In article ,
Capitol wrote:
Not quite true. The gears are in constant mesh, but the one operating is
selected by a clutch band within the gearbox.

Indeed. How else would you change gears with an epicyclic box?

Also, the torque converter
is a lossy liquid coupling which reduces the impact on the clutch bands
and the drive train when the ratio is changed.

But a TC isn't an essential with a conventional auto. Older designs used
fluid flywheels which had near zero 'slip' above a certain speed.

Of course, most modern autos reduce the engine power momentarily on a
change for reasons of smoothness.

The only common
constantly variable drives( other than electric/electronic) are the twin
pulley ones as pioneered in cars by DAF IIRC and now used in some stand
drills. In cars I understand that these latter have an unequalled
reputation for unreliability. I believe the Japanese may now have
engineered a viable unit, but it's not on my acceptable list for a few
years yet.

CVTs. And they do seem to be unreliable.

Audi use a twin layshaft twin clutch synchromesh box where the changes are
servo operated. By having adjacent gears on opposite layshafts it's
possible to have a full power change because as one clutch disengages, the
other takes up the load. Clever.

--
*OK, who stopped payment on my reality check?

Dave Plowman London SW
To e-mail, change noise into sound.