Sunday, February 3, 2019

DeoxIT Notes

Everything you need to know about cleaning and maintaining tiny linear servos from RCGroups:

Questions:

1) CAIG Laboratories, Inc. make DeoxIT in a number of formulations. I've seen mention of D-series and Fader F-series on RCG. Can somebody please tell me what to buy, exactly?

2) Other than cost, is there any down side to using DeoxIT of any formulation? Will it attract and hold dust?

3) Will any formulation of DeoxIT attack foam?

4) How careful must I be with DeoxIT of any formulation regarding the servo motor? Will it soak into the motor housing and strip lubricant from the shaft?

5) Does it evaporate or must it be wiped away?

6) I saw an old video (2015) wherein the gentleman removed the actuator from the PCB to perform a thorough cleaning. Is it necessary to remove the actuator if I use the correct formulation of DeoxIT?

Answers:

1. D5 to clean. F5 to lubricate. 
2. Nope
3. Nope
4. Spray it on there liberally
5. Put a paper towel around the servo to catch the black gunk that comes out
6. Not necessary
  • Yes, I spray the D5 and work the servo back and forth a bunch. I usually don't do so with the F5, just when every other servo's cleaned up, I give each a quick shot of F5 and place the plane back on its rack.
  • That's how I discovered it! Spent 40 years in the music industry as an audio engineer - both live mixing & studio recording. Hundreds of sliders & pots....
  • After using regular old "TV tuner cleaner" & finding that the noise soon returned & the stuff actually caused more problems - I stumbled upon DeoxIT products. For decades, D5 & F5 are the only things I've used for cleaning pots & sliders, sliding contacts, commutators, etc.  Back when the first UMs came out, I tried it on a jittery UM linear actuator & it worked perfectly! I've been spreading the news ever since! 

Thursday, December 20, 2018

Horizon UMX Servo Range

tl;dr: For Horizon UMX planes and an OpenTX transmitter, set output channel to 80%.

From RCGroups:

All Horizon Hobby Ultra Micro (UMX) models, from the very first Vapor nearly ten years ago, use linear servos. This includes the Champ.

These servos are not designed to go beyond limits corresponding to 100% in a Spektrum transmitter (1100-1900uS pulse width). If driven much beyond this range, they may suffer mechanical or electrical damage as their travel is physically restricted. Horizon issue strict warnings not to set the transmitter travel beyond 100%.

For the Taranis and other transmitters that use OpenTX or ER9X, 100% corresponds to 988 to 2022 uS. Thus, it’s essential to restrict the travel to about 80% (actually it’s 78%, but the servos have enough leeway that 80% is close enough).

You can do this by setting the weight on channels 1-4 to 80% in Mixers. A better way, however, is to set the output on those channels to +/- 80 on the Outputs page.

If you have more than one UMX model, set up one model this way, then copy it as many times as needed, changing just the name.

The arithmetic is as follows:
Spektrum_Transmitter: 1500 - 1100 = 400uS for full travel.
Taranis: 1500 - 988 = 512uS for full travel.
400 / 512 = 0.78125 I.e., 78.1%.

Sunday, December 16, 2018

Using the FrSky S6R and S8R Stabilizing Receivers

Here's my notes on setting up and using the SxR receivers. This is a Work in Progress.

Key Points:
  • There are quite a few steps, but most of them are pretty simple.
  • Don't skip any steps, especially the one called "Self Test".  It actually sets your plane's leveling and stick controls.
  • These notes use the Lua programs on the receiver, and not the USB link.  They also revolve around setting up "simple" mode.
  • If you have a voltage sensor, disconnect it from the receiver.  It can overwhelm the telemetry channel and interfere with the procedures below.
Jargon:
  • Manual mode:  The SxR doesn't do anything special, it works just like a normal receiver.
  • Stabilized mode: The SxR corrects for wind buffeting, allowing a plane to fly more smoothly in gusty or heavy winds.
  • Level mode:  The SxR will bring the plane to a flat and level flying position.
  • Recovery mode:  In any of the above modes, you flip a switch and the plane recovers to level flight.
Prerequisites:
  • A flyable model plane.  It's probably good if it's one you've successfully flown before.
  • Ensure your transmitter is running at least OpenTX 2.2.
  • Ensure your receiver has been updated to the latest firmware.  Sadly there's no way of determining the firmware version, so this means you need to update it yourself or trust your vendor has done it for you.
  • We'll assume you know some basics about binding, setting up a model in OpenTX, etc.
Both of these tasks are big enough to have their own blog post.  I'll do that as I go along.

