[HN Gopher] Students break acceleration world record
___________________________________________________________________
Students break acceleration world record
Author : giuliomagnifico
Score : 210 points
Date : 2022-10-12 18:34 UTC (4 hours ago)
(HTM) web link (www.uni-stuttgart.de)
(TXT) w3m dump (www.uni-stuttgart.de)
| jcmontx wrote:
| Now take the tech and apply it to the next gen of Formula E!
| amelius wrote:
| What are those solder joints at 0:50 in the video?
| nsxwolf wrote:
| I'd love a straightforward view of what that really looks like,
| instead of a bunch of fancy camera work.
| Ralo wrote:
| I've been a huge fan of drag racing, and the engineering behind
| it. I've seen the influx of electric cars making their way into
| the scene but they never seem to be competitive, and that comes
| down to their top end.
|
| The extreme end of combustion engines, you really got top fuel
| dragsters. Not much faster land vehicles than those. The flaw
| with those, they got about 2 uses tops before it needs to be
| completely gutted and rebuilt, not great as a weekend track car.
| As well, it's somewhere around $1000/second to drive it.
|
| You can sit more in the middle with people getting 1000hp daily
| drivers. With dynamic tuning, flex fuel, etc you can get the best
| of both worlds. As well, DCT AWD transmissions make grip/shifting
| issues a thing of the past.
|
| However, these middle ground drag cars can still get eaten by a
| $130k bone stock tesla*. The extra weight, infinite torque, and
| zero shifting is a real advantage, even if their top end isn't as
| strong as their ICE counterpart.
|
| I've always dreamed of building a hybrid car with tiny tiny
| battery packs. Maybe enough charge for 4-5 passes. Enough for a
| day at the track. But have a fully built high revving ICE. You
| get the launch in full electric, your ICE can be fully spooled,
| and ready to switch over automatically. Perhaps the smaller
| batteries couldn't put out enough power? Who knows.
|
| *Plaid
| PragmaticPulp wrote:
| > You can sit more in the middle with people getting 1000hp
| daily drivers. With dynamic tuning, flex fuel, etc you can get
| the best of both worlds. As well, DCT AWD transmissions make
| grip/shifting issues a thing of the past.
|
| > However, these middle ground drag cars can still get eaten by
| a $100k bone stock tesla
|
| A 1000HP drag car with AWD and a DCT shouldn't "get eaten by" a
| $100K Tesla (unless you actually meant the $130K Tesla Model S
| Plaid). Not unless someone is lying about their power numbers
| or doesn't know how to set up a car.
|
| The Tesla's drag mode is a neat party trick and perfect for
| singular drag races, but spending 15 minutes preconditioning
| your battery before you can launch is also kind of ridiculous
| by ICE car standards.
| Ralo wrote:
| >unless you actually meant the $130K Tesla Model S Plaid
|
| Rounding error to $100k. Yes I'm referring to the Plaid.
| People have taken those cars and gutted the interiors on
| them, and demolished drag races.
|
| > spending 15 minutes preconditioning your battery before you
| can launch is also kind of ridiculous by ICE car standards.
|
| It's far from rare to see people setting up an array of box
| fans, and bags of ice around their engines to cool it off
| between passes. Many high high powered cars won't even have
| full size radiators.
| slowhand09 wrote:
| Nope, your typical Tesla isn't the rocket you describe. Most
| are quick, but not that quick. I frequently get challenged by
| wannabes while commuting. I rarely take the bait, but I've yet
| to have one live up to the hype.
| gffrd wrote:
| What are you driving that has Tesla drivers wanting to tangle
| with you so often??
|
| Muscle or German?
|
| (Wondering whether the motivator is performance or ideology)
| KindAndFriendly wrote:
| slowhand09: "My daily driver is a Hellcat..."
| Ralo wrote:
| I should have specified, Tesla Plaid. Of course a Model X
| isn't as quick as a fully built 1000hp AWD DCT GTR. Apples to
| oranges.
| masklinn wrote:
| > Not much faster land vehicles than those.
|
| Top fuels top out around 350 mph. The land speed record is 760
| (manned, for unmanned it's a rocket sled exceeding mach 8).
|
| The land speed record has been above 350 since 1938:
| https://en.wikipedia.org/wiki/Railton_Special
|
| There are in fact a fair number of much faster land vehicles.
| Ralo wrote:
| Yes, their top speed is much much faster. But put that same
| vehicle on a 1/4 mile race track, racing a top fuel dragster.
| The top fuel dragster produces around 5g's at launch, the top
| speed cars are very very slow to build up speed. So much so,
| they usually require a pilot vehicle just to start them, like
| you trying to start pedaling your bicycle in 5th gear. You'll
| want a push. It's a different type of racing.
|
| > Not much faster land vehicles than those.
|
| Its a poor choice of words, perhaps 'quick' is a better word?
| gorkish wrote:
| > But have a fully built high revving ICE
|
| Once you do this you are sunk due to weight. If you need
| another torque band, far better to add a second electric motor
| with a different gear ratio (Tesla already does this) or use
| something like a DSG with the single motor.
| jmpeax wrote:
| What an incredibly frustrating video. Here is the actual run
| without all the unnecessary fast-and-furious computer graphics
| rubbish at the start:
| https://www.youtube.com/watch?v=xjDK0LhKkMs&t=76s
| mattfrommars wrote:
| The title should add for electric vehicles. Aren't top fuel
| dragsters quicker?
| semi-extrinsic wrote:
| Yes, IIRC they're doing somewhere around 0.7s? There's even
| been road legal tuned-up versions of the Nissan GT-R doing
| around the 1.5s mark.
| [deleted]
| topspin wrote:
| Jalopnik claims 0-100 _MPH_ (161km /h) is 0.86 seconds.
| ncmncm wrote:
| I wonder if they are allowed to put a fan in to suck it down to
| the road surface, offering better static friction to the tires.
