[HN Gopher] German car that was super-aerodynamic but impractical
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German car that was super-aerodynamic but impractical
Author : davesailer
Score : 58 points
Date : 2021-11-23 18:44 UTC (4 hours ago)
(HTM) web link (rarehistoricalphotos.com)
(TXT) w3m dump (rarehistoricalphotos.com)
| hn_throwaway_99 wrote:
| Random question: how were very accurate curves like that machined
| in the 1930s? What was the process for creating the tooling that
| could create that kind of curved aluminum so accurately back
| then?
| LeifCarrotson wrote:
| To create curved parts, an operator would roll a piece of metal
| between two hard wheels on a machine called an English Wheel.
| The wheels apply significant pressure, and make the metal
| become thinner where you roll it. The same volume of metal is
| still present, so to become thinner it must spread out. If you
| expand the center of a piece, but leave the perimeter the same,
| then it will become domed.
|
| If you'd like to see the machine in operation, here's a video
| by Ron Covell, a masterfully skilled sheet metal craftsman:
| https://www.youtube.com/watch?v=omRlIBONJAM
|
| A craftsman can carefully shape the metal to whatever shape was
| desired. But accurate? Who said anything about accurate? It's
| likely that everyone's paneling was of slightly different
| curvatures. They'd machine the mounting holes after the fact,
| so those would all match and be replaceable, but why would
| anyone care (how would anyone know?) if the curvature of the
| fender was a few millimeters different from another fender?
| jacquesm wrote:
| English Wheel. You can still get them today, or, if you're a
| little bit skilled (and most people that would need one
| probably are) you can make one yourself.
|
| Using them is an art.
| ferlp wrote:
| Here in Argentina, perhaps 40 years ago, my father took me to a
| car restoration workshop where two metal sheet workers
| ("chapistas") were forming a 1936 Chevrolet coupe roof by
| heating a steel sheet in the floor with a torch and curving it
| up by cooling it with damp cloth. That's also a technique to
| remove dents. An English Wheel was used for the smaller radius
| parts.
| timonoko wrote:
| Just by eyeballing and manually moving metal sheet between
| heavy wheels. That is how they make compound curves for luxury
| cars and planes. https://www.tinmantech.com/gallery-of-
| metalwork/wheeling-mac...
| jbay808 wrote:
| As other commenters noted, this is a prototype so it would have
| been done by hand with an English wheel and similar forming
| tools. There would be a set of master profile forms that the
| craftsman would check against to ensure that the panels are the
| right shape along various cross sections. For a production
| vehicle, they would have used a heavy press to stamp the
| panels, as they do today.
| prova_modena wrote:
| The design would be first more-or-less worked out on paper,
| using various drafting tricks such as french curves or
| tensioned wooden strips.
|
| This can then be translated to a series of full-scale wooden
| templates, either interlocking 2D sections, or 3D carved from
| solid. Alternatively, small diameter metal rods can be bent and
| welded together for a same purpose. Either technique allows a
| craftsperson to combine precisely formed 2D curves into a 3D
| shape. Small design changes would also be made at this stage,
| usually by eye rather than to a particular measurement. This
| full-scale reference model is called a body buck or in Italian
| "manichino."
|
| Once you have the complete buck, craftspeople would shape flat
| aluminum panels into to fit on various sections of the buck.
| The craftsperson works iteratively until the shape is right,
| using tools such as an English wheels, bending brakes, mallets
| and sandbags as well as cutting tools like shears and hole
| punches.
|
| Once the shape of each individual panel is correct, they are
| fastened to the car chassis by welding or a mechanical fastener
| like a screw. The appearance and surface of the body is still
| quite rough at this point, so there is an extensive manual
| finishing process before paint is applied. Panel gaps are
| adjusted, bulges and dents are tapped out with hammers, lots of
| sanding. Soft filler materials are applied to fill and smooth
| the body surface- we use "Bondo" for this now but back then
| they used a lot of lead. The "accurate" appearance of a final
| painted car body comes from this hand finishing process.
| However, accurate is a bit of a misonmer as even though the
| body may look smooth and shiny there are often a lot of
| geometrical imperfections and asymmetries. For example,
| headlights in slightly different positions, replacement
| windshields won't fit etc. For certain models, you can even use
| predictable "imperfections" in the bodywork to determine
| whether the body was replaced or majorly repaired at some later
| date.
|
| This technique was in wide use in Italy (probably other places
| too, but idk) through the mid-1960s, at which time modern
| stamping processes became able to cheaply mass produce panels
| with much less manual labor. As this process is so labor and
| skill intensive, it's now a specialty. Even among auto body
| repair professionals, it's uncommon to find someone with the
| skill to shape large panels from scratch to a high standard.
