Multiplex Funcopter

[RocketManRC]

It is only the set screws in the metal parts that have loctite on them. I think that the soldering iron idea is a good one Jeff and I will give that a try.

Rick

[RocketManRC]

After talking to Jeff yesterday I played with the ESC timing tonight and on the "high" setting for the Turnigy Plush 40 things seemed to improve a lot. Plus when I had the foam side piece of the fuselage off, the mechanical "wobble" in the tail that I noticed last night seemed to go away so I put the foam back on carefully and everything seems fine now.

I am keen to try it but I guess I have to wait until Saturday considering the weather forecast.

If I get this working to my satisfaction I am going to sell it at my cost to someone who wants to learn to fly helis. I think it will be a good trainer. If anyone has an interest let me know.

Rick

[Dirt Torpedo]

At the last indoor I discovered that full throttle was giving me a pathetic 2 fps vertical climb rate, which looks quite scale but would not be very flyable with any amount of wind. I attribute the low power to the very low timing advance (3.75 degrees) that I had selected on my ESC -- to avoid the cogging I had experienced on the default timing advance of 15 degrees -- so I went the other way, up to 26.25 degrees advance, and the motor is now torquey as well as being maybe a bit smoother.

Also at the indoor, I also had a single incident of tail vibes like Rick was experiencing (reminds me of some Jamaican gals doing the dance hall booty shake) so I balanced the blades to reduce residual vibrations. There was only 0.2 grams of difference, roughly 5mm x 50mm of electrical tape, but the head seems smoother now that it's balanced. A quick blade tracking check (just below hover power) didn't show any obvious mismatch in blade pitch.

Now I need a calm day (or indoor session) to get the tail tweaked a bit more.

I still can't get over the lift these blades produce at low RPM with only 5 degrees of pitch. I wonder how much is due to the turbulators?

[Coyote]

This has been a good post to follow. Got an mCX2 for Christmsas and using it to chase the cat and land on numerous tables/stools. Hoping you got rid of tail vibration

Now, pretend I'm a newbie and pls explain relationship for Esc timing to rotors

If timing interval too small - not enough power or sin to the head/rotors? If too much, head speed is too high (engine burnout?)

And how do you change ESC timing?


PS: Hope you had a good Christmas and will have a GREAT New Year

[Dirt Torpedo]

Marc,

My understanding is that the timing advance increases motor torque (and power since power=torque x rpm), but it also generates additional heat since there can be a substantial increase in imaginary/reactive power flow associated with the advance. The trade-off depends a lot on the type and construction of the motor so, given that the funcopter has an unusual motor, I was reluctant to push the timing very much. You can also push it too far and have things go to $#!^, not unlike the case with internal combustion engines.

The adjustment is done by changing the settings in programmable ESCs. Often accomplished with "stick programming", sometimes with standalone "programming cards", and sometimes with a USB adapter which is controlled by software on a PC.

I'll put some ESC programming links in another post later tonight.

[Dirt Torpedo]

Here's an example USB programmer:



Here's an example standalone programming card:



Here's an example of stick programming:

This is generally accomplished with various throttle position changes, according to a flow chart, on power up of the ESC. Programming mode is generally entered by putting the throttle stick all the way up, and the ESC communicates and acknowledges commands with special sequences of beeps. This also means at least two of the three motor leads need to be connected, since the ESC uses the motor to make the beep sounds.

[Dirt Torpedo]

Is a strange electrical thing that should be at least partly explained. Reactive current in a motor is real (in the sense that it can be measured) but it can accomplish no useful work. Some of it will become dissipated as heat as it travels through the ESC's power switches (typically FET or IGBT transistors), power leads, and motor windings -- so if there is a lot of reactive power and current it can lead to overheating and failure of the motor and/or ESC.

[Dirt Torpedo]

Looks like they are coming out with:
- a higher kV motor to give 3S batteries a little more kick.
- some tougher tail drive pieces.
- a new flybar to make it fly better.
- some new stickers.

http://www.rcgroups.com/forums/showpost ... count=1916
http://www.multiplex-rc.de/cms/vorschau ... 011_GB.pdf
http://www.rcgroups.com/forums/showpost ... count=1918
http://www.rcmf.co.uk/4um/index.php?topic=79500.0

In other news, my Funcopter is now sporting a Hitec Optima 7 receiver. Looks like I have a spare Orange 6ch for the parts bin.

[tower]

Just picked up a funcopter as well.
Vibration doesn't begin to describe it! This thing really shakes.
I can't imagine it is due to blade balance? I will take it apart and start the investigation.
Cheers
Jeremy

My testing with the Funcopter was very disappointing. Mine has a lot of vibration in the tail, way too much to be normal.

I took the main blades off and ran it that way and still lots of vibration. Then I noticed that when I rotate the tail blades by hand I can see some wobble in the tail assembly. Probably there is a bent tail shaft or maybe a bad bearing. So much for great engineering if the parts aren't made correctly!

Now I have to fix the darn thing before I even get to fly it. Helicopters are such a pain!

Rick

[Dirt Torpedo]

My blades were 47.5g and 47.7g and I balanced it up with a little piece of black electrical tape at the CG. It seemed to reduce the shakes a lot. Since the head speed is so low on these things I don't think the dynamic balancing is quite as important as it might be with a 3500 RPM CP heli. The other thing that helps is to go easy on the throttle stick, you don't want to whack the power to this thing.

Some people on RCG were going on about using the adjustable links to nail the blade tracking but I didn't bother. Since then I think they've all started running mixed blade grips... weird. They claim that a 4* grip on one blade and a 5* grip on the other is effectively 4.5*.

The tail needed a lot of help and I got it in the form of a tiny Assan GA250 MEMS gyro (like $10 believe it or not) and an Ino-Labs HG-D261HB digital tail servo that I had laying around.

I'm running HS-82MG on aileron and elevator and using the inner horn hole, and find that expo makes it harder to handle.