| You would of course start the fan before the wheels.
|
| That would mean you could get by with lighter-weight tires, an
| important concern.
| ihunter2839 wrote:
| Yes, this car uses powered ground effects (PGE) to achieve the
| necessary downforce at low speeds (they mention this in an
| instagram post)
|
| In Formula SAE in the US, PGE systems are not allowed, but in
| the European equivalent they are.
|
| Take a look at the Speirling at Goodwood Festival of Speed for
| an awfully mean fan car.
| https://www.youtube.com/watch?v=xtvT2XYlcOY
| tshaddox wrote:
| That's what this electric fan car does:
| https://www.roadandtrack.com/news/a40424619/watch-an-electri...
| mburee wrote:
| Why wouldn't they incorporate design from top fuel dragsters?
| They reach 100mph (!!) in under a second.
| sethgrisham wrote:
| It's a track car designed for road races, not drag racing. This
| car is essentially meant to be a jack of all trades, whereas
| top fuel dragsters are probably the most purpose built car of
| all time.
| eenell wrote:
| Why would an EV incorporate tech from top _fuel_ dragsters?
| What tech besides tyres and aero would they adopt?
| antonvs wrote:
| Flames, smoke, and the occasional explosion perhaps?
| m463 wrote:
| I'm pretty sure top fuel dragsters are all about tires and
| aero and only inconsequentially the power source.
|
| It might be an easy problem to solve acceleration to 100km/hr
| since you don't have to carry batteries to go an entire 1/4
| mile
| [deleted]
| ominous_prime wrote:
| not many other vehicles have the ability to transfer
| >6000ft/lbs of torque down to the pavement to be able to
| accelerate at 5gs
| orangepurple wrote:
| The clutch which fuses itself into a solid unit instantly
| sbierwagen wrote:
| The video shows it using kart tyres, and I would be
| interested to see what it would do with proper drag radials,
| since they change shape quite a lot during a launch: https://
| www.caranddriver.com/features/columns/a26089565/drag...
|
| >The massive torque channeled through the rear axle shifts
| the load of the car rearward and tries to twist the tire on
| its 16-inch beadlock rim. The sidewalls wrinkle as the tire--
| generally running between 6.0 and 10.0 psi of pressure--
| shrinks in radius by more than six inches and the tread
| effectively balls up at the front of the contact patch. That
| compression of the tire expands the contact patch to almost
| 250 square inches--larger than two side-by-side sheets of
| 8.5-by-11-inch paper. The compression of the tire also means
| that the final-drive ratio is effectively shortened for a
| harder launch. By the time the tire has released the torque
| stored in its wrinkled sidewalls and tread and grown back to
| its original size, the Top Fueler is already pulling more
| than 4.00 g's of acceleration.
|
| >After the car launches, inertia grows the tire to as much as
| 38 inches in diameter, simultaneously lengthening and
| narrowing the contact patch. This effectively lets the final-
| drive ratio grow taller for higher speeds and reduces rolling
| resistance as the vehicle hits terminal velocity.
|
| Effectively a big CVT with no moving parts.
| Animats wrote:
| Wheel spinning and burning rubber?
|
| Electrics going for maximum acceleration usually don't do
| that, because once the wheel is spinning relative to the
| pavement, friction is reduced and there's less acceleration.
| Watch videos of Teslas in launch mode.
| 1970-01-01 wrote:
| FFS. The run is about 82 seconds into the video. In the amount of
| garbage time leading up to it, they could have shown it 56 times.
| https://youtu.be/xjDK0LhKkMs?t=82
| thomastjeffery wrote:
| By putting 4 spaces in front of your link, HN has formatted it
| as a code block instead of a clickable link.
| raydiatian wrote:
| For the amount of spaces he put in front of his link slowing
| me down on my way to YouTube, I could have watched the car
| accelerate to 100 two or three times.
| ivanjermakov wrote:
| More than that, the actual record part haven't delivered a good
| sense of acceleration
| lowestprimate wrote:
| The acceleration record is probably the manhole cover launched
| via nuclear explosion. Accelerated to 125,000 mph in a
| millisecond. https://www.businessinsider.com/fastest-object-
| robert-brownl...
| NaturalPhallacy wrote:
| 100 km/h is 62 mph
| whycombinetor wrote:
| Yes, zero-to-60 (in mph) or zero-to-100 (in km/h) is the
| standard acceleration measure for cars across the world.
| aidenn0 wrote:
| Not for drag racers though, which are usually measured in
| speed attained from a standstill over 1/4 mile.
| squeaky-clean wrote:
| Dragsters definitely measure their acceleration for
| bragging rights, it's usually a 0-100mph metric though. And
| of course bragging rights mean nothing if your car doesn't
| win the actual race. Top-Fuel dragsters race only 1000ft
| because they're so insanely fast it's dangerous to let them
| go farther and build up even more speed.
| unwind wrote:
| I extend the award of most confusing expression to you,
| for "0-100 mph metric".
|
| I _know_ that "a metric" is not the same as "the metric
| (system)", but I really had to stop all neurons and think
| a little.
|
| Also, are 1000 ft a quarter mile? I have _no idea_ , so I
| had to Google and it's not, that'd be 1,320 ft.
| squeaky-clean wrote:
| Haha upon reading it, that is a bad phrasing. My American
| is showing. Funny because I usually watch European racing
| series which use km, but dragsters are fun to keep track
| of and those are imperial.
|
| Also you can be sure 1000ft isn't a quarter mile because
| that's far too evenly divisible.
| elif wrote:
| Do you mean duration and not speed?
|
| Sure the readout gives a max speed reached but the numbers
| they compete over, and the numbers which establish car
| classes, are the time duration for the 1/4mi run.
| megraf wrote:
| Call me old fashion, but I'd really gain more out of the
| demonstration videos if they linked to the time the record (or
| whatever content) started.
