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Originally Posted by Balr14

I'm not sure I understand your dilemma. The HBCP V3 uses 3S motors and battery and so does the HBFP V2, so the DD tail swap was quite common. Using a 3S motor in a 2S system (9116) would make it pretty weak. That's why I suggested the RTF-heli kit fo rht Walkera CB180, which is a 2S system. Am I missing something?

Yupp, you are.
The HBCP3 DD tail mod Zamjustice installed first and I tested too uses a 3s motor in fact. But as the CP3 has a 500mm main rotor and ~400gr and we are taking it for a bird half the size and weight it still is strong enough running on a 2s batt that I had to tame it down with subtrim ~100%left.
It obviously works - now for three different birds.
I was searching for the cheapest tail solution possible for this cheap bird. No more no less. It may work as good or even better with the CB180 tail you mentioned, but that still triples the price.
Edit: The DD kit for the CB 180 uses a 3s N60 motor, too

-mike-

Originally Posted by Rajah235

Hi Skyeblu,
You may have hit the proverbial nail on the head...
Mine is exhibiting "more than normal" vibrations.
After a quick examination, I found that the top ball bearing "housing", (the piece with the anti-rotation bar), has a lot of play in it, allowing the main shaft to move around way too much.
It's not the bearing that's worn, just the plastic housing it.
I intend to replace "that" housing when I get to changing the motor.

L..

I noticed the same thing on mine last night. I pulled a new bearing and housing out of my parts box and they exhibit the same loose fit. So I don't really think that it's wear. I think I'm going to pull it apart and put some ca around the bearing.

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Alright so now you all confused me talking about the torque...

Do you guys think that the torque may have something to do with the tail wag?
Now I remember reading that Steve and Pa trimmed down their main blades and here's something else I am wondering... Out of me being a poor college student I trimmed the main blades to match after a broke one in the cold, and the 9116 was taking of the ground at roughly 45-55% throttle. I hadn't thought to trim more off, but what do you guys think?

I'm having a hard time thinking that I might have to put it down till the DD mod comes in, but it really seems like my tail motor has totally died out, its only got maybe 20 flights on it too....bummer...

The picture is the outline of the main blade, the shaded is what broke and of course the innermost line is the new cut on the blades... at its longest point I ended up cutting about 1.2 inches, but i have not trimmed any other part...

Originally Posted by Steve_

It "should" put the same torque on the shaft...
In the end, you are lifting the same amount, so whether you do it with thicker
blades and lower RPM, or thinner blades and higher RPM, the torque on the shaft
should be the same.

The lightened head has much less rotating mass, and initially (during spool up)
there should actually be less torque on the shaft than the stock head during
changing head speeds, due to the lowered inertia of the lightened head.
Once it is up to speed, the torque should be the same.

Of course, since we trimmed the blades and weights, there is less weight
to lift, so there will be slightly less torque on the shaft due to the removal
of (in my case) right around 6 grams. This is only a 3% reduction in overall
weight, so I wouldn't think it would change the gyro sensitivity, but keep in
mind a stock 9116 is around 235 grams. Adding up all we changed, it is
almost a 20% reduction in total weight, which just might be enough to
mess with the gyro.

(You engineering / physicist types correct me if I'm wrong)

I still get slight wag occasionally, and I wonder if the lightened head
is the source. I will have to swap in a stock set of blades and weights
when I get a chance.

I did not notice any difference after trimming the main blades as far as
tail performance. I actually have mine turned up a few clicks on the trims,
which gets turned down slightly as the battery dumps.

My sub-trims are all centered at 0.

I agree that once up to and maintaining a given speed the torque value would be close, but when do we ever stay at one throttle setting and speed? In my experience that throttle is almost constantly moving to maintain height and forward speed.

I had doubled up the wires to the tail motor. Would that increase it's efficiency enough to help it over power the main? Or is that just a function of the gyro and have nothing to do with the motor's efficiency?

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Is there a better tx available that will work with the 9116? I really don't like the dead feeling around center stick on the stock tx. It's as if the factory has lots of expo programmed in. As we're improving this bird and lightening it, increasing it's agility, this dead spot has become much more obvious. It's sort of like Bair 14 said: each improvement exposes another shortcoming.

Originally Posted by Steve_

We are trimming the trailing edge of the "airfoil", not the length of the blades.
Our goal was to reduce pitch, thereby allowing higher head speed.

The ONLY time you should do this is if your head speed at hover is getting low,
due to the removal of over 25 grams from the bird.
Both Pa Flyer and myself have trimmed roughly 40 grams, and ours would lift
off and hover at 40% throttle or less.

Trimming the ends would lose some stability, I believe.
There would be less blade coning, and I'm not sure how it would
effect disk loading.

Yeah i knew that you were trimming the trailing edge off, I only trimmed the length out of necessity after the blade breaking. I know the weight was down to about 200 grams without the canopy as I have been flying so I thought that might be enough head speed.

I'm just really ticked I have to wait for the new tail to come in before I can safely get off the ground again... Forgive my ranting and way off questions for now haha

Originally Posted by Pa flyer

Is there a better tx available that will work with the 9116? I really don't like the dead feeling around center stick on the stock tx. It's as if the factory has lots of expo programmed in. As we're improving this bird and lightening it, increasing it's agility, this dead spot has become much more obvious. It's sort of like Bair 14 said: each improvement exposes another shortcoming.

There's some mod in the old thread to get rid of the dead spot. Something like adding a cheap resistor somewhere.
Edit: got it:
http://www.rcgroups.com/forums/showp...postcount=2797

Still no step forward using a Th9x - I do not get the rudder problem solved.

-mike-

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Originally Posted by Steve_

True, we change throttle constantly, but mine would wag even in a hover,
with constant throttle input. In that condition, the torque on the shaft should
be the same.

As far as the wires to the tail motor, I have said before, the lower the load
or amperage you are drawing, the less important the size of the wire.

Since a tail motor draws 1/4 what the main motor draws, I doubt changing
to heavier wire would make any noticeable difference, and it might even make
the bird slower from the extra weight.

Of course, it is a longer run, and that matters as well. It's hard to say.

I would actually have to sit down and measure the wire diameter and length
of the wire from the PCB to the tail and then factoring in the resistance (load)
of the tail motor, do the math.

Doubling the size of wire might only give you a 1% power increase, which
wouldn't even cover the extra weight.
Or it could be 10%. It all depends on the load, and the length of the wire run.

Maybe I will crunch the numbers when my headache goes away.

I am just thinking that there "might" some interference in the transmission on the 2.4 Mhz band too. If you have a bunch of 2.4 Mhz equipment , wireless phones etc around you may get some interference. That might be wagging your tail. So take your heli to a different location and see if you have the same issue. One never knows !!

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