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Old Jun 14, 2010, 08:11 PM
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Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
1,139 Posts
Quote:
Originally Posted by Paulofthenorth View Post
Just found this thread after reading about your plane in Fly RC.

Are plans available?
No plans, sorry. We've been asked a thousand times for plans of our varous aircraft... you think we'd do something about that.

Unfortunately the aircraft was destroyed shortly after AEF. The elevator servo, an HS-5245MG failed due to what I can only guess was excessive voltage from an unregulated 2S A123 receiver pack. It went in nearly straight down at a very high speed (150mph+). Better than a $1000 crash.

"Charger II" is nearing completion. It sports a thinner wing, main gear doors, more exhaust pinch, and a much more durable fiberglass finish. All that's left is painting the upper surface of the wing and setting up the servos.

Expect a new thread soon for the Charger II.
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Old Jun 14, 2010, 08:20 PM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
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sorry to hear that josh! glad you got another going though! ive been using A123 unregulated for a while with no issues....so far...
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Old Jun 14, 2010, 08:43 PM
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Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
1,139 Posts
Quote:
Originally Posted by corsair nut View Post
sorry to hear that josh! glad you got another going though! ive been using A123 unregulated for a while with no issues....so far...
I know, right? It was that second flight of the day. I clearly lost elevator control in flight. I still had roll and throttle control, don't know about any of the other systems. I had enough time to yell out "I've lost elevator" a couple times before the crash. After an NTSB style invesigation we determined the pushrods had not failed, nor did the horn on either the elevator or servo. The receiver (what was left of it) departed the aircraft, but all the pins were bent n the same manner from the departure, thus making us believe that the elevator servo was still plugged in at the time of the crash.

So now it's down to the servo or the radio system (tx & rx). I pulled the servo apart and it stank like burnt electronics. The elevator servo was the only digital servo on the aircraft.

After some research on the net, I discovered numerous complaints about certain digital servos failing due to voltages of over 6 volts.

I'm going to run 2 Castle 10amp BECs in parallel at 5.5volts for the radio from a single 2s 900mah to 1350mah pack on the Charger II.

-Joshua
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Old Jun 14, 2010, 11:38 PM
My project: FAIREY DELTA 1
Erik v. Schaik's Avatar
Uden Volkel, Netherlands
Joined Dec 2003
4,976 Posts
HI Joshua,

I am sorry to read your plane went down.
I was thinking about demagging edf motors and figured out small servo motors cannot dissipate heat because they sit in plastic houses. Higher Voltage=higher current=heat waste=demagging and this is the reason why I don't use 2s A123. Now one cannot use 2s A123 and regulator on 6V output (my plane Jetmach60 went down in a cornfield, no damage) so I went to 2s Lipolly and regulator which is fine. However, A 2s1p 900(20c?) pack can only handle 18A and the Voltage will drop so I beefed my Rx pack to 2000mah,25C for extra stability and no recharging during a day. I have extended info about regulators+2.4gHz in my A123 blog.

All the best,

Erik

Btw, it is possible to connect telemetry to the Rx pack to measure max current and Voltage sag during flight.
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Old Jun 15, 2010, 06:08 AM
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Paulofthenorth's Avatar
Owen Sound, Ontario
Joined Jan 2006
65 Posts
Charger crash

Sorry to hear about the loss. Looking forward to Charger II!
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Old Jun 15, 2010, 08:06 AM
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Lboogie's Avatar
Sebastian Fla
Joined Nov 2005
600 Posts
Gutted. Sorry for your loss.

Regards,
Leonard
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Old Jun 29, 2010, 07:06 PM
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Paulofthenorth's Avatar
Owen Sound, Ontario
Joined Jan 2006
65 Posts
What airfoil?

Can you tell me what airfoil you used on this plane, or on the Sparta?

Appreciated,
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Old Jun 30, 2010, 07:10 AM
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Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
1,139 Posts
Quote:
Originally Posted by Paulofthenorth View Post
Can you tell me what airfoil you used on this plane, or on the Sparta?

Appreciated,
Both the Charger and the Spatha use the MH-43 airfoil. The airfoil was modified lightly around the wheel wells for clearance.

Seems to be a very fast airfoil, with forgiving characteristics.

-Joshua
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Old Jul 16, 2010, 07:56 PM
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Paulofthenorth's Avatar
Owen Sound, Ontario
Joined Jan 2006
65 Posts
questions

I'm seriously considering building a plane similar to yours in a 90 mm fan size. I've looked at the basic dimensions you give in the Spatha thread and am scaling them up to about a 45 inch span.

Would you be willing to share the c of g location of the Spatha or the Charger?

Any help would be appreciated.
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Old Jul 16, 2010, 08:15 PM
Xtreme Power Systems
Lake Havasu, AZ
Joined Jun 2005
15,771 Posts
The HS-5245MG servos are rated for 5 cell Nimh (7.2v) packs. I personally use A123 packs with all of my Hitec servos, including the 5245 series, unregulated.
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Old Jul 16, 2010, 09:51 PM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
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Any pics josh???
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Old Jul 16, 2010, 10:41 PM
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Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
1,139 Posts
Quote:
Originally Posted by JimDrew View Post
The HS-5245MG servos are rated for 5 cell Nimh (7.2v) packs. I personally use A123 packs with all of my Hitec servos, including the 5245 series, unregulated.
Jim,

We are exploring one other possible cause. Is it possible to overload just one channel of a receiver? The servo was dawing all of its power through the receiver, rather that "Y"ing into the A123 pack. Do you think this could have caused the failure?


Bret,

Not yet... we've been slacking. I'll get new photos of the Charger II and some of the carnage soon.

-Joshua
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Old Jul 16, 2010, 10:42 PM
Faster!
Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
1,139 Posts
Quote:
Originally Posted by Paulofthenorth View Post
I'm seriously considering building a plane similar to yours in a 90 mm fan size. I've looked at the basic dimensions you give in the Spatha thread and am scaling them up to about a 45 inch span.

Would you be willing to share the c of g location of the Spatha or the Charger?

Any help would be appreciated.
Ya, Let me messure it when I get back to the house, and I'll let you know.

-Joshua
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Old Jul 16, 2010, 11:38 PM
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Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
1,139 Posts
Quote:
Originally Posted by JimDrew View Post
The HS-5245MG servos are rated for 5 cell Nimh (7.2v) packs. I personally use A123 packs with all of my Hitec servos, including the 5245 series, unregulated.
Jim,

Check your math: 5 cells at 1.2 volts = 6v.

7.2v would be a 6 cell pack.

The manual included in the HS-5245MG shows operating voltage at 4.8v to 6v. I still think I smoked the servo.

-Joshua
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Old Jul 17, 2010, 03:08 AM
My project: FAIREY DELTA 1
Erik v. Schaik's Avatar
Uden Volkel, Netherlands
Joined Dec 2003
4,976 Posts
Quote:
Originally Posted by JimDrew View Post
The HS-5245MG servos are rated for 5 cell Nimh (7.2v) packs. I personally use A123 packs with all of my Hitec servos, including the 5245 series, unregulated.
You cannot use an 2s A123 pack+ regulator because the regulator will brown out. You cannot use 3s A123 pack + regulator because the regulator will overheat, reduce current limits and shut down on thermal.

NiCd=1.2V
NiMh=1.1V
Voltage will be reduced under load like Lipolly.
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