DH 91 Albatross

More
04 Oct 2018 20:41 #136 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
All repaired and repainted.

I really don't think the wing will stand any more such a repairs so I will spend some time to make sure the CofG is in a 'safe' position and the props are on good and tight.
I will also do a static power run equivalent to a maiden flight (3 minutes) just to make sure nothing overheats or fails. ;)
Bizarrely it will be hand launched with the U/C down (to provide a finger hold) but flown and landed with it retracted! :woohoo:
Attachments:
Thanks: Klipkopwildlife, THE BLACKBIRD

Please Log in or Create an account to join the conversation.

More
04 Oct 2018 22:29 #137 by Eric
Replied by Eric on topic DH 91 Albatross
Aim to miss the floor, next time, Q! :evil:

if you are calm and collected when all about you are going berserk - you've missed something important!

Please Log in or Create an account to join the conversation.

  • Flytilbroke
  • Flytilbroke's Avatar
  • Offline
  • 1 Grigg
  • 1 Grigg
  • Not Tired, just retired
More
05 Oct 2018 08:41 #138 by Flytilbroke
Replied by Flytilbroke on topic DH 91 Albatross
Very good camouflage of last mishap. B)

Have a nice Day, unless I don't like you.

Please Log in or Create an account to join the conversation.

  • Klipkopwildlife
  • Klipkopwildlife's Avatar
  • Offline
  • Aermodellers Staff
  • Aermodellers Staff
  • I'm supposed to be retired!
More
05 Oct 2018 13:45 #139 by Klipkopwildlife
Replied by Klipkopwildlife on topic DH 91 Albatross
Best of luck Simon

Do it now, you may never get another chance

Please Log in or Create an account to join the conversation.

More
07 Oct 2018 18:58 #140 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
The saga continues!
With the heavier 1800 mAh battery mounted nearly 2" further forward the CofG is now close to 25%. (Don't know what I was thinking as it was at nearly 40% with the small battery so it was hopelessly tail heavy!)
Ran it on the ground at a realistic flight power setting for a full 3 minutes with no problems, except it felt like the tail was going to come off in my hand!
Calm late this afternoon so took it to the field, connected the battery and....... lots of beeping and the fuselage filled with smoke, lots of it! :woohoo: :woohoo:

Fortunately the battery was not yet in its tray so could be instantly disconnected.
Battery and leads still cold so hopefully not much of an overload but clearly at least two ESCs have blown and seriously burnt through the both the wing and fuselage skins. It don't half pong!

Oh! well at least it gives me something to do.:P :P
Attachments:
Thanks: Klipkopwildlife, THE BLACKBIRD

Please Log in or Create an account to join the conversation.

More
07 Oct 2018 22:39 - 07 Oct 2018 22:40 #141 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
A bit more examination.
The wing cut out to extract the damaged bits.

Not too big an area but it a moot point whether I will ever be able to get all wired up and back in. To say the wiring is a bit 'spaghetti' is an understatement!
The two ESCs

Obviously the lower one got very hot as testament to the un-soldered wires!
It is not clear if the upper ESC has actually failed or is just 'discoloured' due to the burning Depron. :woohoo:
I will test it but it will not be reused.

It is clear what happened but not so easy for the why.
It is not as if these 20A ESCs are worked hard with each only passing some 7A at full power.
The Albatross had done a 3 minute 'endurance' ground test with no issue but as soon as the battery was connected again about 30 minutes later - poof!
So was the ESC at the point of failing at the end of the 3 minute ground run? Or did a short develop between the ESC and the motor?
Also of concern is the length of the now extended battery cable which gives a total of 12" to each ESC. These ESCs are intended for a quad where battery to ESC wire length is normally very short indeed.
However two identical ESCs are used in my A350. They are running on 4s and passing some 15A each! To date it has flown a good many times but the battery to ESC distance is however a bit shorter at 6".

Perhaps to be safe I will add a suitable capacitor(s) where the battery cable divides into 4 which is close to the ESCs.
Attachments:
Last edit: 07 Oct 2018 22:40 by Quorneng.
Thanks: Phil Wood, Klipkopwildlife, THE BLACKBIRD

Please Log in or Create an account to join the conversation.

