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Thursday, January 26, 2012

Blade mCP X Tail Blow Out - 100% Fix

Update 2:  The wind was blowing hard but I managed to get enough flying in to repeatedly juice the tail under full power.  The P-51 motor absorbs everything the engine room can dish out, which isn't  exactly explosive power.  Still, my Blade 400's tail fades a little more than the Z8RC mCP X at full bog.  

A Z8RC boom truss is a critical piece of the puzzle.  I banged one end of the truss lose on a hard landing/crash and didn't notice it disconnected until the heli got airborne.  The AS3X-amplified boom resonance was even worse than stock with more rotor power and end mass.

It is a shame E-flite decided to go the rip off route and package a known defective tail motor with the mCP X.  Now that it is common knowledge, it is even more of a shame they refuse to recall and fix their bad helicopters or refund everyone to date.  A 3 cents wholesale more expensive motor from China shows what the electronics can actually do.  

The electric tail is still a bit of a bumble bee as the motor spool up time falls short of belt-driven response, but fixing the manufacturer's defective base design with a larger motor and superior boom design makes this helicopter shine.


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Update:  The UM P-51 motor is even stronger and a slightly easier mod.   Same idea, mod the entire gearbox to slide onto the tail section.  It feels heavier with the extended boom which is probably no longer necessary, but it flies great!  The heli is as about as stable in yaw as my Blade 400.

This is a simple mod that involves a little Dremel'ing of the motor casing and soldering two tail rotor wires.  Takes about 10 minutes start-to-finish.  

Again, the hardest thing is squeezing the tail rotor on the slightly larger diameter shaft; a vice, some padding on the back side of the motor housing and on the prop hub, and a little patience works fine.
The green notch is actually in the other side of my modded
motor case flange, but you get the idea.  Crush the brass 
motor pinion with a vice to remove it.
Original article follows:

See also: http://z8rc.blogspot.com/2012/01/fixing-blade-mcp-x.html

Those trying to flip an mCP X know that the stock tail motor is too weak.  The helicopter loses most of its tail authority during high torque maneuvers and motor punches, spinning uncontrollably until the torque lets up or the ground helps stabilize the tail boom.

So the Z8RC fix is on.

The Flyzone UM Fokker Dr.1 motor is slightly larger than the diminutive mCX main motor included in the mCP X tail boom, so it seemed like a perfect upgrade. Replacement mCP X tail booms with an integral motor run $13, so mod risk is low.
The Flyzone Dr.1 motor is a pretty good fit.  The mCP X 
boom needs to be stepped thinner into a tongue that 
wedges between the motor and its plastic casing.  The 
casing was cleaned up but not structurally altered. 
I left the Fokker motor in its original gear box casing and removed the reduction gear and airplane shaft.  After a few Dremel mods, the case fit like butter over the mCP X motor mount after the stock motor was sliced off at the base of the motor case.  The weight difference is negligible.
Result:  100% blow out fix.

The tail is so solid with the larger motor that when combined with the Z8RC truss mod the mCP X rivals or exceeds my Blade 400 in directional stability.  It is unbelievable how steady the tail can be made during full power punches once the mCP X tail boom is completely redesigned.

The most difficult part of this mod is carefully squeezing the tail rotor blades onto a slightly larger diameter motor shaft.  You have to use wide pliers or a vice that squeezes both ends, the motor backing and rotor blade center hub, at the same time or the shaft will push off the plastic back of the motor casing under the required force (fixable :).
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