crashcrash

This thread is dedicated to the ARK-400 and the Heli-Max MX-400. DIscussion will include parts compatability with the T-Rex, problems encountered, and fixes you have discovered. Other forums have this topic, RCU does not, so I'll kick it off.

I bought my MX-400 a couple weeks ago. I ordered and had on hand before it got here the 120deg CCPM upgrade, and the CNC main center hub. Lets face it, the heli costs $75 shipped and lacks quality (not an opinion, it's a fact). Here's a list of items that MUST be replaced (right out of the box) by either CNC parts or OEM T-Rex parts:

*main center hub (plastic...breaks easily)
*stabilizer control set (it just looks weak)
*vert/horiz stabilizers (made of heated granular plastic sand and breaks easy)
*anti-rotation bracket (broke easily)
*entire tail rotor assembly including the slider (mine was broke NIB)
*flybar paddles (same material as vert/hor stabs).

In my opinion, the 120deg CCPM upgrade is a must. Included with that is a CNC 120deg swash. You get rid of a lot of weight and un-needed linkage with this upgrade.

Other problems included:

* rudder control rod was too short
*Horizontal stab mount bracket broke easily
* rudder servo being hard mounted in the frame causes problems with adjustment.
* pitch adjustment links are too long with the CCPM upgrade.

I am just now getting to the point where it's fairly good flying (getting it set up properly with the DX6).

What I've done to correct short commings:

I decided to use T-Rex OEM parts as replacement parts where I can. I have either ordered or already replaced these items with T-Rex parts:

*flybar control bracket
*flybar paddles
*tail rotor/slider assemblies
*vert/horiz stabs and mount bracket
*rudder servo moved to the tail boom using CNC servo holder for T-Rex
*I made an aluminum anti-rotation bracket from .032 aluminum
*replaced the stock skid poles with T-Rex smoke chrome skid poles.
*replaced the upper collar on the main shaft with one off HoneyBee King v2.

Installed:

DX6/AR 6000
3500kv Copter-X inrunner BL
33a ESC by Copter-X
E-Sky 8g servos x 4 (working fine)
E-Sky 0704A HHG Gyro (working fine)
1500mAh 15C 11.1v Li-Po x4 (too small for this bird)

I've been encountering problem after problem in getting this flight capable. The batteries work, but they get warm....the motor dont. Stability seems to be a big issue but increasing headspeed helped. I can't dial in the idleup settings until I get shorter pitch links because I cant dial in neg pitch because of the DX6 wanting to be set at CP6=60% (this is where it seems to run the best). Moving the rudder servo out of the frame is a must....it just helps so much when setting it up. The elevator servo is an absolute pain to get at to make any adjustments....you need a thin needle nose pliers for it.

Well....that's about it for the night. Anyone else care to share what they know....jump right in.

crashcrash

Update....T-Rexparts.com delivered my package today. As pictured, all the substandard parts I have replaced:

Flybar paddles (Align)
flybar bracket (Align)
rudder servo holder (Align)
tail rotor assembly (Align)
vert/horiz stabs (ALign)
skid poles (Align)
canopy mounting pins (CF rod with fuel tube and shrink tube)
anti-rotation bracket (hand made aluminum)

First outdoor flight with all the new parts. Wind was 8mph gusting to 10mph, temp at 23 degF. Flight went VERY well. The wind tossed it twice and both times I spun it nose into the wind and flew it back with no problem. Has solid stability and good reaction to flight control input making for a very nice flight even in the wind. Dunno if I'll fly iy one more time tonight or not....pretty cool outside.

The way it is.....

The MX-400 is a very poor choice for beginners (not to mention cost to make it decient) and you can plan on replacing a lot of stock parts right out of the box to make it fly well, but once the parts are replaced and the setup is done correctly (and that takes a ton of work), it's a very competative electric heli. I've owned 3 honeybee King v2's which flew well and I liked them. I needed something that will fly well in 15mph winds...the MX-400 will do it and the HBKII will not. As it stands, my MX400 is a better heli than I am capable of flying so I will need to grow into it. I am very happy with the results.

AirmanBob

My Feedback: (14)

YAWN..................

crashcrash

ehhhhhhhh....yeah, it looks that way.

osterizer

I think a) Bob's coming out of hibernation, or b) there's a lot of discussion elsewhere on parts compatibility and so on. There are so many ways to fix an MX it may just all have been said already.

How's the MX flying, Bob? Haven't seen you here in a while.

crashcrash

LMAO...the parts I knew would break did.....waiting for parts. Got into a powerline and had a 25ft drop to pavement on a 21deg day. The only parts lost (that I have to buy) were the see-saw (plastic) and one mixing arm....a whole $13 in damage. Had they been aluminum....I'd still be flying. As soon as I can, I'm upgrading the rest of the head to aluminum. Got the parts ordered, Sat/Monday they should be here. It did give me a chance to do a good reconfigure of the ESC/Gyro/and RX...much cleaner, and everything is in the lower frame now. I had the ESC on the belly before. Mounted the gyro right behind the anti-rotation bracket with a special made aluminum mount that bolts to the frame.

osterizer

That's pretty much what happened with mine. I had an MX450, and bought an MX400 that was halfway upgraded (partially aluminum head and CCPM frames). I finished the head off, then took it apart and rebuilt the whole thing and converted to 4S in the process since I'm going that way with all of them. I wound up with the gyro on the platform, a SportBEC under the gears, radio in the usual spot and the ESC strapped underneath. I made a slanted tray to raise the battery, so if I were planning on flying it hard now I'd probably move the ESC and the rest of the electronics up under the battery tray in front of the motor.