Understanding the DX6i Mixing
Look at the diagrams Carefully!
Understand the Analog Joystick. Back and Left is negative (-), Forward and Right is (+). (From the pilots’ point of view).
Understand the Monitor Screen. THR and ELE are negative (-) to positive (+), left to right. AIL and RUD are positive (+) to negative (-), left to right.
Now turn OFF all mixes and play with the sticks while watching the Monitor Screen. Do this until you realize the above statements are correct.
Now activate the Dissymmetry of Lift Mix as per Mr. Salt’s book:
If you work out the directions of the Slave Servo you will see that (L) is fast backward flight, and (R) is FFF.
Now watch the Monitor Screen and move the ELE stick Forward (+), the indicator on the screen will move to the right (+) 100% (Master). Also notice the AIL (Slave) has moved Negative 60% and a Negative AIL is a Left Roll, just like it’s supposed to be.
My 120SR Sounds Terrible!
If your helo sounds like a coffee grinder, the most probable cause is your Main Motor Pinion Gear to Main Gear interface is to tight.
First if one is using the “Tie-Wrap Mod” said to reduce frame flexing, what actually happens when the frame flexes is the main gear clearance changes. This can actually be heard in flight.
In my opinion, the tie-wrap should be held (CA’ed) to the motor above the frames’ motor support, thus pulling the pinion gear away from the main gear.
Loosen the two screws holding the main motor just enough so it will slide Fore & Aft. It will only move ≈1/8".
You should be able to just barely bounce the main gear back and forth inside the pinion gears’ teeth.
The easiest way the measure the clearance I use is as follows:
With the blades exactly Fore & Aft, turn the helo upside down and line up the blade tip with the tail boom. Rock the main gear back and forth without moving the pinion gear, the blade tip should move ≈1/16” with respect to the tail boom.
The black residue that collects on the main gear is brass oxide off of the pinion gear, and should be cleaned off.
After making the above adjustment the accumulation of the residue should be next to nothing.
I’ve tried to show a close-up of the mesh.
I enjoyed the chance to fly outside with flybar weights today!
I’m making these out of standard house wiring 14 AWG solid copper. The idea here so to start with several inches of wire and form one or more perfect loops around the flybars (Not as easy as it sounds but doable).
Parallel Jaw Pliers and Flush Diagonal Cutters make it easy, but there not really standard tools one would have.
However, the tools allowed me to form the wire just tight enough around the flybar so they will hold their position. The flush cutters allow me to square-cut the ends of the wire so the ends could be pushed together and barely leave a seam. This guarantees the length wire is the same and thus so is the weight.
Both of these flybars actually came out balanced!
My feeling so far is the two wraps are great for indoor flying, full rate (mode 0)…
One wrap is good for outdoors; slide the weights toward the hub for less dampening...
What a flybar actually does.
First calling it a flybar is deceptive, for it does not fly! The pitch of the paddles is always zero therefore it can’t produce lift so it doesn’t fly!
I think a good name for this thing might be: Gyroscopic Dampener. That’s about the best name I can come up with because it explains what it does.
Let’s look at a simple math equation* of the flybars function:
...................Paddle Area X Head RPM X Flybar Diameter
Roll Rate = --------------------------------------------------------------
What's that clicking sound?
In the real world of helicopters this is what is called a “1-Per-Rev”. Meaning 1 vibration per revolution of the main rotor. With real helicopters everything is geared together so basing everything on the main rotor at 100% RPM tells one exactly which part is vibrating.
A 1-Per-Rev on the 120SR is usually the main gear. What has happened is there has been a crash or rotor strike when power was still applied to the main motor. (You must kill the throttle before the impact).
When the main motor is running but the rotor is not turning freely the main gear usually gets a couple of teeth bent or otherwise distorted. This can be very hard to see without High-Power Magnification and attention to detail.
In mild cases its fine to fly with this condition, but the only solution is to replace the main gear.
Whose writing this stuff anyway!
