mCPx: Known issues, fixes, information rollup

[uh1medic]

Oldrich,

Thanks for your response. The death roll I am speaking of is the result of either one or both of the pitch and elevator servos sending the swash all the way up toward the head, respectively. I am going to perform a very detailed once over of the servos, main board and connections, main gear and main motor.

[oldrich]

ur1medic

I still find that a small self-tapping screw works the best to keep the main gear in place. I tried locking the heli on my mill table and running it up. The results were the right servo would dip .030" as I spooled up the heli, then go back flat when I gave the heli "0" stick. I also wanted to find where the vibration was coming from. I used a high speed strobe light and found it was from the tail boom vibrating up and down. I am going to try and balance the TR blade. I think that the high speeds it seems everyone are trying to run the main at which of course means higher tail speeds is causing most of the problems. I know for sure flying in normal mode this heli hovers very well, with the lower rotor speed curve, both throttle and pitch on my DX6i. By the way the tail boom is braced but it is moving up and down, not side to side

oldrich

ywbc75d@hotmail.com

[dna001]

Originally Posted by uh1medic

Oldrich,

Thanks for your response. The death roll I am speaking of is the result of either one or both of the pitch and elevator servos sending the swash all the way up toward the head, respectively. I am going to perform a very detailed once over of the servos, main board and connections, main gear and main motor.

Hi
Is this brushed or brush-less,

Dose it do it with the tail motor disconnected, just to make shore its not coming from there first.

I had this problem for a bout a week and I was pulling My hair out trying to find it, in My case it was the brush-less motor rubbing against the frame and causing static feeding back to main board. I moved the motor out away from the frame and it`s been good ever since. it dose sound like it could be interference of some kind.



.

[TexasC]

I've read through this thread and no one has yet stated which side to put out when installing the T-Rex 250 bearings?
Does the race side or the bearing side face out, away from the main shaft?

[oldrich]

Hi All

I tried unplugging the tail motor and the vibration all but went away. The 250 bearing should be placed inner race side toward main shaft and outer towaed the blade. you got to make sure that you have no--play and no bind in the grips, when done. I am presently running brushed, but have opened up the stock frame to get good gear mesh. I really want to try brushless if I can find a controller that I can run in governor mode and keep the headspeed down like my T-rex 500 which I am using a Phoenix Ice 75 with stock motor and a 13 tooth pinion with 1800 headspeed, sorry I got to eat dinner will be back.

oldrich

ywbc75d@hotmail.com

[caseyjholmes]

Good compilation of DX4E tips and tricks, brushless or brushed!
http://www.helifreak.com/showthread.php?t=381413
Check it out!

[oldrich]

Hi All !!!!

Well I should get a brushless conversion from HeliflighCenter.com today. The reason was the extreme noise riding on the logic level signals. They have a motor that doesn't require cutting the bottom flange mount out of the frame and is plug and play board. These folks are really smart and are fliers. I will keep all updated on how the conversion works out, I'am looking for a stable ship that can still do "3D". I think that is a tall order for such a smaii heli.


Till Later

oldrich

ywbc75d@hotmail.com

[Aerotony]

Originally Posted by oldrich

Hi All !!!!

Well I should get a brushless conversion from HeliflighCenter.com today.


Till Later

oldrich

ywbc75d@hotmail.com

Oldrich,
Should that be www.heliflightcenter.com ?
Tony

[oldrich]

Tony

Yes it is from heliflightcenter.com. It is great, very little frame mods needed, and it responds very well with just a few % of throttle stich and little vibration. Got it with their 8 tooth pinion gear. I'll let you all know the flight results once I have some real time data. To me this should be HH's answere to a lot of issues.

Happy flying

oldrich

(Rich)

ywbc75d@hotmail.com

[oldrich]

Hi

Just thought I would send a note. I got a V2 tail boom the tailrotor is 1/4 inches larger in diameter. I really don't think that will help as being larger it takes longer to respond, and requires more current to run. I will see but it has been really windy 30-40 mph and 50 mph gusts. I tried it in the house but it didn't seem any different.

Happy Flying
Oldrich

(Rich)
ywbc75d@hotmail.com

[ninja636]

hi
does anyone have an idea what is going on with my 1 month old mcpx. when i hover an try a quick lift my heli spins a few times- nose left?

thanks

[J0KER]

Originally Posted by ninja636

hi
does anyone have an idea what is going on with my 1 month old mcpx. when i hover an try a quick lift my heli spins a few times- nose left?

thanks

My guess:

Your tail motor is going out....


On my 3rd motor already myself. IMHO, These seem to be the weakest link on the mCPx.


