Goodbye flybar! A gyro helps a scale makeover

A flybar on the principle rotor head of a helicopter imparts stability within the rotor head system and helps the principle rotor blades change pitch (a type of energy steering mechanism, if you’ll). Removing the flybar makes it extra aerobatic as a result of there’s much less inertia within the rotor system, which is superior for 3D flying however extra importantly for my functions, it makes the helicopter look scale. I can bear in mind as a child watching Towering Inferno and Capricorn One and seeing the flybars within the slow-motion film scenes and understanding they have been mannequin helicopters.

The Cobra seems to be imply, however the flybar was simply bugging me each time I checked out it.

After years of wanting one, I not too long ago discovered an property sale deal on a Hirobo TOW Cobra. They are now not typically out there, they usually value close to about as a lot as a turbine jet once they have been. Powered by a glow engine with an non-compulsory onboard starter, they’re what we time period at this time as 700 dimension; sufficiently big to be cool however not so massive as to be obnoxious to move and retailer.

After an electrical conversion utilizing a Scorpion motor, 10S battery setup, and a Kontronic 80-amp velocity management, I had the Cobra flying extraordinarily nicely. The hassle was each time I checked out it the flybar bugged me as a result of the full-size Cobra makes use of a 2-blade rotor head. I knew I used to be going to should do some customized modifications to the rotor head to realize this so I began taking a look at what elements I would wish.

The very first thing I did was contact Danny at AeroPanda and ordered a BavarianDemon Axon controller ($349.99) and a B-Modul wi-fi Bluetooth interface ($79.99). The B-Modul isn’t strictly crucial however it’s good to have the ability to get into the programming interface on the area with out toting my laptop computer.

Next, I regarded over the rotor head and thought of my choices. I dismantled the flybar and eliminated the blending linkages. The mixing levers must keep to drive the interior ring of the swashplate, however I merely used a Dremel and eliminated the unused half of the blending levers. The head block had the flybar bearing helps remaining, so I dropped it off at a store that fellow RC’er and grasp machinist Mike Speckhahn owns. In the time it took to go to lunch, he had the helps eliminated and a pleasant clean curve on the highest of the top block that regarded manufacturing facility inventory.

The blade grips wanted to be modified in order that the ball hyperlink was centered on the shaft. Fortunately, there’s a set of linkages for the TRex 700 which have balls with a 24mm offset which work completely. They even have a set of linkage rods that embody two of the proper size. The grips needed to be drilled out and tapped for the Align elements and the interior swashplate ring wanted TRex balls to mate up with the ball hyperlinks. Everything on the outer swashplate ring and right down to the mechanics remained inventory Hirobo elements.

The helicopter got here with a Futaba 401 tail gyro that wanted to be eliminated because the Cobra would now not require a separate tail rotor gyro and the rudder servo wire prolonged to the receiver.

Using the software program for the Axon it may be mounted in practically any configuration. I had loads of room proper behind the cockpit compartment to mount the Axon on a pleasant flat crossmember tray. I cleaned the mounting surfaces with alcohol and used the provided double-side mounting pad to mount the sensor.

The Axon is able to binding to Spektrum satellite tv for pc receivers however with the Cobra being the equal of a 700-size mannequin, I wished to put in a separate receiver for max reliability. I additionally wished some flexibility so as to add lights and possibly a servo to function the entrance gun turret in some unspecified time in the future so I would wish the additional channels anyway.

The Axon comes with a wire loom that makes use of an all-in-one plug into the Axon with inputs for all of the servos and achieve controls to the receiver. Several of the controls comprise a single wire however the whole lot works as a result of it will get a standard floor from the servo bus on each the sensor and receiver although the wire loom. When the loom is put in, you then use the BavarianDemon software program to start your configuration. Only when the correct servo output refresh charge is chosen for the servos you’re utilizing do you plug the servos into the Axon. (Note: Pay consideration to this as a result of if it’s fallacious, you’ll be able to dissipate your servos!)

Installation with the wire loom between the Axon and my Spektrum AR9020. The handy flat location within the body made mounting straightforward and entry for programming comfort.

This display screen is the place you’ll be able to obtain and push firmware updates, outline your helicopter dimension, desired flying type, mounting orientation and most significantly, servo specs. Flying type will decide many default settings for achieve and response. I set scale for clean flying on my Cobra, 3D settings are additionally out there.

The contents of the BavarianDemon Axon embody the unit, USB cable, wire loom to connect with your receiver, and a mounting pad.

The B-Modul is the Bluetooth interface that may be certain to a wise cellphone and permits you to make system changes on the area and not using a laptop computer.

The Axon software program was downloaded to my cellphone and laptop computer and I linked the Axon to my laptop computer through the offered USB cable. The software program, whereas an identical on each the cellphone app and laptop computer software program, the laptop computer is quite a bit simpler to see and navigate so I set my Axons up with a laptop computer and use the cellphone app to tweak settings on the area.

A wizard guides you thru organising your Axon by establishing servo connections and achieve controls. You then trim your servos and modify your linkages in order that the whole lot is centered and sq.. Defaults are established by answering the questions in regards to the dimension and sort of helicopter that you just’re configuring. establishing default settings that work completely for all kinds of fashions whereas supplying you with very granular management in the event you’re a compulsive tinkerer that enjoys diving deep into the assorted settings. The backside line is, the Axon might be setup and flown efficiently by most pilots while not having to grasp the complexities but nonetheless exploring them as you achieve expertise.

The software program permits you to save setups to disk so if you wish to dive deep and end up dealing with unintended efficiency you’ll be able to all the time load your final saved setup again to the Axon and also you’re again in enterprise.

While organising the positive factors, I set the top and tail achieve inputs every to a knob and slider respectively. During the take a look at flight or flights, I plan on adjusting the achieve till I acquire the specified really feel. Once I set up the values wanted on the achieve channel, I’ll switch these to the management banks through the software program and disable the knob and slider so I don’t inadvertently change settings whereas dealing with my transmitter.

When it got here time to hit the flight line, I used to be getting the jitters normally reserved for take a look at flying a turbine or massive mannequin. I double-checked that the Axon was correcting within the correct course for every axis then had another person confirm my outcomes simply in case, an previous behavior of not with the ability to examine my very own work when repairing Navy plane.

When I used to be happy that the setup was right, I took a deep breath and switched into Idle 1 and held my breath because the blades got here on top of things. So far so good! A fast take a look at hover advised me too issues, I had means an excessive amount of cyclic throw and I had some ahead and proper drift. You can’t use transmitter trim on the Axon or it should interpret it as stick motion, radio middle calibrated throughout preliminary setup and never throughout gyro boot up, so I needed to land and manually modify the cyclic linkages and took that point to tame down my twin charges within the transmitter. It took a complete of three take a look at hovers to get the linkages setup for zero drift.

The subsequent step was to set the top achieve. I used the knob and punctiliously dialed up the achieve till I began to get a shimmy or oscillation within the head after which backed it off just a few clicks. The similar was finished with the tail achieve. Gradually gaining confidence I elevated ahead velocity in order that I used to be doing quick circuits, and the whole lot appeared strong. It took a complete of two battery units to get the Axon excellent and the Cobra dialed in to my liking.

The final praise to a scale pilot is to listen to somebody say “Wow! That looks just like the real thing!” and I’m completely satisfied to report that the conversion was successful, and the Cobra is flying as nicely or higher than it was earlier than the conversion however seems to be one hundred pc extra scale!

Author Andrew Griffith together with his Hirobo Cobra