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drgitlin posted:No, you keep misunderstanding. CdA tells you the actual amount of drag the actual car has in the actual world. I don’t care about some thought experiment where you pretend they’re both the same size. And stop mentioning Blackbirds and bricks. I don't misunderstand it, I understand it better and more thoroughly and I'm capable of grasping abstractions of it. But in the actual world, the Leaf has more absolute drag than the snub-nosed i3.
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Jan 29, 2018 13:13
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Ola posted:The overhang is probably designed with bumper regulations and aerodynamics in mind, but that doesn't mean overhang is the only way do those. The i3 has no silly overhang, but a lower drag coefficient (0.29 vs 0.32) and obviously also complies with safety regulations. The Leaf has a slightly better NCAP passenger rating, but the tip of the nose is rated "poor" I'm just going to quote Ola here so we don't get lost in all the "you're wrong, no you're wrong, dad she's hitting me, no I'm not" business. Ola is saying the i3 is a slipperier design without having a long pointy nose, which is true. It's also got a larger frontal area, and a lower CdA, which reinforces the point that pug face is still more aerodynamic than fish face, even while presenting a larger surface to the wind (which may seem counterintuitive), so why have fish face?
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Jan 29, 2018 13:18
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Could be that BMW has more experience designing for low overhang, with most of their lineup being longitudinal ICE + RWD anyway. My E87 has a relatively short overhang, maybe half a wheel diameter or so.
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Jan 29, 2018 14:30
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bolind posted:Could be that BMW has more experience designing for low overhang, with most of their lineup being longitudinal ICE + RWD anyway. My E87 has a relatively short overhang, maybe half a wheel diameter or so. That's a good point. Their Mini and 1 series have very little overhang and they are FWD, so you could definitely say that the i3 is a result of optimizing for purpose how they already build cars. Although things like the Note, Versa, and Altima don't have a huge amount of overhang either.
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Jan 29, 2018 15:17
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Ola posted:So the Leaf doesn't need its stupid nose to move smoothly through the air - and that holds for a Leaf at any scale. If you could magically resize the two cars to any size, their absolute values would change, misleading you, but the drag coefficient would not. A 15 ft tall i3 will be very draggy, but its shape will be less draggy than a 15 ft tall Leaf. I don’t think that’s a fair statement as wouldn’t the relative difference change between the two cars at different scales?
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Jan 29, 2018 18:19
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blugu64 posted:I don’t think that’s a fair statement as wouldn’t the relative difference change between the two cars at different scales? Yes, so if you wanted to measure absolute efficiency in strict quantitative terms, for instance which of the two cars can take you to work using the least electricity, you will want to look at absolute values. If all other power consuming factors were equal, the one with the lowest absolute drag would win, because it consumed less power. This might make you choose a smaller car with higher Cd over a bigger car with lower Cd, if the small one is still big enough to do the job. But when you ask "is this shape more aerodynamic than the other?", for instance a bulbous nosed shape vs a snub nosed shape, you have to compare differently. One car might be bigger than the other, but the shape itself can be made at any scale. It is the shape, not the size, that defines the aerodynamic properties. The shape is the formula, the size is just the variable you put into the formula.That's why you can test model aircraft in wind tunnels after all and learn something about the real thing. You could have improved the Leafs drag by simply making it smaller. Then its absolute drag numbers might be smaller than the i3. But for any given size of the Leaf, you can change its shape to that of an i3, and the drag will be lower, because the i3 shape, at any scale, has a lower Cd. You can't scale cars up and down of course, and there are many other factors at work in why a car gets the shape it gets. But the real world implication of this is that the Leaf shape could have been designed better, it isn't as slippery as it possibly could have been, in spite of its bulbous nose.
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Jan 29, 2018 18:56
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Ola posted:One car might be bigger than the other, but the shape itself can be made at any scale. It is the shape, not the size, that defines the aerodynamic properties. Right but all I’m saying is scale matters. Area doesn’t scale linearly.
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Jan 29, 2018 19:06
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And just in case anyone was wondering just how hair splitting we're getting, an i3 has a 10cm^2 larger frontal area than a Leaf, or about the size of an iPhone X. By adding just 5 more cm^2, or just over half a credit card, bringing its frontal area up to 2.43m^2, it would match the CdA of a Leaf. So this whole conversation is a bit pedantic, but that's Aerodynamics!
