Programming ESC's

[toto]

When fitting a " twin motor " model .... for example the DHC 6 twin otter, do you have to generally programme the ESC's in order to balance the motors into " equal delivery of power ". 

 

I'm not sure if I'm getting this correct or not. As far as I'm aware, it's all to do with potential imbalance from motor to motor when it leaves the factory and trying to reprogramme potential outputs so that the delivery of power from both motors are equal.

 

I'm just trying to get my head around it.

 

Cheers

 

Toto

[Philip Lewis 3]

If you need to balance the power delivery between two motors you would do that in the transmitter not the ESC, best way would be to assign a throttle curve, maybe just to one motor or possibly to both motors throttle channels.

 

You should if needed also balance out twin servo channel ailereon and twin elevator servo models on the respective channels as well like that.

Edited June 2, 2023 by Philip Lewis 3
Spelling

[toto]

Thank you Philip for your response.

 

I watch a chap do a build on the twin otter on utube and he spoke of programming the ECS's. That's what raised the question. As always .... there is a lot to read up on with these things but I find it a fascinating aspect of the hobby and like to read ahead for what's to come.

 

Its interesting that you suggest using the throttle curve for this. I did not realise that you could assign two throttle curves to one model set up. If you do a single throttle curve to address the two motors simultaneously,  you are still not addressing the potential imbalance between the potential tolerances that may exist in the individual motors factory manufacturing processes.

 

I would have thought that the EasC programming may allow you to input settings that would make both motors the same then when you input a throttle curve , both motors are working from the same datum.

 

I have had a bit experience with this in the model railway world and setting up DCC programming chips to keep certain loco types within standard performance parameters. I can see similarities in the electronics. 

 

Interesting stuff and worthwhile for me to take a deeper look at this subject.

 

Cheers

 

Toto 

[MattyB]

If you have two of the same motor and they are both brand new this is a non-issue - many (probably most) people will just run them off a single channel with zero problems. Tbh if the motors are identical and of the same age but are giving different levels of power that can be felt in flight it’s probably indicative of an issue in one that should be addressed on the ground via some careful testing, not the sticking plaster of a separate throttle curve.

Edited June 2, 2023 by MattyB

[toto]

Hi Matty,

 

In theory, all manufactured products, made to the same specification ...... would be equal, and, generally within specified tolerances .... are. Before I go any further, I am not trying to find issues that may not he there .... or at least, it's not my intention. However ... like most .... I consult the usual resources when learning new skills etc.

 

The chap I watched mentioned using a programmable ESC in order to achieve reverse thrust for use on his twin otter whilst on floats. However as well as that, he gave me the impression that he was also balancing the motors using the same programming.

 

If one motor comes out of the factory ...... from the same manufactured batch, because of tolerances built into the manufacturing process, there could be slight differences in how each motors output behaves at either the top or bottom end. 

 

He may just be pedantic but .... what could be the outcome of such a difference, is it possible that if one motor has slightly more top end output than the other, could it pull the plane slightly in a certain direction?

 

The difference may be negligible but if you can alter the motors inputs to the ESC so both fall within the same parameters, you could cut out the need to trim out or take other measures. 

 

I'm honestly not trying to create problems, just trying to design out any niggles in the initial set up rather than at the field. Get the setup right as early in the process as possible and use the technology that we are paying for ..... especially if you are spending the money buying in to supposed " smart systems ". 

 

I appreciate your views.

 

Cheers

 

Toto

 

[PeterF]

I have flown 6 twin engine planes and 3 four engine planes with electric power. These include an 80" Mosquito weighing 17lbs with 1.2kW per motor, a 74" Me262 weighing 16lbs with 2.5kW per motor and an 83" Vulcan weighing 25lbs with 3.4kW per motor. I have not done any rpm balancing with the ESC or throttle curves. I checked the WOT rpm and current draw in all cases and found them to be within a few % side to side which is not an issue. I have not checked the rpms over the throttle range and I have just gone out and flown them. I have not done reverse rotation of props either.

 

I have found IC to be a different issue though, here manufacturing could give different performance at WOT. More importantly, the servo and carburetor throttle arms can be a source of different responses in the mid throttle range because despite best efforts to make them identical, a few degree difference can have a significant effect. For IC I use throttle curves to keep the engine rpms more evenly balanced over the whole throttle range. This servo set up issue does not transfer to electric, the ESC is very good at controlling the motor rpm linearly over the throttle range.

 

My experience is that you are worrying about something that is not an issue with electric powered twins.

Edited June 2, 2023 by PeterF
Spulling and grammer.

[Philip Lewis 3]

You could in theory match the full throttle RPM in the ESC's but that would be about it, you couldn't make them match throughout the range if they didn't but even that would be very hard to do in practice. Again, in practice it's really quite the reverse on the transmitter and quite easy to do throughout the range although it does depend on what transmitter you have as to what the programming will allow you to do.