I was active US Navy 1979-1987 a hair less than 8 years as an Aviation Electronics Technician (AT). The first 4 years at Barbers Point HI with HSL-37 (Helicopter Antisubmarine Light) http://www.hsl37.navy.mil/00Home.htm or what is called “LAMPS” (Light Airborne Multipurpose System). Weapon system: SH-2F Seasprite Helicopter. http://www.kaman.com/aerospace/
SH-2G Seasprite: http://www.kaman.com/files/file/PDFs.../Seasprite.pdf
1. Antisubmarine Warfare.
2. Anti-Ship Missile Defense (Kamikaze with the missile to protect the ship).
3. SAR (Search And Rescue).
I journeyed on two “West-Pac’s”, Indian Ocean primarily, but as far north as Russia and south as Australia. Provided SAR when Russia shot down KAL007 Korean Airliner (no bodies recovered). Rescued 78 Vietnamese Refugees. Located and tracked several Russian subs (including mock torpedo attacks).
Second 4 years, at Lemoore CA. NASL (Naval Air Station Lemoore), AIMD (Aircraft Intermediate Maintenance Department), 61A Radio Room, All UHF, VHF, DF, IFF bench level repair for the Seventh Fleet.
I was going to re-up when I tore my knee. Went through surgery, learned to walk again, but got the impression the Navy didn’t want me to go aboard ship again, so it was time to leave, Honorable Discharge not medical.
Irony follows my life… I’m a Disabled Veteran of the Cold War!
As a civilian I’ve worked for McDonnell Douglas Corp. building the AV-8B Harrier, FA-18 Hornet, and the F-15 Eagle.
Now I fly R/C Helicopters…
There’s plenty of How-To’s out there, so I’ll just cover the things most often left out…
WM120 (12W) $40
WP25 (25W) $40
WP30 (30W) $45
WD1001 (85W) $200
Recommending soldering equipment is a tough call…
It depends mostly on the size of the normal work to be done.
The 120SR 5-in-1 board, WM120 (12W) is more than enough.
(Note: The solder on the 5-in-1 board is not 60/40; it’s a higher tin alloy. Which means it takes an extra ½ sec. or so to melt. Good call HH, vibration resistant).
I would have to say the most important thing is not just replaceable tips, but different size tips! Everybody needs a long slender conical tip, and perhaps two different sizes of flat chisel tips.
One of the secrets to soldering is to match the tip size to the work size. Believe it or not, one doesn’t solder with the heating element. One solders with the heat-capacity of the tip. The larger the tip the more heat-energy it has to transfer. This makes more sense when one realizes electronics components are specked at a soldering time of <= 2 Sec. 2 Sec. is barely enough time for the element to reheat the tip.
The next tip is cleanliness! When one pulls an iron from the holder it is tinned with solder and wiped off with a damp sponge! Used within 10 Sec. then wiped clean on the sponge, then solder applied to cover the tip, and then returned to the holder. Be anal about this!!!
The next tip is, always apply solder on-end or perpendicular to the work. Rosin-Core Solder is just that, the rosin is in the core. Applied on-end the rosin melts first and flows over the work to clean it. Then the solder melts and flows over the clean metal.
Apply the heat to one side or end of the work and the solder to the other side or end. This ensures the entire joint is up to the proper temperature before the rosin begins to flow.
Next tip, Practice, Practice, Practice…
Wash your hands when done... Solder is 60% LEAD!
My Dream... My Nightmare…
Imagine! Having a device on your 120SR to “Dial-Out” TBE!
The image shows what may be the secret!
A tiny, self-gripping spring, which can impart a force to the Anti-Rotation Collar to hold it in the precise 45 Deg position.
Notice the control rod for the head: With static drag on the flybar (in-flight) the red line would be parallel to the main shaft.
I’m Close!!! But Man this is Hard!!!
Somebody needs to CMC me one with a adjustment screw…
11 Feb 12
Well I can almost dial-out all the TBE with the spring adjuster, but its way too hard to adjust so… On to Phase Two!
0.025 Sheet Copper is the next best thing I have on hand to work with. I fabricated a new adjuster. The only problem now is finding two bolts and three nuts to small enough to finish it!
Two nuts: One on each side of the adjuster arm “counter-tightened” to hold the adjusting screw in–tension.
Note the curvature of the arm: Spring to absorb rotor-strikes and hopefully stay in adjustment.
The MH Anti-Rotation Collar cannot be turned over, I adjusted the adjustment screw bumper so it rides on the rib at the outter end of the anit-rotation collar.