The Big Picture

The step below are a breakdown of this plan:
  • Initial Benchtop SxR configuration
  • Initial OpenTX configuration
  • Model customization, SxR in plane
  • First flights and SxR Tuning
  • Finalizing SxR configuration.
1. Binding and Failsafe.
  • Binding is standard D16-style binding.
  • Be sure that you specify Channels 1-16 are available.
  • Set failsafe as normal.
  • Do other non-flying bindings (landing gear, prop safety, etc) as per your model.

2. Calibration using SxR_Calibrate program.

This is a one-time step that tells the receiver which way is up and down. Run SxR_Calibrate program to do this. Sticking some servies on channels 1-4 isn't required, but will help you see that you're getting thing right.
  • Long-press to get to radio setup menu.
  • Page to get to SD card.
  • Scroll down to SxR folder and click to open.
  • Scroll to SxR_Calibrate.lua
  • Long-press and select "execute".
  • Now you're on a screen with some instructions to follow.

There's six steps in calibrating.
  • The program will tell you something like "lay receiver flat, facing up."
  • Lay the receiver as told and hold it still.
  • The position data is stored in the receiver, and you are told to press enter to confirm.
Repeat this for all six directions the software tells you, and you're finished.  The receiver has determined which was is up and down and stored this configuration information in the receiver's memory.  You won't have to do this again.


3a. Set up initial transmitter bindings.

We'll change these up in a bit when we're ready to fly.  This is for setup.
  • Channels 1-4 are AETR: Aileron, Elevator, Throttle, Rudder.
  • Channel 9 is stabilization gain.  Set it to Input:S1, Scale:50 Offset:50
  • Channel 10 is flight mode: manual, stabilized, level.  Set it to Input: SC, no modifiers.
  • Channel 11 is unused in simple mode.
  • Channel 12 is for self-test mode. Set it to input SD, no modifiers. We will change this binding before we fly.
3b.  Set up audio announcing of the gain value.

Add this line to the Special Functions menu to play CH9 (the gain) every 5 seconds when switch A is down.

  • SA↓  Play Val     CH9     5


4. Initial Setup using SxR program.

  • Long-press to get to radio setup menu.
  • Page to get to SD card.
  • Scroll down to SxR folder and click to open.
  • Scroll to SxR.lua
  • Long-press and select "execute".
  • There are two screens of configuration information.  Use the page button to switch between the pages.
The first screen specifies the airplane type (normal, v-tail, delta a.k.a. wing) and receiver orientation, how it's mounted in the plane.
  • Set the airplane type.
  • Set the receiver orientation.  There's help at the bottom of the screen
The second screen specifies a lot of parameters.  At this time we only care about a couple of them:

  • SxR functions:
  • Quick Mode:
  • CH5, CH6 mode


5a. Bench Self-test (part 1)


Note that "self test" is a bit misleading.  The procedure also sets the level position of your plane and measures the endpoints of your control sticks.
  • Hook up some spare servos to channels 1 (AIL), 2 (ELE), and 4 (RUD). Hook up channels 5 and 6 if they're going to control AIL2 and ELE2.
  • Make sure your trims are centered.
  • Power on the receiver.
  • Flip switch D three times within 3 seconds to activate self  test.
  • You will see the blue Rx LED flash, and the output channels will be exercised.  You should see all three servos move.  This is commonly called the "servo dance."
  • Now move the AIL, ELE, and RUD sticks through their full range of motion.  This is important, it sets the endpoints.  It will also show you something is wrong if the servos don't move.
  • Disconnect and reconnect the power.
5b. Bench Self-test (part 2)


  • Put switch C (channel 10) in the down (manual) position.  This is manual mode, just like a regular receiver.  Move your Tx sticks and observe that the appropriate servos are moving.
  • Put switch C in the middle (stabilize) position and rotate S1 (gain) clockwise to the max position.   Jiggle your Rx, and you will see the servos jiggle and return to neutral.  Rotate S1 counterclockwise to zero gain.  You will see jiggling has less and less effect, until at the zero position there is no effect at all.  Make sure  your sticks move the servos as well.
  • Put switch C in the top (auto level) position and rotate S1 (gain) to max.  Rotate your Rx in several directions.  You will see the servos respond and hold their positions.  Again, rotate S1 to zero gain and you will see less and less effect, and make sure your sticks move the servos.


