Why the reverse speedo was used? Anybody know the history or reason?

[Randall Thomas]

The history of the legendary Smith reverse rotation speedometer installed in the original Cobras has spawned a range of explanations, some near mythical in nature. In an attempt to find out the real answer for an article for the Superformance Owners Association technical library back in 2004, for several months I sought out the real answer through many phone calls and email transactions to anyone that might have lived and worked at the Smiths factory back in the day, and finally received the final answer from the original Smith's employees in Europe.

ANSWERS: Phone interview with Neal Meakin and Ian John of Caerbont Automotive
Instruments Ltd, on 12/7/2004
QUESTIONS: By Randall Thomas
Caerbont Automotive Instruments Ltd
Abercraf, Swansea SA9 1SH
Tel +44 (01639) 732216 Fax +44 (01639) 732201

This is what they had to say...

"...We have pursued a number of ex (retired) SMITHS employees to gain benefit of their knowledge." and they go on to say... "When the car [Cobra] was being designed, the engineers realised that the cable drive from the gearbox to the speedometer was anticlockwise rotation, instead of the more usual clockwise. The normal procedure for an anticlock drive was to fit a reversing gearbox on the rear of the speedo to convert the rotation to drive a conventional clockwise speedo. Between the Cobra engineers and Smiths Industries, it was decided to offer an anticlock speedo as a feature, and obviously cost reduce the speedo installation by not having a cable drive gearbox. None of the Smiths guys from that time are around here these days, so this summary is an educated guess at what happened at the time. Our part number originally fitted to AC Cobra was SN5346-00, first made at the end of 1965. This speedo was updated by us in Nov 1995, we still manufacture it as part no. SN5346-02. Also recently we've developed a full range of Cobra Instruments with black print on white dials."


Randall