Seamless Shift

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
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SiLo
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Joined: 25 Jul 2010, 19:09

Seamless Shift

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How to seamless shift gearboxes actually work? Surely there is a downtime when the gears are changed and the propshaft has to adapt its speed?
Felipe Baby!

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747heavy
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Joined: 06 Jul 2010, 21:45

Re: Seamless Shift

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"Make the suspension adjustable and they will adjust it wrong ......
look what they can do to a carburetor in just a few moments of stupidity with a screwdriver."
- Colin Chapman

“Simplicity is the ultimate sophistication.” - Leonardo da Vinci

scarbs
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Joined: 08 Oct 2003, 09:47
Location: Hertfordshire, UK
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Re: Seamless Shift

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F1 seamless systems do not use solutions such as Zeroshift. They are in fact quite simple derivatives of the conventional semi automatic sequential gearboxes. Rather than a single selector drum controlling all of the gears. The team use two separate selector drums each controlling alternate gears. So one gear is selected by the first drum, then the next gear is selected by the second selector, the phasing of one gear onto the next is aided by the usual throttle\ignition break and reportedly some clutch slip. Of course the system can select two gears at once and the electronics are the only way this can be controlled.

Scarbs

PS nice to see most of those links using my age old drawing of a c2001 Jaguar gearbox being used.

autogyro
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Joined: 04 Oct 2009, 15:03

Re: Seamless Shift

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SiLo wrote:How to seamless shift gearboxes actually work? Surely there is a downtime when the gears are changed and the propshaft has to adapt its speed?
There is no such thing as a seamless gearbox.
Any propshaft stays at road speed no matter what gear is engaged.
It is the engine that has to change its rpm to adapt to the next ratio selected.
F1 boxes are single layshaft boxes, with selection by dual scroll drum as scarbs explains.
Dual clutch and or dual layshaft gearboxes, wrongly described as seamless, use their dual construction to speed up the gear change by having one gear engaged before disengaging another gear on a different shaft. However there is STILL a gap in the change be it very small.
F1 does not use these boxes because of regulations and also because dual clutch/layshaft boxes take out more torque than the simpler lighter and more compact single clutch/layshaft geartrain.
Last edited by autogyro on 12 Sep 2010, 23:26, edited 1 time in total.

autogyro
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Joined: 04 Oct 2009, 15:03

Re: Seamless Shift

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Zero shift is a neat idea that speeds up gearshifts and places a transitional friction drive beetween bullets and ramp components during the shift.
I contest the validity of the name 'Zero Shift' however.
There is still a shift between stepped ratios and there is still a gap in torque transfer be it very short and considered as the torque loss during shifts at the contact surface of the bullets and ramps. I would expect a higher operating temperature and would also like to see some figures on how long the actual shift component would last in high torque high rpm operation.
Dog rings are very robust and added moving complicated part replacements at the scale shown look vulnerable to me.

RacingManiac
9
Joined: 22 Nov 2004, 02:29

Re: Seamless Shift

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I think they are just marketing/over simplifying terms, makes for nice sound bite. F1 is full of that stuff, from F-duct, to J-Damper...etc. Probably the more accurate term might be "relatively" seamless shift....but that makes a mouthful....

Cogs
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Joined: 05 Nov 2010, 12:18

Re: Seamless Shift

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autogyro wrote:There is no such thing as a seamless gearbox.
This depends on the definition of "seamless" when applied to gearbox functionality. If for this instance we assume that "seamless" means continued positive torque seen at the input shaft of the transmission during a gearshift then I believe this is possible with a technology such as Zero Shift. If I have interpreted the geometry of the Zero Shift components correctly there is no need to relieve the ring currently supplying torque to the output shaft prior to selecting the new ratio (no need to reduce input torque) and also there is no requirement for timing the disengagement (components are self protecting). Therefore "seamless"?

The only question that remains is whether it is possible to cope with the magnitude of the dynamic torque spikes that would ensue? If the engine is coupled, the transmission would have to cope with the synchronisation of its inertia. Maybe this accounts for the reported clutch slip?

I agree that the output torque must change from one value to another but don't see this as being a "gap".

autogyro
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Joined: 04 Oct 2009, 15:03

Re: Seamless Shift

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A good racing driver using a manualy operated dog ring box and performing a 'racing' power on change would still equal or beat any of the current technical tricks.
Bring back proper drivers.

autogyro
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Joined: 04 Oct 2009, 15:03

Re: Seamless Shift

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Cogs wrote:
autogyro wrote:There is no such thing as a seamless gearbox.
This depends on the definition of "seamless" when applied to gearbox functionality. If for this instance we assume that "seamless" means continued positive torque seen at the input shaft of the transmission during a gearshift then I believe this is possible with a technology such as Zero Shift. If I have interpreted the geometry of the Zero Shift components correctly there is no need to relieve the ring currently supplying torque to the output shaft prior to selecting the new ratio (no need to reduce input torque) and also there is no requirement for timing the disengagement (components are self protecting). Therefore "seamless"?