6. Install into Model
  • Remove or disable props and any other potentially hazardous parts of your model.
  • Attach your servos, etc to the receiver.
  • Using the supplied double-sided sticky foam tape, mount the model along the center line and near the center of gravity.  You can be off a bit with no worries.
  • Make sure the Rx matches the orientation set in step 4.
  • For wings, AIL = left wing, ELE = right wing.

7a. In-model Self-test

(WARNING: self-test will exercise channels 5 and 6 even if they are set to AUX.  If you have landing gear on one of these channels find some way to support your plane.)


This is mostly a repeat of section 5, only attached to the plane.
  • Position your plane as it will be in flat and level flight.  Some models like wings need a couple degrees of up-nose.  Do what's right for your model.
  • Power on the model and triple-flip switch D to start the self test.  You'll see the blue lights flash and the servo dance.
  • Fully exercise the sticks to set the endpoints, and reboot.
At this point, your level-point and stick endpoints have been set, so we need to switch channel 12 to be the momentary H switch.
  • Go to channel 12 on the mix menu and set  the input as momentary stick H.
  • If you leave channel 12 on a 3-position switch, you can accidentally trigger the self test while in the air which will be a disaster.
7b. Initial Model Setup
  • Switch to manual mode and reverse any channels needed in the usual way (e.g. stick input menu).
  • Set the gain high, hold the plane level, and switch to auto level mode.  Rotate your plane around the three axes and test if the control surface motions are in the correct directions.
  • If any of the control surfaces need reversing for auto level, run the SxR program and set the direction to INV on the second screen.  Reversing takes effect immediately.  Test your sticks through their full range of motion while moving the plane around.
  • Switch to stabilize mode and repeat the stick tests.  Jiggle the model and you will see the control surfaces respond to counteract.
  • Flip switch H (recovery) in all modes.  Ensure that when the H switch is held the plane is in auto level mode.
  • Experiment with the gain knob, and see how it goes from no effect to maximum effect as you move the plane around.  You can flip switch A down to hear the gain values announced.
[insert video 6/7 here]

8. Initial Flight


  • Take off in manual mode and adjust your trims, etc, as usual.  Fly to three mistakes high.
  • Now we'll test stabilized and auto level modes. Be ready to switch back to manual mode if things go bad.
  • Turn on gain announce by flipping switch A down.
  • Set the gain to a low value, and switch to stabilize mode.  Gradually increase the gain.  If it's windy, you should feel the plane smooth out as the gain increases.
  • Increase the gain a lot, and you'll see the plane start to jitter in the air as the stabilizer overcorrects.  Back off until the plane feels good in the air, and make a note of the gain value.
  • Now switch to level mode.  If you have an incorrect orientation setting, the plane will flip over and otherwise go crazy.
  • Fly around a bit, letting go of the sticks.  When the sticks are in neutral position, the plane should fly flat and level.  Increase the gain until the plane becomes unstable, and back off the gain.  Note the gain number.
  • Test out recovery mode.  You should be able to go from any position to flat and level flight by pulling the H switch.
At this point, you've finished up most of what you need to do.

[insert video 8 here]

9. Final Adjustment of Gain channel


Now that you've got a good stabilize gain value, you won't want to have to worry about keeping the knob in the exact right position.  Go to the mix menu, and change channel 9 to be
  • src = MAX, scale = X (where X is your stabilized gain)


10. Final Adjustment of Auto Level Gain


If you needed a different gain for auto level, run the SxR.lua program and adjust the AIL stab gain and ELE stab gain.  You will have to experiment to get the exact values dialed in.


11. Set Failsafe to Auto Level Mode (optional)


Finally, if you think it's a good idea asdf

[insert video 9/10/11 here]


Sunday, November 18, 2018

JureZ's 13" Nutball

Extracts from RCG:

Mine is 61g AUW , 13" dia. Dollar tree foam with paper off.

using UMX HW and 1S brushed motor and prop ( don't remember which one is the donor...)
had to put six pennies under the nose to get proper CG.
Is windy today to say much about it besides that it is tossed around like a leaf... it flies anyway ...

---
it flew fine, nicely slow, a floater... until I managed to damage the propeller. Grounded for now...

https://static.rcgroups.net/forums/attachments/4/8/6/8/1/9/a11335684-255-UMX%20Nutball.JPG

---
and here is a video, after switching to a 10g brushless motor (custom rewound, Y , 36 Turns per tooth, Kv= 635 RPM/V ) , 
10 A ESC,
Battery 2S 300 mAh 30C, 
APC 7*3.8 SF Propeller , 
FrSky 4 Channel RX.
two UMX Spectrum Linear Servos ,
82g AUW, wing loading = 3.16 oz/sq ft , 
Static test current draw at full throttle : 2.2A @ 8V , 17.6W into the ESC.

https://www.youtube.com/watch?v=qDRXXUVhvio

Thursday, October 25, 2018

Phoenix 1600 ESC Brake programming

The ESC is programmed from the factory to have prop brake OFF.

