Unit Bodies and Where they came from

[enjenjo]

The first unibody car was the Lancia Lambda in 1921. There were only 50 of them made, and there were a lot of problems with them.

The Budd company engineered a unibody in 1930 and in a couple years licenced it to Citroen who came out with the Traction Avant in 1933 the first modern unibody car. They ended up making almost 800,000 over the next 24 years.

Chrysler Corporation also licenced it for use on the Airflows both Desoto and Chrysler in 1934. Chrysler slightly modified the concept by using a box girder that went from the extreme front of the car, over the passenger compartment, and ended near the rear bumper. It still had a vestigial frame make of 14 ga steel that was used to hold the front axle and the drivetrain so it could be assembled on existing production lines. There were 17 body mounts on each side, and the body supported the frame rather than the frame supporting the body. The Airflows were made in 1934 and 1935 in the case of Desoto, and 1934 to 1937 for the Chryslers. There were really no problems in the body assembly, but they looked very unconventional at the time and didn't sell well.

Due to the popularity of the Traction Avant in the late 1930 many European manufacturers started developing unibody cars for the smaller models since they could be lighter than conventional construction. Less material, less cost. And after the war steel was hard to obtain.

The next American car with unibody construction was the Nash 600 in 1941. By 1950 all Nash cars were unibody construction. The same basic construction methods were used by Nash, and AMC through 1986 when they were bought by Chrysler. Through most of the 1950s they had problems with rust but by the early 1960s they had come up with rust proofing method that made it less of a problem. AMC with the Jeep brand was also the first American manufacturer with a unibody pickup, the Comanche.

Chrysler started developing unibody construction in 1954, and many Chrysler cars had an abbreviated frame by 1957 and outside of certain models by 1960 most Mopars were unibody.


In 1960 GM and Ford also started making unibody cars with the new compacts although they both made Unibodies in Europe and other countries long before that. The 1960s were also when they started building several models of car off the same understructure. The BOP compacts all shared the same understructure even though they looked different. The Ford Falcon, Mustang, Cougar, Fairlane, Comet, and Meteor all shared the same platform for several years.

I'll post some more later

[WZ JUNK]

I wish they would go back.  

[idrivejunk]

I didn't know it went back that far. What technically defines a unibody? :?:   :?

[enjenjo]

A unit body would be defined as one that will support itself without a seperate frame.

As time passed there were many innovations in unibody construction. One of the first was the use of a subframe to hold the front suspension and engine/transmission as a unit that could be installed in the unibody at time of assembly GM used this in the Nova and Camaro in 1967. It was also used in the 1966 Riviera and Toronado even though one was rear wheel drive and the other was front wheel drive. Another was moving the front rails to the top of a strengthened cowl and A pillar, using them to hold the top of a Macpherson strut and attaching the lower suspension to the engine cradle. in a collision this directed the force under the passenger compartment making the passengers safer

The use of a rocker panel with a substantial structure connected to the front and rear frames with a torque box allowed the floor to be dropped to the bottom of the rocker, lowering the floors several inches, which made it possible to drop the roof and door tops a similar amount. making the car lower and sleeker without sacrificing interior room. Something difficult to do with a frame. A bad example of this is the early Thunderbirds where you set more on the car than in the car, since they were using a more or less standard passenger car frame.

In about 1978 with government pressure on increasing CAFE standards the domestic manufacturers worked hard to remove weight from new cars to increase fuel efficiency. Weight was removed every place they could find to do it without sacrificing safety. One of the ways to do this was unibody construction. Ford developed the Fox platform that was used initially on the Fairmont/Zephyr. The next year the Fox platform was used on the Mustang to replace the Pinto platform it was being built on as it was being phased out. Over the next several years the LTDII, , Capri, Cougar, and Thunderbird were added to the Fox platform as well as a modified version that became the Taurus/Sable as a front wheel drive. Gm came out with the new X body that was used across all divisions, even Cadillac., and as a stretched version, the J body, was sold as an intermediate sized car by all divisions except Cadillac.

Meanwhile in the US, and other parts of the world, there were many variations of unibody construction. Jaguar for instance on the XJ models used a unibody with both front and rear suspensions bolted on as subframe assemblies. Some high performance car use what is called a backbone frame down the center of the car with torque boxes and rigid rocker sills supporting the outside of the body. There is also the Monocoque construction where the skin of the car is stressed and becomes part of the supporting frame.

Unibody construction depends on making many shapes and welding them together in such a way that they support each other. So if you are modifying a unit body structure you need to replace any element you remove with one that is at least as strong, and braced by other elements to preserve the integrity of the body.

[enjenjo]

There is a serious mistake in the first part of this post that I didn't catch until rereading today. In my defense I got my wrong information from Wikipedia, but I knew better. See if you can find it.

[kb426]

How about DESOTO airflow?

[idrivejunk]

Reading retention is not my strong suit.    I can barely retain my writings. Didn't spot a conflict. :oops:  

The 3 Rs according to Gabby are Riding, Roping, and Raising a Ruckus. One outta three ain't bad. Wait, thats four. :?

I didn't know that about the T birds, but do remember Suzanne Somers looking like she was sitting on an encyclopedia to reach the pedals.

[enjenjo]

How about DESOTO airflow?

Yes, that is a mistake, but not the one I was looking for. I also knew better on that one, after all I build a 34 DESOTO Airflow.

[jaybee]

Great information and thanks! Obviously this is a concept that's been under development for a long time, and it's gotten a lot better with time. Cutting up a unibody without knowing what the parts do can lead to serious structural impairment.

[enjenjo]

Here's the mistake I did catch  

AMC with the Jeep brand was also the first American manufacturer with a unibody pickup, the Comanche

There was another one before this in 1960

[GPster]

Would a Volkswagon beetle be considered unibody? If so there are probably some of it's predesessors that fall into that category and maybe the VW van with a pickup bed. GPster

[jaybee]

Here's the mistake I did catch  

AMC with the Jeep brand was also the first American manufacturer with a unibody pickup, the Comanche

There was another one before this in 1960

Oh yes, so true!

The Ford unibody pickup!  https://www.cjponyparts.com/pub/media/images/resource-center/articles/headers/unibody-pickup-header.jpg

[enjenjo]

No, that was not actually a unibody outside of advertising It had a full frame, the same one the other pickups that year used.

[GPster]

Here's the mistake I did catch  

AMC with the Jeep brand was also the first American manufacturer with a unibody pickup, the Comanche

There was another one before this in 1960

Corvair? GPster

[enjenjo]

Corvair? GPster

Yes. The Greenbriar. There were actually two that year. The second one was the Falcon Ranchero.