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Old Dec 05, 2001, 09:55 AM
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Las Palmas, Gran Canaria, Spain
Joined Jul 2001
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Multis and brushless

I read in the instruction manual of the Simprop brushless and sensorless ESCs that they can drive two motors in parallel.
Is that possible? Until now I had the idea that, with brushless motors, one ESC per motor was the only way to go, but that's something that I remember from the sensor-equipped motors.
Anybody has a clue? Thanks.
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Old Dec 05, 2001, 10:04 AM
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Canada, NS, Lunenburg
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It works OK. Don't ask me how. Of course, you have to wire the motors in parallel so you'll need an ESC with a high current rating.

There are occasional reports of mis-starting incidents on one or both motors but these are rare and are fixed by shutting off and trying again.
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Old Dec 05, 2001, 10:40 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
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Be very skeptical. I had lots of fits with a pair of Jeti brushless motors in a P-38. I'm still screwing with the airplane. Long leads and brushless motors can be a no-no. It turns out that the battery leads matter too- I tried motors with individual controllers and one battery pack- could not get reliable starts. Bench running will also not show if you have back emf troubles generated by the airplane in a dive- the voltage spikes kill controllers if leads are too long or too little capacitance. You'll probably get away with it in things like a pico jet or some ducted fan jets where the motors are in close proximity.

Sam
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Old Dec 05, 2001, 11:33 AM
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It works but there can be problems. See the FAQ http://www.ezonemag.com/pages/efaq.htm#esc11

Steve
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Old Dec 05, 2001, 12:03 PM
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United States, CA, San Diego
Joined Dec 1999
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I have a couple of twins with sensorless/brushless setups. There is what I have seen:

1) not all sensorless controllers will work with twin motors. I have tried a couple different Schulze with poor results--Kontronik controllers were the most reliable. I have not tried the Jeti with 2 motors but since the startup is a bit hard on the Jeti that could cause problems.

2) High rpm motors are harder to get started right.

3) Low mass props and spinners help start up.

4) It might take a couple of tries to get both motors started--after they are running set the throttle trim up so they "idle"

I have a ME110 with 2 1406/4 turn motors on 8 2000scr cells and a single 40 amp Kontronik--work great!

Steve
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Old Dec 05, 2001, 12:32 PM
BEC
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Auburn, Washington USA
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I have tried two motors on one controller on the bench, with Jeti controllers and motors (including one of the new versions of the Jeti controllers). Results - not very reliable. Both motors started less in less than 1 in 10 attempts. I tried the same pair of motors (Phasor 15-4s matched for cogging force) with the schulze future-45Ko that is the subject of my yet to be uploaded November column with the same or worse results. This is with schulze's most current software.

These two 15-4s are the only two matched brushless motors I have so I can't say what will happen with Hacker or Aveox or anyone else.

I think it is much harder to do reliably than Dave's post would suggest, having tried it.

It sounds like Steve's setup with a Kontronik controller is the most well-proven way to go. I was just thinking as I was driving in this morning how this is the one area where brushed motors are still superior - setting up of multi-motored airplanes. With the prices of the Jeti and Mega brushless motors, there's little reason to use a high-quality cobalt or neodym brushed motor in singles over about 100W anymore. For example, Mega's brushless motors are less expensive than their own brushed motors with similar capabilities....

(There is, of course, a huge market for less-expensive ferrites, and for the whole huge realm of indoor/backyard/park flyers.)
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Old Dec 05, 2001, 04:03 PM
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I have also been thinking this area is a "needs improvement" spot for manufacturers to address: ability to run multi motored brushless applications out of the box, with guidelines to limit confusion for the masses.

There seems to be such a varied array of success in this area. Some setups work, some don't. Some setups that work have been "discovered" by lots of trial and error. What isn't general knowledge is that some of these proven setups were the result of LOTS of head scratching and some seriously expensive blown speed controllers and related equipmernt, the result of trying some bad combos along the way. Also, some setups that do work may not be good setups for different model types (F-18 with everything close and tightly wired, vs transport type multi, with batteries in the fuse and motors everywhere).

My hat is off to those that have fumbled through the initial stages of multi-motored brushless setups. You guys really deserve some credit. I've been watching and taking plenty of notes.

