Retropower Spotlight – Gauge Against The Machine
One of the things which helps Retropower builds stand apart from others is a keen eye for detail, and while this often manifests itself in lashings of custom work and one-off engineering, it’s also present in our willingness to foreground exquisite examples of standard, factory fitted equipment. Case in point, the speedo and tachometer of the Alfa Romeo GT Junior, a well known Retropower car that’s come back to us for a clutch upgrade.
There’s a lot to love about the GT Junior in standard fettle, the car littered with clever Italian styling touches from an era when Alfa really did know what they were doing – at least when it came to artistic flair (the less said about its anti-corrosion nous, the better). Its OEM Jaeger gauges are a good example of this, and from the very beginning we understood that there really was nothing to be gained from messing about with them, much less replacing both the speedo and tacho with something different entirely.
Splicing old school styling with modern technology has proved to be both challenging and rewarding
The tacho is actually of a cable drive design from the factory and takes its readings from the output shaft of the engine, while the speedo originally drew data from another cable drive, this one connected to the standard Alfa gearbox. Of course neither the factory engine or transmission are still on the car having been replaced by a Millington Diamond and Sadev six-speed sequential respectively, which in turn presented us with something of a poser – how best to engineer dials able to draw & displays accurate readings while retaining the overall appearance penned by Alfa all those decades ago.
The solution was to purchase a Stack stepper motor tacho with the same diameter as the Jaeger gauge, before machining its frontal section in a lathe. The ‘innards’ of the Stack unit were then combined with the bezel, face, glass and needle from the original, creating a ‘hybrid’ tacho with a full suite of modern functions (including a lap time facility and the ability to record max RPM) yet the appearance of the late ’60s original.
There’s a lot to be said for the OEM Jaeger gauges, especially now they’ve been fitted with more modern hardware
It was a similar story with the speedo, albeit with a stepper motor drive from Speedhut in the USA. This works in conjunction with a pulsed electronic input which in turn drives a cable. This functions with the integrated GPS receiver, a way for the Speedhut unit to define how fast it should spin the cable and thus give an accurate reading – and all without there being a physical cable drive between gauge and drivetrain. It’s the ultimate example of the advantages of associated with blending old school design with modern tech.