Friday, 14 December 2007

2008 Wish list part 2

No Gears

With the end of the year rapidly approaching you can be sure that lots of retrospective views of 2007 are being readied for publication. Rather than look back (which I will do) I would rather look forward and think about some of the cars I’d like to drive in the next year.

Once upon a time I owned a Ford Granada with an old-fashioned 3-speed automatic, which worked well but could have used another ratio. At the other extreme I once borrowed a Land Rover Defender which had ten possible gear ratios by combining a 5 speed gearbox with a low-ratio transfer box. On the road such low gearing was no use but on the whole you can never have too many gears. The greater number of gears the easier it is to keep the engine working either at speeds that offer the best mix of performance and economy (or the best of either if you prefer).

There comes a point where increasing the number of fixed gear ratios becomes impractical. Some Mercedes have 7-speed autos (and they seem to work well) while Lexus have an 8-speed transmission in the LS-series but how far can this strategy go? There must come a point where either the Van-Doorne or Torotrak transmissions, with steplessly variable gear ratios between fixed limits, become a smarter choice.

The logic behind such transmissions is persuasive, the engine turns at a steady speed and the transmission adjusts the ratio as the car accelerates. Eventually the transmission finds a point of equilibrium where the power supplied by the engine is matched by the power necessary to maintain a steady speed. At anything less than top speed the transmission will adjust so that the engine is turning as slowly as possible in order to maintain a steady cruising speed. Steady speeds are not really what I am interested in; I want to know how the transmissions cope with transitions, from cruising speed to acceleration, stopping and starting. A transmission without fixed ratio steps also promises to be an interesting aural experience; it is the one thing that nearly everyone dislikes about stepless transmissions and I want to see how I feel about it.

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