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Antonov AN124 Ruslan

Probably my last big Depron plane.

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Stephen Jones17/11/2019 00:22:38
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2737 forum posts
1597 photos

Well if nothing else it has kept you out of trouble for a while smiley

Steve

Simon Chaddock19/11/2019 22:55:13
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5490 forum posts
2887 photos

With its bulk and weight rising I started to get even more nervous about the thrust that would be available so the first task was to check a finished nacelle would actually run on a 4s.

It certainly screams in a rather satisfactory manner and blows quite a bit of air about.

Next it needed a test stand to measure the thrust reasonably accurately.

teststand1

It will simply sit on a set of kitchen scales.

To ensure a realistic reading the motors wires are the full length as required when mounted in the wing.

To my relief it develops a full 8 oz (226 g) thrust which times 4 makes flying a plane with an estimated weight of 40 oz (1.15 kg) rather more realistic.

This thrust was achieved with a motor tail cone giving a nozzle exactly that of the FSA.

tailcone

However some restriction to as little as 85% FSA has shown to improve the thrust.

Out of curiosity I wondered if a 'pear shaped' tail cone could be used to provide a degree of restriction without altering the outside profile of the nacelle.

tailcone95b

It would be a simple direct replacement of the earlier tail cone and reduce the nozzle to 95% FSA .

tailcone95

To my surprise it raised the static thrust to a repeatable 8.3 oz. Not huge increase but an additional 4% thrust for 'nothing' I will take any day. wink 2

Edited By Simon Chaddock on 19/11/2019 22:57:22

Ace20/11/2019 08:54:19
277 forum posts
16 photos

Impressive Simon - enjoying watching from the wings.

Saw one sat at Perth (AUS) last week - big bugger.

antonov 124 perth.jpg

Simon Chaddock28/11/2019 21:03:58
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5490 forum posts
2887 photos

As i had built the test stand and the exhaust cones were simple to print and change I decided to test a full range sizes from no cone at all to one that restricted the nozzle to 80% FSA.

Nozzle FSA Thrust (oz)

80 % 7.9

85 % 8.3

90 % 8.3

95 % 8.2

100 % 8.1

100% but no cone 8.0

The inlet duct is a constant 116% of the FSA

Each result was duplicated and the battery we recharged to 'full' on the charger before each run.

It does appear that a restriction to 85% FSA does give the best result for this particular duct.

To test the structural integrity of the installation a pair were mounted on the LH wing.

It makes a quite nice noise, nothing broke and it even shut the door!

gliggsy29/11/2019 07:46:40
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99 forum posts
4 photos

Hi Simon, just started reading this build blog today, got to say I'm impressed with your tenacity and engineering skills, it's always interesting to see what technology is being utilised for non traditional balsa bashing. Now I've read so far and following, any chance of posting links to your other builds or is it in your profile.... Glyn

PeterF29/11/2019 09:25:25
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454 forum posts
623 photos

Simon, I love the testing, I think it is great do do this sort of thing to understand what we are dealing with rather than just forging ahead blind. I did similar tests for a 55mm fan a few years ago with a similar stand on kitchen scales and got the result that 85% FSA gave the highest thrust. However, I also had the Wattmeter hooked up and a tacho reading the motor pulses for rpm. The reduction in FSA increases the back pressure on the fan, increasing the fan loading, reducing the rpm and increasing current draw. It is not something for nothing, it is in fact slightly less efficient in terms of grams of thrust generated per Watt of power. If you know fan laws, you can then back calculate an average efflux velocity to see how that increases as the FSA reduces. As I was not interested in high velocity flight with my plane, I stayed at 100% FSA. I think I have posted about this before.

_exhaust test 2.jpg

Test stand with open exhaustdsc01166.jpg

Reading recorded by photographdsc01127.jpg

Duct added to exhaustdsc01493.jpg

Edited By PeterF on 29/11/2019 09:32:49

Edited By PeterF on 29/11/2019 09:37:19

Simon Chaddock29/11/2019 12:32:21
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5490 forum posts
2887 photos

gliggsy

So far I have found no way on this site to search just by "builder" as the search engine appears to be limited to just "thread titles" so you have to be specific.

The best I can offer is to search for some titles for my Depron airliner builds like.

Airbus A350

Bombardier Q400

Concorde in Depron

I hope this helps.

Simon Chaddock05/12/2019 22:22:28
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5490 forum posts
2887 photos

The last big bit are the "tail feathers".

They are big, bigger than my complete EDF DH Venom.

bigtail.jpg

As they are relatively a long was back they are kept as light as possible so no spar or ribs just a 2 mm skin over Depron shear webs. lhservo

The 5 g servo just fits between the skins'.

The completed tail assembly.

tail&fin1

As the fin and rear fuselage are 'generous' it will have no rudder and be flown 'bank and yank' so saving the weight of a servo.

Having satisfied myself the motors both work and seem to provide adequate thrust the wing bolt mountings can be designed and printed. The wing will be held on by 4 nylon M4 bolts, two each at the wing leading and trailing edge.

wingboltsfront

The wing centre section in place.

wingbolton

It certainly feels like the more I complete the more there is to do!

Erfolg06/12/2019 14:14:49
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11445 forum posts
1227 photos

Simon

The venom looks interesting, is there a thread?

Simon Chaddock06/12/2019 16:00:37
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5490 forum posts
2887 photos

Erfolg

Its in the Electric Ducted Fan section. From there a search "A 'not so micro' Venom" will reveal the build thread.

With this search engine the search term has to very specific or it simply doesn't find it.

As I could not remember the thread title I had to go through most of the 293 pages of my posts to find a relevant one so I could identify the section and title. smile o

Moral of story on this site - Keep the thread titles short and very specific. wink 2

Simon Chaddock10/12/2019 22:46:23
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5490 forum posts
2887 photos

With the wing in place at long last the wing root fairings can be completed.

Rootfair2

Rootfair3

I sure they will make no difference but they are an obvious characteristic of the full size. wink 2

Simon Chaddock12/12/2019 23:02:59
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5490 forum posts
2887 photos

The next step is to wire up the motors and as in my other lightweight EDFs using 0.7 mm solid 'magnet' wire. It is only 60% of the weight of silicon insulated flex.

A suitable length is soldered to the motor tails and then fed up through the pylon, through the spar shear web and through the ribs to the wing root. It is then soldered directly to the very small Little Bee 20A ESCs.

The four ESCs are spaced out across the root wing ribs.

ESCmounts

The solid wires are held by small Depron retainers as they pass through each wing rib.

The two batteries will slide into boxes built into the wing "D" box.

The wiring is arranged so that the right hand battery and ESCs power the inner motors, the left the outer.

Each ESC is held in a 3D printed mount.

ESCmount.jpg

The Little Bee ESCs have no BEC and generate very little heat so the generous volume of the wing root should provide sufficient heat dissipation capability, particularly as the flight duration is not expected to be that long.wink 2

Power for the rx and servos will be provided by a separate switching UBEC.

This is rather slow going. As everything will eventually be completely 'built in' each step is carefully tested before proceeding to the next.

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