What I think would really benifit our hobby would be more updated and pertient information in the FAQ's and product specific information that was discovered in these setups. I would also like to see more coverage in the magazines on this subject. An initial goal would be to have the manufacturers make ESC's and motor combos that could be more "out of the box" for multimotor setups, and guidelines for different apps.
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Old Dec 06, 2001, 05:52 AM
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I too think it's great that people do this experimentation and share the results. However I don't think the manufacturers are ever likely to get very involved in this. As a rule they are perfectly happy to sell one controller for each motor, a setup that always works. If they did test and document combinations of different manufacturers motors with a controller they would then be stuck with redoing the tests every time the software or hardware changes.

As a matter of interest why is everyone so keen to do this ? Based on the prices I've seen the saving is not great, particularly if you are looking at replacing 2 inexpensive Jeti controllers with 1 high current, more expensive Kontronik. Even replacing like for like you are only saving about 10% of the total power train cost aren't you ? Does a single controller actually work better in some way once you've got it started ?

Also would I be right in guessing that this is going to be limited to 2 motors ? The chances of more than that starting correctly must be tiny. So a single controller brushless Spruce Goose or Do-X are not all that likely in the near future

Steve
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Old Dec 06, 2001, 08:14 AM
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Actually Steve (Lewin), using one controller on two BL motors in effect turns them into one motor. The BL controllers control frequency. The motor RPM is completely dependent on the frequency of the controller at the time, as well as I understand it anyway.
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Old Dec 06, 2001, 07:03 PM
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Brushless twin

I just received my plans for a F7F Tigercat. I want to use a Phasor/Jeti setup in the plane. Would I be able to use two of everything-battery packs, controllers, without any problems? I would use a choked "y" harnes to tie both controllers to the receiver. All items would be placed in the nacells except the receiver. Opto controllers would be used.
Any thoughts on this? I entertained geared ferrite/cobalt combos but want to really go with BL.

Thanks,
Frank
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Old Dec 06, 2001, 10:32 PM
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Reno, Nevada
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fgroza-The set up you describe is probably the ideal way to do twin brushless. Separate Opto ESCs, and separate Battery packs for each motor will eliminate the start up issues, and the opto feature will keep interference from traveling from one ESC to the other thru the Receiver hookup. Of course you will have to run a separate receiver battery pack, It is best to not try to use BEC with twin BL setups.

Are you sure you will be able to get everything in the nacelles, and still get the plane to balance?

If not then you will have to worry about your battery lead lengths to your ESCs, keeping them as short as possible and twisting the leads to help cancel out the induced voltage spikes.

Brushless set ups are a completely different animal compared to Brushed set ups. A lot more to worry about.

Gordon
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Old Dec 07, 2001, 04:07 AM
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Quote:
Originally posted by GregG
Actually Steve (Lewin), using one controller on two BL motors in effect turns them into one motor. The BL controllers control frequency. The motor RPM is completely dependent on the frequency of the controller at the time, as well as I understand it anyway.
Good point, I hadn't thought that through properly. So one benefit is that you get automatic synchronisation of the motors. Got it, thanks .

Steve
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Old Dec 07, 2001, 07:31 AM
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Gordon,
The Jeti BL opto esc are not bec equipped. I had planned to use a seperate flight pack battery to be safe. The nacells for the Cat are located around the CG so this should not present a problem with the balance. The original plane had .25ci engines on it so the Phasor 30-3 should work. There is no fuel tank to worry about so the battery pack should add a little more weight than the full tank.
I really need to do more research and question asking before starting this project.
Thanks for the reply.
HAPPY HOLIDAYS EVERYONE!!

Frank
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Old Dec 07, 2001, 05:56 PM
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near Nijmegen, Netherlands
Joined Feb 2001
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In this German thread you'll find more on the subject:
http://www.rconline.net/k-forum/Foru...ML/000166.html
It also has a suggestion for high-power motors that one controller cannot manage, put two controllers on one motor!
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Old Dec 08, 2001, 11:33 AM
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...two controllers on one motor... interesting. How many watts are we talking before they had to go to this setup?
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