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Ark › MX-400 Service report
01-26-2007 11:26 PM  10 years agoPost 101
yoadrian

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Talking Rock, GA

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MX-400 Service report

I figured out what the problem was, or what I thought it was. My rudder servo was binding and I think it overloaded the esc and it cut out. Does this seem possible? The rudder servo actually went out is all I know. I replaced every other component and sent my radio to JR. They checked everything out and said everything was fine. I also noticed that some of my ball connections were tight. I replaced all the head components with aluminum parts and am now going to replace all the servos and ball link connectors, linkages and balls. I also don't like the way the blade grips fit into the aluminum head. It seems like there is too much space between the blade grips, plastic collars and O rings. You can push in the blade grips and they click in a couple of millimeters and you can pull them out, so I will be looking for a solution for that. I also am going to set up the servos like the Trex if possible and try to get rid of the ball extenders on the swash plate and see if I can get a better 90 degree connection up by placing the aileron and pitch servos deeper into the frame. I built a Trex SE that I got for Christmas and would like to try and get the 400 as close to it as I can. I also did the Battery mod by attaching a piece of aluminum at an angle to get a better CG. It looks pretty cool. Any advice is always appreciated.

Adrian

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03-02-2007 07:28 PM  10 years agoPost 102
celihopter

rrApprentice

Planet Earth first on the left..

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blade strike

Have not flown for a while - except the simulator to get this inverted flying down.
I now can hover inverted (on the sim) any direction, fly forward and backwards inverted and do nice inverted circles left and right.
Gave it a try on my MX-400 ccpm modified TREX clone. Wahoo – it worked on the first attempt – did some hovering in 100 ft and a reasonable 360 to the left also inverted. Boy - was I excited.
The simulator training paid back big time.
Went to do this 8 more times successful with almost halve the battery inverted on most of the flights – still at safety altitude of about 60 to 150 ft.
Noticed that I hade less climb out inverted. Some error in my setup allowed only for about 7 degrees negative pitch.
Changed the pitch to +10 and –10 degrees and went out again. This time about 10 to 15 mph wind. Nice hover inverted for a minute - until I decided to climb negative – increased to full negative pitch and –Bang-. I watched both main blades depart the heli in pieces and the following bladeless dive into mother earth.
A blade strike (tail boom) as I went to full negative pitch. Guess the blades get pushed up.
I am using 305 mm (cut down 315 mm) TREX blades, a full metal head except for the plastic REX blade holders.
The blades struck the boom not the tail rotor.
Anybody else had an experience like this?

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03-03-2007 01:28 PM  10 years agoPost 103
helimatt

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Lafayette, IN

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What headspeed you running? Which Trex blades (Pro woodies? The original film covered ones, other?)

I posted a couple threads about this a while back. Several boom strikes with my X400 using the original plastic head, and the Ark wood blades. Once during a roll, once during a flip. In both cases the pitch arms were found broken in the post-mortem, and the theory I had was that they broke in flight under pitch loads. I upgraded to metal pitch arms (Trex), and haven't had another. However I also started using stiffer blades, and running higher headspeed (upped the throttle curve) after that.

Since you've already got the metal components, I think the combo of flexible blades and low headspeed at 10 deg pitch is the issue?

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03-05-2007 03:11 AM  10 years agoPost 104
celihopter

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Planet Earth first on the left..

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Thanks helimatt.
My all metal head survived.
I use 315 pro wood blades with original covering.
I cut them down to 305 mm and rebalance.
Just Go Fly DH-400 motor.
Head speed is about 2600.

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03-05-2007 10:38 AM  10 years agoPost 105
helimatt

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Lafayette, IN

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I'd say the flexible blades are the culprit in your case too, perhaps head dampers too soft unless you were just doing the inverted climbout, not pitching to roll or flip at the time.

Try some Trex pro wood or reasonably good carbon blades. I have had SAB's on my X400, and liked them a whole bunch- unfortunately they met an untimely end for non-structural reasons..

I gotta get a sim.

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03-06-2007 03:15 AM  10 years agoPost 106
celihopter

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Thanks, I will give it a try after I pieced it back together again.
My head dampeners are the standard ones and do feel soft.
Did not roll - just a climbout.

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03-06-2007 12:47 PM  10 years agoPost 107
helimatt

rrElite Veteran

Lafayette, IN

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Celicopter, if you are flying the film-covered blades ('315 pro blades with original covering), I think they are too flexible. How do you have the Trex blades shimmed into the wider X400 grips- could possibly be an issue there.

By the way, your write up in this thread is great- I learned a lot when setting up my X400- it was my first upgrade from a Blade CP I learned on. So thank you! Now I've got it and a couple Trex's, Humminbird Pro, and SMJ400 (still sorting out), and a Shogun clone. I still fly the X400 whenever I can- and it keeps getting better, though some of the head parts are Trex metal now (flybar cage, flybar/paddles, mixing levers, feathering levers, swash).

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03-08-2007 02:57 AM  10 years agoPost 108
celihopter

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Planet Earth first on the left..

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Thanks, I am glade it helped.
I use TREX blade grips so no shim is required. The grips are plastic. All other head components are the red ARK metal upgrade parts - except for the swash which also is a TREX part.

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Ark › MX-400 Service report
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