|
| If you're interested in this type of stuff, there's a great
| youtube channel called "cbrwatahiki"[0] where a guy uses manual
| techniques to reproduce aluminum car bodies in his garage.
| Language is Japanese but it's still possible to watch and learn
| a lot if you can't understand. While his methods are not quite
| the same as what a 1930s-50s era production shop would use, it
| still shows a lot of what is involved to fabricate a body based
| on a pattern.
|
| [0] https://www.youtube.com/channel/UCZjqr9ScOlWSkcnTK_mLiSA
| Jenk wrote:
| As well as the English Wheel already mentioned several times,
| the profession of "Panel Beater" is quite literal. The panels
| are beaten into rough shape with various shaped-headed hammers,
| and then smoothed out with flat tools that resemble spatulas.
| It makes one hell of a din and takes a _long_ time.
|
| There are some luxury motor car brands that make a point of
| still using the panel beating (aka panel patting) techniques
| for their production. It adds months to the production time of
| highly skilled, and thus very expensive, panel beaters... but
| that's the price of oppulence.
| zardo wrote:
| It's a one-off, the tooling was at most wooden forms.
| markvdb wrote:
| Two various tidbits:
|
| - The inventor apparently managed to rescue several jewish people
| [0] when designing and prototyping for the Wehrmacht in Riga,
| Latvia.
|
| - This immediately made me think of the little known Volkswagen
| 1-litre car [1]. Something like that with an electric drivetrain
| would be close to my ideal car...
|
| [0]
| https://de.wikipedia.org/wiki/Karl_Schl%C3%B6r_von_Westhofen...
|
| [1] https://en.wikipedia.org/wiki/Volkswagen_1-litre_car
| bserge wrote:
| Yeah, yeah, everyone and their dog in Germany managed to
| "rescue several Jews" during WW2 according to their own postwar
| records lol. Nice VW, though.
| capitainenemo wrote:
| https://en.wikipedia.org/wiki/Aptera_Motors#Production_plans
| Aptera seems to have resurrected... similar form.
| gerdesj wrote:
| "In 1942, engineers took a 130-horsepower Russian aircraft motor
| and bolted it to the back of the car for some test runs."
|
| "Test runs" is likely a euphemism for "got drunk and nearly
| killed themselves playing silly buggers". That thing is a
| steampunk precursor of the insanity that was the ME 163 Komet -
| just add wings and a leather flying hat with goggles!
| imadethis wrote:
| The first flight of the Komet was in 1941, so it seems the
| insanity was concurrent. At least the train never melted
| anyone.
| mhh__ wrote:
| Is the "bionic fish car" mentioned on Top Gear descended from it?
|
| https://youtu.be/ri3CUzsv7Gg
| tromp wrote:
| This modern take on the super-aerodynamic shaves another 30% off
| the Schlorwagen's already low drag coefficient of 0.186:
|
| https://www.youtube.com/watch?v=bDMqEmUGxX4
| camillomiller wrote:
| > In 1942, engineers took a 130-horsepower Russian aircraft motor
| and bolted it to the back of the car for some test runs.
|
| The good old "warum nicht?" of Nazi engineers...
| undebuggable wrote:
| Before entering the post I was certain it's about Tropfenwagen
| [1] displayed in e.g. Technikmuseum in Berlin. Either way for the
| newly constructed highways they indeed shifted to aerodynamic
| cars with the body extending over the front wheels, but to the
| model ...cough... "borrowed" from Czechoslovakian Tatra [2].
|
| [1] https://en.wikipedia.org/wiki/Rumpler_Tropfenwagen
|
| [2] https://en.wikipedia.org/wiki/Tatra_87
| anonymousisme wrote:
| Is that Elon Musk in the photo?
| jacquesm wrote:
| That's a beauty, shape is reminiscent of the Dymaxion.
|
| https://www.youtube.com/watch?v=YlLZE23EJKs
| formerly_proven wrote:
| Another overly aerodynamic car from a few years earlier -
| Mercedes-Benz W 125, which set a speed record that wasn't outdone
| for some 80 years. Incidentally, someone tried to outdo them and
| killed themselves in doing so, which ended car manufacturers
| going for new records.
|
| https://en.wikipedia.org/wiki/Mercedes-Benz_W125_Rekordwagen
| fifilura wrote:
| And also the Ur-SAAB (original SAAB).
|
| https://en.wikipedia.org/wiki/Saab_Ursaab
|
| Saab was originaly an airplane manufacturer so it was natural
| for them to reach for the wind-tunnel when tasked with
| designing a car.
|
| The Ur-SAAB was never in series production but the (at least in
| Sweden) very popular production cars took a lot of inspiration
| from it.
