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Old 06-12-2010, 03:58 PM   #1 (permalink)
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Chrysler Airflow-aero-modded ( Part-1 )

Between 1934 and 1937,Chrysler produced the 'Airflow,'which sold as a Chrysler,DeSoto,and Imperial.
The car was designed by Chrysler's chief of research Carl Breer,who's interest in automotive aerodynamics dates to 1927.
Breer hired Dayton engineer Bill Earnshaw who together with Orville Wright developed a small windtunnel to do model tests.
Soon,Chrysler built a larger tunnel in Highland Park,Michigan and Breer became directly involved.
Testing revealed that automobiles had lower drag,went faster,and got better mpg when going backwards.
The 1933 DeSoto sedan which served as the comparative baseline for the Airflow scored Cd 0.683 'forwards',and Cd 0.546 'backwards.'
The 1934 DeSoto Airflow sedan is reported by Chrysler at Cd 0.546.( Cd 0.675 was typical for cars of this period ).
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After the Airflow went on retail sale Breer and his team continued to experiment with aero-modding.By 1934-1/2 Breer had achieved significant results.
In 1939,Chrysler researchers,W.E.Zierer and J.B.Macaulay,Jr.,revealed that they had achieved up to a 50 % drag reduction through aero-mods.
On June 4,1941 James C.Zeder,Chief Engineer for Chrysler,and brother of Fred Zeder,one of the 'Three Musketeers',responsible for the Airflows development,presented a paper on the aero-modding at SAE's semi-annual meeting and in December,after the attack at Pearl Harbor,Hawaii,the work was published as SAE Paper # 410139 "Is It Practical to STREAMLINE for FUEL ECONOMY?"
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The paper gives a breakdown of the methodology used to quantify results.
Chrysler did experience wide discrepancies between windtunnel results and actual on-road performance.Top speed runs were made,throttle-stop runs were duplicated on the dynamometer,and coasdowns were performed when weather allowed.
Original drag data is given in the form of a K-value,borrowed from :
"Engineering Aerodynamics," W.S.Diehl,Ronald Press,1935
"Aviation Handbook," E.P.Warner and S.Paul Johnston,McGraw-Hill Book Co.,Inc.,1935
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The paper lists seven (7) discreet aero-modding permutations within a table,along with the top speed achieved,and mpg,before and after the final mods.
NOTE: On page 3 of the paper,an '8th' condition is cited which is not reflected in the table.This 'condition' reflects a 44-inch ( 1,100 mm ) 'long-tail' 'stinger' configuration which achieved the lowest drag.
If the images presented in the table are close at all to scale,then this condition '8' is not represented and I have included it,merely drawing the longer 'stinger' over the short tail cone depicted.
All the vehicle images to be posted in PART-2 are normalized as to rear axle position to give an easier comparison of mods.
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One of the most important points of the paper is the effect of gear-matching as related to mpg potential from aero-modding.As the sytreamlining reduces the load,the engine moves into a less efficient BSFC.Even though all the Airflows had Borg-Warner overdrives,Breer found himself forced to change the DeSotos ring and pinion from a 3.89:1 to a 2.74:1 ratio to keep the engine loaded.
Hucho,Janssen and Emmelmann warn of the same thing in SAE# 760185 and Gino Sovran in SAE# 830304.
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Here are the data from the table.Al will try to get the images up in PART-2 so you can get a visual on what Breer and his team did.
(1) Standard DeSoto Airflow sedan------------------------------- Cd 0.546
(2) bumper delete, trim stripped,flush windows,rear fender skirts--- Cd 0.500
(3) new front(lights moved behind grille,raked shovelnose,sm. grille- Cd 0.468
(4) tail modded to pseudo-Kamm w/ straight chop,no added length- Cd 0.417
(5) full bellypan and sill fairings/extreme fender radius fillets-------- Cd 0.367
(6) 21-inch ( 525mm ) boat-tail 'stinger'-------------------------- Cd 0.316
(7) false decogramic 5-panel semi-circular windshield--------------- Cd 0.308
(8) 44" ( 1,100 mm ) plan-tapered stinger w/ plex-covered license-- Cd 0.238

NOTE: No mention of mirror delete.No mention of wiper delete.No mention of plex-covered license plate.No mention of headlight relocation.No mention of engine bay air exhauster gravity-damper delete w/ shape and size mods.
These are observed from photos published by Hemmings from Chrysler Historical Photos.
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PERFORMANCE:
Top speed: 84 mph (135 km/h)-------- increases to 99.4 mph ( 160 km/h )
Fuel Economy: 15.1 mpg @ 60 mph ( 96 km/h )----- increases to 22.8 mpg
51 % improvement

11.3 mpg @ 80 mph ( 129 km/h )---- increases to 17.7 mpg
56.6 % improvement
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Zeder mentions,that as of 1941,Chrysler had a Cd 0.238 car of 200-inch ( 5,000 mm ) overall length 'in the works.'
The 1969 Charger Daytona was measured at Cd 0.29
A 1960s Plymouth Barracuda designed for Bonneville has been measured at Cd 0.20.
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The 1934 aero-modded DeSoto,compared to more contemporary vehicles would have the width of a 1957 Mercedes 300 SL
would be 12.7-inches ( 317 mm ) shorter than a Ford F350 XLT Lariat pickup
the height of a 1984 Isuzu Trooper
weight of a 1991 Nissan Pathfinder
and not quite the frontal area of a 1989 Nissan Access minivan.(25.194 square-feet )(2.33 Meters squared ).
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That's about it for the data,we'll see about getting the images up.

