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Old Jun 24, 2012, 10:16 AM
Picture a worm wearing goggles
snipeworm's Avatar
United States, CA, Roseville
Joined Feb 2012
1,895 Posts
Bummer! I wish the esc's would give you a warning before the lvc. Maybe a 15 sec buzzer before it kicked in would be nice. My first twin met its demise at the hand of the lvc. I underestimated the battery run time and the lvc cut out while I was in a dive. For what ever reason she had a hard time pulling up and nosed into the ground. After that I disconnected one of the bec lines and haven't had a problem since. I guess it probably wasn't a lvc issue but I feel your pain.
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Old Jun 24, 2012, 11:09 AM
How do I land this thing?
fathergoat's Avatar
United States, IN, Warsaw
Joined Feb 2012
217 Posts
It's not a big deal really. The plane sustained very little damage. In fact the rogue gust that blew it over in the parking lot was almost as rough on it. I just didn't realize one motor might kick out before the other.

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Old Jun 24, 2012, 11:22 AM
CNC Cutter
birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
8,604 Posts
Chinese QC/QA ... what Great stuff !
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Old Jun 24, 2012, 11:50 AM
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Drezed's Avatar
United States, VA, Spotsylvania
Joined Jun 2009
283 Posts
Quote:
Originally Posted by fathergoat View Post
The battery got pretty low (10.9v) so I'm guessing lvc kicked in on one motor before the other? I'm using identical esc's. I hadn't really thought of that happening before but I guess I know now.
I've found using a separate BEC, and disabling both of the BECs on the speed controllers helps with this.


Jeff
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Old Jun 26, 2012, 10:14 AM
Registered User
Joined Aug 2010
190 Posts
Quote:
Originally Posted by fathergoat View Post
I was out flying my twins yesterday. The timer on my radio started going off so I was preparing for a landing when I went into a flat spin. I gave it rudder to try and correct but it didn't do much. Luckily my friend yelled at me to kill the throttle, when I did the rudder helped me correct it and level the plane before it hit the ground. The nose got a little wrinkled and the landing gear needs replaced but that's all. When I checked the motors later they both ran. The battery got pretty low (10.9v) so I'm guessing lvc kicked in on one motor before the other? I'm using identical esc's. I hadn't really thought of that happening before but I guess I know now.
Even if both ESCs were exactly the same the voltage is pulled down because of the motor load. One ESC will go into low voltage cutoff a micro second before the other. The voltage will then shoot back up because the load of one motor is gone and the other ESC thinks every thing is fine and doesn't shut down. I use ESCs that I can turn low voltage sensitivity way down. It is either save the plane or save the battery pack.
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Old Jun 29, 2012, 09:34 AM
You're killin' me Smalls
BrownEyedFool's Avatar
United States, NJ, Hillsborough Township
Joined Sep 2011
1,551 Posts
Had a silly thought last night over a cold beverage and figured this thread would be a good place to ask.

Has anyone considered making Lonestar and Barf's ship as a twin?
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Old Jun 29, 2012, 12:34 PM
This Calls for a Sexy Party
StewieRC's Avatar
Minneapolis
Joined Sep 2010
639 Posts
I'm about to order two HXT D2211-1700 (16g) to build a bigger twin ( my 50% with 2 18-11 couldn't haul much weight at all )

How big should i build this plane with 2 16g motor ?
i'm pretty sure that 50% would be too small and 75% would be too big, should i go for 60% ?

i was going to build it running on a 2s, but HK is out of 7x3.5 gws counter rotation props. Would 3 cell on a 6x3 be too fast for this model ( lot of speed but no thrust to haul anything )

here is the motor data :

http://static.rcgroups.net/forums/at...~1570Kv%29.jpg
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Last edited by StewieRC; Jun 29, 2012 at 01:24 PM.
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Old Jun 29, 2012, 01:06 PM
ROFLCOPTER
Iron Savior's Avatar
United States, KY, Louisville
Joined Mar 2011
230 Posts
Quote:
Originally Posted by StewieRC View Post
I'm about to order two HXT D2211-1700 (16g) to build a bigger twin ( my 50% with 2 18-11 couldn't haul much weight at all )

How big should i build this plane with 2 16g motor ?
i'm pretty sure that 50% would be too small and 75% would be too big, should i go for 60% ?