|
| Yes, it's a beautiful video.
| LeifCarrotson wrote:
| Students break acceleration world record...for _electric_
| vehicles.
|
| This isn't close to the record for dragsters; if they can
| increase the energy density per unit mass there are traction and
| downforce improvements that can be used to improve this. It's
| very hard to beat chemical energy like detonating gasoline or
| nitromethane - you're looking at roughly a factor of 100, with
| ~40 MJ/kg for gasoline and 0.4 MJ/kg for a lithium ion battery -
| especially if you're racing through a 15 PSI gas that you can use
| in your chemical reaction without having to accelerate it
| onboard.
|
| I suspect that traction control for an electric motor may someday
| allow electric vehicles to exceed the records held by internal
| (well, mostly internal) combustion engines. You could keep the
| tire at exactly the right amount of slip for maximum
| acceleration, rather than trying to balance centrifugal clutches
| to get just the right amount of power at the right time.
|
| I wonder what the record is for a vehicle that can pick up
| electric energy from a tether/rail/overhead wire...though cables
| that can carry megawatts of energy are probably pretty heavy.
|
| Edit: I think the most interesting category here is the typical
| friction-propelled, human-carrying vehicle of either chemical or
| electric power sources. Railguns, rockets, fan cars (using active
| downforce), and vehicles which engage the ground by rack and
| pinion are qualitatively different. When the question is
| accelerating your own mass forwards using the friction developed
| by your own mass being pulled down by gravity, there's an
| interesting optimization problem trading off weight and power.
| MontyCarloHall wrote:
| >cables that can carry megawatts of energy are probably pretty
| heavy
|
| Required cable thickness (and thus weight) is proportional to
| current, not voltage. Conductors to carry megawatts of
| electricity could be fairly light as long as the voltage is
| extremely high and the amperage relatively low.
| jvanderbot wrote:
| And magnetic force is a function of current, and magnetic
| force is what drives wheels. Technically you are correct, but
| thick cables are actually needed to do lots of translation
| from electricity to movement.
| willmadden wrote:
| I don't think there's a problem with cable weight with
| electric motors. Production EV's today have ridiculous
| amounts of torque and don't require prohibitively heavy
| cables.
|
| The issue with acceleration using wheels is gravity. You
| are limited to 1g, the downforce on the wheels, which you
| use for traction to push the vehicle forward. Spoilers
| increase the downforce on the vehicle beyond 1g, but the
| energy required to do that is proportional to the drag on
| the spoiler.
|
| Short of a rocket engine, the way to accelerate beyond 1g
| with a wheeled vehicle is to have a downforce fan. That can
| be powered by combustion or by electricity. I don't know
| which would offer the highest power to weight ratio.
| [deleted]
| lazide wrote:
| I'm not sure having a 'reverse Helicopter' on the back of
| your vehicle really qualifies as 'ground vehicle' at that
| point. Especially if it's providing enough force to
| literally drive upside down on a ceiling somewhere.
| stefs wrote:
| it's as ground as can be, short of a tunneling machine
| maybe.
| solidr53 wrote:
| BEV used to have around 80kg of copper [1], nowadays,
| manufacturers are moving towards 800V architecture
| attempting to cut the weight in half.
|
| I also feel like 800V cars also maintain their maximum
| power better on lower SoC than 400V systems.
|
| [1] https://www.copper.org/publications/pub_list/pdf/A619
| 2_Elect...
| kroeckx wrote:
| For the torque, you can use a low current using more
| windings, which has the same effect of having a higher
| current with less windings.
|
| The acceleration you can reach is mostly limited by the
| peak current and the force constant, but the maximum speed
| you can reach at that acceleration is mostly limited by the
| voltage you have available because of the back-EMF. A
| simplified formula is that the voltage you need is R * I +
| v * BEMF. The higher the voltage is, the better the
| insulation between the windings needs to be. You need to
| find a balance between the different properties.
| happyopossum wrote:
| More windings = more weight - you're gonna pay for it
| somewhere.
| sudosysgen wrote:
| Sure but the wiring is thinner, thereby somewhat
| equalising.
| [deleted]
| MichaelZuo wrote:
| It does seem like a clickbait title.
| isoprophlex wrote:
| > I wonder what the record is for a vehicle that can pick up
| electric energy from a tether/rail/overhead wire...
|
| Getting dangerously close to "car launched by a railgun"
| territory, hehehe
| tshaddox wrote:
| Yep, it very quickly becomes a question of what exactly
| you're trying to test. If you take energy and power density
| out of the equation by allowing unrestricted access to
| external fixed energy delivery infrastructure, the only thing
| left to test is traction management (assuming you're not
| allowing things like adhesive tires, cog rails, active
| downforce, etc.). If you _do_ start to allow those post-
| traction things, you are as the stage where you might as well
| build a railgun.
| dheera wrote:
| > though cables that can carry megawatts of energy
|
| Not really, high speed train lines do it all the time. They
| usually operate at 25 kV or 50 kV and often consume a few
| megawatts per train.
|
| (At 50 kV, one megawatt is only 20 amps, which you can deliver
| on 12 AWG wire, theoretically.)
| titzer wrote:
| Uh no, do not put 50,000 volts through 12 AWG wire.
| the_third_wave wrote:
| When I went to high school the teacher told about a science
| fair where someone had put a sign next to his project
| reading: WARNING 2 million Ohms
|
| (or something like that, I don't remember the actual number
| of Ohms for this specific project)
|
| A remarkable number of people kept their distance from this
| obviously dangerous experiment.
|
| The chemistry-equivalent of this joke is to warn everyone
| around you of the presence of dangerous _di-Hydrogen Oxide_
| which kills hundreds of thousands of people every year.