TO PROGRAM THE ESC FOR PROP BRAKE: Turn radio and plane off. Turn radio on and put throttle at FULL throttle. Turn plane on. You will hear some tones indicating that the ESC is in "programming" mode. The first tone is a simple beep tone (with just one beep if I recall).

When it changes to a different tone/number of beeps (i.e., the SECOND type of beeping that is DIFFERENT from the first type of beeping - this second beeping is a triplet beep (e.g., dit-dit-dit) if I recall), this is when you want to yank the throttle to the lowest point of its throw. This will turn the prop brake ON.

Then, when you're flying in thermals or slope lift, and you pull throttle down to off, the prop brake will engage and your folding props will fold and now your FPV cam will not be obstructed by the prop spinning.

-- courtesy of Pianoman at RCG

Thursday, September 20, 2018

Shunda TEC-06 Battery Tester



Operation:

  • current used in AH.  Press to start Mode 1 testing.
  • battery voltage. No testing, current voltage.  Mode 1: open circuit voltage (no load). Mode 2: voltage under load.  Press to start Mode 2 testing.
  • final voltage.  Testing stops at this voltage.
  • discharge current in mA.  50-3500.
  • internal resistan in Ω. Reported in Mode 1 with 4-wire harness.

Best reference:
Reverse engineered serial protocol:

Wednesday, July 25, 2018

EastBay RC Guide to Sections 343 and 344.

Disclaimer: I am not a lawyer, etc.  Here's my layman's interpretation of sections 343 and 344 of this document: https://www.congress.gov/bill/115th-congress/house-bill/4/text.  Note that I'm not expressing any opinions, just trying to understand what the bill says.

The top part is my interpretation, followed by my interpretation inlined with original text. Did I come close to getting it right? Let me know what you think!


SEC. 343. SPECIAL RULES FOR MODEL AIRCRAFT.
FAA can't make rules regarding model aircraft. except as noted here.


FAA can require you to register and put your registration number on your aircraft.


FAA can make rules if you have an autopilot or BLOS (beyond line of sight) features and you meet these requirements: fly as a hobby, join a CBO, fly with their rules, less than 55 lbs, fly safely, don't fly over amusement parks, tell airport operators when you're flying nearby. See section 344 below if you don't meet these requirements.


When FAA has an "automated airspace authorization system" you have to use it, unless you're at an approved "permanent location".


CBO-sponsored educational stuff is simple model flying even if you're paid, e.g. sponsored pilots.

They can come after anyone endangering safety, no matter what.


CBOs are nonprofits who further model aviation, provide safety guidelines, support local clubs, and provide support for developing local flying sites.


FAA will publish recognition guidelines for CBOs.
This all becomes effective when the Act passes.


SEC. 344. RECREATIONAL UAS.
This if for everyone who doesn't meet the requirements in section 343 (above) or part 107 (which talks about commercial operations).  I think this is the section that will apply to non-AMA members.


Within 120 days, FAA will issue rules regarding this category of flying, as detailed below.
You have to take an online class.
It's OK if you're under 16.
When "automated airspace authorization system" is implemented, you have to use it.
FAA can't require special licensing, exams, certifications, etc.


---------------------------------------------------------------------------------------------------------


The following is the comments above, inlined with the text at https://www.congress.gov/bill/115th-congress/house-bill/4/text


SEC. 343. SPECIAL RULES FOR MODEL AIRCRAFT.
(a) In General.—Notwithstanding any other provision of law relating to the incorporation of unmanned aircraft systems into Federal Aviation Administration plans and policies, including this subtitle, the Administrator of the Federal Aviation Administration may not promulgate any rule or regulation regarding a model aircraft or an aircraft being developed as a model aircraft,


FAA can't make rules regarding model aircraft. Same as before, but with exceptions below.


except for—
(1) rules regarding the registration of certain model aircraft pursuant to section 44103; and


FAA can require you to register and put your registration number on your aircraft.


