Introduction into the very first application of a computer assisted design in the automotive construction, at the beginning of the Sixties.

Part I:

From 1957 on, Dr. Zimmer at Daimler Benz calculated spatial frames according to the passenger car bodies built in the Sindelfingen plant. This was done with the old calculation methods, which included slide rules, electrical and manual calculators. These same methods were also commonly used in the machine construction as well as in the building engineering. They were state of the art back then.

Dr. Zimmer worked previously for many years as head assistant at the professorship for the “Aircraft static at the Technical Academy” in Dresden. For the implementation of his then new calculation method, Dr. Zimmer used his gained knowledge which he acquired at the TA in Dresden.

Dr. Zimmer succeeded the quantum leap at first with the chance of being aided by a computer: he succeeded to store the so called bar elements, according to the geometrical conditions to be able to store all six possible components (4 bending moments, the thrust and the torsion moment). An automatic running computer programme could capture bar elements as well as area elements, shell elements and spatial elements through their configuration data and their cross section data.

This aforementioned practice for discs, panels, shells and spatial elements were extracted from the dissertation (1963) of Dr. S. Spierig. With that, the basic element existence was expanded for the calculation and so automatically improved closer to reality. A further quantum leap from Dr. Zimmer at the time was the controlling 01 through 24 for any boundary and special conditions, namely the matrix control system. This method is still in use today.

Thanks to Dr. Dirschmid (1964), the matrix became further resolvable. When surfacing of unwanted endless small movements was discovered, the procedure of the weight-rigidity method after design changes was used, as it was used back then. The design changing work was proven with success.

Already at the beginning of the Sixties (1963), Dr. Zimmers frame calculation programme was written, tested and ready to be used. This programme was labelled by him with the identification “RB”. To increase the processing time on the computer, the programming language “Assembler” was used. At that time the calculation team of Dr. Zimmer has come to know, that Hrennikoff in 1940 compiled a Dissertation-Articulated Framework in the USA (there was no Internet at that time).

For this method, the name “FEM” was first suggested in 1960 by the Americans Martin, Topp and Clough. It took yet over 10 years, until this name found worldwide deployment.

Prof. R.J. Argyris known for civil engineering and aero elasticity, created at the beginning of the Sixties at the Technical Academies in Stuttgart and London FEM programmes for area and spatial elements, but not for bar elements like in the RB programme. He called this programme ASKA and published his workings in the Deutsche Gesellschaft für Flugwissenschaften e.V. (German Society for Flight Sciences) Volume IV from 1965. Only much later was ASKA expanded to include the bar programme from Dr. Zimmer and was then called PERMAS.

In 1963 became Prof. Peter Groth Dr. Zimmer’s first co-worker at Daimler-Benz.

The RB programme had confirmed after calculating for the first time after 10 hours the frame chassis of the W 100 (MB 600) measurement results were so precise, that the Test Department was assuming data theft (ATZ 5/2000).

Prof. Groth had optimised and programmed the equation solving. Also he had the special gift to cleverly determine the xyz-basic coordinates, to at any time adapt to real mathematical tasks. Prof. Groth and Dr. Zimmer then developed from the RB programme the follow up programme ESEM-Elastostatic Element Method. Out of the dissertation from Dr. Zimmer in the chapter “Large Deformations” was the programme for axial calculation already described.

In later years, Prof. Groth offered further follow-up programmes, like the TPNOLI (non-linear axial calculation programme calculated on the large Maybach 57/M62) as well as the TPS 10 and TP 2000. Referring to this, special mention must be made, that vibration calculations in the technical mechanics were simulated on the computer even before the order to build a product was made. The same principle applied to the accident research, to worry about optimal passenger protection after a car crash.

Today, the entry programmes run automatically with the experience of national and international feedback. The programmes are being supported through the knowledge from the pioneer days as well as the demands from a more and more complex technology of today.

The demands of high performance computers of today are constantly being increased and met! The software used today has not substantially changed since the Sixties. But there are vast numbers of storage capacities to be handled, all the way to pre-verbalised result-reports, which the programmes of today are able to handle. In contrast, today’s hardware has changed fundamentally and dramatically and is being further developed. To illustrate this, one only has to compare storage from then and now. Then: an unimaginable high pile of punched cards, along with the keypunch machines, magnetic tapes, plotters, verifiers, magnetic pencils and many more.

Today, some car computers possess such a high storage capacity, that they could calculate a moon landing including the journey to and from. Instead of using the unhandy magnetic pencils there are remote controlled “mice” today.

At that time in the calculation department, a Mr. Biesinger was working on self inflating airbags, which he tested and developed to the start of production. The first airbag could only be deployed using rocket ignition. All other previous attempts failed miserably.

ESEM also was proven in a bus. Mr. Biesinger and a colleague assessed that transmission noises develop from tooth flank deformations. By rounding same the result was a less noisy transmission and a considerable longer mileage. The durability from a drivetrain was first tested in a Mercedes 600. With an on-road test was determined, that the computer designed drivetrain had a 10 times higher mileage. Also, a variety of different bus chassis were calculated for their rigidity, using ESAM.

Dr. Zimmer, in 1969 at the Technical University in Clausthal, wrote his dissertation on the “Digital procedure for the economical solution of rigidity problems and other requirements in the elasticity teachings”.

Part II:

With the frame calculation programme RB and the historical IBM computer 1620 was from 1963 until 1965 the first chassis calculations accomplished, with mixed basic elements from the bar elements and the spatial elements. This was done on an Auto-Union F102 and soon after on the first Audi 100, at a time when the Auto-Union still belonged to Daimler-Benz (until 1964).

