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Sunday, July 30, 2017

When Mobile Homes Really Were Mobile: Bowlus and Airstream

Ever wondered why what we call mobile homes are almost never mobile, and usually seem resolutely un-homelike?  As an architect, I've wondered too, and encountering a standard model mobile home forces me to ponder all kinds of design fixes that could make the thing work better. Now and again, though, usually when on a cross-country road trip, I'll see an Airstream, and an Airstream is very much an exception to business-as-usual trailers. If it's parked, I will walk around the friendly, bright metal Twinkie form of the thing, just to admire it. If mobility was indeed ever the goal, it would seem that the Airstream people solved it around 8 decades ago...

Here's an Airstream Clipper being towed by a Lincoln Zephyr.  Both the polished aluminum Clipper and John Tjaarda's unit construction V12 Zephyr made their first appearance in 1936, a full three years before the New York World's Fair gave Americans a glimpse of the World of Tomorrow.  Wally Bayam had formed the Airstream company in 1931.  Before that, like some of today's Tiny House movement innovators, the Stanford history graduate had started by offering sets of plans for people to build their own travel trailers, then moved on to offering ready-made kits for home assembly, finally building trailers in his backyard*. Early Bayam trailers were made of Masonite, a novel but heavy material.  Meanwhile, by 1934 Hawley Bowlus, the designer of the Spirit of St. Louis, had designed the first aluminum trailer with riveted panels echoing aircraft practice.  Bayam, who had also worked in advertising, became involved in selling the new Bowlus Road Chief, and Bowlus was able to build about 80 trailers before suspending production in autumn of 1936...

Here's a Bowlus trailer behind another pitch-perfect tow car, the rear-engined T87 designed by Hans Ledwinka for the Czech Tatra firm (see our post for Nov. 27, 2015 for more on Tatras).  The silver car, with its teardrop forms and dorsal fin, looks ready to float into space with the somewhat zeppelin-like Bowlus.  Somehow, you wouldn't be surprised if Bruce McCall, the cartoonist who popularized Steam Punk before it was called that, emerged from either the car or the trailer.  On Bowlus trailers, by the way, the door was at the front...

That's one way you can tell Bowlus models, like the small Papoose and larger Road Chief above, from the Airstream offerings.  When Wally Bayam bought the Bowlus company at the end of their production run, he adapted their Road Chief design for the '36 Airstream Clipper, moving the door from the front to the side for improved aerodynamics and also easier access to the trailer when still hitched to a tow vehicle.  A variety of tow vehicles could be used, and publicity photos emphasized the Airstream's low weight...   

Even at the original price of $1,200 when roughly half that would buy a new Ford V8 tow car, the Airstream Clipper was a hit. It slept four, offered the convenience of electric lights and a self-contained water supply, and looked like the future.  It may not have hurt the sales effort that when Airstream took over Bowlus, a former ad man took over management from an aeronautical engineer.  Bayam must've done the marketing right, because Airstream was the only survivor of the many dozens (some say hundreds) of travel trailer builders in Depression America to resume production after World War II.

Today, both the Tiny House movement and a revival of interest in the roots of modern design have prompted many to revisit streamlined aluminum trailers. Architect Paul Welschmeyer did a superb job of adapting this Airstream interior for working and living space, making clever use of materials, color and shape to enhance the existing forms. Appliances are solar-powered, and the gauges and dials seem imported from a vintage episode of Science Fiction Theater. The repetitive circles may refer to the aircraft practice of drilling for lightness, as well as forming a link to all those rivets.

It seems fitting that the first Bayam and AIrstream trailers were built in Los Angeles. Another plant was later opened in Ohio, and Airstream still builds trailers in Jackson Center. Production of the Bowlus Road Chief has recently been revived by a Canadian couple who migrated to trailers from the tech industry.   

