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Old Aug 05, 2012, 09:49 AM
215.0 MPH
markusvt's Avatar
United States, VT, Essex
Joined Jul 2007
1,186 Posts
Very good point. I have an Enigma, and a Swist, had a Viper, and numerous 40 inch pylon racers that were very, very fast, but there is something unique about getting a $109 hunk of foam with 2 servo's to go that fast, no one expects it from a cost or performance perspective.

The Enigma prop/spinner assembly alone costs more than the FJU kit!

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Originally Posted by johnnyrocco123 View Post
Those who are looking for 200mph, why not an F5D airframe?
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Old Aug 05, 2012, 09:51 AM
215.0 MPH
markusvt's Avatar
United States, VT, Essex
Joined Jul 2007
1,186 Posts
CG issues with bigger motors and batteries?

Quote:
Originally Posted by E-speed buff View Post
I wanted to share my own design universal outrunner motor mount with you guys.
That has been in use for more than 2 years on several FJU's.
It saves ~20gr on the original motor mount, and has proven to withstand >3Kw.

Grtz René
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Old Aug 05, 2012, 10:40 AM
186mph Funjet Ultra
E-speed buff's Avatar
nieuw vennep, the netherlands
Joined Feb 2010
506 Posts
Quote:
Originally Posted by markusvt View Post
CG issues with bigger motors and batteries?
Hi Markus

With ~200gr outrunners and ~400gr LiPo it is right on the original CofG!

Sebbe it is the camera angle!

Grtz René
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Old Aug 05, 2012, 12:19 PM
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feefo's Avatar
Staffs, UK
Joined Apr 2009
3,601 Posts
Had an 'incident' today....

Powered up and everything was fine, launched no prob and did a circuit. I need to adjust ele trim, Evo 9 has small trim buttons so I cut the throttle, applied a little up, looked down at my trim and adjusted. Went to power up and I got nothing from the motor. Then suddenly it rolled and acted if it stalled, I had no input control. Then gained control for 10 secs or so, then loss of control and another roll and stall, then control again. Finally lost control about 20' from the ground although it didn't stall. It did hit a bloody tree tho....

When I got to it control was fine but the esc to motor wires had come disconnected so I haven't checked that yet. Haven't looked at the Ice log to see if that tells me anything (I doubt it). Nose was bent but the carbon strip saved it from a break, I think. Small split in wing and fuse joint but otherwise ok. probabaly the fact it was going slow saved it from major damage.

So I'm not sure what the prob was/is. Solder joint and wires look ok at the bullet connectors for the esc and CC bec, servo plugs securely in the RX, never had a brown out on MPX, not sure what to do next (other than another range check....). Kinda paranoid about attempting another flight without doing something.

As I walked over to find it I was expecting a control horn to be broken or loose as an explanation of the lack of control, but loss of throttle....not sure. If the Bec wasn't getting power I guess that the esc wouldn't control the throttle. I wonder if the CC Bec got damaged internally when I crashed it and was/is 'limping through'? Maybe I should replace that as a starter?

Or anyone got any other ideas?
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Old Aug 05, 2012, 01:29 PM
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feefo's Avatar
Staffs, UK
Joined Apr 2009
3,601 Posts
OK, wire connections good. Esc and motor reconnected, motor spins up.

Now then, as the battery connection is made, the esc makes it's start up tune, the left wing servo twitches . A couple of times when the connection was made, the elevons actually go to a left elevon up, right elevon down, then they settle to neutral. Then, as the esc sits idle it's fine, but when the esc beeps to let you know it's in data logging mode the left wing servo twitches again, like everytime it beeps it twitches. If I disconnect the CC Bec and just use the esc's bec to power everything, I get no glitch as the Ice esc beeps and no servo movement on battery connection.

So I'm going with a faulty CC external Bec as the prob, but would still like your opinions.

Cheers.
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Old Aug 05, 2012, 01:44 PM
215.0 MPH
markusvt's Avatar
United States, VT, Essex
Joined Jul 2007
1,186 Posts
You disconnected the internal BEC, (red wire) when hooking up the external ESC? What is the Rx?
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Old Aug 05, 2012, 02:22 PM
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feefo's Avatar
Staffs, UK
Joined Apr 2009
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Yes the red wire from the esc was disconnected.