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Jan 29, 2018 19:18
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blugu64 posted:Right but all I’m saying is scale matters. Area doesn’t scale linearly. Yes, scale does matter to absolute drag. But when the scale is given, say we're building a car that needs to meet certain criteria of roominess etc, which shape should it have? A bulbous nose or a snub-nose? A bulbous nose is annoying in parking lots, is it perhaps a fair tradeoff for better energy economy on the highway? Turns out no. A well executed snub-nose can be better at both parking lots and highways. Finger Prince posted:So this whole conversation is a bit pedantic, but that's Aerodynamics! I think after porn, spam and political propaganda, pedantic conversation has to be the #4 generator of internet traffic. Just doing my bit to keep those servers running.
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Jan 29, 2018 19:37
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But maybe it's better for safety?! https://www.youtube.com/watch?v=lgxpGCib0PY https://www.youtube.com/watch?v=l6BKlWD24YQ Oops, nope, the Leaf completely fails the high speed small overlap test.
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Jan 29, 2018 19:53
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i'm surprised at how different those two are (and i love the i3 wheel popping off)
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Jan 29, 2018 21:26
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Jesus Christ what an argument. The shape of the nose doesn't determine if i3 or Leaf is more aerodynamic. There are no conclusions that can be drawn from the reported Cd to the influence the shape of the nose of each of the cars may or may not have on the overall drag. The Cd is much more sensitive to design of many other bits.
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Jan 29, 2018 21:31
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That's cool! The lizard defense, it sheds parts to confuse the predator and scurries off to the side. *braces for 10 page argument about autotomy*
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Jan 29, 2018 21:46
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Man_of_Teflon posted:(and i love the i3 wheel popping off) It has a lever purposefully designed to sheer the wheel off and eject it
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Jan 29, 2018 21:48
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Ola posted:That's cool! The lizard defense, it sheds parts to confuse the predator and scurries off to the side. I also appreciate the door skin being launched into orbit never to be heard from again.
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Jan 29, 2018 22:03
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Three Olives posted:But maybe it's better for safety?! That’s because the design predates that test - no one was building for that back in 2010
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Jan 29, 2018 22:19
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Finger Prince posted:And just in case anyone was wondering just how hair splitting we're getting, an i3 has a 10cm^2 larger frontal area than a Leaf, or about the size of an iPhone X. By adding just 5 more cm^2,
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Jan 30, 2018 01:36
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dissss posted:That’s because the design predates that test - no one was building for that back in 2010 My point is that with a clean sheet of an electric drive BMW chose a snub nose that is aerodynamic, incredibly safe, highly maneuverable and managed to throw some storage in there too so maybe they did a pretty good thing overall even if it looks "weird" compared to ICE designs which were only dictated by the ICE engines in the first place. Three Olives fucked around with this message at 02:00 on Jan 30, 2018 |
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Jan 30, 2018 01:58
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A clean sheet electric car with a gaping hole where the engine goes in the non-range extended i3, sure.
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Jan 30, 2018 02:11
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His opinion is driven only by the badge on the hood. It would be the worst design ever if it had come from GM or Ford.
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Jan 30, 2018 02:33
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roomforthetuna posted:Argh, I assume based on the "for scale" items that you meant (10cm)^2 and (5cm)^2, but what you wrote is usually interpreted as 10(cm^2) and 5(cm^2) which are even smaller areas, by a lot. In a post about being pedantic, you monster! I wouldn't rule out doing my estimates wrong. I think I got the iPhone size right, but the list of colloquial area sizes kind of limits you to common coinage and football fields.
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Jan 30, 2018 03:08
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Finger Prince posted:I wouldn't rule out doing my estimates wrong. I think I got the iPhone size right, but the list of colloquial area sizes kind of limits you to common coinage and football fields. Beer coaster, credit card, dollar bill, frisbee, etc.
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Jan 30, 2018 03:27
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Finger Prince posted:I wouldn't rule out doing my estimates wrong. I think I got the iPhone size right, but the list of colloquial area sizes kind of limits you to common coinage and football fields. Edit: I wish the meaning of 10cm^2 was the way you did it though, because then my new 223m^2 house would be loving huge. roomforthetuna fucked around with this message at 04:22 on Jan 30, 2018 |
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Jan 30, 2018 04:03
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Edit: Oh nm.
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Jan 30, 2018 04:18
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roomforthetuna posted:An iPhone is certainly larger than 10(cm^2) unless maybe you're talking about the side-view cross-section or something. But (10cm)^2 seems about right for it. Yeah I just pictured it and quite literally (figuratively?) realized the size of my error. See kids, numbers only get you so far, sometime you have to use your ~*imagination*~!
