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Old 02-25-2012, 08:12 PM
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Default 58-64 GM x-frame pics, info, discussion

GM used this design for 6 model years which included some of the most historic cars of all time. Wonder what the engineers were thinking?







Ford and GM debated the design:
A case in point is the “X” or “cruciform” type chassis frame. This frame was introduced in 1957, primarily to reduce the problem of restricted headroom and difficult entry into the “low-profile” automobiles that were becoming popular after the mid-fifties. The X frame construction does not have side rails along the passenger compartment, as did most previous conventional frame designs. From the time the cruciform type frame was introduced, it was widely used by General Motors on Chevrolet, Buick, and Cadillac. The Ford Motor Company continued to use frames with side rails, and it was evident that the two companies held strongly different opinions about the two designs.
In the fall of 1959, a photograph of a Chevrolet Impala that was broken in half after striking a tree broadside was widely circulated in newspapers throughout the country. The frame had severed at the intersection of the X. The report of the General Motors investigators who rushed to the scene attributed the severance of the frame to the semi-airborne position of the car as it struck the tree. This had apparently allowed the engine mass to act as the head of a sledge hammer. At the General Motors engineering center in Michigan the conclusion was that “automobiles are not designed to withstand such tremendous lateral forces - this would be extremely uneconomical.”
General Motors spokesmen continued to defend the cruciform type frame as offering substantial resistance to side impacts because of the rocker panel and floor pan underbracing members — even though by 1965 all General Motors models except the Buick Riviera had abandoned the design in favor of the perimeter type. In 1960 the General Motors technical center offered proof that a unitized structure with side rails can also split into two pieces. A picture of a Ford Thunderbird, torn in half after slamming against a telephone pole and tree, was offered as evidence to critics of the X type frame.
This comparison enraged Ford engineers. Fletcher N. Platt, a highly talented research engineer at Ford, retorted that the Thunderbird case involved a telephone guy-wire that had “acted as a knife on the entire body structure.” In contrast, he said, “the Chevrolet that broke in half failed at the center of the X frame after hitting a tree.” Platt said, “The X frame has no advantages from the standpoint of passenger protection. It requires less material to support the four comers of the car, but it is obviously less rigid and provides little lateral [side] protection to the passenger compartment.” He suggests consulting any “‘unbiased’ structural engineer regarding these two designs.” Mr. Platt might not consider Mr. Harry Barr, vice president for engineering of General Motors, qualified for the designation ‘unbiased,’ but Mr. Barr did admit grudgingly, under questioning, that the Oldsmobile perimeter type frame had some advantages over the Chevrolet X type frame in side-impact crashes at speeds of about fifteen miles per hour. Further proof that some General Motors engineers agreed with Ford’s Platt came in the form of an internal memorandum prepared by the Oldsmobile division in 1963 in which the Oldsmobile “guard-beam” frame was described as offering an “extra margin of protection” over the X type frames of Chevrolet, Buick, and Cadillac.
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Old 02-25-2012, 08:16 PM
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The ’59 Chevy became famous in 2009 when it was crashed into a new Malibu, and (not surprisingly) fared rather poorly. The X frame probably played a relatively small part in that, given all the other aspects that were so different between these cars. And who knows how rusty the Chevy frame and/or body were. Speaking of, the X-frame is rather notorious for rusting, and there is a pretty brisk business in replacement frames, often reinforced. One wouldn’t want to start throwing a Chevy low-rider hydraulically four feet into the air with a rusty frame.
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Old 02-26-2012, 02:14 AM
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Huh, interesting. I've always liked the Rivs but didn't know much about the frames.
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Old 02-26-2012, 09:42 AM
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Some articles say all 58-64 GM's used the x frame, it appears that '59-'60 Oldsmobile took quite a bit different route. They were also the only ones using rear leaf springs. The Super 88 & '98 Olds also had a different wheelbase than the Dynamic 88.

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Old 02-27-2012, 08:25 AM
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Your ahead in a Ford all the way!X frames = death in a side impact.Olds had it right.
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Old 02-27-2012, 02:43 PM
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Back in the day, I owned a few X-frame cars. In high-school, I owned pair of '64 Buick LeSabres. Both had the variable-pitch Twin-Turbine Dynaflow trans. The first one had a stock 401 cid nailhead 4bbl. I didn't know that the car had been in a serious wreck, and that the front-end had been welded back together. One day, I had to do a panic-stop from about 80 MPH when a cow decided to stop in the middle of the road. The front suspension folded, and the wheels came right back into the fender-wells! I swear that I could feel the back end lift off the pavement! That was one hell-of-a ride I don't care to repeat!

I picked up a second LeSabre with a bad engine. I knew where there was a wrecked '65 Riv Gran Sport with the dual-quad 425 cid 'Super Wildcat' nailhead. I bought the car for $35. My hot-rodding buddy & I used his dad's Farmhand-equipped tractor to drag the Riv home, pull the engine & drop it into my LeSabre. This LeSabre had a factory posi rear-end. We put shorter gears in it. With the maroon paint that had faded to a strange purplish color, the car was ugly as hell. It was a real sleeper, though. On a good day, she'd run the quarter in 14.5 sec @ 100 MPH - which wasn't bad for a 6-passenger 4-door back in the early '70s. I taught my high-school girlfriend how to drive in that car. I also taught her some other things in that car, but most of 'em required both of us to sit in the back. Years later, I owned '60 Chevy Parkwood wagon w/235 I6. It had a three-on-the-tree w/factory overdrive. I used it to haul band equipment.

Never got T-boned in an X-frame car, so I have no first-hand experience with their crash-worthiness. I do remember that replacing the split-driveshaft center bearing in the LeSabre could be a real PITA!! And if you liked to race, it needed to be replaced often!! The rubber mounting couldn't stand up to repeated hard launches. When it let loose, the driveshaft would literally flop around in the center section!!

Buick also did their own thing with frames back then. The 56-57 Buicks used a frame that looks quite similar to the Olds frame from the same era:




In '59, Buick dropped the X-frame completely & came out with this:



However, in '61, they went with the traditional X-frame. Seems like they took a step backward as compared to their Equipoise chassis:


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Old 03-01-2012, 03:45 PM
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If I had that first X frame in my '63 I would have cut out the X part. I hate that frame and the 2 piece driveshafts. I broke more hanger bearings and a bunch of those puney driveshafts that I care to admit. I still like our 63 Biscayne, I just wish Chevy would have seen the light on frames before the 65 model year with the new perimiter frame.
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