(2) rules regarding unmanned aircraft that by design provide advanced flight capabilities enabling active, sustained, and controlled navigation of the aircraft beyond the visual line of sight of the operator, if—
(A) the aircraft is flown strictly for hobby or recreational use;
(B) the model aircraft operator is a current member of a community-based organization and whose aircraft is operated in accordance with the organization’s safety rules;
(C) the aircraft is limited to not more than 55 pounds unless otherwise certified through a design, construction, inspection, flight test, and operational safety program administered by a community-based organization;
(D) the aircraft is operated in a manner that does not interfere with and gives way to any manned aircraft;
(E) the aircraft is not operated over or within the property of a fixed site facility that operates amusement rides available for use by the general public or the property extending 500 lateral feet beyond the perimeter of such facility unless the operation is authorized by the owner of the amusement facility; and
(F) when flown within 5 miles of an airport, the operator of the aircraft provides the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport) with prior notice of the operation (model aircraft operators flying from a permanent location within 5 miles of an airport should establish a mutually agreed upon operating procedure with the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport)).
FAA can make rules if you have an autopilot or BLOS features and you meet these requirements: fly as a hobby, join a CBO, fly with their rules, less than 55 lbs, fly safely, don't fly over amusement parks, tell airport operators when you're flying nearby. See next section if you don't meet these requirements.


(b) Automated Instant Authorization.—When the FAA has developed and implemented an automated airspace authorization system for the airspace in which the operator wants to operate, the model aircraft operator shall use this system for authorization to controlled airspace unless flown—
(1) at a permanent location agreed to by the Administrator; and
(2) in accordance with a mutually agreed upon operating procedure established with the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport).


When they have an "automated airspace authorization system" you have to use it, unless you're at an approved "permanent location".


(d) Commercial Operation For Instructional Or Educational Purposes.—A flight of an unmanned aircraft shall be treated as a flight of a model aircraft for purposes of subsection (a) (regardless of any compensation, reimbursement, or other consideration exchanged or incidental economic benefit gained in the course of planning, operating, or supervising the flight), if the flight is—
(1) conducted for instructional or educational purposes; and
(2) operated or supervised by a member of a community-based organization recognized pursuant to subsection (e).


CBO-sponsored educational stuff is simple model flying even if you're paid, e.g. sponsored pilots.


(e) Statutory Construction.—Nothing in this section may be construed to limit the authority of the Administrator to pursue enforcement action against persons operating model aircraft who endanger the safety of the national airspace system.


They can come after anyone endangering safety, no matter what.


(f) Community-Based Organization Defined.—In this section, the term “community-based organization” means a nationwide membership-based association entity that—
(1) is described in section 501(c)(3) of the Internal Revenue Code of 1986;
(2) is exempt from tax under section 501(a) of the Internal Revenue Code of 1986;
(3) the mission of which is demonstrably the furtherance of model aviation;
(4) provides a comprehensive set of safety guidelines for all aspects of model aviation addressing the assembly and operation of model aircraft and that emphasize safe aeromodeling operations within the national airspace system and the protection and safety of individuals and property on the ground, and may provide a comprehensive set of safety rules and programming for the operation of unmanned aircraft that have the advanced flight capabilities enabling active, sustained, and controlled navigation of the aircraft beyond visual line of sight of the operator;
(5) provides programming and support for any local charter organizations, affiliates, or clubs; and
(6) provides assistance and support in the development and operation of locally designated model aircraft flying sites.


CBOs are nonprofits who further model aviation, provide safety guidelines, support local clubs, and provide support for developing local flying sites.


(g) Recognition Of Community-Based Organizations.—In collaboration with aeromodelling stakeholders, the Administrator shall publish an advisory circular within 180 days of enactment that identifies the criteria and process required for recognition of nationwide community-based organizations. This recognition shall be in the form of a memorandum of agreement between the FAA and each community-based organization and does not require regulatory action to implement.


FAA will publish recognition guidelines for CBOs.


(h) Effective Date.—Except for rules to implement remote identification for unmanned aircraft that by design provide advanced flight capabilities enabling active, sustained, and controlled navigation of the aircraft beyond the visual line of sight of the operator and for rules regarding the registration of certain model aircraft pursuant to section 44103, this section shall become effective when the rule, referred to in section 532 of the FAA Reauthorization Act of 2018, regarding revisions to part 107 of title 14, Code of Federal Regulations, becomes final.


This all becomes effective when the Act passes.


SEC. 344. RECREATIONAL UAS.
(a) In General .—Not later than 120 days after the date of enactment of this Act, the Administrator of the Federal Aviation Administration shall issue rules and regulations relating to small UAS flown for recreational or educational use, and that are not operated within all of the criteria outlined in the special rule for model aircraft in section 45505 of title 49, United States Code, or the requirements of part 107 of title 14, Code of Federal Regulations.


