G
Guest
Guest
John
| Regarding the auto V the manual, what is the torque converter
| for and why does the auto have one and not the manual box.
| I would also like to know why the Auto box has different
| fluid in it compared to the manual.
You can think of a torque converter as being like two propellers facing
one another inside a bath of stiff oil. One propeller is connected to
the engine and the other to the gearbox, and when the engine turns it
rotates its propeller, which rotates the oil, which in turn rotates the
propeller connected to the gearbox.
The advantage of the system is that any difference in speed between
engine and gearbox is taken up smoothly by the oil being stirred,
effectively achieving what slipping the clutch in a manual box does; the
disadvantage is that stirring things dissipates energy in them causing
lower efficiency (=3D higher fuel consumption) and also heating - which is
why a hard-working auto box needs an extra oil cooler.
It's called a "torque converter" because its real shape allows rotation
speed to be traded off for torque. In effect the engine can spin fast at
relatively low torque, and the gearbox can be driven slowly at higher
torque. This is why most auto-box LC users only need to use low range
very occasionally, whereas we manual box folk make rather more use of
it. Also why auto gearboxes tend to have fewer gear ratios than manual
boxes.
Torque conversion is good for starting and acceleration, but not so good
for cruising at constant speed, so in cars the actual shape is a
compromise between the ideal for torque conversion and the ideal for
simple transmission of rotation. There is also a "lock up" that
effectively forces both sides to rotate at the same speed.
| Are the gears different between the two or is there another reason.
Identical in concept, but different in layout. Autos tend to use
"planetary" gearboxes where a central "sun" wheel has "planet" wheels
spinning around it. The advantage of this system is that to change gear
all you have to do is to lock up or free the rotation of different
"planet" wheels, which can be achieved by a series of clutches.
This suits the automatic system since the clutches can be hydraulically
or electronically controlled, and no gear levers have to be stirred
around. The old Sturmey Archer 3 speed gears on bicycles work this way
- think how easy they are to use.
.=2E. Which about sums up the sum total of my knowledge about auto boxes!
Christopher Bell
____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses
| Regarding the auto V the manual, what is the torque converter
| for and why does the auto have one and not the manual box.
| I would also like to know why the Auto box has different
| fluid in it compared to the manual.
You can think of a torque converter as being like two propellers facing
one another inside a bath of stiff oil. One propeller is connected to
the engine and the other to the gearbox, and when the engine turns it
rotates its propeller, which rotates the oil, which in turn rotates the
propeller connected to the gearbox.
The advantage of the system is that any difference in speed between
engine and gearbox is taken up smoothly by the oil being stirred,
effectively achieving what slipping the clutch in a manual box does; the
disadvantage is that stirring things dissipates energy in them causing
lower efficiency (=3D higher fuel consumption) and also heating - which is
why a hard-working auto box needs an extra oil cooler.
It's called a "torque converter" because its real shape allows rotation
speed to be traded off for torque. In effect the engine can spin fast at
relatively low torque, and the gearbox can be driven slowly at higher
torque. This is why most auto-box LC users only need to use low range
very occasionally, whereas we manual box folk make rather more use of
it. Also why auto gearboxes tend to have fewer gear ratios than manual
boxes.
Torque conversion is good for starting and acceleration, but not so good
for cruising at constant speed, so in cars the actual shape is a
compromise between the ideal for torque conversion and the ideal for
simple transmission of rotation. There is also a "lock up" that
effectively forces both sides to rotate at the same speed.
| Are the gears different between the two or is there another reason.
Identical in concept, but different in layout. Autos tend to use
"planetary" gearboxes where a central "sun" wheel has "planet" wheels
spinning around it. The advantage of this system is that to change gear
all you have to do is to lock up or free the rotation of different
"planet" wheels, which can be achieved by a series of clutches.
This suits the automatic system since the clutches can be hydraulically
or electronically controlled, and no gear levers have to be stirred
around. The old Sturmey Archer 3 speed gears on bicycles work this way
- think how easy they are to use.
.=2E. Which about sums up the sum total of my knowledge about auto boxes!
Christopher Bell
____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses