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Old Jan 20, 2013, 06:22 PM
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More Flights = Less Crashing
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United States, WI, Beloit
Joined Nov 2012
5,138 Posts
Originally Posted by Laidback_racer View Post
I have something similar to yours, I havent had a chance to test yet but I am hoping for less loss of revs when applying cyclic.
If you are losing power when applying cyclic, your servo throws are set too far.
If the RPM drops, it's because you are binding up against the main rotor shaft.
You could also have a dying swashplate bearing that is partially seizing under

I understand that for a stock 9116, pushing the extreme limits on swashplate
travel is the only way to get decent cyclic action.

That is the point of 90% of my mods, to increase cyclic authority.
The less it weighs, the easier it is for the swashplate to push it around.

I measured the slop / play between the main shaft and the pivot bushing
on a new swash and got .010 inches (0.25mm), roughly the thickness
of 3 sheets of printer paper.

Then I measured one that had 200 flights, and got 0.020 inches (0.5mm),
so they seem to wear well.

The biggest problem is that any play in swashplate is amplified by the head.
That swash Pa Flyer runs sure is looking good, and the V912 looks like it might
work too.

Less slop means more cyclic action, so this is a worthwhile upgrade.

Pa Flyer, yup I drilled out the bottom plate, and plan on drilling out more
parts the next time I do some major repairs.

The lower aluminum side plates I modified may look fragile, but actually they
are still plenty stiff. Another benefit is that in a violent crash, they will bend more,
and absorb more energy. In stock form, they are too stiff to bend in most crashes.

After removing another 8 grams, the head speed at hover was getting low,
so I ended up trimming the blades some more, and now they are 20.3mm at
the grips, and 18.5mm at the tips.

To reduce any chance of a flybar strike to the battery, I shortened it by removing the
threaded portion of the rod (roughly 6mm on each end).
The weights I'm using are 1.1 grams.

I still have not been able to fly it outside due to high winds, but it sure flies great

It has gotten to the point where it's behavior is not far off from my CP 6ch.
When I send it off in any direction, it seems to hold it's speed and heading
until you tell it to stop. The tendency to auto stop and self center has been
reduced by a large amount, and I may have finally got rid of the dreaded
pendulum effect.

The only downside is that now you actually have to fly the helicopter, it
will no longer fly itself. I can hold it in one spot no problem, it just requires
more correction.

I can't wait for the wind to die down outside so I can see how it does
in extended forward flight.
__________________________________________________ __________

There are 4 things left that I want to fix:

The first thing is the tail assembly, and those parts are on the way.

The second is a more precise swashplate. Pa Flyer is using a nice swash,
and the V912 swash will probably work too. An aluminum swash with
precision bearings would be nice, but I'm trying to keep weight down.

The fourth is the strange action of the PCB. There is a large dead spot in the
forward cyclic. When going from neutral to forward on the sticks, the servos
do not move until I get to at least 10%. There is a huge deadband.
Also, I don't like how it moves the right servo around for you based on throttle
input. I don't need the PCB trying to help me fly.
The strange mixing (where both servos work in one direction, but only one servo
works in the other) might be needed for this type of swashplate and head design.

We will find out when someone buys a V912. Hopefully the V912 PCB does
not have all of the same flaws. The board layout looks very close, but the mixing
is probably done in software so it would be an easy fix for the manufacturer.

The fourth thing is the main motor. I don't really need more power, I just want
it to last more than 50 flights, and not cost 4 times what a stock motor costs.
The $14 Xtreme 180 motor is not a much better deal because after shipping
the brushes are close to the cost of a stock motor.
If the brushes last 100 flights or more it would be worthwhile, but it would
take 150 flights for it to begin paying for itself.
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Last edited by Steve_; Jan 20, 2013 at 08:16 PM.
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