How does a "Seamless Shift" 'box works?

[magracer]

How does a "Seamless Shift" 'box work?

I'm looking for the basic concept not the detailed maps of the 'box...

Is it related somehow to the DSG box found on VWs? Or is it more related to a CVT? It's also been described as "constant torque".... is that engine torque? How do they manage that?

Edit: From every torque curve I've seen in my life, achieving constant engine torque would requiere running at a single rpm speed, wouldn't it? That would require CVT. Williams' seamless box doesn't run at single engine speed, does it? So IMHO CVT not equal to seamless.

[h00t_h00t]

I think its a CVT, it depends on the indiviual maufacturers designs. I think it means a constant amount of torque is available at all times, its more advertising speak than anything technical. Its all controlled with computers, sensors and witchcraft.

www.howstuffworks.com probably has something on CVTs that would help.

Here ends my knowledge on the subject.

[Matra et Alpine]

"Proper" CVT -- ie ones that run the engine at it's peak torque or most efficiency and use the CVT ratio to provide the wheel speed were found to be unliked by drivers.
I remember the old Daf, it was just weird to hear it rev up and the car not move very much and then the car go faster and faster and the revs not change.
So "modern" CVT tend to program in "proper" revs as we're used to

But where did you get the term "seamless shft" ? As the Zeroshift might be called that as it always maintains drive during shift

[SLoppYJeeP]

Yeh, I agree with Matra, although they acctually reduce acceleration times, manufactures build in shift points into CTVs to give them the feel of a normal gear box. Also, these gear boxes DO shift, but they just do it an infanate amount of times. A shiftless gear box would be a direct drive, or a 1 gear gearbox, right?

[Matra et Alpine]

Nice try, SJ, but CVTs dont' actually ever "shift" gears they actually MODIFY the driving and driven gear size and hence ratio. Good point to be pedantic over tho'

[2ndclasscitizen]

I seem to remember a few articles saying that can be a bit annoying, the constant droning from the engine and that it can be very easy to drift over the speed limit as the engine noise doesn't increase

[SLoppYJeeP]

I dunno....if the ratio between the two gears is changing....then i would consider that a shift....albiet a long one.

[drakkie]

"Proper" CVT -- ie ones that run the engine at it's peak torque or most efficiency and use the CVT ratio to provide the wheel speed were found to be unliked by drivers.
I remember the old Daf, it was just weird to hear it rev up and the car not move very much and then the car go faster and faster and the revs not change.
So "modern" CVT tend to program in "proper" revs as we're used to

Drivers loved them but the FIA banned them for being so much faster

[Matra et Alpine]

Drivers loved them but the FIA banned them for being so much faster

I was talking road use.
The DAF race car didnt' outright prove itself tho was interesting. ( technology for the cones and belts were the issue back then )
Tecno did well for one season but no more
Rallying the little 55 did well with many class wins and a finish in London-Sydney !!!
But in the end it came to little.
Not seen ANY comment from current drivers on the Williams FW15C. If you've any links to any I'd love to read it as getting info on it is VERY hard.
Needless to say FIA banned it during it's development.
As it removed gear changes from the driver control then it was kind of obvious it would be questioned !!
( probably more liekly because it would have raised MAJOR issues if it DID prove itself over patents for other teams competing -- no doubt the big manufacturers pressurised FIA )

[drakkie]

I was talking road use.
The DAF race car didnt' outright prove itself tho was interesting. ( technology for the cones and belts were the issue back then )
Tecno did well for one season but no more
Rallying the little 55 did well with many class wins and a finish in London-Sydney !!!
But in the end it came to little.
Not seen ANY comment from current drivers on the Williams FW15C. If you've any links to any I'd love to read it as getting info on it is VERY hard.
Needless to say FIA banned it during it's development.
As it removed gear changes from the driver control then it was kind of obvious it would be questioned !!
( probably more liekly because it would have raised MAJOR issues if it DID prove itself over patents for other teams competing -- no doubt the big manufacturers pressurised FIA )

i only know fro ma man(retired test driver of all cars oincluding racers) in the DAF museum. we talked a while with him. he said every colleague of his liked the cvt in the f2 car of DAF,compared to a none-cvt car. i dunno about the fw15c though

[culver]

I'm not sure what you mean by seamless shift. Many good, conventional autos (MB, GM etc) can feel seamless. CVT's are the only type that I'm aware of that doesn't "shift". The Borg Warner DSG boxes use two clutches so in effect one gear is being released as the other is being engaged.

These guys have an interesting design that basically shifts VERY fast. The power delivery wouldn't have a drop off but it's not "seamless" as the change in engine speed and gear ratio is likely to be felt by the driver.

http://www.zeroshift.com/

[M Doe]

CVTs are not allowed in F1. Therefore, I think you can be reasonably sure that no team on the grid is using one.