| elliottkember wrote:
| 2 million ohms? Not bad, not terrible. Vasily, get the
| good Ohmmeter from the safe.
| rascul wrote:
| > The chemistry-equivalent of this joke is to warn
| everyone around you of the presence of dangerous di-
| Hydrogen Oxide which kills hundreds of thousands of
| people every year.
|
| https://dhmo.org/facts.html
| comboy wrote:
| In their defense, maybe those people didn't know if it's
| a project by a very clever student or by the one who
| mixes up units ;)
| quickthrowman wrote:
| Why not? You obviously wouldn't do it to a THHN conductor
| that is rated for 600v, but there are certainly #12 AWG
| conductors rated for higher voltages. They have a whole lot
| more insulation/layers than a regular 600v rated conductor,
| see: https://www.powerandcables.com/wp-
| content/uploads/2019/10/Fi...
|
| High voltage utility distribution lines aren't insulated by
| anything other than porcelain bushings and air.
| gooseyman wrote:
| Came here to say this. Romex/THHN might be a bad idea,
| but that's because they weren't insulated for this
| purpose. 12 AWG would work.
| jefftk wrote:
| What goes wrong?
| WJW wrote:
| Most store-bought wires won't have sufficient covering to
| prevent arcing, so you might get a short circuit
| somewhere. If you insulate the wires sufficiently
| however, any wire will take almost any voltage. It's the
| current you should worry about, as other commenters have
| already mentioned.
| cesaref wrote:
| As has been stated, voltage isn't a limitation, its the
| current that. Go and look at the HT wiring used in a
| cathode ray tube display, and you'll see it's a lot less
| that 12 AWG, and happily carries 10-20kV.
| josephcsible wrote:
| The term "12 AWG" only specifies conductor thickness.
| Voltage is limited by insulation and current is limited by
| conductor thickness. Assuming sufficient insulation, it's
| safe to run arbitrarily high voltages through any
| conductor, since it doesn't even "see" the voltage.
| [deleted]
| spinningslate wrote:
| yes, but:
|
| 1. You need a _lot_ of insulation at 50kV 2. I'm no expert
| but I very much doubt you could run a motor at anything
| approaching that voltage. Current electric cars, for example,
| run c400V as the main motor supply. So there would need to be
| voltage conversion, which adds weight and bulk.
| tomek_ycomb wrote:
| There already is conversion. The motors are inductors and
| phase current can be much higher than battery current
| quickthrowman wrote:
| I know for certain there are 13.8 kV motors, I don't see
| any reason why higher voltages aren't possible for motors.
| bobthepanda wrote:
| Usually you need to transform power anyways on a train,
| because
|
| * lights, plug sockets, etc. are all at normal household
| voltages
|
| * often trains will run on multiple voltages, so a
| transformer needs to be involved anyways
|
| * lower voltages let you have thinner insulation, so
| thinner wires let you save space for things that matter
| more like a bigger passenger cabin
| kwhitefoot wrote:
| Quite a few of the newer EVs have 800 V batteries to make
| fast charging more practical with cables light enough to be
| handled by ordinary humans.
|
| You can make an electric motor run on pretty much any
| combination of voltage and current. You just have to make
| the appropriate trade-offs in insulation, conductor cross
| section, etc.
|
| ABB (my former employer) makes motors that run on 13.8 kV
| with a power of up to 29 MW. See
| https://new.abb.com/motors-generators/high-voltage-
| induction...
| jackmott wrote:
| whartung wrote:
| As a visceral experience, there are few things that top a Top
| Fuel drag race. They're really something worth experiencing at
| least once personally. You really just have to be there.
| naikrovek wrote:
| yeah the real "all I hear is ringing" experience can't be
| beaten.
|
| I've been to two Top Fuel drag races and I left feeling like
| I was surrounded by people who have just enough
| sophistication to know that they like to play with fire
| whenever possible.
|
| they are not like that, of course, but they were definitely
| caught up in the visceral feeling of watching a race and I
| was caught up in the idea that I'd never be able to hear
| again.
|
| I do not recommend races, myself.
| alfalfasprout wrote:
| Bad take. Wear ear protection. Problem solved.
| karamanolev wrote:
| Earmuffs? Isn't it worth seeing (maybe just once) even if
| you do wear hearing protection?
| naikrovek wrote:
| I was wearing hearing protection. have you ever been to
| one of these? or maybe a concert? hearing protection does
| not block incoming sound, hearing protection attenuates
| incoming sound. after hearing protection it's all still
| very, very loud. loud enough to cause ringing immediately
| and for days afterwards.
| yamazakiwi wrote:
| Worth seeing to whom? I'm not trying to be contrarian but
| none of that seems enjoyable or a Top 3 visceral
| experience when I'm not actually involved with the
| action.
|
| It's weird to hear someone say something is in general a
| Top Experience.
| whartung wrote:
| Even in todays world of crazy sound systems and 8K video,
| some things are simply worth experiencing live. "You have
| to be there."
|
| Like live music, like going to a playoff game, watching a
| rocket launch. Even if you don't care about the race, the
| game, or the music. The energy of being in these places,
| experiencing it, feeling it, the spontaneous giggles, the
| sense of awe being caught in the middle of it, has a
| value all its own. You can watch the race on TV, catch
| the game in a pub, listen to the live recording over, and
| over, and over again.
|
| But it's not the same as being there.
| yamazakiwi wrote:
| Oh, I don't have interest in seeing a drag race in video
| either which is what is leading me to believe it wouldn't
| be that exciting.
|
| I agree with what you're saying about live events vs
| video.
| samatman wrote:
| Some of us like very loud sounds punching us right in the
| chest.
|
| Video is completely useless for this. Drag racing is not.
| WalterBright wrote:
| Wearing top quality ear protection is a requirement. They
| work, and do not subtract from the enjoyment.
