An embarrassing story: Why the Isabella is especially safe.
May none of us ever have an accident, but it´s nonetheless comforting to know: from all reports, the Borgward Isabella is one of the safest cars of its era in front-end collisions. As an example, Ray Harrison (founder of the Borgward Car Club of Austrlia Inc.) once rescued a motor from the wreck of an Isabella that was written off in a head-on collision. The driver and his wife and family had survived without injury. 
Christian Steiger, in his book „Fräulein Wunder“ quotes a case of an Isabella owner whose car was destroyed in a head-on collision with a truck in 1965. The distraught owner ordered a replacement from Wolfgang Schätzle, a mechanic who built some 140 Isabellas from left-over or specially manufactured parts until 1967. All too early, the Isabella owner wrote, had he been separated from that wonderful vehicle – the odometer reading had been only 261 220 km. The significant thing was that, after a head-on collision with a truck, the owner´s biggest concern was to get a new Isabella. 
An even more vivid testimony comes from British racing-driver Bill Blydenstein, who wrote of an accident he had at the British Silverstone racing circuit in July 1961. „At Stowe Corner on the third lap the three 1600 cc class leaders, Peter Harper in a Sunbeam Rapier, myself in Borgward Isabella and Alan Hutcheson in the Riley all crashed heavily. I was lucky to step out of that car in one piece. The Borgward Isabella would pass the present day crash test with flying colours. Its deformable structure saved my life and I was able to rebuild it from the front bulkhead forwards.“ A photo shows the car, its cabin intact and the front end virtually squashed – a classic case of excellent, life-saving design in practice.
The Isabella, deservedly, receives much praise as one of the world´s best engineered automobiles of its era. German car companies had been at the forefront of crash testing and vehicle safety (DKW was crash testing in the nineteen thirties), but unfortunately we have to admit that the Isabella´s superb controlled-crumple front end was not meant to be that way.   Carl Borgward had an opinion on vehicle safety (as he did on everything else!): „I build my autos for people to drive, not for them to have accidents in!“ (Ouch!) Despite this, he was fully responsible for the outstanding crash safety of the Isabella. How come? Read on!
An informative Borgward book has been written by a former Borgward experimental engineer, Heinrich Völker („Der Weg zur BORGWARD Isabella – Unbekanntes aus der Versuchsabteilung“, Edition B6, Süsted, 2000) The title translates to „The way to the Borgward Isabella – unknown (information) from the experimental section“, and it tells the story of the Isabella´s safe construction.
The Isabella was Borgward´s first attempt at a unit-construction body. The previous model, the Hansa 1500/1800 had had a stable central-tube chassis, and a central tube was accordingly made part of the Isabella structure (the propellor shaft runs through it), giving the central cabin exceptional strength. This feature had been insisted on by Dr. Borgward himself. The front and rear suspensions were mounted on bolt-on sub-frames, ensuring that the suspension (and engine) mounting was strong and stable, and also insulating the body from road shocks. Similar sub-frames were introduced as a major advance by manufacturers in other countries twenty or more years later.
To ensure that the new body was at least as strong as those of competitive manufacturers, the body of an Opel Olympia was tested by firmly mounting it where the rear axle was mounted, and then subjected to loads by a girder mounted to where the front axle would be mounted. Deformation of the body was recorded for various loadings, then a prototype body shell of the Isabella was subjected to the same test. Disaster! The Borgward´s firewall, or cowl, crinkled, the A-pillars (beside the windscreen) deformed by up to 3 cm under moderate loading. There was simply no suitable structure to transfer the forces from the sub-frame to the central tube. Part of the problem was also the vertical firewall of the Isabella (there is no sloping footrest, as in other cars), which was also a feature that Dr. Borgward had insisted on, but which was weaker than the normal angled variety. 
Heinrich Völker writes that he tried to convince Dr. Borgward that a re-design was necessary, but he got an angry reaction. A re-design was not possible, the tooling had already been ordered and much of it delivered! There was no choice but to reinforce the body as best as was possible with steel presings welded to critical areas. You can see some of them on the inner fender panels, beside the motor. If ever you see an Isabella from which the front fenders have been unbolted, you will see the rest of them. They made the body strong enough for normal use, but the front end was still relatively weak, so that it crumpled readily in a crash. Modern cars have exactly the same feature by design, but the Isabella has it by happy accident!
This same weakness, incidentally, made the re-engineering of the body for the Cabrio (convertible) version difficult and costly, and is a big part of the reason why the convertibles built by the body firm of Carl Deutsch were extremely expensive. Steiger write of the Cabrio: Damals zu teuer, heute unbezahlbar – back then too expensive, today beyond anyone´s reach!
Written by Marius Venz Copyright © 2010 Borgward Car Club of Australia Inc. May be printed by other not-for-profit car clubs provided full credit is given.