HTH

[thegeek]

Originally Posted by TexasC

I've read through this thread and no one has yet stated which side to put out when installing the T-Rex 250 bearings?
Does the race side or the bearing side face out, away from the main shaft?

The closed looking side always faces the load. So if there are 2 bearings in the blade grips, one has the 'closed' side facing inwards to the mainshaft and other backed in with the 'closed' side facing out to the blades.

The bearing facing the mainshaft has to deal with the step on the brass spacer and the bearing facing the grips has to take the load of the spindle screws.

Same for mainframe bearings - top bearing 'closed' side up - bottom bearing 'closed' side down.

HTH

[stevec]

I just replace the frame on my mcpx nd the top main shaft bearing fell to bits on me when I removed it from the old frame.

quick trip the the shed...I had an old tail from a hk450 and I found that the bearing on the blade grip that sits near the hub has a bearing in exactly the same size as the mcpx...



saved myself a few pence in fuel and 4.99 for new main bearings

/Steve

[Waffleman]

My tail boom Cracked on the second "unexpecyed meeting with the ground," and completely snapped off when the heli hit a basketball goal. (Don't ask.) Is the tail boom a weak link in this model? Also, can I remedie it by smearing one with Epoxy for residual strength and then covering it in shrink wrap? Pleae help. It might also be a good Idea to mention that this is my second heli, the first being a coax mcx2. I have lots of sim time, but I do crash frequently when trying to manuver. Will this fix save my tail boom?

[UKHeliBob]

The hollow tail boom is one of the weakest parts of the stock mCPX but something has to be. You would be well advised to replace the stock tail boom with one made from solid 2mm carbon fibre which is much stronger.

Look at the stickies in this forum to see how to do it and advice on lengthening the tail boom at the same time to help prevent tail blowout. Horizon are now selling a longer, solid tail (see threads in this forum). I wonder where they got this idea from ?

[oldrich]

Hi Bob and all

It's been awhile since I have been on for a Post. Well, I have played with the brushless motor and it works really well. Liftoff is about 2000 main rotor speed and it takes off level and straight up in calm weather conditions. The high vibration is all but gone, although I ran the tailrotor against a sanding bolck and actually with the new longer tailrotor blade (V2) it ended up almost the same length as the old (V1) blade when the tail vibration went away. I have put carbonfibre braces on the tail boom as well 1.0 mm. I also found that if you spool up the heli slowly you will see the left servo start to pull down. You have to get the bird in the air asap or it will tip and crash. Once in the air it works well with the gyro and there is no hint of trying to crash itself. As for the tailboom I find they tend to split along their lenght so I fill then with C.A. glue and they are just fine. Just for those who want to know the tailrotor is turning at 16,000 to 20,000 RPM on average.

For Now Happy Flying

Oldrich

[snuvet75]

Originally Posted by Stevendavis

I picked up my mxp-x yesterday and have it on a DX6i. I've put about 6 or 7 batteries through it just flying around. Today I tired high rate and a flip. Did'nt work out so well. As soon as the heli was upsidedown, it started piroing out of controle. This is the first time its been upsidedown. It ended up hitting the ground and the blade grip bearing failed. Don't know why it wacked out upside down. Any ideas??

Same thing's been happening to me. Everytime I try to flip upside down by the elevator(no pun intended -_-), instead of making straight line, it goes sideways, sort of diagonal. Collective moves fine and I leveled the swash plate out at all pitches. But when I put the heli on table, put throttle hold(trainer switch) on and move around the right stick, the range of servos between aileron and pitch servos are different. And when I give elevator up, instead of the back of the swash going straight up, it sort of goes a bit toward right side. I assume every mCPx is like this cuz the linkage to elevator servo is not right in the middle of the heli. I even bought a new set of servos and all the linkages are straight and normal. So the swash going a bit sideways can be normal I guess??
Now the lengths of linkages between the two servos are a bit different after I leveled out the swash. Could this be a problem?
I even considered buying a spektrum transmitter thinking that my crappy DX4e that came with the heli is the problem since it doesn't have EPA, expo or subtrim functions. Especially EPA. I currently have Futaba T7C for my Trex. It sucks that I can't use my lovely Futaba transmitter for it!!
I don't know. Help!!!!!