i was going to build it running on a 2s, but HK is out of 7x3.5 gws counter rotation props. Would 3 cell on a 6x3 be too fast for this model ( lot of speed but no thrust to haul anything )

here is the motor data :
[img]http://static.rcgroups.net/forums/attachments/1/7/1/7/8/a2395535-168-HXT%20D2211-1700%20%28~1570Kv%29.jpg[img]
2x 16g motors with 6x3's should be able to handle 75%. How much thrust do they generate?
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Old Jun 29, 2012, 01:25 PM
This Calls for a Sexy Party
StewieRC's Avatar
Minneapolis
Joined Sep 2010
639 Posts
around 300g on 2s and around 400g on a 3s.
i'm still not sure about the battery size and stuff. i got a 460mah 3s laying around, should i pick up a few more or buy a bigger 3s battery ?
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Old Jun 29, 2012, 01:32 PM
ROFLCOPTER
Iron Savior's Avatar
United States, KY, Louisville
Joined Mar 2011
230 Posts
Quote:
Originally Posted by StewieRC View Post
around 300g on 2s and around 400g on a 3s.
i'm still not sure about the battery size and stuff. i got a 460mah 3s laying around, should i pick up a few more or buy a bigger 3s battery ?
That will give you about 28oz in thrust on 3s. I'd say you're safe for 75% as long as you don't overbuild it. I'm planning on using 5x3's on my 75%'er if I ever get around to it. This oppressive heat may just drive me to building it.
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Old Jun 29, 2012, 02:41 PM
This Calls for a Sexy Party
StewieRC's Avatar
Minneapolis
Joined Sep 2010
639 Posts
i forgot to mention, 300g on 2s and 450g on 3s are for both motors.
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Old Jun 29, 2012, 03:03 PM
ROFLCOPTER
Iron Savior's Avatar
United States, KY, Louisville
Joined Mar 2011
230 Posts
Quote:
Originally Posted by StewieRC View Post
i forgot to mention, 300g on 2s and 450g on 3s are for both motors.
Well 14g isn't unreachable on the 75% plan. That's just under 1lb.
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Old Jun 29, 2012, 03:28 PM
This Calls for a Sexy Party
StewieRC's Avatar
Minneapolis
Joined Sep 2010
639 Posts
Quote:
Originally Posted by Iron Savior View Post
Well 14g isn't unreachable on the 75% plan. That's just under 1lb.
i dont get what you mean by 14g isn't unreachable on the 75% plan.

_________________________

I can push the motor a little bit by using a 8x4 on 2s, so i'll get around 550g on 2s. ( it get pretty hot down in TX right now, not sure about pushing the boundary. )
if i'm using a 6x3 on 3s will produce around 600g ( both motors ) but with a 10mph faster pitch speed. I'm not an expert on RC so i'm not sure whether the extra 10 mph pitch speed will effect the twins performance.

a more in-depth stat of that motor : http://innov8tivedesigns.com/PropCha...-2211-1700.htm

This is the list of electronics that i'm planning to use on my twin :
  • x2 16g motor ( undecided on whether to use 3s or 2s, about 550g of thrust )
  • x2 Plush 10 Amps ESC ( around 20g for 2 esc )
  • x4 HXT500 servo for Aileron, Elevator and Rudder
  • x1 3.7g Hobbyking servo for Gear door
  • Flysky receiver ( around 5gram)
  • Undecided on battery, hopefully someone can help me pick one.

plane will be build out of 99% $tree foamboard with paper removed.

50%, 60% or the 75% of The twins cargo plane would be a good match ?

p.s : how do you guys determine how big the plane should be for a specific set of power system ? so i don't have to ask this kind of questions again.
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Old Jun 29, 2012, 03:30 PM
ROFLCOPTER
Iron Savior's Avatar
United States, KY, Louisville
Joined Mar 2011
230 Posts
Quote:
Originally Posted by StewieRC View Post
p.s : how do you guys determine how big the plane should be for a specific set of power system ? so i don't have to ask this kind of questions again.
By the estimated weight of the plane vs the thrust provided by the power system. I don't think 10mph is going to make much difference regardless of which scale you decide to go with.
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Last edited by Iron Savior; Jun 29, 2012 at 03:38 PM.
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Old Jun 29, 2012, 06:49 PM
Registered User
Joined Aug 2010
190 Posts
I have two 75% twins with 1550kv motors at 12 amps each max with 2 cell lipos. It has enough power to hover but won't climb vertically. The props are 7X3.5 I think.
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