  • Klipkopwildlife
  • Klipkopwildlife's Avatar
  • Offline
  • Aermodellers Staff
  • Aermodellers Staff
  • I'm supposed to be retired!
More
08 Oct 2018 10:21 #142 by Klipkopwildlife
Replied by Klipkopwildlife on topic DH 91 Albatross
Heat soak maybe? They're in a well insulated area with very little air flow. It was also a 'worst case' scenario, full chat and then stop, in the air your landing phase would tend to cool everything off and there would be air flow.
Just saying!

Do it now, you may never get another chance

Please Log in or Create an account to join the conversation.

More
08 Oct 2018 12:31 #143 by Eric
Replied by Eric on topic DH 91 Albatross
The only thing that springs to mind is that the enamelled motor wires were 'chattering' together, somewhere, and wore the enamel away.
Phut went the FET's!
-
That model appears to be jinxed!

if you are calm and collected when all about you are going berserk - you've missed something important!

Please Log in or Create an account to join the conversation.

More
08 Oct 2018 17:12 #144 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
Eric
I was carefull with the enamelled wires to pass each through its own hole in the printed ribs so they should always be physically separated but you never know.
Klippy
When the new ESCs arrive (from China!) the wing is still plenty strong even enough without the removed skin to be able to repeat the ground test to see just how hot they get.

I have cobbled up the electrics to test whats left. The radio, UBEC, the two right hand motors/ESCs and the aileron servos all function as they should so it looks like the damage has not spread.

The next test is to couple each left hand motor to a spare ESC to check they run normally.
Then its just a wait for the postman!
Thanks: THE BLACKBIRD

Please Log in or Create an account to join the conversation.

More
05 Dec 2018 18:26 #145 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
With the "Cessna Bits" complete and just waiting for the weather (could be a long wait!) it is back to the Albatross.

Having moved the battery forward twice in response to the so far "unsuccessful" flights I am concerned at the battery to ESC lead length and wondered if this is what caused one of them to blow.
My intention is to move the ESCs right forward in the wing so to be closer to the battery which also means they will be further away from the Rx. The downside is it requires quite a bit of 'surgery' to get them out and still more to get them all back in!:woohoo:

Hopefully it should result in a the electrics being a bit less of the "sardine can" arrangement it was before. ;)
Attachments:
Thanks: Klipkopwildlife, THE BLACKBIRD

Please Log in or Create an account to join the conversation.

More
07 Dec 2018 00:26 #146 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
Still struggling to arrive at a solution that keeps the battery leads short and avoids the complete mess of wiring with 4 ESCs, a UBEC and the rx all squashed into the wing centre section like it was.

It worked but as I found it really was just a disaster waiting to happen. :woohoo:
So the proposed solution is to mount the ESCs in a cradle on top of the wing so they poke through a hole in the underside of the fuselage.

This arrangement will keep the battery leads down to about 6", greatly reduce the complexity of the wiring within the wing centre section and still mean only the elevator and rudder servos have to be connected to mount the wing.
Well that the plan but I have to wait for some suitable 22 AWG silicone 'power' wire to arrive from Bury St Edmonds of all placed before I can proceed.
Attachments:
Thanks: Klipkopwildlife, THE BLACKBIRD

Please Log in or Create an account to join the conversation.

  • one tenor
  • one tenor's Avatar
  • Online
  • 2 Grigg
  • 2 Grigg
  • johnpcalex@gmail.com
More
08 Dec 2018 23:51 #147 by one tenor
Replied by one tenor on topic DH 91 Albatross
No more odd than Bangor though

Anything will fly given enough power

Please Log in or Create an account to join the conversation.

More
Yesterday 10:46 #148 by Mowerman
Replied by Mowerman on topic DH 91 Albatross
Makes me think perhaps speed 400 motors in parallel with one ESC were not so bad after all, at least the wiring was simple.

Please Log in or Create an account to join the conversation.

More
Yesterday 12:06 #149 by Quorneng
Replied by Quorneng on topic DH 91 Albatross
Agreed and as I found out the high frequency pulses of current they require can cause them to 'react' to each other when all connected to a single battery but on the other hand brushed motors are so relatively heavy, particularly in my light Depron structures.

Please Log in or Create an account to join the conversation.

Time to create page: 1.450 seconds