Having quickly established that most pairs of measurements were different, the next task was to check all measurements against those published. In the process, establish exactly what type of chassis I´d purchased.
The fact that measurements were different to those published would not be of major concern; as no suspension mounts were present. The fact that one side of the car had different measurements to its´ partner was.
The main chassis types include:
After much measuring, it was concluded that the chassis I had was a modified McSorley 442. However, the measuring process also showed that several measurements did not completely line up with the drawings.
The previous owner of this chassis had removed some of the original fabricators work and poorly tack welded numerous tubes crudely cut using a disc cutter. I instantly knew all of these tubes will end up on the scrap pile.
One tube was found to be placed 27mm different to its partner, several key tubes were never present, whilst others had been removed allowing the frame to twist and distort freely etc. To rectify the faults and install an IRS I would have 32 tubes to rectify, wishbones to fabricate and dozens of non-standard brackets cut and shape.
If I were to straighten this chassis, I would need to determine a new set of dimensions that were somewhere in between those published and those measured. What I had, would deserve the title McSorley 4+3.2+2, as it is only 3inches longer than standard.
Unfortunately, after a professional assessment of the chassis; on a jig; my findings plus many, many more were confirmed.
Do cars with this quality of workmanship make it onto public roads?
A lot of the measurements on this chassis were only 1mm or 1° different to those published. However, all these small errors added up to huge instantly visible errors.
All measurements should be referenced back to a single datum in three dimensions.
If you are undertaking a project such as this, a lot of additional calculations and trigonometry will be needed to gain the unpublished data required to gain any accuracy of build.
With lesson learned, the decision was made to start from a custom set of drawings, incoporating additional bracing. By using my own CAD drawings I could start building from a single datum point, with all measurements and angles taken in three dimensions.