Plugs and Steering

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Sir,

There are two small points in the September issue of your magazine which caught my eye and on which I should like to comment.

The first concerns the special sparking plug developed by Champion and used in the Ferrari fiat-12 engine. I hope I am not revealing too many company secrets but some ten years ago I was employed as an undergraduate physicist at GEC’s research centre in Wembley; one of the projects I was involved with was a study of a jet engine igniter [made by, I think, Lodge] with identical geometry to the spark plug under discussion. The idea behind the design was the same in both cases, to get more energy into the discharge; as you can imagine lighting cold paraffin, even as a vapour, requires quite a healthy spark.

This unconventional igniter had a specially treated alumina insulator with a semi-conducting surface which allowed the spark to “grow” across it and thus propagate at a lower voltage. This is important in aircraft as both the volume and the weight of the associated ignition system can be reduced. The lower voltage has another advantage at high altitudes, when if the engine “flamesout” it must be relit and thus the igniter fired. In reduced air pressure HT electricity leaks out of its cables and connectors with remarkable ease so any decrease in the voltage is extremely helpful.

One other thing, although racing improves the breed the original idea for this plug came from Germany in the last war. Although I cannot recall if the plugs were only used in piston aero engines or whether they were also installed in the Junkers Jumos which powered the Me 262 jet fighters. If it was the former then I am more than ever convinced that history goes in circles and there is nothing new under the sun!

The other point (at the risk of becoming long-winded) concerns C.R.’s criticism of the heavy steering of the Ford Capri Ghia. I suffered the same problem with my Mk. II Cortina GT which I lived with until I drove an earlier Cortina Lotus which was a revelation! This car was fitted with ball bearings at the top of the MacPherson struts instead of the later rubber bush which twists as the steering goes on lock. Fords claim these were an improvement as they help to damp out wheel shimmy. I think they are just cheaper and nastier, the ones on my car broke! I replaced them with the earlier type which however are designed for larger diameter struts so I machined up four stainless steel bushes to take up the difference. The steering is now much lighter and more precise and I’ve had no trouble with wheel shimmy!

Judging from the photograph on page 948 the Ghia has those rubber top mountings. Ford would do all their customers a service if they replaced them with the older variety and, if necessary, added an hydraulic steering damper. It must be cheaper (and nicer!) than power steering.

Rober E. L. Cox, B.Sc.

Kauterackerweg, W. Germany.