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Seamless Gearboxes


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#101 gruntguru

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Posted 25 February 2012 - 04:55

Many clutch plates in ordinary powertrains have radial shock absorbing springs.
However under full torque transfer, (maximum acceleration), these radial shock absorbers placed in the torque path will already be fully compressed.

Why? There is no reason they should be designed to be fully compressed at maximum engine torque, in fact it would be foolish to do so. I would design them to withstand full engine torque PLUS whatever transient and shock loading might be anticipated in the system.

Any other parts of the powertrain capable of wind up will also be fully wound up. (bit like me I suppose :lol: )

Why? And what does "fully wound up" mean? - that the drivetrain is at its elastic limit? - again it would be foolish to design the drivetrain to be at its failure limit under these conditions.

Therefore non of the items you list can play a part in assisting the shift mechanism when it is asked to transfer torque during your suggested maximum torque upshift.

I didn't say anything about these items "assisting" the shift mechanism. You asked how the next gear could increase the speed of the output shaft when the output shaft is connected to the rear wheels and I answered you - the connection is elastic!

I should modify my original statement to say "engagement of the new gear increases the speed of the output shaft slightly while simultaneously reducing the speed of the input shaft. This allows the dogs (bullets) to disengage the previous gear."

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#102 gruntguru

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Posted 25 February 2012 - 05:01

Perhaps the marketing department is referring to the acceleration of the vehicle rather than the torque applied to the drive train as being seamless, because the end user is more interested in the former than the latter. It does not matter if there is a torque spike or dip for that matter, if the shift is quick enough acceleration would continue, the only true seamless system, by your definition is already invented and is intalled on a lot of road cars, but is banned in F1.

No - there really is NO GAP in torque flow.
- At the beginning of the shift torque flows through the lower gear.
- During the shift the torque is shared by both gears - with the higher gear handling a constantly increasing proportion until -
- At the end of the shift 100% of the torque is flowing through the higher gear.

#103 Wuzak

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Posted 25 February 2012 - 05:39

No - there really is NO GAP in torque flow.
- At the beginning of the shift torque flows through the lower gear.
- During the shift the torque is shared by both gears - with the higher gear handling a constantly increasing proportion until -
- At the end of the shift 100% of the torque is flowing through the higher gear.


Does it work going the other way - ie downshifting?

I suppose it doesn't have to and the gains are less.

#104 Wuzak

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Posted 25 February 2012 - 05:44

I would think that it is immaterial that a "seamless" gearbox shifts more slowly than an expert gear shifting driver using a manual box - the gain is in there not being a gap in the power being transmitted.

The point in having faster shifts was to reduce the gap in power transmission and minimise drive loss. But without the gap, making changes faster doesn't gain a whole lot.

#105 24gerrard

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Posted 25 February 2012 - 09:37

It is not essential that the torque be reduced. If the zeroshift box is upshifted without reducing engine torque the is simply a spike in output shaft torque prior to settling to the steady-state torque available in the new gear. There is NO GAP and no reduction in torque to the output shaft. Torque reduction is only required to smooth the spike for comfort, driveline durability, driver control etc.


'The Zero shift has a negatively bevelled dog which cannot transmit any torque until it is fully engaged and fully "torque capable".'

Your words grunt.



#106 24gerrard

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Posted 25 February 2012 - 09:45

Great to watch specialists equipment in it's environment.

Notice he gets it all out the way by half distance then uses torque to accelerate him through the tough half.

Wait, what .... :lol:


http://www.youtube.c...eature=youtu.be

Which simply proves he is driving a very heavy car with the aerodynamics of a brick and using a powertrain more suited to hauling cargoe of a ships deck.

Makes a nice noise though, almost as good as a B52 bomb load going down in the middle east.

Edited by 24gerrard, 25 February 2012 - 09:47.


#107 24gerrard

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Posted 25 February 2012 - 09:58

Does it work going the other way - ie downshifting?

I suppose it doesn't have to and the gains are less.


Very importany question Wuzak.
F1 downshifts are automatic, upshifts have to be manualy demanded.

With KERS's also using overrun to charge the system the shifts can seriously upset the cars braking both over all and front to rear balance.
This is yet another result of the regulations preventing development of KERS, braking systems and powertrains to meet the demands of modern technology.
The currrent F1 cars use brakes that are one step away from throwing out an anchor, gearboxes that have not changed in basic principle since the 1890.s and KERS systems that are so tightly controlled in the regs that there is now absolutely no way to apply new ideas.

The ONLY reason non of this is obvious is because it is all masked by the STUPID level of downforce the cars are still allowed to use.

People like Patrick Head have left in disqust to develop energy recovery systems in the real world where technology is now leaving F1 for dead.

Edited by 24gerrard, 25 February 2012 - 10:00.