This if for everyone who doesn't meet the requirements in section 343 (above) or part 107 (which talks about commercial operations).  I think this is the section that will apply to non-AMA members.


Within 120 days, FAA will issue rules regarding this category of flying, as detailed below.


(b) Regulatory Authority.—When issuing the rules and regulation pursuant to this section, the Administrator shall—
(1) require the completion of an online or electronic educational tutorial that is focused on knowledge of the primary rules necessary for the safe operation of such UAS and whose completion time is of reasonable length and limited duration;


You have to take an online class.


(2) include provisions that enable the operation of such UAS by individuals under the age of 16 without a certificated pilot;


It's OK if you're under 16.


(3) require UAS operators within Class B, C, D and E airspace to obtain authorization, as the Administrator may determine to be necessary within that airspace, but only after the Federal Aviation Administration has developed and implemented an automated airspace authorization system for the airspace in which the operator wants to operate; and
(4) include provisions that provide specific operational rules for UAS operating in close proximity to airports in class G airspace.


After the "automated airspace authorization system" is implemented, you have to use it.


(c) Maintaining Broad Access To UAS Technology.—When issuing rules or regulations for the operation of UAS under this section, the Administrator shall not—
(1) require the pilot or operator of the UAS to obtain or hold an airman certificate;
(2) require a practical flight examination, medical examination, or the completion of a flight training program;
(3) limit such UAS operations to pre-designated fixed locations or uncontrolled airspace; or
(4) require airworthiness certification of any UAS operated pursuant to this section.


FAA can't require special licensing, exams, certifications, etc.


(d) Collaboration.—The Administrator shall carry out this section in collaboration with industry and community-based organizations.


----------------------------------------

Tuesday, April 24, 2018

Stepper Motor: Microstepping

A coworker explains it to me:
TL;DR; is that instead of just having full forward/reverse current or not on each winding, the driver can also do things like 90%/10%, 80%/20%, 70/30, etc. current for the two windings to position the motors at angles between the full/half step positions. the actual ratios aren't quite this simplistic, and are designed to achieve something close to constant holding torque and even step spacing, but since the exact angle achieved for any winding current ratio depends on the motor design, and application, it's more or less impossible to get microstep positions that are a precise fraction of the full step angle for all motors/applications. this is mostly OK because 1) you're not making the full step positions any less accurate, 2) you're still making motor motion smoother by taking smaller steps.
a longer explanation can be found at https://hackaday.com/2016/08/29/how-accurate-is-microstepping-really/. if you want to go deeper that that, there are lots of motor controller app notes out there with all the gorey engineering details.

blogodex = {"idx" : ["electronics", "stepper motors", "microstepping"]};

Tuesday, November 14, 2017

Donkey Cars!

Chris Anderson started DIY Robocars, and Adam Conway and William Roscoe's response is the Donkey Car.  And EastBay RC is building two of them!

http://www.donkeycar.com
Build Guide

blogodex = {"toc": "Donkey Car"};

Tuesday, September 19, 2017

TurboParker's Guide to UMX Radian Trimming

Copied from RCGroups:

Initial balancing & trimming:

1) MEASURE the CG on your plane. Do whatever is necessary to adjust it to 31mm, which is the factory recommended starting point. Do this before you try anything else.

2) Zero your tx trims. If your transmitter allows, adjust the trim-steps to the smallest setting. (Usually "1".)

3) Power-up the plane, but do not engage AS3X. Then disconnect the battery.

4) Mechanically trim the elevator so that it's neutral with respect to the stab.

5) Take the plane up for a flight with the CG @ 31mm & see how it behaves power-off & power-on.

6) If it glides smoothly & doesn't balloon under power, you're done.

7) If it porpoises during the glide and/or balloons under power - add down-trim until it glides smoothly, then zero your tx trim & transfer the tx trim to mechanical trim.

8) Note the degrees of down-trim with respect to the stab. If it's only a few degrees or so, you can call it good - unless you're trying to squeeze every last bit of glide performance out of the airframe that you can get. If you're trying to set a personal UMXR glide record, adjust the decalage accordingly, so that no visible trim is needed for best glide with the CG at 31-32mm. If the plane needs a lot of visible down-trim with the CG at 31-32mm, the decalage is off enough to warrant fixing it or returning the plane & getting a replacement.