The only question that remains is whether it is possible to cope with the magnitude of the dynamic torque spikes that would ensue? If the engine is coupled, the transmission would have to cope with the synchronisation of its inertia. Maybe this accounts for the reported clutch slip?

I agree that the output torque must change from one value to another but don't see this as being a "gap".
If this is not a gap where either no torque is tranfered or torque is converted to heat and wear, what is it?

Cogs
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Joined: 05 Nov 2010, 12:18

Re: Seamless Shift

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autogyro wrote:If this is not a gap where either no torque is tranfered or torque is converted to heat and wear, what is it?
The point I was making was that the word "gap" suggests the need to break torque to the output shaft which does not seem to be the case with this system. The torque change at the output side is an unavoidable result of changing discrete ratios but may be managed through slip or torsional compliance (I agree that if this excess torque were managed it would convert to heat/noise) resulting in a controlled change not a gap.

I guess the definition creates more discussion that the mechanical design itself?

Enjoying the topic though.

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flynfrog
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Joined: 23 Mar 2006, 22:31

Re: Seamless Shift

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autogyro wrote:A good racing driver using a manualy operated dog ring box and performing a 'racing' power on change would still equal or beat any of the current technical tricks.
Bring back proper drivers.
sorry this is completely wrong a human is no where as fast as a computer controlled dsg box or even a simple airshifter any.


Back on topic instead of rants. Couldn't a double clutch transmission use two sprags to maintain "seamlessness" You could then engage both shafts at the same time until the next higher gear was up to speed. Any look at telemetry will show you this.

Cogs
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Joined: 05 Nov 2010, 12:18

Re: Seamless Shift

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flynfrog wrote:sorry this is completely wrong a human is no where as fast as a computer controlled dsg box or even a simple airshifter any.


Back on topic instead of rants. Couldn't a double clutch transmission use two sprags to maintain "seamlessness" You could then engage both shafts at the same time until the next higher gear was up to speed. Any look at telemetry will show you this.
Couldn't agree more. Which as far as I can see is exactly what Zero Shift is....two bi-directional sprags.

autogyro
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Joined: 04 Oct 2009, 15:03

Re: Seamless Shift

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It is not a rant and proves that certain people do not know the capabilities in how to change gear with a manual layshaft box.
The time it takes for a driver using lever actuated shift, to move a dog ring selector from one gear to another can be just as fast as any modern trick method.
The difference is the skill and experience involved. Now sadly lacking in most performance drivers.

It matters not one iota the mechanical method of engageing one gear and disengaging from another, there will always be a 'gap' where the engine rpm/torque has to be matched to the new input rpm.
You just cannot get away from it with a layshaft gearbox whether it be, twin clutch, twin shaft, intigral shaft, speed shift,zero shift, dog clutch, syncro or any other method of shift.
There will ALWAYS be a 'gap' where either no torque is transfered from input to output, or the toque being transfered is converted in most part to heat and wear.

Cogs
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Joined: 05 Nov 2010, 12:18

Re: Seamless Shift

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autogyro wrote:There will ALWAYS be a 'gap' where either no torque is transfered from input to output, or the toque being transfered is converted in most part to heat and wear.
Correct me if I'm wrong but isn't the second half of your statement "torque being transferred is converted in most part to heat and wear" contradictory to the first "There will ALWAYS be a 'gap'"?

If prior to a dynamic torque spike the clutch was pre-conditioned to just above the current driver demand this would allow the input shaft (and coupled components) of the transmission to synchronise immediately upon engagement. The remaining synchronisation of engine to the input can be easily controlled and allow speed matching without a gap in torque transfer.

Hence the tag "seamless"

autogyro
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Joined: 04 Oct 2009, 15:03

Re: Seamless Shift

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You are over complicating your explanation.
Yes the clutch can be allowed to 'slip' during the shift to allow the engine to increase in rpm to match the new gear engaged to output.
A similar effect is achieved by either disengaing the clutch during the shift altogether or by just backing the ignition to reduce torque output from the engine. The engine can also be throttled down or even turned off completely, resulting in little or no torque transfer.
I cannot see a dynamic torque spike during a gear shift. I can see a sudden reduction in torque at the output shaft. This is a result of the 'gap' which is either a complete disengagement from the engine or a result of the torque being tranfered being absorbed by the components in the shift mechanism or main clutch.

The 'gap' is a time period where there is little or no torque to be measured at the output shaft. This 'gap' is always present in a stepped gearbox and is the reason why the description 'seamless' is untrue and simply a marketing term.