[oldrich]

HI ALL

Well I am confused (not hard to do) when you say elevator up I guess you mean the cyclic control stick (either forward or aft). well when you pull the stick toward you that is elevator up, fly backwards, etc. That means the swashplate should tilt straight back, the pitch and aileron servos, (the two on the sides,) should go up and the rear servo should go down. It is very important that all the sub trims and stick trims be at "0" before trying to level the swashplate. I do this by setting throttle hold to on and the collective pitch stick to center position (throttle stick), which if throttle hold curve is set at "0" ,(unplug the battery from the heli,) that will be the point to adjust the swashplate linkage to make it level. I take the blades and fold them both back in the same direction, I also tighten the blade grips so that it takes a bit of force to move the blades (when done leave them snug). I then turn them back over the tail boom or close as they (the blades) one will be on either side of the boom. I then adjust he rear servo linkage so the blades are even and parellel with the tail boom. Then turn the head 90 deg. ccw and adjust the servo linkage on the right side, count the turns up or down you go and note it on a piece of paper. Turn the blades 180 deg. centered over other side (left) servo and again align and count the turns and note then. You should probably start with the rear servo down 4 full turns and go down some with the front two, keep rotating the folded blades until they stay aligned no matter where they are turned and are parallel with the tail boom when they stradle it. Now the fun part place the heli on a smooth surface that is level and try some low liftoffs, ie, don't go crazy, lift off completly as quickly as possible, time and if it goes to the right adjust the left linkage down 1 turn and the same applies for the rear servo if it goes forward turn the rear servo linkage down a turn. I find the blades have to be fairly snug in their holders. The one thing that really kills the stability is vibration. Make sure you can get s piece if regular paper between the pinion on the main rotor motor and the rotor shaft drive gears. Also balance the tail rotor with a needle ointed at both ends and a magnetiic balancing holder like the little one that heliflightcenter.com sells. I have spent a lot of time workng with this little heli and it is really a great flier. I also got a brushless conversion from them and a version 2 tail assy. Both of which made a real improvement, especially in vibration, a tail boom support won't hurt either. HAPPY FLYING oldrich (Rich) ywbc75d@hotmail.com

[snuvet75]

Originally Posted by oldrich

HI ALL

Well I am confused (not hard to do) when you say elevator up I guess you mean the cyclic control stick (either forward or aft). well when you pull the stick toward you that is elevator up, fly backwards, etc. That means the swashplate should tilt straight back, the pitch and aileron servos, (the two on the sides,) should go up and the rear servo should go down. It is very important that all the sub trims and stick trims be at "0" before trying to level the swashplate. I do this by setting throttle hold to on and the collective pitch stick to center position (throttle stick), which if throttle hold curve is set at "0" ,(unplug the battery from the heli,) that will be the point to adjust the swashplate linkage to make it level. I take the blades and fold them both back in the same direction, I also tighten the blade grips so that it takes a bit of force to move the blades (when done leave them snug). I then turn them back over the tail boom or close as they (the blades) one will be on either side of the boom. I then adjust he rear servo linkage so the blades are even and parellel with the tail boom. Then turn the head 90 deg. ccw and adjust the servo linkage on the right side, count the turns up or down you go and note it on a piece of paper. Turn the blades 180 deg. centered over other side (left) servo and again align and count the turns and note then. You should probably start with the rear servo down 4 full turns and go down some with the front two, keep rotating the folded blades until they stay aligned no matter where they are turned and are parallel with the tail boom when they stradle it. Now the fun part place the heli on a smooth surface that is level and try some low liftoffs, ie, don't go crazy, lift off completly as quickly as possible, time and if it goes to the right adjust the left linkage down 1 turn and the same applies for the rear servo if it goes forward turn the rear servo linkage down a turn. I find the blades have to be fairly snug in their holders. The one thing that really kills the stability is vibration. Make sure you can get s piece if regular paper between the pinion on the main rotor motor and the rotor shaft drive gears. Also balance the tail rotor with a needle ointed at both ends and a magnetiic balancing holder like the little one that heliflightcenter.com sells. I have spent a lot of time workng with this little heli and it is really a great flier. I also got a brushless conversion from them and a version 2 tail assy. Both of which made a real improvement, especially in vibration, a tail boom support won't hurt either. HAPPY FLYING oldrich (Rich) ywbc75d@hotmail.com

Hi, Oldrich. I really appreciate your lesson. First off, I mentioned "elevator up" as stick goes away from me. It was my mistake.
Secondly, I'll try to level the swash plate again as you directed. I did it mostly right but I might have forgotten to center the trims though they were almost center.
Third, I had this serious vibration issue and saw some youtube video clips and solved the problem by putting the rubber gromet in the swash plate arms where the servo linkages connect the swash plate.
Fourth, I didn't know if I can adjust the gear bite between main gear and pinion. How do you do that? The bolts that hold the main motor are not adjustable.
Lastly, when I said the heli flips diagonally when I flip it(elevator down), I was saying that the travel amount between left and right servos is different. Is this also because of incorrect swash leveling?? The heli hovers pretty decent. I haven't tried to flip it sideways by moving the aileron yet.
Thanks for your help in advance.