McLaren wrote:
Anyway, a cvt is a "Continuously VARIABLE Gearbox" not a "Continuous DRIVE Gearbox" so even if they could have seamless shifts (assuming there is no 300 ms rule) it should be legal.
With a continuous drive you are necessarily having also a continuous variation of the gear ratio, being it for the whole time or just during the engine rpm variation while passing between two different, fixed, gear ratios. Speed is almost constant in that situation so if the power is transmitted also during the engine rpm drop (that is obviously continuous and requires a finite time) caused by the upshift, the gear ratio in that interval must be continuously varying, how it’s achieved isn’t important (for example via clutch slippage), in that situation you are mimicking a CVT.
Also at the car’s launch you are de facto using a CVT, via the clutch slippage, that’s obviously allowed but there’s a set of rules governing the launch, to do the same thing during the shifting is a different matter. It’s probably the same thing that makes non legal the twin clutch gearbox. But we can’t be sure, that’s one of the many obscure (for us) parts of the rules, you’ll find little on the document you can download from the FIA website because that one isn’t complete, it doesn’t include the several clarifications that are made during the year(s) to give more precise indications about many different details.
As for the rule on the 300 ms, it wasn’t a time required for the shift, it was the maximum time allowed for the automatic shift (and clutch control). The discussion about it was in 2001 when people suspected that Ferrari was already using the TC before it was made legal in Spain, and AFAIK, it resulted to be just the clutch control during the shift, the actual shift time was a lot shorter than the maximum time allowed (I don’t remember if it was exactly 300 ms though) so for the remaining part it was all about automatic clutch control, the effect was basically a TC but in a legal way. If now things are the same or not I don’t know, as I said these details are mainly a matter of clarifications and discussions between FIA and the teams’ technical directors.
On the FIA rules we can discuss about bodywork dimensions and general things because these are pretty clear, but when the discussion is about for example transmission system or torque transfer in the differential or anything involving an electronic control, things are lot more intricate and only FIA and teams know all the details about what is allowed and what is not.
