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 Elevator- Fore/Aft Cyclic linkage modification.

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Raptor 60 ballooning: Stock machine tends to pitch up in full fast forward flight, full collective. An example would be coming out of a huge full speed  loop, at the bottom the machine would tend to "want" to do it again.
This is not to be confused with "porposing", the tendency of a heli to feel "pitchy" in most flight modes, even at lower flight speeds. That is a topic for another day :).

This modification tends to hold nose down at full collective, high speed upright flight. Solid feel thus far in testing. Have not tested enough to recommend this mod.

This situation on the Raptor may be able to be  handled by radios such as the 9Z by using offsets or other mixing functions. I am trying to get to the point mechanically that is comfortable and handles better than stock without using mixing functions. The mixing functions can then be used to fine tune tweak the machine if necessary to dial it in for the individual if needed.

This set up replaces the stock 2 linkage rod system and its intermediate bell crank
with a single push rod from the servo to the elevator yoke arm. The purpose was to test my theory that there is induced input from the 2 link rod system that causes the heli to balloon up if no forward cyclic is held while achieving full speed forward flight. The situation becomes worse if there is any slop in the linkage from the servo or excessive backlash slop in the servo itself.

I used a 2 mm stainless rod threaded on both ends. I then slipped a piece of CF rod over the 2 mm rod to stiffen it. The CF rod was tapered on both ends prior to installing and was then glued to the 2 mm link rod with medium CA, offset towards the servo for rod to frame clearance on the other end.

To gain clearance requires that the link rod ball stud be spaced out at the elevator yoke drive arm. The spacing is equivalent to one extra ball and requires a longer screw.

To gain additional clearance at the frame required grinding the CF chassis on an angle, feathered down to the frame bolt.

Spacing out the ball stud on the elevator control arm creates a problem with the stock plastic arm and yoke. It flexes quite a bit and I am not sure this would give satisfactory results in flying. I did not test it with the stock plastic units.

I used the aluminum upgrade elev. yoke and arm with the extra ball stud spacing. There is no flex in this set up and the link rod will just touch the chassis at full bottom travel of the collective seesaw which is about 14 deg of pitch with the modified linkage set up I am running. I do not know what the stock linkage (bell mixer/hiller) arms provide in total pitch travel.

With this elevator mod there is interaction between the collective seesaw movement and the elevator yoke. With the helicopter trimmed for neutral hover you can expect, in level forward flight, that the more the speed increases, the more the heli will tend to sink as more positive collective is added.
The stock set up has the opposite effect in that as more collective is added the tendency is for the heli to climb. The stock setup induces aft cyclic input and this will tend to cause pitch up when flying at full collective/throttle. It is most noticeable when flying into a headwind. The heli will want to climb. If there is any slop in the flybar to swash linkage or in the fore aft cyclic linkage, this problem is even worse.

As I said, this direct set up will tend to do the opposite, pull the nose down in fast forward flight. The amount will depend on the size (dia.) of the servo wheel used on the elevator/cyclic servo. I used the largest servo wheel I had in the first flight test series. I Then switched to the smallest servo wheel I could and still have the frame clearance I needed, in the second flight test series.

I was only able to get a couple of flights in, in either series, with this setup and have not had enough flight time to fully evaluate it. (ran out of fuel in the middle of a tight piro-flip, folded the blades back, and chopped the heli to pieces-Oh joy! :)) This mod definitely changes the way the heli feels as it no longer wants to climb in fast forward flight, it actually sinks some. In some respects this makes the heli feel more solid, like it tracks better. It will take a few flights to get used to the machine dropping some rather than wanting to climb.

I am working on a setup that will eliminate either situation as I prefer the heli to track dead on no mater what the situation is..

Note: I have modified the slot in the chassis that the elevator yoke "pivot" bosses travel in. These slots are the banana shape curved slots that are in either side of the frame. I ground the plastic away on the top and bottom in the radius just until the frame is exposed. This adds another 2 degrees of travel positive and negative.

WARNING: I have not had enough time on this set up to fully evaluate this modification and cannot recommend it at this time. My initial response is that I prefer this, but have not had enough  enough test time to determine if there are any problems associated with the modification. As an example, I have not had any extensive inverted flight with this set up yet.

If you do try this or any modification, please let me know how you like/don’t like it compared to stock.

Pete Schmidt

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