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Aurelia cams – revised

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. The purpose of that work was:

1) to collect in one place all available data on Aurelia cams

2) to publish rare and unknown factory drawings

3) to determine which cams Lancia used in what cars, and why

There was one other purpose as well – to explore the Lancia mystique in yet another way. – to understand the complex interplay between Lancia’s prowess in making a product and our enjoyment in using it. A look at these cams gives a glimpse inside the heart of the Aurelia motor. Far from marketing, this is a portal into the essence of Lancia engineering.

As a non-engineer (I’m an architect) it was intriguing to try and understand what Lancia did and how they did it. The design of the Aurelia cams showed that even within the limits of their manufacturing capability, Lancia again fiddled with the design of the cams (a most precise element) in a creative fashion.

Cam design is essentially a very conservative discipline. Ferrari kept the same lobe design for their cams for decades. Alfa Romeo took a different approach and their  motors are designed to benefit from modifications to their breathing, and onde they figured this out, they made progressively hotter cams for their cars through the late 1950’s and 1960’s. But Lancia’s work is earlier (Aurelia cams were modified through the early 1950’s) and thus they fall in-between these two approaches.

Nowadays, we look at cams to see how they actuate the valve – and its how the valve works that is important. But then, matters were more limited: making the valve do what was necessary was part of the puzzle – making the cam lobe itself was another issue. There was no CNC controlled milling – designs were drawn, patterns made, machining followed. So the design of the Lancia cam lobe (the “tri-arc” lobe) had to be done in such a way that both the designer and the patternmaker could make it work. With use of simple geometries and very precise dimensions, cam lobes were made. This by itself was not unique and was followed by other cam makers at the time. What was of interest at Lancia was:

a)    they maintained a very high level of in-house design control over the cam (no surprise!)

b)    they modified their cams for different models – to address both performance and wear. These changes were done using a range of techniques – including changine size, timing and lobe profile. Not just one item was changed.

c)    they utilized their in-house manufacturing abilities to make cams in very small production runs. The B24 Spider America for example has its own unique cam.

Of course, unravelling this was a journey in itself. Information came from many different sources and needed deciphering.  So too some author education was needed.

In the end, I believe the mystery of Aurelia cams has now been unravelled. Between testing existing camshafts (some in better shape than others) and use of Lancia data sheets, drawings and parts books, the story now comes to a conclusion.

Lancia made 5 different cams for Aurelias. They each vary, but they do so differently.

GG

12.6.06

below: here is a part of the puzzle – This factory “summary drawing” shows 4 different lobes, which were used in five different camshafts.  

Written by Geoff

December 6, 2006 at 12:00 pm

Posted in Aurelia

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