| sixQuarks wrote:
| I went for the first time couple of weeks ago. Standing right
| by the starting line, when the top fuel funny cars take off,
| they get engulfed in a bubble of blurriness, caused by the
| burning nitro, coupled with the tremendous rumbling which
| causes your eyes to shake, it's impossible to get a clear
| view of the cars on takeoff. It's insane.
| WalterBright wrote:
| There are some things that audio recordings simply cannot
| capture. Top Fuel is one of them. When I go, I wear ear muffs
| that are made for target shooting.
|
| The pulses are so loud it is like being punched in the chest.
| Sometimes the engines explode which is also fun as the
| smoking parts fly around.
|
| Once, the Top Fuel driver had the silly thing in reverse. The
| christmas tree turned green, and he launched backwards. He
| had lightning reflexes, chopping the power incredibly fast.
| The thing still flew back nearly 100 feet, and if it had
| continued would have climbed up the grandstand behind it.
|
| I never, ever, ever stand in front or in back of a dragster
| when its engine is running. I also do not stand radially to
| the engine (when they blow, the parts fly out radially).
|
| Other than that, it is great fun to go to a race in person.
| It's the only motor sport left where the attendees can go
| into the pits and watch the mechanics at work. Watching a
| team rebuild a V8 engine in minutes is amazing. Then they'll
| fire it up to test it. Blipping the throttle produces shock
| waves that you can see hitting the bystanders.
|
| The barely restrained violence of those machines is just
| crazy mad fun you'll never get from watching it on TV.
| rootusrootus wrote:
| > It's the only motor sport left where the attendees can go
| into the pits and watch the mechanics at work.
|
| Definitely not true. We walk the pits every time we go to
| an IndyCar race. And of course we do the same at the lower
| level SCCA-level stuff. Trying to think the last time we
| couldn't get a pit pass and coming up blank.
| WalterBright wrote:
| I've bought a "pit pass" at several motor sport events,
| and there remained a fence separating the public from the
| pits.
| VBprogrammer wrote:
| > It's the only motor sport left where the attendees can go
| into the pits and watch the mechanics at work.
|
| It's almost certainly not useful for you but one other
| motorsport which is comparable in this way is the IOM TT.
| You can walk around and speak to the guys on the pit crews
| as they work.
|
| It also offers some visceral experiences, like standing 2ft
| from the bikes passing you doing the best part of 200mph.
| In fact when I went a couple of years ago selfie sticks
| were banned, as you are so close to the action that there
| is a real danger of hitting a rider with one.
| skewbone wrote:
| Rocket launches feel the same way. I got to see STS121
| launch from the VIP area at Kennedy Space Center a couple
| of years back, and it felt like a continuous pressure wave
| pounding on my chest until the rocket was above the clouds.
| Crazy feeling.
| eterm wrote:
| > a couple of years back
|
| Sure feels like it; don't dare look at a calendar.
| dylan604 wrote:
| I know a camera guy* that decided he wanted to get footage
| he'd never seen anyone else get. He got permission, but
| everyone just shook their head and suggested it not being a
| good idea (yes, please read foreshadowing there). This was
| back in the day of using a BCSP over the shoulder camcorder
| that brand new easily cost $75k with the particular lens
| being used. He was behind both cars standing between them,
| and when they took off, the forces were so violent it
| caused the spinning heads in the camera to stutter so badly
| the footage was unusable. Viewing the footage, the image is
| fine right up to the point of start, then the image goes
| crazy in the way only an analog system can do, then
| stabilizes again when everything calms down. Not only was
| it not usable footage, but he spent hours peeling/scraping
| melted rubber off of everything. IIRC, the driver of one of
| the cars was legendary John Force.
|
| * I swears it that it wasn't me in the "asking for a
| friend" manner
| jvanderbot wrote:
| Does the engine weight count in that MJ/kg?
| LeifCarrotson wrote:
| No, I suppose not, but neither does the electric motor count
| towards battery density.
|
| In top fuel events, they're burning roughly 20 kg of fuel per
| second, so a 200kg engine still doesn't equalize the density
| of that chemical fuel.
| tim333 wrote:
| I think probably the fastest accelerating ever car with a
| driver was the Vanishing Point drag racer which did 0-60 in
| about 0.25 secs using a peroxide rocket. Not very practical for
| everyday transport though https://youtu.be/7QC6tymIvKA?t=209
| karamanolev wrote:
| The differences are massive between road-going (on an asphalt
| surface, ~1 friction coefficient), drag racing type (on a
| drag strip, which has massively more grip, ~4) and rocket
| driven (no friction at all, just the thrust/mass ratio)
| vehicles. It should be clear they are in totally different
| classes and advances in any of those classes are exciting and
| worth mentioning, I feel.
| Sharlin wrote:
| Well, dragsters are laughably slow to accelerate if we're just
| talking about "acceleration world record" without qualifiers.
| (Assuming that "acceleration" here means "acceleration of a
| ground vehicle with a human driver" is just as arbitrary as
| "...of an electric ground vehicle...", after all. Actual
| acceleration world records of macroscopic objects are in the
| 10,000s of _g_ s...)
| andbberger wrote:
| i have an ultracentrifuge in lab that can do 100,000gs
| sustained for hours
| colordrops wrote:
| What is it used for?
| throwaway4PP wrote:
| Centrifuges are used for separation. An ultra is usually
| used for separating nominally-stable colloids (such as
| fine nanoparticle colloids), and miscible liquids where
| such high centrifugal force causes them to density
| separate.
| thelittleone wrote:
| I was also curious and found this youtube [1]:
|
| Summary (found in video at 10:48)
|
| 1) separation of subcellular organelle (DNA/RNA) 2)
| extract solutions in biological fluids from aqueous to
| organic solvents 3) seperate lipid components 4)
| pelleting of ribosomes 5) pelleting of macromolecules
|
| [1] https://www.youtube.com/watch?v=lRT_8nFc2Tk
| HeyLaughingBoy wrote:
| Ha. On a hunch I watched that video and hunch confirmed
| in the first second: I used to work for those guys, but
| not in the Centrifugation division :-)
| jeffbee wrote:
| Military-funded experimental railguns are in the 10s of 1000s
| of gs. Are these the record-holders of whom you speak?
