SOLIDWORKS and the Tucker Torpedo Part 3
This is part three of a blog series covering how a group of car and engineering enthusiasts are bringing the Tucker Torpedo concept car to life. If you haven’t read the other posts in the series, here is Part 1 and Part 2.
The entirety of this blog is dedicated to the fabrication of the Torpedo’s body. This is a huge undertaking and felt that it was worth writing an entire blog post on the topic. In order to understand what it takes to hand make a car body, let’s go back in time 100 years to when coachbuilders were the norm in the manufacture of automobiles.
Coachbuilders were prolific in the early days of automobile manufacturing. In those days, you would order a rolling chassis from a manufacturer and then contact a coachbuilder who would build a personalized body to fit the rolling chassis. The coachbuilder would hire highly-skilled craftsmen, such as metal workers and carpenters, in order to build a body. Back in these days, car makers like Duesenberg, Cadillac, Rolls-Royce, and Delahaye all used coachbuilders. You probably remember seeing the Cadillac’s “Body by Fisher” emblem on the inside rocker panel doorsill. Fisher was GM’s coachbuilder for many decades.
In fact the town I live in, Fleetwood, PA, is noted for the Fleetwood Metal Body Company. The company is long gone, but the building is still in downtown Fleetwood. The Fleetwood name was used by Cadillac for decades adorning several series of their cars. Fleetwood was purchased by Fisher in 1925 and integrated into General Motors in 1931.
This is a 1929 Cadillac 341-B Imperial with a body by Fleetwood.
This is a 1999 Cadillac Fleetwood Limited.
As automobile manufacturing evolved into mass production, coachbuilders were only used on specialty cars and on-off prototypes. Typically, car bodies are mass produced using very large metal presses such as these:
Once all the pieces are formed, they are welded together using robots as seen here:
There can be more than 5,000 individual spot welds used for a typical modern car body. As manufacturing processes change who knows- maybe someday a car body will be printed using additive machining processes instead of stamping the metal and welding it together!
In the case of the Torpedo, we have to go back in time and use manufacturing techniques relied upon by the old coachbuilders in order to fabricate the body. To get the right design means using an English Wheel to form the body. I touched on the English Wheel in the first blog post and will go into some detail here on what it is, how it’s used, and how we utilize SOLIDWORKS to help get it right.
The English Wheel that Rob Ida uses is a MetalAce as seen here:
The English Wheel weighs about 2,000 pounds and can handle very large pieces of aluminum or steel, which is necessary if you’re making car body panels. The main components are the “C” shaped frame, the smaller anvil wheel, and the larger rolling wheel. Pressure between the two wheels is controlled by turning the handle below the anvil wheel. Increasing the pressure determines the degree to which the metal will stretch. A piece of metal is “wheeled” between the anvil and rolling wheels and is stretched thus creating a convex surface over the anvil wheel. It takes many passes through the wheels in order to shape the metal to the correct curvature.
Now in order to know if the metal has been shaped correctly the piece is laid on a wooded “buck”. The buck, as shown below, is really the first step in creating a car body. It was created from the scanned data from the plaster model as shown in this image:
The buck represents the overall shape of the body. Each piece is formed on the wheel then laid on the buck. This process is repeated many, many times in order to know if the piece has been formed correctly. It may take several days to form a single panel correctly. To complete this part of the body correctly you have to have patience. Rushing the process will cause a misshapen part and if that happens, you start over again.
According to Rob Ida, “Hand making a metal body is a very labor intensive undertaking. Every step is a time consuming matter, so accuracy is paramount. If you are chasing a shape that’s incorrect, you can literally waste days of effort before you can see the surface is incorrect. By using SOLIDWORKS, we can trim down the wasted wheel strokes and hammer blows resulting in a more efficient metal shaping process. There are many instances in which having a SOLIDWORKS model has made us realize a problem before we got to metal. I can’t image building the Tucker Torpedo without it.”
The buck for the Torpedo above and fitted with parts of the body below:
Using an English Wheel is no trivial matter. It takes skill and what Rob calls speaking the “language of metal”. Knowing how to “talk” to the metal will let it know how you want to shape it. The trickiest part is knowing where to “wheel” the metal so the desired shape is produced. It also takes some artistic talent. It’s tough enough producing accurate body panels, it’s another level of craftsmanship producing identical left and right hand panels that are accurately symmetrical. You don’t want to look at the front or rear of the car and see differences in the shape of the panels. No amount of paint will hide those problems.
Rob adds, “When it comes to working out things like door jambs, hinges and hardware, Tucker didn’t leave us a blueprint. The best choice in this case is to take our SOLIDWORKS 3D model and create the parts on screen. Then when it comes time to kit the components into the sheet metal skin, we reduce the chances of going back to make physical changes on a metal body. The time savings in that process is amazing, not to mention the increase in quality.”
As the work continues on the Torpedo body I’ll document it here. There is a large amount of work to be done before we can get to the next major step; marrying the body to the chassis. A supporting structure for the body will need to be designed and how it will integrate into the chassis to provide structural rigidity.
In the next blog we’ll focus on the chassis and how the fabrication is progressing.
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