#108 gruntguru

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Posted 25 February 2012 - 11:37

'The Zero shift has a negatively bevelled dog which cannot transmit any torque until it is fully engaged and fully "torque capable".'

Your words grunt.

Sure, but until it is fully engaged the previous gear continues to transmit 100% torque.

#109 Wuzak

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Posted 25 February 2012 - 11:41

Very importany question Wuzak.
F1 downshifts are automatic, upshifts have to be manualy demanded.


I believe this is incorrect.

Shifts have to be commanded both up and down - the gearbox software can reject a downshift (maybe an upshift too) but cannot do it automatically.


#110 Wuzak

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Posted 25 February 2012 - 11:42

With KERS's also using overrun to charge the system the shifts can seriously upset the cars braking both over all and front to rear balance.
This is yet another result of the regulations preventing development of KERS, braking systems and powertrains to meet the demands of modern technology.
The currrent F1 cars use brakes that are one step away from throwing out an anchor, gearboxes that have not changed in basic principle since the 1890.s and KERS systems that are so tightly controlled in the regs that there is now absolutely no way to apply new ideas.


Haven't electric motors and batteries been around snce the 1850s?




#111 24gerrard

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Posted 25 February 2012 - 12:53

Haven't electric motors and batteries been around snce the 1850s?


Of course and they had proper practical electric cars at that date as well.
It has been the dominance of fossil fueled vehicles that has prevented development.
It is also why there is a HUGE potential area of development in electric traction and a very real revolution in the technology slowly gaining pace.
Sadly the motor heads continue to keep their blinkers on and are content in F1 to just play with model aeroplane technology.

Still, as long as they can keep things from the public they will carry on coining it it.
I suppose any change will have to come from Rupert Murdoch, he now controls the sport.

#112 ferruccio

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Posted 25 February 2012 - 14:24

Didn't realise some thought seamless boxes meant 'stepless' boxes. Guys, seamless implies no gap in Torque delivery. There is no confusion on this except in this thread. F1 boxes are 100% seamless. There is no gap in Torque. This gap is worth eliminating in F1 simply because an F1 car that is coasting is actually decelerating in excess of 1g thanks to massive aero drag. The time lost in 'coasting' adds up to something significant over a race distance.

#113 24gerrard

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Posted 25 February 2012 - 14:32

Didn't realise some thought seamless boxes meant 'stepless' boxes. Guys, seamless implies no gap in Torque delivery. There is no confusion on this except in this thread. F1 boxes are 100% seamless. There is no gap in Torque. This gap is worth eliminating in F1 simply because an F1 car that is coasting is actually decelerating in excess of 1g thanks to massive aero drag. The time lost in 'coasting' adds up to something significant over a race distance.


Seamless can imply many things. The term itself is designed for maximum confusion.
It helps perpetuate the layshaft gearbox from the 1890's to the blinkered motor heads.
It is the marketing people who define it as no gap in torque delivery.
It is not an engineering term.

I cannot see a connection with 'coasting' or decelerating at 1g.
A manual shift with a dog ring box can easily achieve a speed of operation sufficient to deal with the same powertrain demands.
Of course 1g of aero produced deceleration simply confirms the rediculous levels of aero downforce and the equaly stupid waste of energy to achieve it.
Hardly a reflection of efficient top level vehicle technology is it.

The reasons for the current so called 'seamless' gearboxes in F1.

Because of the stupidly high developing levels of downforce, the braking distances became so short that it became impossible for a driver to manualy shift down on corner entry without almost certainly missing shifts.
The development of semi and fully automatic layshaft gearboxes allowed this 'problem' to be overcome but the FIA needed a way to structure things to continue the 'illusion' of full driver control and skill. The answer was to regulate the auto shift systems to be sequential, only seven gears and to make the driver operate at least the upshifts. This with the pre-program clutch bite point, gives us the arcade game powertain control we have today.
If downforce levels were reduced by 50% as they should be, the current drivetrains would completely unsettle the cars, mostly under braking. Therefore we are stuck with gearboxes from the 1890,s brakes closer to throwing out an anchor than modern technology and a completely neutered KERS technology that might as well be the same for everyone for what sense it makes to development in the real world.


Edited by 24gerrard, 25 February 2012 - 16:47.


#114 Tony Matthews

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Posted 25 February 2012 - 15:04

There's none so blind as will not see.

#115 24gerrard

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Posted 25 February 2012 - 15:13

There's none so blind as will not see.


Your right Tony.
Most people today simply believe everything marketing and the media throws at them.
The much lower education standards dont help either.

#116 carlt

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Posted 25 February 2012 - 15:56

Seamless can imply many things. The term itself is designed for maximum confusion.
.
It is the marketing people who define it as no gap in torque delivery.
It is not an engineering term.