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Jan 30, 2018 04:43
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roomforthetuna posted:An iPhone is certainly larger than 10(cm^2) unless maybe you're talking about the side-view cross-section or something. But (10cm)^2 seems about right for it. Area and volume are definitely a weak point in the metric system. With most units, you never have to have more than three digits because at the point a fourth digit is necessary, you’ve moved into the domain of the next prefix. With area and volume, I am forced into writing big numbers one way or another. Ten thousand cubic metres† is still only 0.001% of a cubic kilometre. The inconvenience of these units is probably why the the litre and are are still used for volume and area. In conclusion, you can say you have a twenty‐two deciare house. †Which is one hectare flooded to a depth of one metre. Platystemon fucked around with this message at 05:12 on Jan 30, 2018 |
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Jan 30, 2018 05:05
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Volvo throws a bigger hat in the PHEV ring: https://www.facebook.com/Teslabjorn/posts/766362710223526 They were charging at 24 kW at 89%, which I guess is pretty good. 30 kWh should guarantee an all electric commute for a lot of people.
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Jan 31, 2018 15:26
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The California 2017 Self Driving Car disengagement reports are out https://www.dmv.ca.gov/portal/dmv/detail/vr/autonomous/disengagement_report_2017 Summary here: https://www.reddit.com/r/SelfDrivingCars/comments/7ucvoj/california_disengagement_report_link_works_for/ Tesla drove 0 autonomous miles on California roads in 2017 
Frinkahedron fucked around with this message at 03:36 on Feb 1, 2018 |
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Feb 1, 2018 03:31
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"We don't test our software, our customers do".
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Feb 1, 2018 14:29
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The EA approach.
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Feb 1, 2018 16:38
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Ola posted:"We don't test our software, our customers do". That's what happens when consumers have no patience and are willing to pay to beta test. Like the video game industry is getting into vehicles. Soon everyone will have cars that are limited to 25mph until you've earned xp with safe driving or buy the loot boxes that have a chance to contain items that increase the limit by 1mph each. Either an extra $10,000 in loot boxes purchased from your indash touchscreen or 5 years of safe driving to be able to approach highway speeds.
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Feb 1, 2018 16:42
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Phuzun posted:That's what happens when consumers have no patience and are willing to pay to beta test. Like the video game industry is getting into vehicles. Soon everyone will have cars that are limited to 25mph until you've earned xp with safe driving or buy the loot boxes that have a chance to contain items that increase the limit by 1mph each. Either an extra $10,000 in loot boxes purchased from your indash touchscreen or 5 years of safe driving to be able to approach highway speeds. Delete this post before Elon sees it.
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Feb 1, 2018 17:39
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Phuzun posted:That's what happens when consumers have no patience and are willing to pay to beta test. Beta test? Tesla is getting people to buy fully autonomous packages for their cars right now that don't exist and have no estimated delivery or even guarantee that they will ever be delivered.
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Feb 1, 2018 17:58
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Ola posted:Volvo throws a bigger hat in the PHEV ring: electric V90 pleeease
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Feb 1, 2018 18:29
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Three Olives posted:Beta test? Tesla is getting people to buy fully autonomous packages for their cars right now that don't exist and have no estimated delivery or even guarantee that they will ever be delivered. See also: Kickstarter
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Feb 1, 2018 18:29
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I just want a goddamn three row electric that isn't the model x and that can do at least 140miles of ev range. Give me a Pacifica full Ev for fucks sake. I'll accept considerably reduced cargo space, even.
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Feb 1, 2018 18:34
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Stefan Prodan posted:electric V90 pleeease In Norway, an electric V90 would sell like hotcakes enhanced with sliced bread technology.
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Feb 1, 2018 18:43
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Ola posted:In Norway, an electric V90 would sell like hotcakes enhanced with sliced bread technology. yeah I realize I would have the literal only one in the US oh well
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Feb 1, 2018 19:10
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I saw a Model 3 today on my morning commute here in San Diego. First one I've seen in the wild. It looked sleek as hell. That's my story thanks for reading.
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Feb 1, 2018 20:04
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eyebeem posted:I just want a goddamn three row electric that isn't the model x and that can do at least 140miles of ev range. The stow and go seating could be replaced with a whole lotta batteries. Edit: the plug in hybrid already ditched the stow and go. Oh well. CannonFodder fucked around with this message at 01:17 on Feb 2, 2018 |
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Feb 2, 2018 01:11
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