Calibrating ESC 's on a twin prop.

[toto]

As it says.

 

When calibrating a twin props ESC's are they calibrated separately or both at the same time as one task?

 

I'm thinking about my Twin Otter and my B25 Mitchell Bomber ....... in fact .... I have a four prop B24 Liberator as well. I need to check how many ESC's are involved in that set up.

 

Any comments welcome.

 

 

[Philip Lewis 3]

I doubt it would matter but personally I would do them one at a time just so that I made sure I heard the confirmtory beep for each one.

[Andy Gates]

I agree with Phillip, calibrate each one separately before linking them up in a plane.

However if you are using different receiver channels for each speed control, then you can still calibrate each one individually via each channel.

[Merry Mark]

Just be sure to do so with props off and look after those digits. 👍

[Peter Beeney]

Hi toto,

Re your B-24 Liberator, a number of years back now I was considering building an electric B-17 Flying Fortress. I actually made a start by obtaining a complete power train, which was just simply four of everything really. I put it all together on the bench in more or less the configuration that it would be in in the model and gave it all a really good helping of activation, indeed some of it a bit ‘vigorous’ because I do tend to like to fly models quite hard at times.

Each prop had its own complete assembly, motor, ESC and battery. I was using a MPX radio at the time which was very versatile so I simply plugged the 4 throttle control cables into 4 receiver channels and just ganged them together. But I could still add a couple of tx slider controls plus virtual unlimited mixing and individual switching if I wanted - particularly the rudder of course. Having said that and then tinkered with it as well, had I eventually built the model I would probably have never used most of it anyway…

I can say, as far as I can remember at least, I never found any problems at all with this trial of multiple motors. It all gave me total confidence it would always provide plenty of pulling power. At one point I cobbled the 4 battery packs together in parallel which made no noticeable difference to anything; in fact, I would have been most surprised if it had done so. Also I must admit that I've never quite understood why the positive (red) wire connection is disconnected when multiple ESCs are used in parallel so I've never bothered to do that either. However, it does generally seem to be the number one most important thing to do when using twin ESCs and I certainly don't have any problems about that at all as well. In both cases power is still supplied to the receiver.

You mentioned the number of ESCs possibly required for 4 motors, MPX do supply a 2 in 1 ESC for their TwinStar but I don’t know if this is available separately. I suspect it maybe though, they do sell spares I believe. But a colleague has recently had ongoing problems with his newish TwinStar and has now bought new motors and separate ESCs. I have the original which I’m hoping to try out when I get the time. It’s just two complete output units - the switching transistors - on the same PCB but both controlled by one control signal from the receiver and one voltage regulator aka the BEC supplying the power to it.

 
Hope this may be of some interest, please come back if there are any points that may require any clarification…

Good luck

PB

Edited January 15 by Peter Beeney
Text added

[Simon Chaddock]

Toto

If you are really worried about it run up all the motors to full power and listen for the prop "beat". If its slow then the props are all rotating at pretty nearly the same speed.

https://www.youtube.com/@simonchaddock4274/videos

On the full size the pilot would individually adjust the throttles during cruise so any beat was very slow simply for the crew comfort.

Note in tis case they are ducted props so no finger issues. You would need to be very careful do this with "open" props.

   

[Chris Walby]

On 13/01/2025 at 21:11, toto said:

As it says.

 

When calibrating a twin props ESC's are they calibrated separately or both at the same time as one task?

 

I'm thinking about my Twin Otter and my B25 Mitchell Bomber ....... in fact .... I have a four prop B24 Liberator as well. I need to check how many ESC's are involved in that set up.

 

Any comments welcome.

 

 

I will answer the question twice 🤣

 

For anything ARTF (and for all of mine, P38 x2, OV10, & PZ Mossie) I have never had to calibrate the ESC's and I would expect the same with your B25 & B24, if it isn't broke then don't mess around with it. I even did the P38 motor and prop upgrade and still didn't touch the ESC's

 

If you are building a new model or replacing ESC's then test the set up before calibrating as I am struggling to think when I calibrated either of my BH mossie, Ta154, Focke stick, Grumpy Tiger Cub or WooHoo. Its normally very noticeable as either one motor starts before the other or one does not achieve full speed at WOT and you can hear the unsynchronised noise. As a twist I actually like the slightly out of sync sound with an IC twin...as I know that both are still running! 

 

Its good to know what to do if they are out of sync, but I would not go out of my way to induce a fault, only to then have to fix it.

[Philip Lewis 3]

What you are doing here is not so much calibrating the ESC what you are doing is calibrating the ESC to the specific signal output of your TX, different brands of TX have different minimum and maximum outputs in milliseconds, Spectrum for instance is 80% of the 1000 -2000 microsecond range considered by many as standard full range and Futaba is somewhere  in between, so if the ESC has been set up for Spectrum and that is what you are using then fine but you likely don't know anyway, and an ESC set up like that would, on a FrSky TX have a dead point at the last 20% of the stick travel at each end where nothing would change.

 

Looking at the opposite for an ESC set up to expect 1000 - 2000 microsecond range then without calibration a Spectrum TX wouldn't even get the ESC to arm and even if it did it would never achieve full throttle.

 

That is also why some elecrtric retracts refuse to work with Spectrum TX's, they are expecting more that the TX is outputting and won't work until the limits are extended to extend the output levels to trip them ino opperating.

 

Either way you should absolutely calibrate the ESC to your own TX output, it may well appear to work but you might not be getting the best out of it if you don't. 

Edited January 16 by Philip Lewis 3
Spelling

[toto]

Hi Philip,

 

I think you are confirming my understanding of why this calibration is required.

 

I have watch a utube video or two on this and the demonstration showed the throttle not kicking in when the throttle stick was initially moved on the transmitter. It kicks in further into the throttle sticks movement range.

 

After the calibration exercise, it's the demonstrated that the throttle now kicks in immediately. 

 

I think my simplistic explanation is the same 

 

Feel free to correct me though.

 

Toto

[Philip Lewis 3]

22 minutes ago, toto said:

I have watched a u tube video or two on this and the demonstration showed the throttle not kicking in when the throttle stick was initially moved on the transmitter. It kicks in further into the throttle sticks movement range. After the calibration exercise, it's the demonstrated that the throttle now kicks in immediately. 

Yes that is demonstrating what I said above, the effect you might notice in that scenario would be an throttle that is more sensitive than it needs to be because you wouldn't be using the full range of the stick.