![PreWar Workshop]()
As most people in the hobby know, a large portion of the pre-war car enthusiasm is sourcing or repairing parts which have been worn out or destroyed in some other way.In this case, it’s a cast-iron cylinder head which has been repaired over and over again over the years. Last time, David Palmer of Cast Iron Welding Services Ltd did a fabulous repair on it, which lasted a while but at another spot it cracked again. It’s just tired after 90 years of service!
So now it’s time to cast a new one. Since I’m very familiar with additive manufacturing technologies, I decided to explore this possibility instead of traditional patternmaking for this part. This has the large advantage that any detail can be easily altered by choice, the dimension accuracy is much easier to control and the location of the core, which is a rather large one in this casting with little support, can be controlled very well. This gives uniform wall thicknesses overall, which the original casting didn’t have.
First a model needs to be made of this head. This is done by 3d scanning it completely, and then working from there in a CAD program to add every dimension and add wall thicknesses etc. With the 3D scanning process, every detail is caught and it gives a very accurate model.
Simultaneously, in this process the machined version is being made, from which the machining afterwards can be done much easier on a CNC machine, since there is already a machined 3D model for the machine to work with.
After the scan, the mold is being made from this in a CAD program. On the computer, all the vent holes, sprues and risers and the casting position are being added to the model, and a complete mold is being made digitally. The biggest advantage of this is that you need no draft angles at all, which makes mold design and core design much easier.
As a final stage, the completely digital mold is being 3d printed in casting sand, and when this print is done, it’s cleaned up and cast-iron can be cast straight into it.
This will be a 2-part article on this cylinder head. After a few weeks when I have the completed castings, I will give you an update. For now, please enjoy the photos of the scanning process! And if you have any parts that would need casting like this or if you need one of these Alvis FWD heads, please contact me for any questions at workshop@prewarcar.com
The photo album can be found here: https://goo.gl/photos/Puc28VNfHE55mSzT8
Article by Jos van Genugten
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