Carl F. Thelin

S&S at General Motors

No, I’m not writing about SS Nazis at GM.

I believe that the Structure and Suspension department, in its role as overseer of chassis engineering for the General Motors Corporation would have had the influence to bring some logical control to the amazing diversity at GM in the 1957-59 eras.

Some things besides the well-documented health care and pension legacy costs might explain the financial difficulty that General Motors has in the 21^st century.

I was a young engineer at the Engineering Staff of the GM Technical Center. In 1959 I began to ask why and how GM could waste so much money compared to Ford Motor Company and Chrysler Corporation.

Ford had three divisions: Ford, Mercury and Lincoln.

Chrysler had Plymouth, Dodge, DeSoto, Chrysler and Imperial.

At GM, we have five main divisions: Chevrolet, Pontiac, Oldsmobile, Buick and Cadillac, plus the almost sixth “division” GMC Truck.

Unlike the competition that was selling all those brands with a small family of engines, transmissions and body platforms, GM had essential five completely separate competing car companies – and even bragged about it internally. We at the Corporate Technical Center were told that our superiority was due to the internal competitive nature of our five car companies. We at the Tech Center and the Milford Proving Grounds were the corporate overseers to help pick out the best ideas.

You can guess, even without an engineering background, that the V-8 engine and the automatic transmission are the two most complicated and expensive parts of any automobile, then or now. However, each division had its own unique engine layout. The Buick vertical valve cylinder head was most unique. Olds, Buick and Cadillac had huge engines compare to Chevy and Pontiac. Olds, Pontiac and Cadillac shared the Hydramatic four speed automatic transmissions that used only a simple fluid coupling. Chevrolet used a two speed automatic with a torque converter. Buick had versions of the Dynaflow automatic with torque converters of various capacities. Consider that, with few exceptions, car buyers had no idea about the details of the brand differentiations listed below.

Brakes: They were all different in drum width and diameter. Some were finned, and Buick alone used aluminum drums. Disc brakes were not in production yet.

Wheels: These too were all different diameters and widths. Even the five-bolt patterns were un-alike. Ditto for the spacing between the wheel and the hub. Frames: Chevrolet and Buick used X-frames that were similar, but not alike. The others used Hip frames, also different in detail. Suspension arrangements: There were a variety of front and rear suspensions and steering linkage arrangements. All were unique. Coil and leaf springs: The Corporation including the Chevy – GMC truck group had an amazing variety of springs with different coil and wire diameters and even a variety of coil-end treatments and eyes of the leaf springs.

The only major things common to the car divisions were the Saginaw hydraulic power steering gear, the Delco-Remy power brake vacuum booster, and the Frigidaire air conditioner compressor. Each was covered by patents and was brand-named.

These photos illustrate the most amazing performance by the engineers in the Chevrolet Division. The 1957 model Chevrolet shown below had slight styling changes applied to the basic body introduced as the 1955 model – the one with the first V8 engine in a Chevrolet in modern times. The first had 265 cubic inches, but the 283 is the engine everyone loved.

The following year, the 1958 model had an all-new body design, rather than the fourth iteration of styling face lifts, as was usual at GM. This car also offered the first Chevy rear axle held in position with control arms instead of leaf springs, and air springs were an option to the coils springs, front and rear. Now you could get a big-block engine with 348 cubic inch displacement.

This car was built like a pro football player. It had powerful engines available.

The wrap-around windshield was extreme - and kind of stupid, too.

Then, even more amazing was the totally new 1959 Chevy with the bat-wing rear end, and an X-frame underneath. These had the same engine choices as before. The horsepower race began with the 409 CI in 1961 and the (7-liter) 427 Cubic Inch engine in 1963.

AIR SUSPENSION

Von D Polhemus was my boss at the General Motors Engineering Staff. His rank was one notch below Vice President of General Motors. He headed the department known as Structure and Suspension. Our department, using the whole third floor of the South wing, handled everything except engines, transmissions and overseas cars – such as the Australian Holden, the German Opel and the British Vauxhall as well as kits cars assembled elsewhere.

He lost a lot of career opportunities, I am sure, because he became known as the father of the Air Suspension System. The air springs were available as options on all GM divisions beginning in 1958. They were standard on the Cadillac Eldorado Brougham which was known also for its stainless steel roof. These air spring suspensions were truly engineered, not at all like the crude air bag springs used on buses and trucks. I wholeheartedly supported Mr. Polhemus when he was criticized by others of his rank in meetings, and risked my career defending the air springs, too.

Mr. Polhemus had another foresight that was ignored at greater harm to GM.

FRONT WHEEL DRIVE

When the BMC Mini designed by Alec Issigonis was introduced in England for 1959, Von asked me to make a copy of it using US parts and a one liter displacement engine. The Mini had only 0.850 liter displacement, then. I was to make the first General Motors front wheel drive (FWD) car. There was a problem. GM did not have a production four cylinder engine that small, nor was there anyone still at the Engineering Staff that knew how to design a manual transmission, with a floor shift and four forward gears.

Nevertheless, we designed and built the tiny car. It was very underpowered and crude. After that I made another one with a 1.5 liter cross-wise engine like the Mini. This engine, transmission and differential, all aligned laterally was better, so we did learn from the smaller car what not to do. The Mini used a common lube (oil) for the engine, transmission and differential. That was too crude, and would not work at all with a hydraulic automatic transmission.