-------------------------------------------------------------------------
PART-2 ( photos )

I found a copy of '70 YEARS OF CHRYSLER' by George H. Dammann at the used book store.On page 196 was a side view of Breer's aero-modded DeSoto.
He credits John F. Bunnel,Corporate Historian,Chrysler Corp.,and H. Donald Schaerer,Archivist,Chrysler Archives.The photo would be from the Chyrysler Historical Collection.
I've included this image,along with two others,also from Chrysler Historical,which appeared in Hemmings Motor News',Special-Interest AutoS,April/May,1973,No.16,P.19.
These photos are better than the drawings I was working on.
The upper photo depicts the 'short' stinger configuration,the lower-left image depicts the 44-inch 'long' stinger.

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Last edited by aerohead; 06-26-2010 at 01:18 PM.. Reason: add pics add PART-2 ( photos )
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Old 06-22-2010, 03:15 AM   #2 (permalink)
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22.8 mpg in a 4,200 lb yacht with an antiquated engine at 60 mph is very impressive!

The engines found in the musclecars of the late 1960s had much more efficiency than what was in that. Gives you an idea of what could have been done during the 1970s oil embargo when people were demanding fuel economy. The car companies, instead of streamlining their V8 models, decided to punish the consumer for daring to demand fuel economy by selling crap like the Pinto and Pacer, which got about the same fuel economy as the musclecars they replaced, with much less performance. No wonder imports sold so well in comparison...
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Old 06-22-2010, 01:34 PM   #3 (permalink)
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Toecutter: the problem was that the Japanese had "small" down to an artform. The big-3 tried to compete with the Japanese cars by trying to make Japanese cars (small car, small engine) instead of streamlining the bigger cars. It was all about image and perception. If you had a big car that was streamlined, it would still "look" big and clunky. Besides, going from the early '70s to the early '80s, everything got all square, boxy, and straight-up ugly.
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Old 06-23-2010, 12:25 AM   #4 (permalink)
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...it's "funny" how almost everything was invented or designed many, many years before it eventualy came around to being produced or sold.
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Old 06-23-2010, 12:56 AM   #5 (permalink)
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LOL. It is pretty impressive, but check out this car.

Tatra T77 - Wikipedia, the free encyclopedia

Czech made Tatra T77 1934-1938
Coefficient of drag, (are you ready?) .212
75 HP motor, top speed 93 mph

Sorry, no story, but you can read it your self on wiki.

Pictures

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Old 06-23-2010, 01:29 AM   #6 (permalink)
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That car appears to have polymastia... or an "extra" headlight.

Too far? I keed...
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Old 06-23-2010, 03:27 AM   #7 (permalink)
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More photos on the Tatra T77

1938 Tatra T77 Images, Information and History | Conceptcarz.com

But I will let this thread carry on as intended.
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Old 06-24-2010, 05:36 PM   #8 (permalink)
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rear engine

Quote:
Originally Posted by hendan View Post
More photos on the Tatra T77

1938 Tatra T77 Images, Information and History | Conceptcarz.com

But I will let this thread carry on as intended.
I guess I could mention that Breer had hoped to do a coupe with rear engine,which would allow the plan taper of the body to begin 'sooner'.
They encountered unacceptable oversteer and defaulted to the front engine layout.
Walter Chrysler insisted on a 6-passenger car and the Airflow ended up with virtually zero body camber in plan view,requiring the 44-inch tail to get any significant taper there,unlike Kamm's K-cars which started coming within a few years of the Airflow.
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A side note: it has been reported that Tatras,commandeered by the German forces in WWII demonstrated such significant oversteer,that officers were ordered to hold speed to no more than about 35-mph in curves to prevent crashes.
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Old 06-26-2010, 02:23 PM   #9 (permalink)
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Quote:
Originally Posted by Christ View Post
That car appears to have polymastia... or an "extra" headlight.
...nah, just the unknown "father" to the Tucker (ha,ha).
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Old 07-17-2010, 04:02 PM   #10 (permalink)
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( Part-3 ) Closing Remarks

I'm trying to put this thread to rest.I've been on a circular quest which has left as many questions as answers.
As it turns out,more than one car was involved in the experiments,and rooflines came and went.
All Airflows shared sheetmetal behind the cowl,provided by the Edward G.Budd Co..
The SAE Paper dealt with the DeSoto Airflow 4-Dr Sedan.
By the time they had the Koenig-Kamm truncated tail,they had switched the roof to that of the Coupe,or secret Trifon 2-DR Sedan Fastback of 1932.I'll probably never know.
All the photographs of the car are actually the #2 Trifon Special,4-DR Sedan with quarter-windows,developed in total secrecy at Struble's Farm,200 miles north of Detroit.
Examination of the photos reveals an exposed B-Pillar post and doors with top and lower radius corners,not present in any of the production cars,be they Chrysler,Imperial,or DeSoto.
It is the Trifon ( named after Demetrion Trifon,Chrysler mechanic/test-driver )which sports the large 'stinger' boat tail which gave the roof and plan taper ( Jaray,Fachsenfeld,Lay,Kamm ) to get to Cd 0.23.
These 'Trifons' were registered as built-ups and so named to camouflage them from industrial espionage.
Also,not mentioned in the paper,was that the nose was extended forward approx. 7-inches and the stinger was only about 37-inches in length,not 44 as inferred in the paper.
A small photo shows the Trifon being loaded onto it's carrier van with clear dusting line at the aft-body,exactly where the streamlining mods picked up.
The dirt roads of the farm provided Breer with direct evidence of flow separation on the car's body.All he had to do is fill in the blanks 'til it disappeared.
It would take Kamm 4-years to catch up to Breer.

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