Photo credits:
Top:  archiveboston.com
2nd:  tincantourist.com & wikimedia
3rd:  hemmings.com
4th:  rvshare.com
5th:  bolide.co.uk
6th:  rvshare.com + Impressive Magazine

Friday, July 28, 2017

Shipshape, From an Aircraft Point of View: Jaguar D-Type

When Jaguar won Le Mans the second time in 1953, it had become a pretty competitive scene, with serious contenders from Ferrari, Lancia, Maserati, Gordini and Aston Martin. Mercedes had won the previous year with their 300SL in its debut at the 24 Hours. During that same year, the Coventry engineers came up with a prototype that explored some new frontiers in structure and aerodynamics, but held to a tradition which was key to Jaguar's success: doing a lot with a little. While the Italians explored new engine architecture including V6, V8 and V12 configurations along with the usual inline fours and sixes, the Coventry crew settled on refining their existing engine design while saving weight, and cheating the wind, with an aircraft-inspired integration of body and chassis.  After all, they already had a reliable power unit, and felt there were bigger and easier gains to be made in structure and aerodynamics.  Also, winning with the proven twin-cam six would enhance the sales appeal of road-going Jags, all of which used the same basic engine design...

Innovation showed up in the design of the stressed-skin central chassis tub, comprising the cockpit, front and rear bulkheads in elliptical section, and side bulkheads, largely formed in sheet aluminum.  To the front bulkhead a tubular aluminum subframe attached, and this carried the engine and front suspension, along with rack and pinion steering.  Front and rear suspension were adapted from the C-Type, so they employed torsion bars. The live rear axle was suspended by trailing links connected to a single transverse torsion bar. Based upon experience with the C-Type, engineers had decided a live rear axle would suffice at Le Mans, and winning there was their main objective.  Four-wheel disc brakes carried over from the C-Type, but these were still a novelty in endurance racing.  The new car would be about ten percent lighter than the C... 

Along with the simplified structure came a new aesthetic reduced, as in a piece of modern jazz, to a series of repetitive, almost-hypnotic essentials.  The car would be oval in plan and section, and the shape would be repeated in elliptical elements like the fender profiles, wheel arches, tapered tail section, and most memorably, in the air intake which replaced the traditional grille.  It replicated the elliptical section through the stressed-skin cowl and side bulkheads, and added another refinement: the edges of this opening were in themselves curved in section, so the air intake more resembled something from a jet aircraft than just a hole punched or cut into sheet metal.  As Robert Cumberford pointed out, it was a civilized way to make an opening.  The body design was created in-house by Malcolm Sayer, an aerodynamicist who had worked in the aircraft industry and who drew his plans and sections at full scale with ship's curves on the wall.  Along with the aircraft-inspired structure, the D-Type adopted a deformable fuel bladder mounted in the tail, and a vertical stabilizing fin merged with the driver's headrest on many examples.

Sayer insisted on keeping frontal area to a minimum, so the engineers adapted a dry-sump lubrication system to the 3.4 liter XK engine to reduce height, and canted it 8.5 degrees from vertical. The engine retained the iron block and aluminum head configuration from the C, but larger valves were added to the wide-angle head in 1955, and engine displacement was increased to 3.8 liters in 1957, the third year in a row, and final one, that the D-Type won Le Mans. D-Types also won at Reims and Montlhery, and closer to home at Silverstone and Goodwood. The D-Type was rare viewed against the background of production cars, but it was a very popular racing car.  In addition to the 18 cars built for Team Jaguar from 1954-57, 53 customer cars were built.  These figures include both the original "short-nose" type and that "long-nose" variation which appeared in 1955. When the 16 road-going XK-SS versions of the D-Type are added (these had weather protection and bumpers, sort of), the tally is 87.  Maserati and Aston Martin built far fewer of their comparable road racers.  Back during the car's schematic phase, test driver Norman Dewis would sometimes walk into Jaguar's design studio and puzzle over the big drawings covered with formulas, section markings and Malcolm Sayer's scribbles, and he'd say he wasn't sure he could see a car in there.  Now, with the 20-20 vision that hindsight brings, we can all clearly see the car... 

Footnote + Thanks
I want to thank Dennis Varni of Los Gatos, CA and the Revs Institute in Naples, FL for allowing access to their cars. The dark green Varni D-Type is a 1955 example that raced at Sebring. The Revs Institue car is also from 1955, and is one of the five "long-nose" examples on the starting line at Le Mans that year.  The low-penetration nose is 7.5 inches longer, and incorporates additional intakes flanking the central air intake.

I also want to thank Ian Avery-DeWitt for sorting through about 700 photos taken at the Revs Institute this past winter.