| kragen wrote:
| I'm thinking probably alpha-particle decay exceeds that by
| a lot.
| jeffbee wrote:
| I imagine that's why the other person qualified their
| remark as referring to "macroscopic" objects.
| kragen wrote:
| Hmm, good point. Maybe small objects not quite close
| enough to a hydrogen bomb to be vaporized by the flash,
| then?
| Sharlin wrote:
| Related: the "nuclear manhole cover" [1] (actually a 900
| kg piece of armor plate) which may have accelerated to
| several times Earth's escape velocity over the course of
| a few meters (tens of millions of g's which is
| _definitely_ impressive for such a heavy object). It was
| likely vaporized due to compressive heating before
| escaping Earth 's atmosphere, however.
|
| (I'm rather amused by the idea that some manager type
| evidently thought that a hunk of steel might contain a
| _nuclear explosion_ in what was in essence a very large
| cannon!)
|
| [1] https://en.wikipedia.org/wiki/Operation_Plumbbob#Miss
| ing_ste...
| kragen wrote:
| A big enough hunk of steel can certainly contain a
| nuclear explosion.
| Sharlin wrote:
| At 900 kg, we're talking about a fairly small hunk.
| vizzier wrote:
| Like the borehole cap on
| https://en.wikipedia.org/wiki/Operation_Plumbbob Pascal-B
| dtgriscom wrote:
| If you can only accurately know the position OR the
| momentum, is acceleration well-defined?
| ben_w wrote:
| Sure, ignore the position, just focus on the rate of
| change of momentum with respect to time.
| labcomputer wrote:
| Well, that doesn't quite work either. Energy and time are
| also conjugate variables, so there exists an uncertainty
| relationship between them.
|
| And since you can relate energy to momentum in a well
| defined way...
| Sharlin wrote:
| I think my "10,000s of gs" was maybe a slight
| underestimate. A light-gas gun [1] can accelerate a
| projectile to velocities of several km/s over a distance on
| the order of a meter, giving an acceleration on the order
| of 1,000,000 g by a quick calculation.
|
| [1] https://en.wikipedia.org/wiki/Light-gas_gun
| lazide wrote:
| Don't forget explosively formed penetrators!
| Sharlin wrote:
| Good point!
| [deleted]
| WalterBright wrote:
| Top fuel drag racers already have traction control. The slip is
| adjustable and getting it right is a big factor in winning.
| jcampbell1 wrote:
| The clutch slips for about 2/3 of the 1/4 mile. It is a huge
| factor.
|
| My college motorsports team got to meet with John Force, and
| someone suggested a flexible rear spoiler for variable
| downforce. He was quick to note it likely would be faster but
| would almost certainly get you killed.
| jcims wrote:
| I just saw a breakdown of a crash where the engine shut down,
| allowing the clutch to stop slipping. That final clamp dumped
| a huge impulse into the drivetrain and ripped the tires off
| the wheels. (At least that's the way I understood it).
|
| Clay Millican has an amazing YouTube channel that brings you
| behind the scenes of an NHRA top fuel team - https://www.yout
| ube.com/channel/UClT3GT7hxLbNnypukfyxelQ/vid...
| abfan1127 wrote:
| its my understanding that the clutch designers are the
| highest paid crew members. Choosing how the clutch performs
| is the critical piece to winning, based on track
| temperatures, weather conditions, engine performance, etc.
| twobitshifter wrote:
| Think like a purpose built dragster. You only need enough
| energy for 1.5 seconds and that's as long as the wiring needs
| to take the current for. I think a purpose built electric
| dragster might be lighter just because of the parts you don't
| need. The motors may reverse the energy weight savings
| lazide wrote:
| As long as the copper doesn't vaporize until the end, we're
| all good?
| bumby wrote:
| Small nit:
|
| > _detonating_
|
| Should be deflagrating because the ICE flame is designed to be
| subsonic.
| slowhand09 wrote:
| Not sure this applies here Top Fuel engines are nearly
| burning a liquid rather than a gas. And yes I know you can't
| really compress a liquid. The typical ratio is 1.7 pounds of
| air to burn 1 pound of Nitromethane. It burns slower than
| gasoline tho. And normal gas engine runs in the vicinity of
| 14.5:1 air to fuel.
| bumby wrote:
| > _And yes I know you can 't really compress a liquid._
|
| Sure you can, it's what the bulk modulus measures.
|
| You may be right. My assumption is that, by definition, a
| detonation is an uncontrolled pressure wave and controlling
| the pressure in an ICE cylinder is a big deal that a lot of
| engineering goes into. As you point out, the major benefit
| to nitromethane is that is requires less air because it
| brings it's own oxygen. So the size of the combustion
| chamber isn't as much as a limiting factor. I don't think
| it's intent is to change the flame regime, though. It just
| crams more energy into the cylinder.
| lazide wrote:
| Keep in mind, there is a very common type of ICE that is
| really a IDE (internal detonation engine) - diesels.
|
| With strong enough engines, detonation isn't ruled out.
| Someone wrote:
| > I wonder what the record is for a vehicle that can pick up
| electric energy from a tether/rail/overhead wire...though
| cables that can carry megawatts of energy are probably pretty
| heavy.
