Seamless Shift Conspiracy

[peanutaxis]

Hi,

(I am just throwing this out there. I have not done extensive research or searched this topic thoroughly.)

I have a pet-theory hunch that the common story about how seamless shift gearboxes in f1 work is nonsense. The common claim that I have heard is that the gearbox engages two gears at once and then before it becomes a problem it disengages the previous gear. I think this is a half truth.

I think that there is a ratchet-like system where as soon as the driver actions the next gear, the next gear picks up some finger-like pawls. Just like if I was pushing a supermarket trolley, holding the handle on the LHS, and then someone comes up from behind moving faster than I am on the RHS and picks up the trolley and moves it forward faster than I was moving.
In this way the claim "both gears are engaged at once" is kind of true for a nanosecond but....is a misdirect. This also explains why drivers are told that changing down while accelerating is a no-no (I haven't seen this in years in any footage).

Again this is a not-thoroughly researched pet theory. I'd be interested to hear evidence as to what is really going on in a F1 seamless shift gearbox if anyone has alternate info.


p

[saviour stivala]

Who on God's green earth will ever attempt to change-down WHILE accelerating?

[Tommy Cookers]

backlash (rotational slack existing within each non-driven gear pair) is about 45 deg
2 gear trains can safely be simultaneously engaged until the backlash has been consumed
the backlash is consumed in about 1 rev of the output shaft (the 2 output gears rpms are about 13% different)
so the backlash gives at worst a shift time window of about 3 millisec in NA F1 and 5 millisec in hybrid F1
and the actuator timing can have some lead (ie the actuator response might not need to be faster than 5 or 8 millisec)

easy like shelling peas !

[gruntguru]

Who on God's green earth will ever attempt to change-down WHILE accelerating?

I do it all the time. Press the throttle and realise I need more thrust - shift down. I imagine even in F1 a driver may occasionally go to accelerate after a corner or after being baulked by a slower car or debris and realise he needs a lower gear.

[gruntguru]

backlash (rotational slack existing within each non-driven gear pair) is about 45 deg
2 gear trains can safely be simultaneously engaged until the backlash has been consumed
the backlash is consumed in about 1 rev of the output shaft (the 2 output gears rpms are about 13% different)
so the backlash gives at worst a shift time window of about 3 millisec in NA F1 and 5 millisec in hybrid F1
and the actuator timing can have some lead (ie the actuator response might not need to be faster than 5 or 8 millisec)

So - is the backlash built into the gear-shaft connection? And is the "backlash" lightly prelaoded in one direction with a spring.

[saviour stivala]

Down shifting while accelerating. - ''I do it all the time. Press the throttle and realize I need more thrust''. Silly me - Yes of course your type of driving can. But in your type/standard of driving you will actually stop the accelerating you have started in order to shift down which is a totally stupid example to come up against the subject at hand - formula one racing driving style - using a formula one engine and a formula one sequential shift simi automatic present type of gearbox. I say that if a formula one driver tries shifting down while under acceleration, depending on how lower the shifted gear is, chances are his eyes will most probably pop-out of his eye sockets.

[Farnborough]

Backlash is usually dependent on the space in front of, or behind the "dog" engagement design.

This, the understanding of the gearbox, may depend on the viewers knowledge of what's inside a gearbox as to visualisation from the written word description.

The boxes are ordinarily "constant mesh" type, meaning that each corresponding gear pair (whether being used or not) are running together all the time the gearbox is turning. Selecting which ratio pair is being used is by sliding those dogs into and out of engagement.
When one dog set is driving actively, then torque is transferred from the drive set to the driven set (think two sets of castellated lumps on opposite faces), there has to be space to swap them in and out out use, that space is behind the driven dog while driving.
If you now leave that pair driven, then at the same time engage the next higher gear pair dogs, these first dogs are released from their torque by the driven shaft now outstripping the first pair in speed (higher ratio) just as that happens the first set of dogs are completely free to be removed by their actuator, but must be done before that original slack/space is taken up. This has transferred the drive seamlessly to the higher ratio just by a timing "ballet" of controls.

That's easy going up in ratio as all the gaps/slack/backlash/timing etc falls more in the right sequence to facilitate this very easy changing of the ratio, without torque interruption and without exploding (remember MB gearbix fail in Austria, they described as being too aggressive with change timing) but going down ratio is far more of a problem as all those gaps etc are now moving in the opposite direction from the above.
In effect, going down has to firstly remove the driven dog set to give neutral, then blip the shaft speed (down change throttle blip) to bring synchronisation of components, only then to flip the actuator to engage next ratio down.

The two are very different methods, downshift is most unlikely to be seamlessly achieved. They may use clutch to "soften" this task, but not really needed going upward.

