Thursday Trivia

Thirsday Trivia
Welcome to Thursday Trivia where we offer up a historical automotive trivia question and you try and solve it before seeing the answer after the jump. It’s like a history test, with cars!
This week’s question: What the heck was “Rope Drive?”
If you think you know the answer, make the jump and see if you are right.
One of the ways that WWII was different from WWI was that in its aftermath the Allies helped their former enemies rejoin the World community through financial assistance in rebuilding their economies. This was called European Recovery Program or as it’s better known, the Marshall Plan.
One of the outcomes of the stimulus was an acceleration of industrial rebuilding and the vision to seek new markets in which to sell the wares coming off the shiny new assembly lines. That led to American imports of foreign cars starting with a trickle and quickly increasing to a volume that the domestic producers couldn’t ignore.
Part of reason that foreign makes increased in popularity in the 1950s was their pricing. Typically smaller both is size and cost the new imports took advantage of an economic downturn in the States that spanned the middle of the decade.
1963_Pontiac_LeMans_coupeThe American automakers didn’t sit on their fat cat hands, they reacted to the import assault with new small cars of their own. Some, like Ford’s Falcon and AMC’s Rambler were big car tropes made in a smaller scale. GM on the other hand, decided to create small cars that were nothing like their larger predecessors. The Corvair, with its rear-mounted air-cooled engine was perhaps the boldest and most unique answer to the most popular new import, the Volkswagen.
John Z DeLorean, then Director of Advanced Engineering at GM’s Pontiac division, sought to emulate both the roominess and sportiness of the imported interlopers, only in a Mama Bear size – not too small and not too large. His vision was a 6 passenger compact car made possible by a flat floor. With far fewer sales than Chevrolet, Pontiac had to make-due with a lot of off the shelf parts to build their ambitious compact.
From How Stuff Works:

DeLorean wanted a car that was more than just a compact. In addition to offering lower purchase and running costs, the new design needed to possess a “big-car” ride and offer comfortable seating for six adults. The smaller size also suggested an inherent sportiness and DeLorean believed he could meet these objectives, as well as achieve the ideal 50/50 weight distribution by using a flat floor, a rear-mounted transaxle, and, of all things, a flexible driveshaft. Buick and Oldsmobile, however, were not planning on using any such exotica on their small cars, preferring to stick with conventional drivetrain layouts.
The design was truly revolutionary, though not always understood by the public. It soon earned the nickname “rope drive,” which was not an accurate depiction of the driveshaft. The shaft was actually a forged-steel torsion bar, which featured high nickel, chrome, and molybdenum content. Tempests with manual transmissions featured a shaft diameter of ’75 inches, while automatics received a ’65-inch-diameter unit. Since the shafts were transmitting engine torque that was not multiplied by the transmission, they were understressed and could easily afford to be as small in diameter as they were compared to a conventional driveshaft.

Rope Drive wasn’t the Tempest’s only innovative difference. While other GM compacts – as well as Ford’s Falcon – went with six cylinder power for the base engine in their cars, Pontiac introduced a four-cylinder engine, basically half of a 389 V8. The lowest tier of the “Trophy 4” produced 110-bhp on regular gas. Adding a 4bbl, hotter cam and tuned for premium fuel, Pontiac’s four-pot was good for 155-horses.
On the downside, the 195-cid Trophy four was an inherently unbalanced engine, a problem that the Rope Drive was used to solve. Soft motor mounts and the curved driveshaft with its rubber bushings helped to limit transmission of the engine’s shaking to the rest of the car. The whole package proved a success and Motor Trend magazine was sufficiently impressed to give the car its 1961 Car of the Year Award.
The first generation Tempest ran for three model years before being replaced by a larger, and more conventional model in ’64. Pontiac would go on to introduce a SOHC straight six in the latter part of the decade, however they wouldn’t have a technological tour de force to equal that first Tempest until the Fiero of 1984.
Image: Wikipedia

0 Comments

  1. Are you kidding? A zillion years ago (okay, more like 35 years ago) I read all about rope drive and how to repair it, in the Pontiac shop manuals at the local public library.

  2. While Pontiac used rope drive (to lower the center hump in the floor) and a rear-mounted transaxle with swing axles similar to the Corvair, Oldsmobile’s F-85 used a conventional transmission and live rear axle, and a two-piece prop shaft with a double Cardan joint in the center.

  3. The Trophy four also had early problems with durability of the timing chain (from all the engine shake), which they solved by upgrading to a high-strength chain.

  4. What’s really crazy is that Pontiac used ‘rope drive’ in the ultra bad-assed 421 Super Duty Tempests too.

    1. And the rope drive was also put in to help cope with the engine shake. Engineer Malcolm McKellar called it “a traveling fatigue machine.” This was the guy that did a lot of the design work on Pontiac engines in the ’60s, including designing the fiberglass-reinforced timing belt for the OHC 6, Ram Air, etc.

  5. Curbside Classics had a feature on the Tempest and rope drive several years ago. It seemed like a solution in search of a problem.

  6. From one of my favorite movies:
    Mona Lisa Vito: No, there’s more! You see? When the left tire mark goes up on the curb and the right tire mark stays flat and even? Well, the ’64 Skylark had a solid rear axle, so when the left tire would go up on the curb, the right tire would tilt out and ride along its edge. But that didn’t happen here. The tire mark stayed flat and even. This car had an independent rear suspension. Now, in the ’60’s, there were only two other cars made in America that had positraction, and independent rear suspension, and enough power to make these marks. One was the Corvette, which could never be confused with the Buick Skylark. The other had the same body length, height, width, weight, wheel base, and wheel track as the ’64 Skylark, and that was the 1963 Pontiac Tempest.

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