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Comment Re:This guy has a better idea (Score 1) 221 221

Hopefully this isn't going to remain the case for much longer as regenerative braking systems do seem like a low hanging fruit with the potential for extremely high efficiency. I'm not sure if the F1 KERS solutions employ anything with more general promise than flywheels but it is bound to be a fairly active area of research by others. Toyota and Mazda have tried super capacitor solutions and I don't think it will be very much longer until it is normal to recover almost all the available potential energy when braking in any conditions.

Comment Re:Please be an Onion link please be an Onion link (Score 1) 221 221

Actually the 11-16% converting to 2.3kW in the Tesla doesn't really make sense as a conclusion. Also both those links actually seem to point to the significance of rolling resistance as they include the ICE and the combustion inefficiency dominates everything else.
Looking at the fueleconomy.gov link and only considering the useful output power which is what I was really imagining above; probably less than 55hp for the typical car at cruise and ~22kW for the Tesla. Then while maintaining a cruise the useful power is only split between:
  • Rolling Resistance = 7-11%
  • Air resistance = 11-16%

Depending on speed either drag or rolling resistance are going to dominate the power required. I really had never considered rolling resistance to be of great importance to a car despite my experiences on a bicycle.

Comment Re:Please be an Onion link please be an Onion link (Score 1) 221 221

Thanks, my gut tells me the rolling resistance figures given there are too high. The 11-16% aerodynamic drag given in your two links matches up nicely with the 2.3kW which I estimated was required to overcome drag in the Tesla.
I've got an EcoBoost Fiesta and during the winter here (Canada) the pressure gauges on most of the air pumps at the gas stations seize in the cold and so are practically useless. When it was finally warm enough to accurately check the pressure in my tires they were all around 30-32psi. After inflating them back to the recommended 38psi I noticed my economy improved from 6.5 l/100km to 5.5 l/100km although admittedly the average temperatures had also warmed up from around -15 to -5C. Even so it was enough of an improvement that I was surprised and will be checking tire pressures more frequently in future.

Comment Re:Please be an Onion link please be an Onion link (Score 1) 221 221

I just checked the aeodynamic drag for the Tesla S (0.24cd) using the formula here.
At 60mph the air resistance will be about 85N or about 2.3kW. This is far less than I would have thought and appears much less significant than the typical rolling resistance.

Comment Re:Please be an Onion link please be an Onion link (Score 1) 221 221

A typical rolling resistance of a car on asphalt is 441 N. So the power at 60 mph (or 26.8 m/s) is

441N x 26.8 m/s = 11.8 kW

Using wikipedia figures the Tesla seems to require approximately 22kW at 60mph but it is extremely low drag and probably has lower rolling resistance than the typical value above. However I'd bet most cars are using 40kW (~55hp) or less to cruise at 60 resulting in the rolling resistance being responsible for 25-50% of the power requirements. I'm not convinced it would be worth it in many cases but recovering 10% of the energy could provide 1kW, the same as a 70A alternator.

Comment Re:Now if I could just type... (Score 1) 165 165

I assume the whole point is that it is easy to move the brains around with you. A MHL cable instead of HDMI would provide power along with a more flexible cable. Putting the brains and the input interface to a touch based OS in an easily portable devices could be a much more flexible solution than the Chromecast and its ilk.

Comment Re:If you don't want to upgrade your box (Score 1) 100 100

I've built a a handful web servers hosting live HLS streams for PEG and hospitality customers and RAM disks are a very simple solution that works great for me. It doesn't take much memory to store just ~30 seconds of a hundred different streams, the encoders can use webdav to push the streams onto the server and Nginx (but probably almost any other webserver) can easily serve 10's of Gbps on the cheapest of the E3 Xeons.

I can't think of a cheaper and easier solution than a RAM disk for this particular application.

I'm trying to do a similar thing on the RPi to build a CCTV system. Live streams straight from RAM but to then use the hardware calculated motion vectors to trigger recording onto an SD card. Unfortunately I'm currently stuck trying to find a tool that can perform the HLS packaging of the segmented elementary streams the RPi camera can produce.

Comment Re:Inspections? (Score 2) 169 169

England had yearly safety inspections (the MOT) but in Ontario they do not exist and a safety test is only required when the vehicle registration is transferred i.e. when ever a second hand car is sold to a new owner. I don't think the safety check is required when transferring the ownership to a family member but I wouldn't swear to that.
I've been utterly shocked at the state of many cars on the road here with no sills left and nothing but rust in other structurally essential parts of the car. I think the OPP can stop cars that they deem unsafe but there certainly is no annual safety inspection and the only required test is a bi-annual emissions check.

Gosh that takes me back... or is it forward? That's the trouble with time travel, you never can tell." -- Doctor Who, "Androids of Tara"

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