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Comment Re:I hate them all. (Score 1) 316

There's actually a pretty good range of ultra-wide APS-C lenses now. Canon has a 10-22mm. Nikon has a 10-24mm. Sigma has an 8-16mm, a 10-20mm, as well as circular and diagonal fisheyes. Tokina has a 11-16mm. Tamron has a 10-24mm. There's others. They're very proud of them too, judging by their prices.

I went a cheaper route and got the Samyang 8mm fisheye. When I want rectilinear output, I convert it with hugin.

Comment Re:30$? (Score 1) 135

Another way to calculate this: Google "c/1.8GHz" and it'll give you the result in centimeters. Then just divide by two to get a half-wavelength dipole or divide by 4 to get a 1/4-wave ground plane length.

If you want a high-gain directional antenna for >1GHz you're probably best off with a dish, perhaps using a cantenna-like feed horn.


Hyundai Overstated MPG On Over 1 Million Cars 238

Hugh Pickens writes "Reuters reports that Hyundai and its affiliate Kia Motors conceded that they overstated the fuel economy on more than 1 million recently sold vehicles, and agreed to compensate owners for the additional fuel costs after the EPA found the errors in 13 Kia and Hyundai models from the 2011 to 2013 model years. The findings were a blow to the two carmakers, which have centered their marketing campaigns on superior fuel economy. The mileage on most labels will be reduced by 1 to 2 miles per gallon, with the largest adjustment being a 6-mpg highway reduction for one version of the Kia Soul, the EPA said. Hyundai previously touted the fact that many of its models get 40 miles per gallon on the highway. Now three Hyundai models, the Elantra, Accent and Veloster, as well as the Kia Rio fall short of that mark, as will the Hyundai Sonata and Kia Optima hybrids."

Comment Re:Vaastu Temple withstands 150mph (Score 1) 289

of course, these days, for anyone in the building trade to quotes believe quotes that this is even remotely possible would require supercomputers and fluid dynamics analysis

Or a small scale-model wind tunnel that could cheaply and easily be built with some plywood, some fans, and maybe some smoke or thread to show wind direction. It shouldn't cost more than $100.

You sound like you have something to prove here. Get on it.


Why Does a Voting Machine Need Calibration? 398

New submitter Shotgun writes "I heard on the radio that there were some issues with voting machines in Greensboro, NC (my hometown), and the story said the machines just needed "recalibration". Which made me ask, "WTF? Why does a machine for choosing between one of a few choices need 'calibration'?" This story seems to explain the issue."

Comment Re:Mechanical coupling more efficient than Gen/Mot (Score 1) 543

Now, to properly compare apples to apples, look at this graph (on page 10) regarding the Prius motor's efficiency at various power outputs (you've probably already seen this since you mentioned it earlier). Below 5kW, it's at 25%. At 10kW, it's at 33%, and that's a realistic highway speed power output. If we can assume 33%*90% (drivetrain) we get 29.7% - with a 38% Stirling engine, if we get 90% from the rest of the system (generator, battery, controller, wiring) - and I've already posted links showing that's do-able - then if your motor exceeds 87% efficiency you come out ahead. At 5kW output you just need 67% motor efficiency to come out ahead. It's nearly a wash, plus there's lots of tricks you can pull with electric motors when you have a handful of them (vs just one engine).

Comment Re:Mechanical coupling more efficient than Gen/Mot (Score 1) 543

Again. Who is using these to power a real car sized EV? No one.

Google for 'brushless dc ev' and you'll find lots and lots of product hits.

"Back in the 1990s all of the electric vehicles except one were powered by DC brushless drives. Today, all the hybrids are powered by DC brushless drives, with no exceptions. The only notable uses of induction drives have been the General Motors EV-1; the AC Propulsion vehicles, including the tzero; and the Tesla Roadster." (Granted this is from 2007 but still a good article on the differences between the two types.)

Comment Re:Mechanical coupling more efficient than Gen/Mot (Score 1) 543

It's not theoretical best case when it's already been done, and I was not cherry picking numbers. Here's some that are closer to the state of the art, for comparison: A 99% efficient BLDC controller - most of the controller inefficiencies are from band-gap voltage drop, which gets smaller as you use higher voltages (as does resistive losses in the wiring). Here's a 98% efficient motor, used on the CSIRO-UTS solar racer..

Are you really claiming that (for example) a modern 50kW motor would shed 5kW heat? Mid-90s efficiency is typical today for larger motors - it is not a cherry-picked exception!

Comment Re:Mechanical coupling more efficient than Gen/Mot (Score 1) 543

90% is too conservative. Brushless DC motors (the sort you'd pair with a VFD in any electric car) are pushing 96%: Lithium Ion battery efficiency is, depending on your source, 95% or 97-99%. So your 27% figure could be 34%. More importantly, since you have a drivetrain capable of driving the car at highway speeds in pure electric mode (something current parallel hybrids lack), a series hybrid could potentially be cheaper to operate if charged at night, and you can recoup more energy through regenerative braking.

Comment Re:Mechanical coupling more efficient than Gen/Mot (Score 1) 543

I don't think I have actually seen a case of practical application exceeding ICE efficiency, especially not a in practical size for automotive use.

NASA pursued this in the 70s and 80s for the DOE: The numbers they list for both ICE and Stirling are pretty laughable today but they serve as a reminder of just how much we've improved on engine tech in the past 30 years.

Power density in a Stirling is largely a function of working fluid density - a good chunk of NASA's research work regards how to change that on the fly (as you floored the gas pedal), something that isn't necessary in a series arrangement.

Comment Re:Mechanical coupling more efficient than Gen/Mot (Score 1) 543

One other (currently untapped) benefit of a series hybrid is that you can use a more efficient engine design that isn't able to change power levels quickly - for example the Stirling or Kalina cycle external combustion engines. No, I would not expect a poorly-funded group to be able to pull this off.

BTW the Fisker Karma is 5300lb. A Corvette is 3200-3600lb, and a Volt is 3800lb. Certainly doesn't explain all of it, but that's one lead sled.

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