A collection of note-to-self's
After comparing half a dozen heli’s, and changing my mind every other day, I finally bought a replacement for my Raptor .50. The verdict became the Align T-rex 600E Pro. Since I was planning to use a Castle Creations ESC anyway, I went with the Super Combo.
I never had a course in aerodynamics. If I had, I might have programmed a power-calculator myself, but I doubt that it would have been as complete and easy-to-use as this calculator.
Place: Halle
Raptor
Tanks flown: 1
Time flown: 0h18 (cumulative model timer: 32h07)
Rx battery recharged with: 428+197 mAh
Tx battery recharged with: 548 mAh
Glow heater battery recharged with: 1246 mAh
Starter battery recharged with: 450-ish mAh (forgot to note down)
miniTitan
Flights: 0.5
Time flown: 0h06 (cumulative model timer: 3h23)
Heli battery recharged with: (2) balanced 2181 mAh;
Tx battery recharged with: see above
Comments:
Went flying after dinner, the wind had calmed down and the rain had stopped.
I had some trouble starting my Raptor (glow heater indicated only 1A instead of the usual 5A). Since it’s been a while since I charged it, the battery was dead. A few minutes at the charger solved the problem.
In the mean time, I took my miniTitan out. Did some flying back and forth and a few stall turns to regain confidence. Next I did some back-flips. This is where it went wrong. On my 3rd back-flip, I intended to keep the heli inverted for a second and continue the back-flip, but the ground intervened…
Place: Halle
Tanks flown: 2
Time flown: 0h30 (cumulative model timer: 31h49)
Rx battery recharged with: 1244 mAh
Tx battery recharged with: 491 mAh
Glow heater battery recharged with: 1397 mAh
Starter battery recharged with: 54 mAh
Comments:
A very windy but beautiful day. Did some basic flying around (stall turn, circuit). Also retried flying inverted for several seconds with success.
Added 1 turn of pitch to the “black” blade to adjust the tracking
Place: Halle
Raptor
Tanks flown: 2
Time flown: 0h27 (cumulative model timer: 31h19)
Rx battery recharged with:
Tx battery recharged with: 559 mAh
Glow heater battery recharged with: 1300 mAh
Starter battery recharged with: 1250 mAh
miniTitan
Flights: 2
Time flown: 0h21 (cumulative model timer: 3h17)
Heli battery recharged with: (1) balanced 1934 mAh; (2) balanced 2137 mAh;
Tx battery recharged with: see above
Comments:
Went flying after work. It was fairly windy, but the wind was fairly constant. I practiced the maneuvers I’ve been doing in the sim lately: autorotation and inverted flight, both successful!
Inverted flight worked out fairly well. I started by doing backflips. Next I stopped halfway through the backflip and tried to keep it stable. I only need to work on my reflexes to get me out of inverted trouble. Obviously pushing the throttle/pitch up is not the best idea… Luckily I had (just) enough height to correct my peculiar situation.
The miniTitan held up fairly well in the winds, although I was more busy fighting the wind than flying. I increased the CCMP-mixing from 50% to 75% on the elevator and ailerons. Now it is more vivid, just like my raptor. I tried some backflips as well, but the wind made this a challange.
One of the things to pay attention to when building any RC vehicle is the setup of the servo’s. In (almost) all cases, the servo is connected to the controlled handle using linkages. One of the rules-of-thumb is that the servo, connecting rod and slave handle need to be at right (orthogonal) angles. Obviously I wanted to know WHY. John Vugts explains this in more detail, but I still wasn’t satisfied.
So I went through the math and ended up with a calculator to draw the curves on-demand. It’s a standalone JavaScript calculator, so it can be used offline. It uses Open Flash Chart to draw the graph.
Note that the angles are measured in the mathematical way: counterclockwise starting from the horizontal X-axis.
I got myself a new RC helicopter. It’s an electric one so I can fly indoors.
Here is the partlist and some basic specs:
Place: Halle
Tanks flown: 2
Time flown: 1h01 (cumulative model timer: 24h20) (including a lot of setup-time for the governor)
Rx battery recharged with: 268+1472 mAh (same behavior as some weeks ago)
Tx battery recharged with: 554 mAh
Glow heater battery recharged with: 439 mAh
Starter battery recharged with: 141 mAh
Comment:
I just bought myself a governor and needed to test it out. Besides that, a fairly calm day at the field. Besides testing out the governor, I continued to exercise my figure-8’s and nose-in hoover. After the last flight, I noticed that the rotor wasn’t rotating as freely as it used to.
When investigating this at home, the tail rotor made a slight rubbing sound:
The locking pin to keep the tail rotor shaft in place came out of its place. Pushing it back and re-tightening the set screw solved this problem.
Also, I basically undid the tracking adjustment: “black” was too high, so I decreased its pitch by 1 turn.
A governor is a device that stabilizes the rotor speed using a feedback mechanism. The Futaba GV-1 uses a Hall sensor to detect the magnets attached to the engine-fan. Here is the report about the device itself, its installation and the first test results.
From the 2 flights I did with the governor, I’m fairly happy with it. It does what I want it to do: govern the throttle to keep constant RPM. I must admit that I don’t (yet) do very demanding maneuvers…
Place: Halle
Tanks flown: 0.5 + 1.5
Time flown: 0h59 (cumulative model timer: 22h28)
Rx battery recharged with: 787 mAh
Tx battery recharged with: 475 mAh
Glow heater battery recharged with: 275 mAh
Starter battery recharged with: 55 mAh
Comment:
Mainly a short flight to check the new balance tape and correct the tracking: the “black” blade needed 1 turn more pitch (which roughly gave it +1° compared to the other blade). After that some basic flying around with stall turns. Did some adjustments on the throttle-curve to keep the rpm up when braking with some negative pitch.
When it came to tuning my nitro engine, most guides referred to subjective measurements: “enough smoke”, “accelerates swiftly”, “sounds good”, … I, as a nitro-engine newbie, did not know what an engine should sound like and how much smoke it should produce.
I finally found some objective criteria to figure out whether the engine is too rich or lean: the temperature. This PDF by Tony Chaveiro reviews a CarbSmart needle controller, which uses the head-temperature as a feedback mechanism.
Apparently, 100°C is a nice head temperature to aim for. Leaning the mixture will increase the temperature, giving more fuel will cool it down.
I don’t know how I’ll use this knowledge to tune my engine, but at least I have an objective way judge the mixture.
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