Antonov AN 124 Rusian

After much cogitation (and some reasonable weather) I stripped out and folded down the seats of my car to see if the full AN124 fuselage duct taped together would fit into the Clio Estate with the tail plane and fin attached. With its nose removed It does - just!
This was a relief as it will result in a significant tail weight saving from it all being permanently built into the fuselage.
Pics to follow as it happens.

Having constructed but, certainly not finished, the 'construction' part of the whole air frame the time has come to see if the thrust is likely to be anywhere near enough to fly at:woohoo: its target weight of 1.2 kgs. I do have a plan B but lets not even consider it!

For CofG reasons the battery/s (?) will have to be well forward but hopefully still part of the wing structure.
To keep the ESC to battery distance to a minimum will mean the motor to ESC wires will be long, indeed for the outboard motors they will close to 900 mm long!
Given the lengths required lacquered 0.71 mm magnet wire will be used to save weight and the first bench test will use 900 mm wires as it represents the worst case scenario.
Fortunately the 'Little Bee' ESCs are tiny.

No BEC so a separate UBEC is required which is actually slightly larger than the ESC!

Only a quick test run so far. The Wattmeter showed just 4.95 A on a not fully charged 4s.
It makes a very realistic noise and certainly seems to pull pretty hard. I shall have to find a way to measure it reasonably accurately.
I am looking for at least 5 oz (140 g) thrust from each nacelle but even that would be pretty marginal.

With the house quiet this morning I made a video of the first test of a complete nacelle.

Surprisingly quiet but to be fair 'hand held' does eliminate any resonance which the complete air frame certainly will. It should sound quite impressive with all four going.
Still got to work out how best to measure the thrust. If it is too feeble then it is on to 'plan B' before going any further.

That really does sound very good. With all four running it should be pretty impressive ! Any more thoughts on how you are going to "launch" it ?
PS. If you can't find some paperwork that was on your desk It got blown down the back !

Crash
The thing that went down behind the desk was actually an envelope that contained my old cut up driving licence that I was going to send to the DVLC until I noticed it required a stamp! So I think it can safely remain behind the desk for the time being.

A bit more progress, a thrust test stand.

It will push down on a set of kitchen scales.

At the moment the exhaust is exactly the FSA (Fan Swept Area) whereas the inlet is 1.16 times it.

Conventional 'EDF' wisdom suggest maximum thrust is obtained with an exhaust at about 85% the FSA and peps have actual test results to prove it.
However this is for multi blade EDF fans and to my mind mostly with questionable inlet ducts. Few actually measure the EDF in free air probably because they don't really want to know how much thrust the ducts actually loose!
I can make a 'pear' shaped tail cone that could reduce the exhaust area so out of curiosity I might take the opportunity to test the theory but I will be amazed if it make a measurable difference.

Finally a bit of a disaster.
I dropped one of the pylon motor mounts onto a hard floor. It had the motor attached so the weight did some damage on what is about the most highly stressed part. Still its only another 2 hours 24 mins to print a replacement but it will at least be exactly the same.

Neat idea with the test stand ! If the scales are going on the base, shouldn't the motor be the other way up ?

Nice work indeed! Question: Does that truly qualify as a "ducted fan"? not sure when a cowl becomes a duct.....
I suppose it could be described as a non rotating "kort nozzle"

"Doh", yes of course ! Chalk that up as a blonde moment then shall we !

To my great relief the nacelle works a bit better than I expected. It delivers almost exactly 8 oz of thrust.

This means I could be looking at a thrust to weight of about 80% which would greatly improve the chances of it flying properly.

I then produced this rather exotic shaped exhaust tail cone.

Its bulge reduces the exhaust area to 95% of the FSA.

To my amazement with it installed the thrust went up to 8.3 oz.
I then removed it and did two tests, first with the cone removed altogether - 7.9 oz, then with the simple 'FSA' cone - 7.9 oz again. I then put the bulged cone back on - thrust back to 8.3 oz.
All the test were done on the same battery without any recharge.

It appears I have to eat humble pie! but 0.3 oz (3.75%) extra thrust for nothing is worth having.

That's brilliant ! Just goes to show a little bit of experimentation can often be worthwhile, bearing in mind that's 0.3 X 4 !

Took most of the day but the left hand motors and nacelles now installed on the inner section of the LH wing.

The motor wires run just behind the spar web.

The ESCs are just temporarily placed for testing.
The motor wires are soldered directly onto the ESCs so you are faced with having to re solder a pair if the motor goes the wrong way.
I actually did it on 3 occasions and each time it was wrong. Given its a 50/50 chance of being right Sod's law was obviously working well!

It was a bit late last night to actually run them so a video of this morning's test using a 4s.

Its starting to get quite loud!
The throttle ranges of the drone "BL Heli" ESCs are not particularly well matched and they beep periodically as well as if rearming although once running they work ok.

Well they've certainly got some puff! saw the clothes hanging on the door!
Even though it's well known I'm not a electric fan ( no pun) they did sound good, with a more linear throttle they could be mistaken for jets.