Antonov AN 124 Rusian

Not surprisingly Christmas has got a bit in the way of modelling, however the wing centre section is nearing completion.

The battery hatch will be a one piece affair held on with magnets to give as much room as possible to slide in & connect the batteries.
A small hatch still has to be cut out of the rear fairing to access the rx.

A little trivial but this is an end view of the Depron battery hatch that contains what is hopefully the very last 'printed' part.

The reason for my jubilation? at achieving this milestone is it the last of no less than 245 of them! Talk about a kit of parts. :woohoo:

Yes it could have been made of Depron but it only used 60 mm (2.25") of printer filament, weighs ¹/₂ g and took under a minute to print so I just couldn't resist doing it.

I have come up against a significant problem.
The Little Bee ESCs are apparently programmed for "BL Heli" software and are "tuned' for operation with a drone control chip. The end result is that on an 'ordinary' Rx they do not arm automatically and require the throttle range to be set at each power on.
This is a real problem as the don't all enter the 'throttle range set' mode at the same time and if you don't set the throttle after 3 seconds it starts all over again.
It is simple 'pot luck' to get the four ESCs to throttle set and arm all at the same time and if you don't you either end up with one or more motor no responding or worse bizarre throttle ranges that can cause instant full power. :woohoo:

The previous Little Bee ESCs in the A350 do not have this issue but then there are only two and are both driven from one battery. By the same token the 4 Little Bees in the DH Albatross worked ok (most of the time!) but they too were all driven from one battery.

It looks like I will have to think hard about how best to over come this.

Little Bee ESC USB Linker Programming Tool (Silabs) I don't know if one of these would help ? Sorry I can't post a link but you can find it easy enough online.

Crash thanks for the heads up.
I had already looked at one of those and it may yet be necessary to reprogram the ESCs to remove its other problem. The brake is 'on' by default. With the motors on a thin pylon snap the throttle shut (or a loose power) and the sudden opposite torque generated from full revs almost twists the nacelle off.:woohoo:
As far as I can tell the other parameters that can be set do not cover the arming sequence.

My sneaking suspicion is down to using 2 batteries coupled with the UBEC powered from just one of them. I think it could mean some stray voltages in the signal commands to the ESC pair connected to the other battery upsetting the arming sequence.
My first trial will be to join the battery leads together so as far as the ESCs are concerned they will all see exactly the same reference voltage.

If push comes to shove I could end up using just a single battery as even a pair of the motors on a fully charged 4 s only take 9.8 A at full power. :woohoo:
A total of 20 A from a 1400 mAh battery is only 14 C which would give a quite acceptable full power duration of 4¹/₄ minutes.

Quorneng wrote "If push comes to shove I could end up using just a single battery as even a pair of the motors on a fully charged 4 s only take 9.8 A at full power. :woohoo:
A total of 20 A from a 1400 mAh battery is only 14 C which would give a quite acceptable full power duration of 4 1/4 minutes. "
Well looking on the positive side that would mean less weight, wouldn't it ? Plus, flying that monster for 4 1/4 minutes would probably feel like half an hour to me ! :woohoo: :lol:

To test the 'one battery' hypothesis I made up a 'gash' connector that allowed one battery to feed both the existing XT60s.
It has certainly made it possible to run all four motors but the ESCs certainly do not operate normally and still expect the throttle range to be set every time. Indeed if you leave the throttle closed for more than a few seconds the ESC start the 'throttle range set' routine again!
Anyway being at least able to run all four I fully charged the 4s.

The Watt meter showed 21.3 A peak and 338 W. At a 'one battery' target weight of 45 oz (1275 g) that gives 120W/lb. A bit low for an EDF but quite reasonable for props.

The actual positioning of 'one battery' was a concern until the obvious answer hit me - use two 2s batteries and connect them in series so two Floureon 1500 mAh 2s 35C are on order.

The final design job is to create a suitable hand launch 'finger hold' in the underside of the fuselage.

So providing the ESC 'waywardness' does not prove to be insurmountable I really can see the end!

To try to identify exactly what is causing the ESCs to misbehave I took a spare ESC and coupled it up to a spare drone motor on the bench operating through an old Orange DSM2 rx. It was bound to the same Tx channel as the Lemon used in the AN 124.
It behaved perfectly normally!
This suggests it is either because there are are 4 ESC driven together or there is something about the throttle output on the Lemon gyro Rx.
It was relatively simple to swap the UBEC 5V supply and the throttle output plugs onto the Orange rx.

Lo and behold it worked perfectly! All four ESCs armed in perfect unison although I had forgotten how long a DSM2 rx takes to do it.

So I now know what is causing the problem but I have no idea why or what I can do about it. As far as I am aware the fact it is a 'gyro' rx has no influence on the throttle channel.
Due to the AN124's almost nil crash resistance I would like to keep the gyro at least until I know it flies adequately.

Quorneng wrote "So I now know what is causing the problem but I have no idea why or what I can do about it. As far as I am aware the fact it is a 'gyro' rx has no influence on the throttle channel.
Due to the AN124's almost nil crash resistance I would like to keep the gyro at least until I know it flies adequately. "
That's really odd! Between Stefan & I we now have 5 Lemon stab plus rx's & so far have had no problems with then. Of course they are all single motor applications, so that may be the difference.

It is indeed odd. I have 3 other planes that use the same gyro Lemon without difficulty.

A little more experimentation.
I coupled the spare motor and ESC to the Lemon in the AN124 and it armed and worked perfectly so it not the Lemon 'per se' suggesting there something amiss with the four ESC and motor set up.
I tried again with the original set up and the tones and beeping started all over again. :woohoo:
I found a description of some of the Little be tones and it certainly sounded like the throttle range set up tones but these same ESCs worked fine when driven by the Orange rx. Very puzzling.

All my 'plane' ESCs up to now have required both a minimum throttle and minimum trim to even arm and my DX6i is set like that but was it possible that the Lemon was sending a 'closed' throttle signal so low that the drone ESCs did not recognise it whereas the Orange rx did not?
Simple enough to check so I added 5 clicks of throttle up trim and bingo! everything worked perfectly normally. Well I never!
I disconnected & switched off everything and it still worked normally when reconnected.
The late hour 11:45 pm precluded any thorough 'full power' testing though.

Three days of worry and testing and all it needed was 5 trim clicks.:ohmy:

The solution finally clicked, then? :woohoo: (Sorry!) :evil:

Pleased you got it working Quorneng. That solution is well worth knowing, for future reference!
Nice one Eric ! :lol:

Remember this problem only seems to apply to a Lemon stab rx and 'drone' type ESCs which have rather different characteristics programmed in (BL Heli firm ware and 0neshot125 communication protocol) to conventional 'plane' types.
Just to prove it a video from today with it run up to full power.

I had to hang on quite firmly to stop it flying away!
Note the bedspread starting to lift in front of the starboard inner nacelle! :woohoo:

Who said electric flight was quiet? [badass]

Eric wrote: Who said electric flight was quiet? [badass]

And who was the old gezzer in the background??