Remember that you must re-trim the elevator for best glide whenever you change the CG. That is absolutely mandatory. If you don't, you will simply end up chasing your tail & get frustrated with the process of flight-trimming. When you get it right, you will be rewarded with a plane that glides smoothly & efficiently, and exhibits very little (if any) throttle-pitch coupling under power. See the video below for an example of how the plane is supposed to behave when it's trimmed & balanced correctly, and the decalage is about right. Be sure to turn up the sound, as I narrate during the flight. It's a bit long, but the 19 minutes it takes to watch the entire video will most likely be worth it for those who are new to sailplanes.

Here's another method of fine-tuning the CG:

1) Take the plane up high, trim for level flight @ say 20-25% throttle. Better yet, trim for the flattest stable power-off glide (no porpoising).

2) Enter a power-off dive at a 45-degree angle, then release the sticks, and observe the plane's behavior:

A. Plane pulls sharply out of the dive as soon as you release the elevator: The plane is extremely nose-heavy. Move the CG aft, take the plane back up, re-trim as described above, then repeat the test.

B. Plane starts to dive more steeply (tucks toward the belly) when you release the elevator: The plane is tail-heavy. Move the CG forward, take the plane up, re-trim as described above, then repeat the test.

C. Plane continues on its path: The CG is at the neutral-handling point (often called the sweet-spot), which provides the greatest sensitivity to lift (the plane will indicate weaker lift than it will when it's nose-heavy). A neutral CG also results in the lowest stall-speed & the least amount of drag. But it also makes the plane neutrally-stable in pitch, so it will not self-correct in a dive. Many competition sailplane pilots prefer a neutral CG, but some pilots prefer a slightly-forward CG.

D. Plane starts to gently pull out of the dive when you release the stick: The CG is just slightly forward of neutral. The plane will still indicate light lift (albeit not quite as well as it would with a neutral CG), and it will be more stable in pitch than it is with a neutral CG. Some sailplane pilots prefer this CG position, as the slightly positive pitch-stability makes the plane less-apt to suddenly enter a dive or climb on its own when it gets perturbed by the air currents. The slight loss of efficiency is rarely noticeable to casual sailplane pilots who are not concerned with getting every last bit of performance from the airframe.

Remember that at this scale, moving the CG just 1-2mm is noticeable in flight. Avoid making large changes unless you're sure that the the CG is way off. Also, remember to re-trim for level flight each time you move the CG. This is absolutely critical. Failure to re-trim as described above will negate the entire process.

Also remember that CG is not a fixed number. Move it forward a bit for better wind-penetration on turbulent days, or for increased glide speed on windy days. Move it back to the sweet-spot in calm conditions and/or when lift is very light & you want to stay aloft on the farts of field-mice alone.

If the decalage is correct, you'll end up with the elevator level or close to level with respect to the stab after the above tests. If not - then the decalage is likely off. Which means you'd need to do the decalage test.

Decalage test:

1) Zero your elevator trim on the tx, then mechanically neutralize the elevator with respect to the stab.

2) Take the plane up, but do not re-trim the elevator in flight. This is absolutely critical, as re-trimming the elevator after neutralizing it before the flight will screw up the test & render the results useless.

3) Perform a power-off vertical dive from high altitude, release the elevator stick, and observe the plane's behavior:

A. Model continues straight down: No change needed.

B. Model pulls to canopy: Increase stab incidence with respect to the wing.

C. Model pulls to belly: Reduce stab incidence with respect to the wing.

Adjusting the CG as described above is the next step after verifying that the decalage is correct.

Here's where the batt ends up on mine to get the CG to the sweet-spot for best glide performance & power-on behavior. You can also see the CG 'sweet-spot' marks on the wings:


TurboParker's Narrated Video:


blogodex = {"idx" : ["UMX Radian", "Trimming"]};

Sunday, September 17, 2017

NutBall Aerobatics

GoldGuy, the inventor of the NutBall, reveals some NutBall tricks and his propensity for poetry:

1.  Next time your out, experience the distinctive sound made by a NutBall. Here's how............

Take it to altitude with the nose up, instantly give it full down and full left. It will flip over and go into a violent but controllable spin. Hear that sound it makes? It's the only model I know that does it. To slow down it's decent, just cut the throttle. To get out of it, just relax the controls, then feed in a bit of up. Cool eh?

2.  The snap roll is similar. Flying straight and level fed in some up and then do the same, down and left. If you time it right, you'll get one complete violent snap in an instant. Practice at altitude and when you get it right, do it at eye level for best effect and you'll come out looking like a pro.

