Akom's Tech Ruminations

The Mystery B6

I got this charger because the little unit that was included with my R/C plane just did not inspire a lot of confidence. It did charge, just took hours, and gave no hints about why. So I figured I'd go and buy something that gives me a little more information. And I found it. In Hong Kong. But now it's on my desk.

For being able to charge anything, the $50 and two weeks of waiting simply doesn't seem excessive.

As far as I can tell, the Mystery B6 gets a fair amount of negative commentary on the forums. People seem to question its voltage precision and balancing accuracy. So I thought I'd run a very simple test.

Continue reading "The Mystery B6 balancing LiPo/LiFE/NiCd/NiMh/Pb charger (review, sort of)"

New Wheels next to old wheels

I upgraded the wheels on the Pitts plane, and what a difference it makes. I never thought it could land (and sometimes even take-off) on grass! (Well, short grass, anyway). I don't nose in every landing now. Just got those 2.50" Sport wheels from the hobby store. The stock wheels are just way too small. I did need to cut the wheel pants slightly to fit them, but I think it is cute the way they stick out. And as you may have noticed, the Fiji bottlenose got a paint job.

Now about those thrust vectors...

Continue reading "On Wheels, Thrust Vectors, and Gorilla Glue"

I did it! I flew straight and level. Video is available.

Since the side of the fuselage seems to be the best place for the 215g that is the camcorder, I needed 200+ grams on the other side... or less all the way at the tip of the wing? Then it hit me... I have two lipo batteries, about 100g each. And that is how the balanced Fiji Bottlenose was born.

Balanced Payload

In addition to balancing the plane correctly, I finally got to cleaning the camcorder lens, which helped a bit with the sunspots and artifacts. I also covered the microphone with a bit of soft grey packing foam to act as a windsock - and the sound is no longer clipping from the airstream.

The details...

Continue reading "Pitts S2A third video flight, straight and level"

This morning I thought I'd test my luck a little more, and mount the camcorder (Panasonic SDR-S10 at 220 grams) on the side of the fuselage. Visually, it just seems safer there - in a crash I expect the wings to protect it. On the downside, it unbalances the craft a lot - 635g plane with 220g of now unbalanced payload! But I did it anyway.

Camcorder on the side

See the video...

Continue reading "Pitts S2A second on-board video flight"

I didn't see this coming - hesitated in my landing approach, caught a gust of wind, clipped a cute little pine tree - and dove straight down 15 feet, carefully missing the soft lawn and hitting the packed dirt road. Front end demolished - engine cowl and engine mount are in pieces, fuselage cracked. The prop saver may have helped the motor survive this adventure.

New Engine Mount (mount cross is inside bottle)

I tried to find suppliers for these parts (again), but nothing turned up. Other than buying a whole new plane, I don't see a way of getting a new motor mount (that seems a little silly, no?). The fuselage is easy, Gorilla glue got that back together in an hour or two. (In fact, I've already glued the fuse with it once, and that weld did not break).

But the mount?

Continue reading "Pitts S2A Bottlenose motor mount rebuild"

I've been thinking about aerial photography for some time, and I've worked out exactly what equipment I'd get too, but for now I'm not allowing any funds for this expenditure. I figured that AP is way in my future, but this morning I just decided - what the heck. FPV (First Person Video) may not happen right now, but at least I can record the flight and watch it later. So I went and weighed my SD camcorder... Panasonic SDR-S10. 220g or so - not too bad (My ultra-compact Optio S550 is 270g, and that's only a still camera!!!). The plane is 635g with battery. Hmmm...

Continue reading "First Video Flight!"

This was annoying. Whenever the blackberry was plugged in (USB), windows would ding and show a baloon saying "USB Device not recognized", and this would continue forever, repeating about every 10 seconds! Clicking the baloon would show you the USB device tree, with a very helpful "Unknown Device" shown in bold. It took some time to figure out that it's happening only when the BB is connected. It sort of seemed as if someone is rapidly connecting/disconnecting the USB cable.

Well? Turns out that this is sort of what was happening. It was a bad cable. OK, perhaps not a bad cable, but one that the blackberry didn't like. And, unlike what some people suggested, having it plugged in through a hub is not the culprit. Interestingly, the cable that was malfunctioning was heavy duty, with ferrites. The cable that works is thin and flimsy.

Or the infamous "Or you can add an exception" thing.

Apparently since Firefox 3, if you stumble on a site with an invalid SSL certificate, be it expired, self-signed, or bad in any other way, you are greeted (as before) with a warning. Only this warning requires 8 steps to bypass, not all of which are intuitive to the normal power user. Moreover, in my experience, Firefox will prompt you again and again once your restart it, despite the fact that you checked "Permanently store this exception". And why do I need to "download" the certificate anyway? The browser must have already retrieved it by now since it's warning me about it.

I actually considered downgrading to Firefox 2... but I found a solution.
Here is what you do:

Continue reading "Firefox 3 Uber SSL Security madness for Self-Signed Certificates"

I killed the motor. Apparently ramming into pavement at full throttle (don't ask. From now on, when something goes wrong on takeoff, I abort) is not such a good thing for a long thin shaft and a firmly bolted prop. A few flights later, the motor died and started singing instead of spinning. One of the windings seemed to be busted (based on measuring voltage with a drill).

Measuring Current

Anyhow, I did some measurements when it was all good, and here are some specs: With the stock Sapac 2830 motor and the 3-blade 9x8 prop, the battery put out as much as 12.5A at full load (my measurement, massive analog meter). The battery is 10C, 1200mAh, meaning that 12.5A is about as much as you could ever expect it to put out, in other words - running dangerously high. I also got a 10C 1800mAh battery and the plane had noticeably better thrust (haven't measured the current), so it actually did want more than 12A!

Continue reading "Sapac Pitts S2A electricals and motor replacement"