[gruntguru]

Down shifting while accelerating. - ''I do it all the time. Press the throttle and realize I need more thrust''. Silly me - Yes of course your type of driving can. But in your type/standard of driving you will actually stop the accelerating you have started in order to shift down which is a totally stupid example to come up against the subject at hand

Nonsense.
If I was driving a car with a seamless gearshift, accelerating after a corner, realise the revs are too low - I would simply press the downshift paddle while keeping the throttle fully depressed. The engine revs and my rate of acceleration will increase. At high speeds in an F1 car you could do the same thing without loss of traction.

[saviour stivala]

Down shifting while accelerating. - ''I do it all the time. Press the throttle and realize I need more thrust''. Silly me - Yes of course your type of driving can. But in your type/standard of driving you will actually stop the accelerating you have started in order to shift down which is a totally stupid example to come up against the subject at hand

Nonsense.
If I was driving a car with a seamless gearshift, accelerating after a corner, realise the revs are too low - I would simply press the downshift paddle while keeping the throttle fully depressed. The engine revs and my rate of acceleration will increase. At high speeds in an F1 car you could do the same thing without loss of traction.

Nonsense. -If you were driving a "RACING CAR (the subject here) WITH a seamless gearshift", You would have shifted down before you started your acceleration, If not probability would be you not be sitting in that driving seat.

[saviour stivala]

Backlash between gears/dogs/splines-on-shafts gears are sliding on or not. No gear will be disengaged by normal gear change forces under acceleration/power unless said power is removed/interrupted. But the latest seamless shift gearboxes, were no gear/dog sliding action is used anymore, will be a different story, eliminates all said above.

[Farnborough]

Down shifting while accelerating. - ''I do it all the time. Press the throttle and realize I need more thrust''. Silly me - Yes of course your type of driving can. But in your type/standard of driving you will actually stop the accelerating you have started in order to shift down which is a totally stupid example to come up against the subject at hand

Nonsense.
If I was driving a car with a seamless gearshift, accelerating after a corner, realise the revs are too low - I would simply press the downshift paddle while keeping the throttle fully depressed. The engine revs and my rate of acceleration will increase. At high speeds in an F1 car you could do the same thing without loss of traction.

This isn't mixing a "road" type application with the F1 gearbox type is it ? They are completely different in design if that's the case.

[CMSMJ1]

Hi,

(I am just throwing this out there. I have not done extensive research or searched this topic thoroughly.)


p

Go and have a look at some research?

What about Motogp gearboxes..they are as bonkers.

[gruntguru]

Down shifting while accelerating. - ''I do it all the time. Press the throttle and realize I need more thrust''. Silly me - Yes of course your type of driving can. But in your type/standard of driving you will actually stop the accelerating you have started in order to shift down which is a totally stupid example to come up against the subject at hand

Nonsense.
If I was driving a car with a seamless gearshift, accelerating after a corner, realise the revs are too low - I would simply press the downshift paddle while keeping the throttle fully depressed. The engine revs and my rate of acceleration will increase. At high speeds in an F1 car you could do the same thing without loss of traction.

Nonsense. -If you were driving a "RACING CAR (the subject here) WITH a seamless gearshift", You would have shifted down before you started your acceleration, If not probability would be you not be sitting in that driving seat.

I imagine even in F1 a driver may occasionally go to accelerate after a corner or after being baulked by a slower car or debris and realise he needs a lower gear.

[gruntguru]

Down shifting while accelerating. - ''I do it all the time. Press the throttle and realize I need more thrust''. Silly me - Yes of course your type of driving can. But in your type/standard of driving you will actually stop the accelerating you have started in order to shift down which is a totally stupid example to come up against the subject at hand

Nonsense.
If I was driving a car with a seamless gearshift, accelerating after a corner, realise the revs are too low - I would simply press the downshift paddle while keeping the throttle fully depressed. The engine revs and my rate of acceleration will increase. At high speeds in an F1 car you could do the same thing without loss of traction.

This isn't mixing a "road" type application with the F1 gearbox type is it ? They are completely different in design if that's the case.

The (side) discussion is entirely about whether the desire might ever arise to downshift at full throttle. I say - of course it might.

[saviour stivala]

Nonsense.
If I was driving a car with a seamless gearshift, accelerating after a corner, realise the revs are too low - I would simply press the downshift paddle while keeping the throttle fully depressed. The engine revs and my rate of acceleration will increase. At high speeds in an F1 car you could do the same thing without loss of traction.

Nonsense. -If you were driving a "RACING CAR (the subject here) WITH a seamless gearshift", You would have shifted down before you started your acceleration, If not probability would be you not be sitting in that driving seat.

I imagine even in F1 a driver may occasionally go to accelerate after a corner or after being baulked by a slower car or debris and realise he needs a lower gear.

A formula one racing driver that 'realizes that he needs shift to a lower gear after he starts accelerating is no racing driver and shouldn't be sitting in that driving seat. A racing driver always first shift to a lower gear (if need be) and than accelerates, and not shift to a lower gear while accelerating.