESC, and you'd need to use a battery which gives twice the voltage, but the same amps, that one motor would need.

Two identical brushed motors can also be run in parallel off one brushed ESC, but then you'd need to use a battery and ESC that can handle the same volts that one motor needs and handle twice the amps that one motor needs.

But with brushless motors, like in your link, except in very specific circumstances it's strictly one ESC per motor. The ESCs are normally run in parallel in multi-motor setups
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Old May 03, 2010, 12:01 PM
SVX
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Oh I intend on buying 4 ESC's. When I mentioned wiring, it was concerning wiring the battery to each ESC.

Thanks, Dust
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Old May 03, 2010, 01:48 PM
An itch?. Scratch build.
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South Wales U.K.
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I'm using four motors, four ESC's, two batteries.

ESC's are in the fuselage, long three wire runs between ESC and motor, (short ESC to battery wires).

Both inners to one battery, both outers to another battery.
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Old May 03, 2010, 02:25 PM
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Quote:
Originally Posted by SVX View Post
Oh I intend on buying 4 ESC's. When I mentioned wiring, it was concerning wiring the battery to each ESC.

Thanks, Dust
Ok, but I'm still not sure we're on exactly the same wavelength It's the "in series" bit that I'm concerned about -- you can wire two batteries in series to give a higher voltage (e.g. two 3S LiPos in series will give you a 6S LiPo), but you can't wire two ESCs in series because they probably won't share the load equally and, if anything goes wrong with one, the other one and its motor may be toast as well because it might then get double the voltage its rated at.

You can, and we normally do, connect two ESCs in parallel -- i.e. both red battery wires together and both black together.
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Old May 03, 2010, 03:54 PM
An itch?. Scratch build.
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Here's a picture -
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Old May 04, 2010, 12:21 AM
SVX
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Okay thanks abenn, I reread your posts and realized that I was in fact confused. If I want to run
brushless I have to run them in parallel. I think I have it.

Now, thanks to your picture eflightray I see you are running two pairs in parallel. So if I wanted
to try and use a single battery I would just have to run a larger Mah pack correct? It looks like
the Sunderland was done this way with all 4 in parallel to a 2500 Mah. battery.

Thanks for the patience guys, I think I almost have it.,

Dust
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Old May 04, 2010, 02:50 AM
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Good diagram from eflightray

Yes, you can use one large battery instead of the two shown in the diagram. Your choice may depend on what packs you have available, and how they best fit in your model whilst achieving the correct c of g.

You can also leave one of the ESCs' BECs connected, and not bother with the separate receiver battery. But you need to consider if that single BEC can provide enough power for your receiver and servos -- if you use ESCs with switching BECs built in, then it quite possibly can -- and whether you're willing to risk running off an electronic power supply, which might fail, rather than a supposedly more-reliable receiver battery.
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Old May 04, 2010, 11:59 AM
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Based on experience with my twin brushless motored ME-262, with two esc's paralleled to on Lipoly pack. One of the esc's will go into LVC mode before the other if I don't land soon enough, resulting in assymmetric thrust and loss of control, unless I chop throttle ommediately and land dead stick. When one esc goes into LVC mode, the other "sees" higher voltage and runs on with normal thrust. Use of brushed motors allows use of one speed control and LVC would cut all motors at once. If you use four brushless motors, and one battery pack, wiring so that the two outer motors will cut out first, due to LVC in their speed control, will allow you to land under half power from inboard motors. If you use a 2.4ghz receiver on 3S lipo power, use a switching-type BEC to power receiver and up to six small servos.
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