Photo credits
Top:  Jaguar Cars, as featured in primotipo.com
2nd:  George Havelka
3rd:   the author
4th:   carblueprints,ru
5th:   the author
6th & 7th:  Ian Avery-DeWitt

Sunday, July 16, 2017

Game Changer: Jaguar XK-120

Jaguar's XK120 changed the car industry and, along with the MG, put sports cars on the map in the U.S. market which was key to Britain's postwar export drive.  A lot of this success was due to the engine design, which equalled the power of the new Cadillac V8 for 1949. The first thing Americans noticed, though, was that roadster body design.  Like the British who first viewed the car at the Earl's Court show in 1948, they were pretty much hypnotized by it (Clark Gable was the first customer). Most people aren't aware, however, that the impetus for the whole design can be traced back to decisions made in Germany by others...

In 1937, BMW aimed to increase the race-winning abilities of their 328 roadster, and asked (ordered, really) their design department to come up with a lightweight, aerodynamic roadster. Designer Wilhelm Kaiser (you can't get much less British than that) sketched out a body to be formed in alloy over a tubular frame.  The resulting Buegelfalte (named for the "trouser crease" at the fender tops*) and its Italian-bodied sister cars were light enough and slippery enough that BMW took 1st, 3rd, 5th and 6th places in the Mille Miglia for 1940, a year when most people were thinking about other things...

Things like the Luftwaffe's bombing of England, for example. Soon the industrial center of Coventry was bombed, and Jaguar chief William Lyons did fire-spotting duty on the roof of the factory (by then in use for storing aircraft fuselages) with some of his team, which included stellar engineers: William Heynes, Harry Weslake, Claude Bailey and Walter Hassan. Apparently when they ran out of generic topics like the survival of Western civilization, their conversation turned to engine design, and the idea of replacing Jaguar's line of engines, which had most recently consisted of inline units manufactured by Standard Motors (postwar Standard Triumph of TR fame) with Jaguar-designed OHV heads. The engineers wanted something with hemispherical combustion chambers and twin overhead cams (like an Alfa Romeo) and Lyons wanted something beautiful to look upon, and (with an eye towards the future American market) with ample reserves of effortless power.  

You'll note that the engine in the photo is a 4-cylinder unit*.  Right after the war, the Jaguar crew began experimenting with various head and block designs, running through prototypes XA through XK, a 2 liter twin-cam with those hemispherical combustion chambers. It's helpful to remember that Jaguar's domestic competition consisted of somewhat fusty outfits like Alvis, Lea Francis and Riley, and not-so-fusty Aston Martin, all of whom offered four cylinder engines in the 2 to 2.5 liter range.  Also, fuel rationing made gas consumption important. But the little four was too rough-running to satisfy Lyons, and the team informed him that it would be no more expensive to tool up for a six.  In a move that proved decisive, Lyons decided to produce a 3.4 liter twin-cam six (XK) offering about a third more power than a Bentley, for about one-third the price.  The first destination for the new engine was to be a luxury sedan, but Lyons decided to build a couple hundred 2-seater roadsters to showcase it. After that first 1948 showing, demand far outstripped supply, and in the scramble to make roadsters, the new sedan was delayed. Several sources of inspiration for the XK120 body design have been suggested, including French and German ones. The year before the XK debut, the Frazer Nash people (see our posting for 1-27-17) had brought over one of the two post-Buegelfalte BMW roadsters built by Touring of Milan (they'd erased those fender creases) and displayed it with a Frazer Nash grille. With the BMW-derived 2 liter Bristol engine, they'd suggested this for sporting drivers, but at a Bentley price...

Specialist builders like Alvis and AFN didn't yet realize it, but Jaguar would soon have them in checkmate. Using racing success to garner publicity (Jaguar won at Le Mans in '51, '53, '55, '56 & '57) and making cars with Bentley levels of style at Cadillac prices, Jaguar took over a lion's share of the home market for performance cars (including sedans) while it established a firm foothold in America.  It's hard to imagine today, but the most popular import in California by 1956 was not VW, it was Jaguar. On the home front, Jaguar bought out competitor Daimler in 1960 (the year Armstrong-Siddeley folded its automotive tent) and Alvis was extinct by 1967, with Bristol turning out tiny handfuls of overpriced, obsolete chassis designs powered by Chrysler V8s after 1961.