As soon as I can find some screws and nuts… Until then, I’m Screwed!
17 Feb 12
Found some hardware at the LHS and finished this...Continue Reading
Designing Your Own 120SR Light Set.
An understanding of Ohms Law is necessary! We need to know how to adjust the brightness of our LED’s and to limit the current draw from our battery. If you understand the basic equations below and can use a calculator you can do it!
I = E / R
R = E / I
E = R * I
R = E / I
E = R * I
I is “Current” like pressure in a water hose, it Does Work.
E is “Voltage” like water in a water hose, Capacity to do Work.
R is “Resistance” to Current flow, like a smaller hose. Limits Work.
Water in a hose is just like Voltage (E) on a wire.
Voltage (E) overcomes Resistance (R) so Current (I) can flow, and Work is done…
What is important to understand about LED’s?
They are an electrical Current (I) devices. Too much Current (I), they burn out.
Current (I) only flows in one direction, they are a diode.
Light output is measured in mili-candela, which is approximately 1/1000th candle power. For more on this: http://www.theledlight.com/lumens.html
The Voltage required to light an LED is around 1.8 to 3.3 Vdc, too high a Voltage (E) can burn it out but 4.2V shouldn’t hurt it with the current limiting resistor.
Powering them from a 1S LiPo is what? 3.2 to 4.2V, one should use the Max value in the equations.
A safe starting Current is about 20mA, too high a Current (I) it burns out.
Hooked-Up backwards (reversed biased), at the correct V & I, it does nothing.
So let’s...Continue Reading
Video Reconnaissance Pod
By the name you can tell I really get into this right?
Well there’s my final 808 Cam Mount.
The Images show, CA’ed to the Orange Heat-Shrink LiPo holder a 1/8 inch thick Sorbothane® Rubber triangle. This material is expensive to buy but the resourceful type can get free samples!
On top of the Sorbothane® rubber is 0.050 in. thick fiberglass, on to which, are CA’ed to 2 disc shaped rare-earth magnets. The magnets should-have-been counter sunk into the fiberglass to make the mount lower profile.
The VRP: Video Reconnaissance Pod (Ok… 808 Cam.) has on its back a rectangular rare-earth magnet CA’ed to it. These magnets were chosen because 1 it’s what I had on hand and 2 because of the way they behave.
Rare-Earth Magnets are dangerous, please read up on them: http://www.kjmagnetics.com/safety.asp
This arrangement allows a strong hold yet easy removal by rotating the camera 45-90° and then tilting the camera off. Replace the same way. This will prevent shattering the magnets.
This arrangement also allows the VRP to break-away during an impact to minimize damage.
A couple of fishing swivels as a lanyard might not hurt either.
And the orange paint job on the VRP? Well you know… So you can’t lose it… Ask me how I know…
I found it, it just took awile!
Installing a Swashplate Pivot Bearing into a Flybar.
What we gain here is a flybar that is more stable and doesn’t wear out as fast.
The problem is most hobbyist don’t have a complete drill set, there expensive and good ones are real expensive.
The good thing about them is, there’s already a hole in the flybar and it is centered. With a drill set one can start with a drill slightly larger than the hole and drill it with the bit in your hand (soft plastic). Then work your way up one drill gage at a time, to the final drill size. This keeps the hole round and centered. This is called “Step Drilling”.
A drill press will grab and tear with plastic this soft if not done very carefully, plus it’s very hard to hold the flybar down and centered without damage.
Google “Standard Drill Sizes” for charts converting gage to inch/ mm equivalent sizes, pick out the chart you like the best.
The “Press Fit” method is the easiest.
Installing a Swashplate (BLH3109) Pivot Bearing into a Flybar (BLH3111), Press-Fit Method.
1. Press the pivot bearing from the inter-race of the swashplate bearing. May require loosening by inserting an X-Acto® blade from the bottom, between the inter-race and the pivot bearings’ outer housing.
2. Trim off the inter-race plastic and all 4 control ball posts flush with pivot bearing housing.
3. Drill out the flybar, Step Drill by hand up to an “A” gage drill.
4. Press pivot bearing housing into flybar until centered in the flybar.
5. CA glue...Continue Reading
120 SR Control Rod Adjustment