|
| We had one of these when I was a kid
| https://en.wikipedia.org/wiki/Saab_96
|
| This is an earlier model with even more similarities
| https://en.wikipedia.org/wiki/Saab_92
| wfme wrote:
| This looks vaguely similar to the Volkswagen XL1 [0] - similar
| internal layout but with a much longer nose.
|
| [0] https://en.wikipedia.org/wiki/Volkswagen_1-litre_car
| aliswe wrote:
| 8l / 100km? thats in the ballpark of my prius 2006, that consumes
| around 7l/100km. but this was 1939 ... have we come so non-far?
|
| whats in play here? weight? fuel quality? engine? ...
| HPsquared wrote:
| Most of the innovation in engine design over the decades has
| been in increasing "dynamic range". That is, the ability to
| produce high power when required without being super
| inefficient in the other 99% of the time when you're just
| cruising or coasting.
|
| A small, simple old-tech engine will have similar fuel economy
| to a modern engine when cruising but will have much less peak
| power and refinement, and produce more noxious fumes from the
| tailpipe.
| pengaru wrote:
| You don't even need to go to this crazy extreme to find
| relatively modern levels of fuel efficiency. The classic
| 60s-era Mini could get ~40mpg with a plain old carburetor.
|
| As ICEs became more fuel efficient, the vehicles became both
| larger and heavier, negating the gains. Modern ICE vehicles
| have become so overweight they've managed to make EVs look
| somewhat average in the weight department.
| AdrianB1 wrote:
| Weight, that is mostly coming from safety requirements (NCAP
| starts come with heavy weight and increased fuel consumption).
| That car with a modern engine can go as low as 3 liters/100 km,
| I did drive regular cars with 3.5l/100km over a 200km trip.
| sxates wrote:
| No doubt this car would have weighed a fraction of what a
| modern Prius weighs.
| kingkongjaffa wrote:
| Your Prius is in another galaxy regarding safety and
| infotainment, that's why.
|
| Also likely cruise speed in 1939 was much slower, and drag is a
| function of velocity^2
| jjtheblunt wrote:
| > drag is a function of velocity^2
|
| i have to explain that to (fellow but new) EV drivers, that
| blasting down a highway at high speed for a fixed distance
| seems to drain the battery, because of drag, far more than
| travelling the exact same distance at slow speed.
|
| I still feel like i've not sorted out the equations involved.
| deelowe wrote:
| I did an experiment on the interstate and drove at highway
| speeds to see if the mpg was comparable. It wasn't, so
| there's definitely another factor there. Here they cut
| groves in the concrete pavement on the interstate where as
| the highways are smooth asphalt. I've wondered if maybe
| rolling resistance is also a factor here. It was a pretty
| huge difference. Like more than 10% IIRC.
| Tade0 wrote:
| I don't have reliable numbers on this, but rolling
| resistance appears to be the main factor up to about
| 60-80km/h, above which drag takes its place.
|
| Looking at the fuel consumption in my hybrid it's around
| 50-60% higher at an average speed of 100km/h than at
| 70km/h.
|
| The difference would have been 2x if was just due to
| drag.
| mhh__ wrote:
| Does the car have a power usage estimator? Or would that
| perhaps be dangerous if one misses traffic changes due to
| following the dial
| black6 wrote:
| Similar in appearance, drivetrain layout, and problems as the
| Dymaxion Car.
| cpcallen wrote:
| Though the Dymaxion car at least did not put the engine
| _behind_ the rear wheels...
| WalterBright wrote:
| > Schlorwagen was a wing on wheels.
|
| Meaning it will lift at higher speeds. Oops!
| rkagerer wrote:
| Those aesthetics! Looks like the type of vehicle Apple would
| design.
| clouddrover wrote:
| A present day German car with a drag coefficient of 0.200:
| https://www.cnet.com/roadshow/news/2022-mercedes-benz-eqs-ev...
|
| A present day American three-wheeler with a drag coefficient of
| 0.13: https://www.aptera.us/
| WalterBright wrote:
| > very vulnerable to crosswinds
|
| So was the VW bus. I know from experience. It's a very dangerous
| car on the highway when you've got a stiff crosswind. You have to
| cant the steering wheel into the wind. If you drive through a
| cut, the car will veer into the wind, and leaving the cut, it'll
| will veer the other way. If you're not anticipating this, you can
| find yourself in the other lane facing oncoming traffic.
|
| I don't miss that beast.
| mhh__ wrote:
| I'm not familiar with the history of the VW bus so this maybe
| unfair, but it's interesting reading books on the evolution of
| the aeroplane and comparing them with the evolution of the car.
|
| It took much longer for the production car to start to be
| engineered holistically and it's dynamics considered in the
| same manner one would if developing an aircraft.
|
| That being said even formula 1 teams get caught out by the
| interaction of aero and (say) steering angle sometimes, so
| perhaps the problem is harder.
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(page generated 2021-11-23 23:01 UTC)