Learning to Drive

[Guest]

Thanks Nick!![]

Still not sure about 4) though - double declutching only serves to match engine and gearbox speed, however revs are matched reduces Syncromesh wear. Careful changing and planning can match these without the need for DD. Even a gentle hesitation when changing up will do this (if timed correctly), although achieving this changing down is, granted, more difficult. In essence unless you're trying to make rapid progress you can do so without DD'ing (although I often use it for changing down - complete with my laughable Heel and toe technique!)

Roy

 

[nfearn]

The point you make wrt DDC is largely right, although the action of reconnecting the engine and gearbox via the clutch in the middle of the DDC does ensure that the synchro is basically not used.

My experience is that a DDC change (up or down) requires less effort when moving the gearlever from the neutral position to your chosen gear, which argues to me that the synchro does a little bit of work even when you think you've got the revs matched. I suppose even at modest revs, say 3,000 at the flywheel, you've only got to be 60rpm or 2% out (i.e. you should have had 3,060 or 5,940 revs) for the synchro to have to reduce the speed of the engine-driven cog by 1 revolution per second, which takes a finite amount of time and effort on the synchro's part.

Vic Elford, in his Porsche High Performance Driving Book bemoans the fact that Porsche wouldn't remove the synchro from their boxes even though the changes, for a really top driver at least, would be quicker using DDC.

The planning aspect of DDC - it's a bit slower for most drivers and therefore forces you to think ahead - is probably the biggest advantage in day to day circumstances but I do think the wear advantage is present, though perhaps marginal in modern boxes. It's a useful technique to have in your armoury though.

regards
Nick

 

[Guest]

Nick,
They wouldn't know an engineer's bend... I've never found one in England, especially here in Isle of Man.... they follow the horse & cart.
In england, most roads follow the old roman roads - except the romans built true straight roads .... funny --- they didn't have or call them motorways.
A true engineer's bend has camber, postive on the outside, with constant radius.

 

[Guest]

except the romans built true straight roads

Except where they put kinks in them - which they did to solve problems, just like nowadays.

 

[nfearn]

Peter

That's interesting. I hadn't realised that the superelevation was a requirement for an engineer's bend, but that just goes to show that you do keep learning new things.

cheers
nick