It seems that it is only you who is using the term for maximum confusion


If there is no gap in torque delivery then seamless is the perfect terminology to describe the event

They are NOT explaining this to engineers , but to the general public

#117 carlt

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Posted 25 February 2012 - 16:04

The much lower education standards dont help either.




From the Merriam Websters English learners Dictionary

seam·less /ˈsi:mləs/ adjective
1 : having no seams
▪ a seamless rug/boat
2 : moving from one thing to another easily and without any interruptions or problems
▪ ▪ a seamless transfer of power

#118 24gerrard

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Posted 25 February 2012 - 16:49

It seems that it is only you who is using the term for maximum confusion


If there is no gap in torque delivery then seamless is the perfect terminology to describe the event

They are NOT explaining this to engineers , but to the general public


They are NOT explaining it period.
THAT is the problem.

#119 24gerrard

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Posted 25 February 2012 - 16:51

From the Merriam Websters English learners Dictionary

seam·less /ˈsi:mləs/ adjective
1 : having no seams
▪ a seamless rug/boat
2 : moving from one thing to another easily and without any interruptions or problems
▪ ▪ a seamless transfer of power


Absolutely, non of these apply to a current F1 box or any form of so called 'seamless' stepped geartrain.

Edited by 24gerrard, 25 February 2012 - 16:51.


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#120 gruntguru

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Posted 26 February 2012 - 02:01

Absolutely, non of these apply to a current F1 box or any form of so called 'seamless' stepped geartrain.

Your opinion only. Everyone else here is quite happy to refer to a transmission which provides uninterupted torque flow during shifting, as "seamless".

We all understand you have a barrow to push (a transmission you feel better meets your definition of "seamless"). We get it.

Now excuse us while we continue to use the term (quite appropriately) to describe boxes like DSG and Zeroshift.

#121 24gerrard

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Posted 26 February 2012 - 09:26

Your opinion only. Everyone else here is quite happy to refer to a transmission which provides uninterupted torque flow during shifting, as "seamless".

We all understand you have a barrow to push (a transmission you feel better meets your definition of "seamless"). We get it.

Now excuse us while we continue to use the term (quite appropriately) to describe boxes like DSG and Zeroshift.


Dont try to bulldoz acceptance grunt.
There is NOT an uninterupted flow of torque through the shifts with one of these gearboxes.
I will only accept it when the designers and builders rename the method of operation.

If you wish to claim the term, I claim the right to call all layshaft gearboxes 19th Century technology and F1 obsolete.

The gearbox design I have, I do not describe as seamless, although it meets your incorrect definition more than any layshaft gearbox.
It is a stepped gearbox with distinct fixed ratios and there is a variation in torque during the shift overlap.
The difference is it has an increase in torque, not a reduction forced by weak components.
Methods to smooth out and speed up gear shifts in layshaft gearboxea are no more than compromises to retain ancient technology.
It helps vehicle manufacturers and teams avoid meeting the need to develop new technology for the 21st century.
The public are being subjected to this illusion in the service of the greed system in many other areas, it is a con established by corrupt politicians and media.


#122 gruntguru

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Posted 26 February 2012 - 10:16

There is NOT an uninterupted flow of torque through the shifts with one of these gearboxes.

There is no interruption of the torque flow. There is no point during the shift when torque is not transferring from the engine to the final drive. If you truly believe otherwise you haven't read and understood the description of operation.

#123 carlt

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Posted 26 February 2012 - 10:27

Dont try to bulldoz acceptance grunt.


The gearbox design I have, I do not describe as seamless, although it meets your incorrect definition more than any layshaft gearbox.
It is a stepped gearbox with distinct fixed ratios and there is a variation in torque during the shift overlap.
The difference is it has an increase in torque, not a reduction forced by weak components.


Sorry , re read your own post

A "variation in Torque" is not a seam by any definition of seam I can find in any dictionary



You have dug yourself a huge hole , put the shovel down

#124 24gerrard

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Posted 26 February 2012 - 11:00

Sorry , re read your own post

A "variation in Torque" is not a seam by any definition of seam I can find in any dictionary



You have dug yourself a huge hole , put the shovel down


This describes my gearbox which is NOT a layshaft gearbox.
There IS a gap in torque 'flow' in so called 'seamless' layshaft gearboxes.

#125 24gerrard

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Posted 26 February 2012 - 11:10

http://www.zeroshift...5_Zeroshift.pdf

Read this and you will believe there is no gap in torque flow, until you realise that at the instant the bullets spring out and the other bullets take up drive, there HAS got to be a gap.

