12/7/04 - Here is the story behind the Smiths reverse rotation speedometer used in the original Cobras

History of the Legendary Smith's  Reverse Rotation Cobra Speedometer
by Randall Thomas - 12/07/04   *** EXCLUSIVE ****      copyright © 2004 Superformance.Org

The history of the legendary Smiths reverse rotation speedometer that was installed in the original Cobras has spawned a range of wide ranging explanations over the decades where some have reached near mythical proportions. Some of these theories include but are certainly not limited to the thought that the reverse sweep of the needle reduced confusion between the Tach movement and the Speedometer movement during racing. Of course, race cars rarely if ever have speedometers in them. Another popular theory was that with the sweep being reversed when used in the street cars, the driver could more easily see the needle movement from 0 to 60 mph due to his hand on the steering wheel otherwise being in the way of a normal sweep speedometer. Now, if they really thought this was a problem and wanted the driver to see the speedometer, it would have been moved up front where the tach is right over the steering wheel. And the list of theories and guesses go on and on, ranging the gambit from the incredible, to the absurd.

For several months, Randall Thomas sought out the real answer through many phone calls and email transactions, and even checking into some of the old English nursing homes looking for surviving Smith's employees from the 1960's, was not at all out of the question. After months of searching and research, Randall found the final answer from the original Smith's employees in Europe on an otherwise quiet December morning.

A brief history of Smiths from then to today, Samuel Smith Junior began selling clocks and watches in London in 1871 and later began to manufacture automotive speedometers. The automotive instrumentation side was sold to Lucas in 1984 and later renamed as Caerbont Automotive Instruments Ltd (CAI).

After months and months of searching, here is the transcript of the phone interview with Neal Meakin and Ian John of Caerbont Automotive Instruments Ltd in Abercraf, Swansea, on December 7, 2004 conducted by Randall Thomas and recorded verbatim as it occurred.

"...We have pursued a number of ex (retired) SMITHS employees to gain benefit of their knowledge. 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..."

Neal and Ian were confident that the Smiths reversed sweep speedometer was actually the result of a Shelby inspired cost savings measure due to the odd rotational gearbox that was used at the time.

When asked, the legendary Peter Brock told me that "...this was usually the reason behind many of Carroll's decisions, so it sounds about right...".

Ironically what started out to be a cost savings decision back in the 60's by making the Smiths speedometer rotate in a reverse rotation to match the transmissions used then, this now requires replica owners to pay up to $180 extra to add a "reverser" unit which attaches to the back of the speedometer head that purposely reverses the cable direction of modern transmissions to make the original style reverse speedometer to be used in these newer cars for nostalgic sake.