The Audi 100 was the big moment for Dr. Dirschmid, who constructed the weight-rigidity according to the calculation methods of the RB programme.

In the spring of 1969, Dr. Zimmer and his calculation department were assigned to calculate the Wankel sports car C111 (W101), using computer technology and the ESAM development programme.

They started with the calculations at a point in time, where there were no technical drawings, only working with existing guidelines from management. The basic idea for this vehicle: it was supposed to have gull wing doors, a roll-over bar, as well as a new drive with a three or four disc Wankel as a mid engine. All of this being calculated using the computer and the ESEM programme!

Out of this, a scientific and commercial film for Daimler-Benz and IBM was being made. Daimler wanted to document their advance in technology and IBM wanted to increase the sale of their computers. Both realised their goal.

The scientific film with the title “The car that came out of the computer” with Dr. Zimmer and the C111 was shown to about 200 engineers in Cannes. The film won first price in the category “Industrial film”.

When visitors come to Sindelfingen to pick up their new car, they can see a current commercial film. In it they show for a few seconds the workplace from Prof. Groth, who was shown in the 1969 film!

At Daimler-Benz headquarter, the transfer from the RB programme into the ESEM programme around the team of Dr. Zimmer was being constantly improved and optimised. This led to a reliable, error free and practical programme.

As a result of these calculations a large number of vehicles in series were created. They dominated the market for many years. This was the beginning of long delivery times in the history of Daimler-Benz. Many customers dreaded the thought of having to wait very long. On the other hand, employee’s cars which were less than 1 year old, were selling with a small profit to the delight of their owners. The competition viewed the vehicles with the star with envy and amazement.

In the initial stage, the cars most affected were the Pagoden-SL W113 E 28, the W115, the follow up model W116, all the way up to the flagship 6.9 litre of the S-Class. This vehicle was awarded as one of the best and most innovative cars of the world! Further cars hit the market, such as the R107. A sports car that was writing history because it was without competition for over 18 years as far as technology, rigidity, driving dynamics (calculated front and rear axels) and passenger protection was concerned. The improved safety systems for the A-column and the improved crash deformations were developed through extensive impact tests. This technique was later simulated on the screen with CAD programmes (TPS10) and was accomplished more cost-efficient.

Part III:

Later, the programme for assembly of one, two and three dimensional

FE-Methodology was being put in place for the following technical mechanics: Deformation, stress, vibrations, optimisation, shape-changing work per weight, also graphical, spring supports with and without freewheel, inclined bending – all of that could be calculated with the aid of this programme. At the same time, the boundary conditions were incredibly diversified. All of this happened already in the years 1963 through 1969.

The term Finite-Element-Method (FEM) can now simply be applied to the large elements. In 1960 for the first time, R.W. Clough’s suggested phraseology is being used everywhere since the Seventies.

With the FEM programme, nearly all activities of technology can be simulated on the computer. At the same time any body (gaseous, liquid or solid) can be fragmented in preferably small elements of simple form (bar, triangle, square, tetrahedron, pentahedron or hexahedron), which at their corner points (“Knots”) are firmly jointed. Small elements are important, because that approximately by linear equation formulated behaviour of the elements is only valid for the infinite smallest element, yet the calculation time requires the finite large elements. The approximation to reality will be so much the better, the smaller the individual elements are.

(Quotation from Prof. Groth from the “Bosch Handbook 2006)

For the sake of completeness, I would like to mention the old master Leonardo da Vinci, who in the middle ages discovered the FE-Method (constructively) with which he calculated an archway!”

The application of the FEM programme in practice started in the early Sixties, first in the air- and space travel industry and soon after in the vehicle construction. The methodology is also based on the work at today’s DaimlerChrysler AG in Stuttgart, who installed the self-developed FEM programme ESEM, long before the computer-assisted construction (CAD) started in the Eighties.

Meanwhile, this method is being used in all areas of technology, including weather forecasting and medical technology. In vehicle construction, from small parts to motor and chassis and all the way to the calculation of the auto body including crash behaviour. Also other areas of application are in the shipbuilding, aircraft construction, in the nano technology, in the entire machine construction, in the building engineering and also in high construction and bridge building.

Increasingly it is to observe, that more and more FEM-Professorships become firmly established at universities, technical colleges and in particular at the Fraunhofer institute.

The best FEM programmes were made available to help the world’s largest passenger aircraft, the Airbus A380, to be able to take off. Same is true for the construction of large new shipbuilding like container ships, tanker ships, passenger ships and large motor construction worldwide.

Until today, in all programmes are parts of Dr. Zimmer’s early developments.

I take the liberty of adding a personal closing to this article:

“I have totally under-estimated the impact of my work at the beginning of the Sixties. All the more I am pleased today, that I was able as a pioneer to contribute to this development. The way I see it, the time was ripe for technological changes, to view our working world in a new way and to be part of the change. The software and the then simple hardware motivated scientists all over the globe. For the good of all people they and I wanted to make technology more comprehensible and also make the world a little safer.”

Yours sincerely,

Dr. Alfred Zimmer Winnenden, February 24th 2007

Literature information:

„Elementmethode der Elastostatik“ (Element method of the elasto-static) including a ready to use calculation programme on the ESEM basis.

from A. Zimmer/P. Groth

published in 1970 by the Oldenbourg Verlag, Munich and Vienna

festschrift for the 80th birthday of Dr. Alfred Zimmer.

magazine ATZ 5/2000