|
| For a one-off design, those cables could be very short. You
| could even have a very small pantograph
| (https://en.wikipedia.org/wiki/Pantograph_(transport))
|
| I am not sure the end result would be faster, though. You'll
| need grip to get up to speed, and starting from a standstill,
| you won't get that from aerodynamics. you'll need mass. Take
| away the batteries, and you may have to add a similar mass in
| dead weight (could be used to add a good Faraday cage to
| protect the driver from mishaps with the electricity supply)
| karamanolev wrote:
| I think what you care about is to have enough power to be at
| the limit of the grip of (all) your tires. If you are
| heavier, you need more power to reach at point. If you do
| have enough power, then it's all about maximizing grip -
| tires, surface, downforce and so on.
|
| More mass and more power are roughly equivalent to less mass
| and less power, if the above holds. Maybe even with less mass
| it's easier, since you can produce significant downforce with
| smaller wings.
| rainbowzootsuit wrote:
| A cable that can carry 1.21GW is only about the diameter of
| your finger.
| 3000000001 wrote:
| Great Scott! That's surprisingly small. In all seriousness
| though, that's probably not at useable voltage, you might end
| up with a 5 ton transformer on the car if you delivered 33kV
| in such a small cable.
| mrb wrote:
| << _~40 MJ /kg for gasoline and 0.4 MJ/kg for a lithium ion
| battery_>>
|
| That is correct. Out of curiosity, I looked it up and for the
| Tesla Plaid that's 0.65 MJ/kg (or 181.5 watt*hours per
| kilogram)
|
| But my follow-up question is: if gasoline has an energy density
| about 100 times higher (well, 60 times) why are dragsters not
| even faster? This Stuttgart EV does 0-100 km/h in 1.461 seconds
| (1.87g), and dragsters do it in 0.8 seconds (3.42g). It sounds
| like with such a phenomenal energy density, gasoline-powered
| dragsters should be able to accelerate at much more than 3.42g,
| maybe 10g, or more. Intuitively this indicates that the
| bottleneck isn't energy density, but mechanical factors (gears,
| traction, etc). Therefore if battery energy density can
| increase just a little more, maybe to 2 or 5 MJ/kg, this may be
| sufficient for EV to be able to beat dragsters.
| dreamcompiler wrote:
| > you're looking at roughly a factor of 100, with ~40 MJ/kg for
| gasoline and 0.4 MJ/kg for a lithium ion battery
|
| If you only care about acceleration, energy density doesn't
| matter very much. What matters is _power_ : The rate at which
| you can move energy from the storage medium to the wheels. In
| that respect a capacitor-powered dragster could probably smoke
| a top fuel dragster, even though the energy density of
| capacitors is pretty lousy. No idea if anybody has tried to
| build a full-size capacitor-powered dragster. Or if any human
| would be brave enough to drive one.
| LeifCarrotson wrote:
| Having investigated some of these questions with respect to
| quadcopters and micro-mouse 'bots, the power density (both in
| mass and volume) of capacitors is pretty terrible. Whether
| you're talking about aluminum electrolytic traditional
| capacitors or double-layer supercapacitors, they're inferior
| in most cases to a lipo. That's especially true if you're
| open to high-discharge 50C or 75C lipos, which can dump their
| entire energy capacity in ~60 seconds.
|
| If you only need a few milliseconds of 'zap', yeah, a
| capacitor bank is great. It's the only option if you need to
| do that more than a couple hundred times in the life of the
| battery; a chemical battery will wear out but a capacitor can
| last for millions or billions of charge/discharge cycles.
|
| But even a time as short as 1.461 seconds is probably on the
| far side of the inflection point where capacitors make sense.
|
| If you like, run through the options on Digikey:
|
| https://www.digikey.com/en/products/filter/electric-
| double-l...
|
| ex:
|
| https://www.eaton.com/content/dam/eaton/products/electronic-.
| ..
|
| Also remember that an ultracapacitor is about as far in
| behavior from a physicist's ideal plate capacitor as you can
| get - they're not linear, they have highly significant
| internal series resistance...
| TheSpiceIsLife wrote:
| Also remember that top fuel dragster engines only run for a
| handful of seconds before they need to be rebuilt, and will
| be destroyed in a non-recoverable way after more than a few
| handful of seconds of run time.
|
| I'm not sure if anyone is building electric dragsters with
| run-once components, or how that might change assumptions?
| dreamcompiler wrote:
| I was thinking more in terms of ordinary capacitors than
| supercapacitors because the former are vastly superior in
| terms of power density. However, ordinary caps are so poor
| in energy density that it just might matter, even for a
| very short duration energy dump application.
|
| IOW I'm not sure there's enough volume in a dragster to
| meaningfully power it with ordinary caps. But if there is,
| it would be a very quick car.
| greggsy wrote:
| > Or if any human would be brave enough to drive one.
|
| From the perspective of being that close to being fried, or
| with respect to the acceleration?
|
| To be honest though, I still think it's amazing that people
| casually handle extremely flammable and volatile hydrocarbons
| whenever they visit the gas station. The safety ecosystem is
| very well tuned, albeit after a hundred+ years of accidents
| and research.
| dreamcompiler wrote:
| > From the perspective of being that close to being fried,
| or with respect to the acceleration?
|
| I was thinking the former. One does not casually fuck
| around with big capacitor banks and live to talk about it.
| ccn0p wrote:
| anybody else let down from the video? there was no just simple
| observer perspective in real time. maybe because it would have
| been funny going really fast for 20 meters.
| kleiba wrote:
| Amazing: there's one girl on the team!
| moritonal wrote:
| That video was brutally edited. I guess it's marketing but it
| somehow manged to be two minutes long and reduced the actual
| content to look like a toy car slowly launching without any frame
| of reference before quickly cutting to a bird?
|
| Like, watch Mythbusters or Slow-mo guys and try again.
| renewiltord wrote:
| https://youtu.be/xjDK0LhKkMs?t=85 to cut to the chase. It's
| hard to discern from a routine Tesla with the pedal down
| perhaps because we're bad at telling small amounts of time
| apart.