After that, I started working on a series of full sized front wheel drive cars using a full sized Oldsmobile 394 CI V8 engine. I designed the experimental car so that it could also use the aluminum V12 that Cadillac planned to compete with Lincoln. Even though it was a 60-degree-bank V12, it would fit under the hood because it had a novel overhead cam arrangement that made the block short enough. Originally, we stayed with the lateral layout, but the Oldsmobile division insisted that we had to use their production V8, which required a fore-aft alignment. We did what they asked – it became the XP-784 that went on to Lansing, Michigan. The GM XP-784 had early versions of front disk brakes but the production car had only four drum brakes. They lost a lot of FWD advantages doing it.

One other great idea that came from the Polhemus work with the XP-784 was the use of water-hydraulic-cooled disk brakes. With the all-lateral layout, the engine oil was separated from the fluid used in the automatic transmission and the differential. We could use ATX fluid in the differential because there were no hypoid gears requiring high pressure lube grease. With ATX being circulated through the transmission and through the bottom of the front water radiator we could do something really novel. We added an ATX multiple-disk clutch pack to each side of the differential, just inboard of the inboard constant velocity universal joints. That made for brakes that would never wear out and never fade. Oil cooling of the ATX fluid enabled that – which we proved would allow the XP-784 to coast down Pike Peak, in neutral, using only the foot brake to limit the speed. We said that you might boil the water in the radiator, but brake fade would not be a problem. Of course, we had to admit that this was a very expensive idea. It has been used on giant earthmovers that climb from open pit mines and then coast back down.

FLAT FLOOR

Next, and last for me, was an experimental full sized Oldsmobile Toronado Station Wagon – the original Vista Cruiser wagon, styled like the GM Greyhound Cruiser bus. This station wagon had the glass-framed hump in the roof above the second seat and a raised roof above the third seat. Based on the Toronado, it was much bigger than the Olds F-85 Vista Cruiser, which was based on the intermediate size car body. Because the FWD permitted us to avoid the huge ordinary rear axle, the floor was flat from the back of the front seats all the way back to the open tailgate. The car had a third seat which was very accommodating because it was fully behind the wheel house. The second and third seats fold flat into the floor that was only eighteen (I hope I remember that right) inches above the ground at normal load. Other station wagons had a floor at least 25 (?) inches up.

Unlike most GM sedans of the era, this wagon did not have its fuel tank under the trunk with the fuel filler exposed behind the license plate. Our car had a vertical tank in one rear fender and the spare in the other.

THE INNOVATIVE TAILGATE

We were very proud of a feature that never appeared elsewhere. It was the dual-mode tailgate, much like the one then standard on full sized wagons. It was hinged at the bottom and had an electric powered roll down window. The tailgate could be lowered to the position with the inside surface level with the inside floor – so low that we had the center part of the back bumper attached to the tailgate. Now, by operating the inside release lever a second time, one could drop the tailgate down another 30 degrees of so. The inside surface of the tailgate had two layers. The top layer was a panel with a piano hinge on the back edge. The user could flip that panel up and back and lower the back edge to the ground. Now he had a sloped ramp from the ground up into the (lower than normal) inside floor.

This is a similar tailgate found on the internet.

The tailgate on the XP-784 station wagon folded the other way, so that the top of the part on the ground went up and folded flat against the top of the part hinged on the floor.

This is a picture of a normal tailgate for a pickup truck. I colored the links on each side of the tailgate leaf, which is the part that swings down. On some pickup, that link can be disconnected so that the leaf will hang down loosely. On the XP-784 wagon, you just pulled up on the flush lever, shown green on the upper surface of the leaf. That pulled cables to release the pinned joints at the junctions of the green and pink links, on both sides, to lower the leaf.

This is from another ad on the internet.

At GM, we made a movie (there was no video then) showing a woman wheeling a baby buggy into the back of the XP-784 station wagon, sort of like this guy is doing.

FORESIGHT LACKING

My best friend was assigned to develop a smaller FWD car, based on the German Opel Capitan 4 door sedan. This car had a unitized body made by Germans who knew how to do it right. The car used the Oldsmobile aluminum V8 from the smaller F85 model. The Buick Skylark aluminum V8 could have been used or even the Buick cast iron V6. All of these could be used with the crosswise layout. GM even considered using a Pontiac cast-iron overhead valve inline six cut down to a four that would fit the narrow engine. compartment.

That car was a beauty. It could have been ready for sale instead of my 1966 Oldsmobile Toronado. I said that in meetings when I realized that Olds was going to go ahead, but was told that Chevy and others did not want to risk their bread and butter cars with a novel FWD concept. With the engines we had, that car would have anticipated and been superior to the 1980 GM X-bodied cars: the Citation and others with fours, V6 and aluminumV8s. Mr. Polhemus would have retired as a hero with those compact-sized FWD cars in production.

Chevrolet had these cars in the stable during the 1960 -1966 era while the XP784 was being developed: Nova, Corvair, Chevelle, Chevelle SuperSports, Biscayne, Impala, Caprice, C-1500 Pickup, Van and Corvette. Talk about risky car designs – who recalls the Nova and Corvair? Who remembers the ugly Chevy Van instead of the Ford Econoline van?