The first 242 XK roadsters were bodied in aluminum over ash framing; after that, construction switched to steel bodies with alloy doors, bonnet and boot lids. During these years, Jaguar regularly updated and expanded the line, including a "fixed-head coupe" version of XK120 in 1951, the year after they introduced the Mark VII luxury sedan. Both cars featured generous amounts of polished wood and leather inside, and a curved rear roof form which seductively followed the side window shape and nearly mirror-imaged the rear fender shape. No BMW influence here; it was a bit like the prewar teardrop Figoni-bodied Talbot in red below... 

Upgrades to engine power came along too, and are summarized in the footnotes.* A drophead (convertible to Americans) followed in 1953 with a similar interior featuring a standard heater, padded top and roll-up windows, unlike the side-curtained roadster which was usually driven with the top down anyway.  You just drove a bit faster to keep the rain off...

When it became apparent that a lighter, more rigid frame than the 120's modified Mark V ladder layout would be needed to keep the car competitive in road racing, the engineering team and aerodynamicist Malcom Sayer came up with the XK120C in 1951, giving it 4 wheel disc brakes during 1953.  The new car adapted the independent front suspension by torsion bars from the XK120, but substituted a torsion bar trailing link system at the rear for the 120's leaf springs.

The compact, lightweight car gave Jaguar its first wins at Le Mans, but it was almost as far from an XK120 production car as the contemporary Mercedes 300SL was from a standard 300 sedan. Maybe as a result, it quickly became known as the C-Type, and it was produced in 54 examples, while the standard XK120 concluded production in 1954 after well over 12,000 cars had been sold*, mostly to Americans. 

The XK120 wasn't a perfect car, of course, and by 1954 even diehard Jaguar fans (especially tall ones) were wishing for more space, better ergonomics (though nobody used that word then) and more efficient cooling for both the engine (sometimes a victim of that narrow grille opening) and the cabin. Road race fans were aware, too, that the C-Types often won because they stopped better than other cars, and they were wondering when the road cars would get those disc brakes. Maybe because a good number of Jaguar owners raced their cars on weekends, the complaints made it back to Coventry and provided food for thought in the engineering section. In Part 2 of our Jaguar saga, we'll see where those thoughts went.

*Footnotes:  The four-cylinder prototype engine is in the Collier Collection at the Revs Institute in Naples, Florida.  It was intended for a possible junior version of the roadster called the XK100, but the project was cancelled.  According to the Revs Institute, some 4-cylinder engines were sent to dealers for display.  One 4-cylinder engine was released to Goldie Gardner for a record run in the MG Ex135 streamliner, and it achieved 176 mph.  

Engine & performance notes:  Power from the 3.4 liter XK-120 was increased during the car's production life from 160 bhp at model introduction to 220 for a Weber-carbureted C-type. All engines featured a cast-iron block with 7 main bearings, and an aluminum head. Tallies of total XK120 production range from 12,055 (Wikipedia) to 12,078 (Consumer Guide to Collectible Cars), counting the 242 alloy-bodied cars produced in 1948-49. In their road test of an XK 120M coupe (180 bhp, 3,100 lb.) in February 1953, Road & Track achieved a 0-60 time of 8.5 seconds and a one-way top speed of 123.3 mph. In their test of Masten Gregory's Golden Gate Road Race-winning C-Type (210 bhp, 2,550 lb.) that same month, Road & Track achieved 0-60 in 6.6 seconds and a one-way top speed of 134.3 mph. The car's final drive ratio of 3.92 to one was well-suited to the Golden Gate course, but not to the best top speed run, and R & T noted that with the standard 3.31 ratio the top speed would rise to above 140. Road & Track also noted that it was the fastest-accelerating car they'd tested to date.