| kube-system wrote:
| And it's hard to judge speed from a video anyway.
|
| https://youtu.be/54Oy75Bnu_Q
| renewiltord wrote:
| Good one. The static camera shots from distance with human
| references are probably better on this video anyway
| https://youtu.be/bO7HlsAbhQk?t=50
| Nition wrote:
| Video games use this trick all the time. When the player
| sprints or gets a speed boost, give them some actual boost,
| but also increase the FOV.
| [deleted]
| Krasnol wrote:
| My thought exactly.
|
| There is not a single normal shot of that car accelerating from
| outside the car so you can actually see it accelerating fast.
| It's infuriating.
|
| I guess the marketing department of the university did the
| video editing...
| spinningslate wrote:
| came here to say this. I mean, if the car actually did break a
| record - and I'm not questioning that - then _actually showing
| it happen_ , in a visually recognisable way, might be, you
| know, a good idea?!?
|
| Dubious video aside, congratulations to the students. It would
| be great to see/hear what they did to achieve it. For example:
| I'd imagine traction off the line would be a big challenge for
| something so small (and presumably light). They did warm the
| tyres (video at least showed that) but what else? Traction
| control? Most likely yes. Anything novel in its implementation?
|
| Be good to get some detail behind the result.
| LeoPanthera wrote:
| Mythbusters isn't a great example, to the point that there are
| re-edited episodes floating around that remove all the
| superfluous teasers, "coming up"s, and unnecessary repeated
| shots.
|
| https://www.reddit.com/r/smyths/comments/8gix4w/streamlined_...
| topspin wrote:
| This is why I, and you, read the comments first.
| marginalia_nu wrote:
| Maybe I'm misremembering, wasn't Mythbusters like
|
| https://tenor.com/view/truck-speed-loop-gif-17654345
| Confiks wrote:
| Zeno's Truck.
| Dylan16807 wrote:
| That wasn't mythbusters.
|
| https://www.youtube.com/watch?v=3JtZDDQga4o&t=85s This
| example seems just fine.
| mwint wrote:
| Usually they would do that, cut to commercials, and then show
| the full thing in slow motion. Irritating, but not quite the
| same.
| incahoots wrote:
| I hate you for this but this gif will never not be
| entertaining
| Animats wrote:
| Yes. There's so much slow motion and fast motion there's no
| sense of how fast the thing accelerated.
|
| Admittedly they're trying to dramatize something that took 1.2
| seconds, which is hard. But still.
| jws wrote:
| That's an average acceleration around 2g. This seems beyond the
| limits of tires and friction. Do aerodynamic down forces kick in
| fast enough to make more force usable against the road at these
| relatively low speeds? Do the tires have more than static
| friction going for them (say, fine scale interlocking with the
| pavement)?
|
| Drag racers can do 3gs, but that's at higher average speed.
| agloeregrets wrote:
| Aero might play in a tiny way at the 40-60 MPH space, not
| meaningfully enough.
|
| As for tires, no actually you can go much further than this.
| The big detail is wear and heat caused by tire softness and
| pressure. Road car tires can't enable 0-100KPH much faster than
| 1.9s or so purely because they can't be so soft as crusing on
| the highway would cause excess wear(practicality), heat
| (Danger), and friction(Range).
|
| Drag Racers can accelerate way faster, 0-60MPH in .8s.
| ihunter2839 wrote:
| The aero packages for these vehicles create a pretty
| significant amount of downforce at relatively low speeds -
| for example, our car last season produced ~140 lbs of
| downforce at 35 mph.
|
| Edit - A lot of that comes from the rear wing though, which
| the green team didnt run for this particular event.
| Karstographer wrote:
| These formula student/fsae cars have aero packages which tend
| to be designed around 30mph average track speeds, so they will
| get contribution from that, especially in the latter half of
| the run. Even so, the tire friction involves both physical
| interlocking due to deformation and chemical adhesion.
|
| You can see the tire warmers in the video being removed in
| addition to their approach burnout which imparts additional
| heat into the tires, so that the tires more effectively stick
| to the ground.
|
| For all of the questions about why they don't compete with
| dragster techniques, the student race series they participate
| in has very strict regulations regarding vehicle layout which
| forces them to be more of an autocross car, these kinds of
| (heavily couched) records being produced are really somewhat
| incidental.
| ihunter2839 wrote:
| Although the other comments are correct about the 30mph
| optimization for the aero package, this car uses active
| underbody aero (aka, fans) to create additional downforce even
| when at a standstill. See the recent runs of the Speirling at
| Goodwood festival of speed to see a purpose built "fan car" in
| action.
|
| Interestingly, this setup wouldn't be allowed due to rules in
| Formula SAE in the US but is legal in the german competition
| cause those teams are just built different.
|
| Edit - Quick plug! If anyone is interested in supporting FSAE
| and the awesome engineering that goes into these cars, I am a
| member of the San Jose State team and our aero team is in need
| of HPC access to run their CFD simulations. My email is in my
| profile. Cheers.
| raydiatian wrote:
| Ohhh, it's 100 kmh
| notum wrote:
| 257HP on a vehicle that weights less than some people.
| Exceptional! Congratulations to the team.
| slowhand09 wrote:
| I'm surprised you had to dig a bit to see it is in KM. A US
| audience might assume MPH.
| zwieback wrote:
| Yay, my Alma Mater - the city of Mercedes, Bosch and Porsche.
| You'd expect some cool car stuff coming from there.
| js2 wrote:
| 0-100 kmh (~ 62 mph) in 1.461 seconds exposes the driver to ~
| 1.94 g.
|
| For reference, a top-fuel dragster can do 0-100 mph (~ 161 kmh)
| in about 0.86 seconds, exposing the driver to nearly 5g.
|
| https://jalopnik.com/the-fastest-0-60-time-a-person-could-ac...
|
| http://www.procato.com/convert/
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