RX is a Multiplex RX-6-DR light M Link 2.4g. They're a dual receiver model, so I don't believe it was a brown out, I think it was the external Bec.
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Old Aug 05, 2012, 03:00 PM
Why the dirt on the wings?
moparmyway's Avatar
New York
Joined Jan 2009
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Quote:
Originally Posted by feefo View Post
Yes the red wire from the esc was disconnected.

RX is a Multiplex RX-6-DR light M Link 2.4g. They're a dual receiver model, so I don't believe it was a brown out, I think it was the external Bec.
Most times you can alleviate glitches from BEC's by increasing their set voltage output.

Try that on the ground and see if there are still glitches. I probably wouldnt fly it though, if it stops glitching, maybe your new ground test receiver ?
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Old Aug 05, 2012, 03:08 PM
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Staffs, UK
Joined Apr 2009
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I'm pretty sure Bec voltage is 6.1v as you recommended Morpar.
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Old Aug 05, 2012, 07:06 PM
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FlyBillyFly's Avatar
Rogersville, Mo
Joined Jun 2008
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Our Heat spell broke...Finally!!!!!!!!!...hope to also git the megas first flight in also..

Nice Flight Rim!!!!...

Hope ya figure out the prob Feefo...We Fly tues..I'd like to get some of that 180 stuff too Rim....Sounded very good.....

Billy
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Old Aug 05, 2012, 07:57 PM
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Alberta,Canada
Joined Nov 2009
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Quote:
Originally Posted by FlyBillyFly View Post
Our Heat spell broke...Finally!!!!!!!!!...hope to also git the megas first flight in also..

Nice Flight Rim!!!!...

Hope ya figure out the prob Feefo...We Fly tues..I'd like to get some of that 180 stuff too Rim....Sounded very good.....

Billy
Just please be careful with your hot weather,prop up slowly and check temps,it will be a screamer with those pylons!!!
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Old Aug 05, 2012, 08:57 PM
215.0 MPH
markusvt's Avatar
United States, VT, Essex
Joined Jul 2007
1,186 Posts
There are sometimes issues if the external BEC is mounted very close to the Rx.

Quote:
Originally Posted by feefo View Post
Yes the red wire from the esc was disconnected.

RX is a Multiplex RX-6-DR light M Link 2.4g. They're a dual receiver model, so I don't believe it was a brown out, I think it was the external Bec.
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Old Aug 06, 2012, 12:01 AM
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Denver, CO
Joined Nov 2007
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--Here is a standard FJ that I torqued rolled into the ground at WOT. The 4000 4s battery flew about 75ft into a storage container after the FJ hit the dirt. Warning-- a certain f- word was emitted by the camera man.

FJ Crash at WOT (0 min 37 sec)



--On the topic of speed, here is an 1800 watt F-16 -- Ultra would smoke it with the same power

--:40 and 1:05 seem to be the fastest passes -- high 140's -- low 150's -- with aft cg, cooler day, fresh pack, and perfect run, may reach high 150's -- 160's at sea level
--elevation 5200 ft at 80 F --at altitude, speeds seem to be a little slower than sea level

--Notice no torque roll on launch -- courtesy of ducted fans -- it did torque on the go around because I punched the throttle at low speed and it has a an outrunner

F-16 5s Doppler cut (2 min 52 sec)
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Old Aug 06, 2012, 02:33 AM
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feefo's Avatar
Staffs, UK
Joined Apr 2009
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Quote:
Originally Posted by markusvt View Post
There are sometimes issues if the external BEC is mounted very close to the Rx.
Nope, RX is in the nose, esc is behind the spar.



Good for 'ya Billy, looking forward to some reports and vids. Take it easy, it's another (long) wait to have a Mega fixed and you've waited long enough already. Have fun....
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Old Aug 06, 2012, 03:32 AM
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GryphonRCU's Avatar
United States, CA, SF
Joined Mar 2008
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Billy,

I read about both of the motors in different posts, not sure which one you are starting out with(I lost track).

Does not make a difference to me....but you might not want to use a prop with enough pitch to make the plane very high speed capable "on a maiden flight".

So double check your static data by sending it Rim or other friends for review.

No need for aggressive prop during maiden....even if you intend to use lower throttle setting.


Gryphon
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