German to English translation:  Christa Rosza notes that the buegel (iron) makes the falte (crease); the English translated the name loosely as "trouser crease". But subsequent interpreters of the Buegelfalte idea thought these creases were a pain to make in aluminum and got rid of them.  Here are the creased fenders in plan view; note the tight seating area front to back, a feature also of the XK120:

Photo credits:
Top:  Wikimedia
2nd and bottom (12th):  bmwblog.com
3rd:  the author
4rd:  AFN Ltd.
5th: The author thanks Dennis Varni for showing his XK120 and D-Type (to be featured soon).
6th:  carstyling.ru
7th:  britishmotoringjournal.com
8th:  fantasyjunction.com
9th & 10th:  Wikimedia
11th: Jaguar Heritage Trust

Tuesday, July 11, 2017

Lamborghini Miura: Mini Cooper's 2nd Cousin, Twice Removed

Hearing that the cars pictured above and below were inspired by the  British Motor Company's stubby, breadbox-shaped Austin / Morris Mini twins from 1959 will likely strike the reader as implausible, somewhat like the story that Frank Lloyd Wright's Imperial Hotel (in Tokyo, of all places) was inspired by Mayan architecture.  But both stories happen to be true; we'll get around to that hotel project in a future essay...

Right now, we're going to take a brief tour of Dennis Varni's Lamborghini P400S (the red car below), a Miura which he's had for many years...

The car's creation saga has been told before; here's the quick outline.  Lamborghini had only been building cars for about 2 years when chief engineer Gian Paolo Dallara began thinking about a car that would attract more attention than the company's first automotive product (unless you count farm tractors), a svelte but fairly conservative (by Italian standards) front-engined coupe called the 350GT. The company was also seeking something that would generate real profits, as it had spent plenty on tooling for the Bizzarrini-designed V12 that powered that car. The idea of a higher-volume sports car had some appeal (remember, this was a tractor company) and apparently the project team approached BMC about using the engine and transaxle unit of their transverse-engined, front-drive Mini Cooper, but located behind the driver, for what would have been the first widely-available mid-engined car.  Rebuffed in their search for cheap, off-the-shelf power, Dallara took the Lambo GT's aluminum V12, now in 4 liter size, turned it sideways like the Mini engine, and sketched out a sheet-steel semi-monocoque chassis around it, leaving just enough space for the power unit, driver and passenger.  Well, maybe not quite enough; one feature common to the P400 and the BMC Mini was that the engine shared its oil with the transmission to save space. And when Marcello Gandini's body design for the new P400 was first shown on the Bertone stand at the 1966 Geneva show, the engine lid was locked and the space was filled with ballast, as the crew had been unable to shoehorn the power unit into the space.  It might have lacked its engine, but the car had acquired the name Miura, after a famed breeder of fighting bulls...

Even with the engine lid locked, the car attracted the desired amount of attention, and generated scores of orders. The young engineering team (Dallara, Paolo Stanzani and test driver Bob Wallace were all in their late 20s) set to work refining the prototype and getting the car ready for production. 275 of the original P400 model (2,850 lb., about 345 hp) were sold between 1966 and '69, at around $20,000 apiece.  The first major revision began production in December 1968 and this is the P400S, of which Dennis Varni's car is an example.  Intake manifold revisions raised horsepower to 365, the interior gained power windows and an overhead console, a locking glovebox as well as more luggage space, and single release levers for the one-piece alloy front fender section and rear engine lid including fenders which pivot up for easy access to the mechanicals.  Doors, roof and rocker panels are steel, as on the original car.  Just under 340 of the Miura S were built. 

In 1971 the Miura SV was released, with revised cam timing and carburetors allowing 380 hp, and wider rear wheels to get the power to the ground.  Outward signs of the new model were the recontoured rear fenders, deletion of the metal "eyelash" grilles around the recessed, pop-up headlights, and new tail light units.  But the most significant mechanical revision affected only the last 96 examples of the 150 SVs built; this is the split sump which separates the gearbox lubrication from the engine sump, permitting the oil in each to be specific to use.  Like many Miuras, the Varni 400S has had this modification, because it avoids the potential expensive rebuilds sometimes caused by the shared oil system.  In addition, Varni's red car has a front spoiler to avoid lift at high speeds, and he has had the rocker panels below the doors (usually painted silver at the factory) painted red to emphasize unity of form.  Lamborghini badges from horn buttons have been affixed to the triple-eared knock off hubs to personalize the car, because Varni is more concerned with having a car which pleases his driving sense and visual sense than concours judges.  

Photo credits:
Top & 2nd from top:  the author
3rd from top:  George Havelka
4th:  the author
Bottom:  lambocars.com