Also, in that inverted flat spin mode you can use the throttle and elevator to go up and down. Hold in the rudder the whole time..................throttle back, it will come down, add throttle and a bit more down and it will go up. You can go up and down in that inverted spinning mode as long as you wish.

You will have to move the battery back for a 30 to 35% CG for best flopabatics.

3.  Rolling the NutBall is an easy to do and a basic maneuver. Once you've mastered it, the roll becomes the basis for the snap roll, spins, inverted flat spin (complete with sound effects), the inverted 'elevator', both up and down, plus other silly weird stuff.

Rolling is more than just slapping over the rudder stick with the NB, although with models like the Simple Delta, flat and with elevons, that's all it takes to look good. What you want is to practice nice smooth rolls where the speed of rotation is the same throughout the 360 degrees of travel, it can be done almost axel, it's all in the timing and rolling to the left is easier to start off with. Make sure you set the CG at 25 percent to start, you can modify that as you progress, fly the maneuver at a MEDIUM speed at first and pay attention to the amount of movement on the rudder and elevator, not too much (???) is lots. The big problem in rolling the NutBall is that with too much rudder throw it wants to flip over very quickly once past inverted. How much movement is all apart of fine tuning. Having a low wing loading is a big aid in flying aerobatics as everything is much easier to do. If there's too much of a breeze, mount a bigger battery or some lead ballast, keeping the CG unchanged.

So, here's what to do to start off with.....................

Fly along straight and level at a brisk speed, but not full tilt (yet), and just before you enter the roll, add a tiny bit of up elevator to rise the nose, then feed in the rudder nice and smooth and when it goes inverted give it a tiny blip of down elevator and let off on the rudder just after is goes past inverted. What you need to do in the beginning is to form a pattern or tune in your brain. Practice in your shop with the model in front of you, try and picture in your mind what's happening. I learned four point rolls by repeating this to myself as I moved the sticks in the proper sequence and at the proper speed................ta da, ta da, ta da, ta da. It's like a tune in your head and you keep to the timing. Not sure what key I'm in, but it works. Got that from the best 3D pilot I know.

When you go out to practice, by yourself seems best and concertrate on the one thing and do just that.

#4 Here's another easy fun one anyone can do, the 'upright elevator', although it's all down elevator, no up. You'll need a rearward CG for this one, but start off with what you've got to see the difference it makes. Gain lots of altitude and point the nose straight into the wind. Now, hit full up and hold, and kill the thottle at the same time (again, it's in the timing) and use just the rudder to keep it facing into the wind. It should float down like a leaf, and with a low wing loading and a nice breeze you can plop it right down on the wheels. You can do this one inverted too.

Have fun with it.............all it takes is a bit of practice and a little more after that............your starting to look like a pro now...............keep it up



Most aerobatics it will do
And referring to how it flew,
If someone shouts, "a NutBall, WOW"
I wouldn't bother takin' a bow,
Cause they're probably talkin' about YOU

Wednesday, September 6, 2017

2017 Shopping List

Here's what you need to get started in Remote Control Aeromodelling!  This is everything you need except for actual aircraft.


Transmitter and Battery (one each)

https://alofthobbies.com/frsky-taranis-q-x7.html
https://alofthobbies.com/72v-2600-aa-nimh-qx7-transmitter-pack.html


4-Channel Receiver and Voltage Sensor (one each, for each model)

https://alofthobbies.com/frsky-d4r-ii-4-8-channel-receiver-with-27ms-cppm.html
https://alofthobbies.com/frsky-battery-voltage-sensor-fbvs-01.html


8-Channel Receiver (if you need more than 4 channels)

Get one of these instead of the 4-channel if your model needs more than 4 channels.

https://alofthobbies.com/frsky-d8r-ii-plus-8-channel-receiver.html


OrangeRX DSM2/DSMX transmitter module

If you want to fly a plane that uses a Spektrum DSM2/DSMX compatible receiver

https://hobbyking.com/en_us/orangerx-dsmx-dsm2-compatible-2-4ghz-transmitter-module-v1-2.html


Battery Charger and Accessories

Charger:
https://hobbyking.com/en_us/turnigy-accucel-6-80w-10a-balancer-charger-lihv-capable.html

Charging Cables:
https://hobbyking.com/en_us/multi-function-charge-lead-with-4mm-banana-plugs.html


Power Supply

The above Charger doesn't include a power supply.  You can use an old PC power supply or laptop power supply if you've got one.  If not, this one will do what you need.

https://hobbyking.com/en_us/t240-power-supply.html