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silence_kit posted:Or maybe never in the case of airplanes, if there is no groundbreaking development in battery technology to improve their energy density. Energy density of the powering source is way more important for airplanes than it is for cars. It's really, really easy to underestimate just how energy-dense that hydrocarbon fuels are. Batteries and solar panels are piss-ant poo poo compared to a big tank of JP1 powering a turbine. Almost all large-scale electrical balancing systems use something like pumped hydro, compressed air, or molten salt because trying to store that much electicity in a battery is loving stupid. I was on the very bleeding edge of powering model aircraft with electric, and it only really became workable about 15 years ago even at small scale (high-quality name-brand NiMH cells for high-discharge applications, LiPo for higher capacity but reduced discharge). Nowadays the tech is real solid for model-scale airplanes (barring the really big 50cc type stuff) but even still you can't beat the endurance and power of nitro aircraft. You need a more and more energy-dense powertrain the larger the plane gets. Sanyo 1950mah 4/5A FAUP cells, rated at up to 45A on the sticker and would tolerate being discharged at up to 70A in practice (i.e. 23-36C discharge). And the Mega 16/15/3 would eat up whatever you could feed it 
Paul MaudDib fucked around with this message at 02:13 on Feb 12, 2016 |
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Feb 12, 2016 02:02
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MaxxBot posted:I've seen some really powerful electric setups for even the big 100cc+ planes since the motors themselves have a pretty good power to weight ratio, but yeah gas still has a pretty big advantage in endurance. I'm sure it's come a long, long way. Way back when the only chance of doing that was an Inner Demon gearbox to gear two massive (and expensive) Hacker motors together. I once saw a 0.40-sized NASA demo airplane fly at my local airfield about 14 years ago - it had a single giant Hacker motor and a massive battery pack that was probably something like 3P8S sub-C NiMH cells. Way beyond what I could field of course, and even so the endurance was indeed garbage. Like 10 or 15 minutes tops, even given that they were nursing it along. My first plane was a foam Cessna replica with a Graupner 600 motor using repurposed car sub-C packs, circa 2000. Barely flew, but it was a hell of a time for experimentation in terms of figuring out a way to make that loving powertrain work right. Ended up using a Kyosho Magnetic Mayhem car motor at way over the stock voltage, at which point it made a decent sailplane in moderate winds. Then circa 2003 I went to a Zagi-style airplane (the Bird of Prey to be precise). Brushless right from the start, originally a Mega 16/15/4 with 1800 mah HeCells. I eventually tried KAN 1100 cells in a high-voltage pack, but it ended up being too light and didn't deliver the current the label claimed it did. Took a gamble and tried a single top-shelf Sanyo pack and welp, double the current on the pack. Going to a 16/15/3 moved me from the "reasonable performance" into "unlimited vertical" territory and the packs lasted literally 5+ years despite being abused like poo poo. They probably would work right now if I cycled them a couple times. I used to get laughed out of the field for flying "toys" since I had a Sig Kadet. Nowadays there's more electric than gas flyers. Also, I put my spare 16/15/4 on a tiny model that can hit 70+ mph. It was the fastest thing on the field as of about 5 years ago. I've been thinking about getting back into it with a "diesel-electric" style model where power is generated in a small motor which provides power to the other motors. In theory, you can use brushless motors and if you wire them directly to another identical motor they'll spin at 1:1. You could do some cool multi-engine historical/scale models like that if you could keep the nitro motor cool. Bringing it back to the thread - I'm much more optimistic about pretty much any energy storage/transportation tech besides batteries. Like, fixing alternate fuels from atmospheric carbon might well have a better overall performance ratio if we optimized that, since you are transporting a much smaller volume and/or weight of fuel. Paul MaudDib fucked around with this message at 04:49 on Feb 12, 2016 |
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Feb 12, 2016 04:23
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