brushless query

It has been done so it can't be said it won't work, however.......

The brushless ESC and motor are a closed-loop system. Feedback from the motor tells the ESC what the position of the armature coils is with respect to the magnets, and this determines the timing of power pulses from the ESC. For two motors in parallel, they would have to be very closely matched in sync for it to work at all. Definitely not a condition likely to occur reliably, and so not recommended.

With a twin, you will have enough concerns dealing with the issue of avoiding a one-engine-out situation, which frequently leads to an abrupt demise of the aircraft. The issue that seems to be of most concern is low-voltage cutoff occuring simultaneously for both motors/ESCs. Vco is a must if you are using LiPo's, but perhaps should be disabled when using nickel batteries. Using a single battery to supply both ESC/motors eliminates one source of problems in this regard, but leaves the accuracy of Vco set points in the separate ESCs an issue. Real-world tolerances in components make it unlikely that both motors would shut down at the same time. Best practice (at least if using LiPo) appears to be timing the flight to ensure that Vco will not occur.

Multi-engine models sure were a lot easier when we used brushed motors

- no problem running them in series or parallel from one ESC.

Abel

Hi Abel, many thanks for your explanation and help and confirmed it was much more complicated than it looked, I would like to build a twin and have fair plans for a Me 210, Ta 154, Ju 188 and a He 177 also a Mosquito FBVI so may just go back to some of these redundant brushed motors I have in my box for one of those, I want to be able to enjoy flying it not be worrying all the time about battery voltages and so on and one engine turning into an airbrake,

regards, Terry

This isn't supposed to work, but . . .

If you feed in the throttle slowly, they will probably synchronize just fine. Once synchronized, the props will turn at identical RPMs, and the relative positions of the blades remain the same. If you disable the brake in the ESC, the motors will remain in sync as they windmill with power off.

I think I would try it. If it does not work, you will know it before takeoff.

-- Mike Norton

"Mike Norton" wrote

Correct. They will be in *perfect* sync.

About the workings of a brushless controller:

Vriendelijke groeten ;-) Ron van Sommeren near Nijmegen, the Netherlands

I think it depends a lot on the motors, and probably somewhat on the ESC. We have been flying and selling our JINX twin aerobat for 1-1/2 years now with two brushless CD-ROM motors fed through a single Castle Creations Thunderbird-9 or Phoenix-10 ESC. Works great, and very reliably on either 2 or 3-cell lipos.

Randy Model Airplane Engineering

The message from "R.J. Roman" contains these words:

Hi Randy, correct me if I am wrong but with two motors running off the same ESC if the battery or the ESC goes down both motors pack up and take no further part in the proceedings? better I would have thought than have one motor go down and you end up flying an asymetric brick, better to have a lousy glider than a Kamikazi chicken,

regards, Terry

"Terence Lynock (MSW)" wrote

Most (including full sized twin pilots) would go with the lousy glider. Impacting the ground in control _always_ has a better outcome than losing control (because of asymmetrical thrust) and hitting the ground in an unusual (and normally very fast) and unknown attitude.

So, take from this the knowledge that it is better to chop the power when you lose an engine, and figure out your best landing spot available. Full sized pilots have the advantage of being able to keep airspeed exactly right, and a strong enough rudder and instruments to keep the yaw at an acceptable level. Unless you have airspeed and turn ball information radioed back to you, best bet is to find a place to land, quickly.

However its pretty dubious trying to run two brushless motors off one ESC..which motor will the ESC synch to?

Sometimes they get in synch and run. Sometimes one runs and the other judders and expensive smoke comes out.

With brushed motors one ESC is definitely bets, if only cos its cheaper!

Hi Terry - You are correct... it's a pretty sweet setup. Check out the JINX videos on our site.

Randy Model Airplane Engineering

After flying our single ESC twin motor setup for more than a year now, I have never smoked a motor or ESC... so I consider it pretty reliable. Most of the time, both motors start; occasionally neither starts... but nothing burns up. Just pull back throttle and try again...

Randy Model Airplane Eng> > "Terence Lynock (MSW)" wrote

This topic is now a bit dated, but I came across this article 'from the horses mouth' (Joe Ford, Product Specialist at Castle Creations):

from Abel Pranger contains these words:

Thanks Abel, looks like it could proove an expensive job if you get it wrong, for what it costs I think I will go with two ESC when using brushless motors,

regards, Terry

In general yes. Some people have got it to work, on some combos. Most fail.