Akom's Tech Ruminations

Various tech outbursts - code and solutions to practical problems

Toys On Wheels, Thrust Vectors, and Gorilla Glue

Posted by Akom • Tuesday, October 21. 2008 • Category: Toys
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...

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Toys Pitts S2A third video flight, straight and level

Posted by Akom • Wednesday, October 15. 2008 • Category: Toys
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...

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Toys Pitts S2A second on-board video flight

Posted by Akom • Tuesday, October 14. 2008 • Category: Toys
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...

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Toys Pitts S2A Bottlenose motor mount rebuild

Posted by Akom • Monday, October 13. 2008 • Category: Toys
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?

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Toys First Video Flight!

Posted by Akom • Sunday, October 12. 2008 • Category: Toys
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...

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Toys Sapac Pitts S2A electricals and motor replacement

Posted by Akom • Monday, October 6. 2008 • Category: Toys
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!

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