 

I don't fly any twin motor planes and I agree that both motors should be within acceptable limits the same BUT, I do fly competition twin elevator planes with high quality MKS servo's (read that as not cheap) and there is a noticeable difference between two brand new servo's, so I balance out the elevators and ailerons, most club flyers propably wouldn't notice and I'm not sure that I would either, because the differences between the servo's are quite small (about 6%) and that coupled with the relatively weak rolling forces induced also being quite small means that the overall effect is almost negligible, but if you can match them perfectly then why not do so, especially if it's so easy to do.  

[toto]

Hi,

 

Again, thanks for all the responses ..... it's only putting the question out there.

 

Ì , since my last post, phoned one of my freinds who I often refer to ..... in times of trouble. .

 

He has corrected me in what I am trying to do and explains that the motors dont have any feedback facility which would aid in " speed mapping ".

 

So with the greatest respect and thanks for folks entertaining my mumblings I'll accept defeat on my original thoughts. 

 

I'd like to think that all questions / theories no matter how incorrect are still welcome though as no matter how wrong they may be ..... still invoke debate and opinions ..... new ideas .....innovation etc.

 

Sometimes, we have more technology at our disposal than what we think. We dont realise the full potential / capability of what we have at hand..  So until my next bright idea ......

 

Toto 

[Philip Lewis 3]

Feel free to keeep asking as far as I am concerned and I'm sure I speak for the vast majority on here. Knowledge doen't do any harm, even if you don't actually ultimately use it, that was was the spirit of my answer anyway.

 

You are unliikely to need it but one day you might be in the position where you do want to match two different outputs and want to know how to do it, even if you don't really need to. 

[Simon Chaddock]

toto

To be honest you are quite likely to get as much difference between two identical props as between two identical electric motors.

Like Phillip I have also flown a number of electric twins and fours without worrying about any thrust differences. On a ground run tethered run you could hear a slow "beat" between the motors suggesting they were turning at close to the same revs.  

Most multi engine planes also have big fins and rudders to cover a possible 'engine out' situation so you just wont notice any small thrust differences. There is always the rudder trim if you notice it is not flying quite  as straight as you might want. A motor failure in flight will be a significant issue for you too.

What is important is to program the ESCs so they both recognise the same Tx throttle start and maximum points. Not ideal if one motor starts turning well before the others. Having said this I have found ESCs, like motors, are remarkably consistent from the factory and needed no range adjustment.

 

By the way do keep asking questions. Even if the answer proves to be a 'non issue' you will still have gained some knowledge. 

Edited June 3, 2023 by Simon Chaddock

[steve too]

I have an electric twin where, despite having nominally identical motors and ESCs, I had to adjust the ranges to get the same arm point and power at the top end.

 

I would also always have rudder/throttle mixes for ground handling. For both my glow and electric twins, these mixes are only active when the gear is down.

[toto]

What's the script with regards programming cards. I have 2 x electrospeed boost 30 motors and ESC's for the twin otter. Are programming cards manufacturer specific to their own products as infant see an electrospeed version.

 

And no .... I'm not about to build or fly the otter .... just doing my homework for later.

 

Cheers

 

Toto

[Dale Bradly]

Are programming cards manufacturer specific to their own products?

In a word: yes. Assume one brand won't work on another.

The question is really "do i need a programming card?"

The answer i would give is "no".

For 98.3% of electric models, you won't need one. Most models don't need ESC programming, beyond maybe throttle calibration. All usual programming options can be done from the transmitter. I firmly believe that programming cards are a case of "if you make it, someone will buy it". (Or a fool and his money are easily parted?)

The remaining 1.7% might benefit, but when you're buying this model/esc, you'll know what you're up to. (high end, competition stuff etc that probably comes bundled with one, or USB connection etc  to serve the same purpose).

I must have had 30 electric models, yet to purchase a separate programming card.

 

Edited June 8, 2023 by Dale Bradly

[toto]

Well answered kind Sir.

 

I can forget about that then. Sometimes I've seen products in the model rail hobby that are exactly that as well ....... there for the sake of it. It's just nice to be able to spot these before you find out the hard way.

 

Cheers

 

Toto

[Frank Skilbeck]

On 02/06/2023 at 23:19, toto said:

 

 

He has corrected me in what I am trying to do and explains that the motors dont have any feedback facility which would aid in " speed mapping ".

 

 

Toto 

Not strictly true, all brushless motors produce back emf which is what the esc uses to apply the power "pulses" at the  correct moment. You can get sensors that monitor this and provide a motor rpm reading. My Unisens E sensors have this ability.

 

Also some.helicopter ESCs have a governor mode, where the ESC senses the motor speed and adjust the power to maintain a constant motor (and main rotor speed) as the rotor blade angle, referred to as collective, is changed.

 

But as regards a twin fixed wing I've not found the need to adjust the ESC on each motor, the only thing I've done.is add a rudder throttle mix on my Catalina for better water handling.