#126 carlt

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Posted 26 February 2012 - 11:30

http://www.zeroshift...5_Zeroshift.pdf

Read this and you will believe there is no gap in torque flow, until you realise that at the instant the bullets spring out and the other bullets take up drive, there HAS got to be a gap.



from what I read , and from what was posted by others before and repeated a number cof times


The bullets can only spring out when the next set have 'already' taken up drive

There is NO gap in torque delivery




Maybe the reason why nobody has taken up your revolutionary esuro transmission is because you are such a cuss
you must be a nightmare to work with

#127 Wuzak

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Posted 26 February 2012 - 11:35

http://www.zeroshift...5_Zeroshift.pdf

Read this and you will believe there is no gap in torque flow, until you realise that at the instant the bullets spring out and the other bullets take up drive, there HAS got to be a gap.



from what I read , and from what was posted by others before and repeated a number cof times


The bullets can only spring out when the next set have 'already' taken up drive

There is NO gap in torque delivery



That's teh way I understand it too. The reason why the first bullets disengage is because the the second bullets have engaged, and giving drive, and caused the first bullets to "spring out".

Edited by Wuzak, 26 February 2012 - 11:35.


#128 24gerrard

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Posted 26 February 2012 - 11:51

That's teh way I understand it too. The reason why the first bullets disengage is because the the second bullets have engaged, and giving drive, and caused the first bullets to "spring out".


Some of the bullets partialy engage on the high gear dog face and this overruns the lower gear, allowing it to disengage.
During the instant of disengagement no torque is transfered from input to output.
Torque from input is only enough to rotate the dog face on the higher gear with friction bullet contact to achieve this overrun until the bullets fully engage in the high gear dog.
As the bullets engage fully in the next higher gear there is a spike. This is because the lower gear is no longer engaged and the higher gear is engageing.
I do not care if the gap is half that in time as for the 'big bang', it is still a gap in torque transfer.


#129 24gerrard

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Posted 26 February 2012 - 11:58

from what I read , and from what was posted by others before and repeated a number cof times


The bullets can only spring out when the next set have 'already' taken up drive

There is NO gap in torque delivery




Maybe the reason why nobody has taken up your revolutionary esuro transmission is because you are such a cuss
you must be a nightmare to work with


I suggest you read it again this time with a little more care and less emotional expression.

#130 carlt

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Posted 26 February 2012 - 12:03

As the bullets engage fully in the next higher gear there is a spike. This is because the lower gear is no longer engaged and the higher gear is engageing.
I do not care if the gap is half that in time as for the 'big bang', it is still a gap in torque transfer.


I can't see the graphs big enough to read clearly on your link
but from the written word there is no break in torque transfer to the rear wheels

On the graph - does the 'torque spike' go to zero ?

#131 gruntguru

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Posted 26 February 2012 - 22:10

Some of the bullets partialy engage on the high gear dog face and this overruns the lower gear, allowing it to disengage.
During the instant of disengagement no torque is transfered from input to output.
Torque from input is only enough to rotate the dog face on the higher gear with friction bullet contact to achieve this overrun until the bullets fully engage in the high gear dog.

As I suspected, you do not understand the operation.

1. The instant the bullets fully engage the higher gear, it is still not transmitting any torque, but the lower gear is still transmitting 100% torque.

2. An instant later the higher gear is transmitting a tiny amount of torque and the lower gear is transmitting a tiny amount less than 100% torque.

3. This "handover" process continues until the higher gear is fully loaded and only then is the lower gear fully unloaded. This is the crucial point - THE LOWER GEAR CAN ONLY UNLOAD TO THE EXTENT THAT THE HIGHER GEAR HAS TAKEN OVER THE TORQUE LOAD.

4. At this point the lower gear begins to "over-run" and the bullets disengage from the lower gear.

5. Shift completed and NO GAP in torque delivery.

#132 carlt

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Posted 26 February 2012 - 23:18

Its gone quiet , I think he's stopped digging

#133 kikiturbo2

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Posted 26 February 2012 - 23:29

This is the crucial point - THE LOWER GEAR CAN ONLY UNLOAD TO THE EXTENT THAT THE HIGHER GEAR HAS TAKEN OVER THE TORQUE LOAD.


I think you will find that even that is not seamlesss enough for our mr gerrard.. :)

Hell, even porsche's twin clutch, where they have both 1st and 2nd engaged at the same time during the shift is not enough.. :)

#134 GreenMachine

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Posted 26 February 2012 - 23:57

My experience riding in a new Porker with flappy paddles is that it was slow and inneficient and a normal manual box was far better. Even watching in car with modern sports cars it really does not seem any faster.


I spent a lot of yesterday just listening to gearchanges (yes, I know I need a life ... :rolleyes: )

Apart from the Ferrari (oh that noise :love: ), there were two 911s - and clearly they used different 'boxes. One was a manual (it seemed), the other was clearly 'assisted'. No way was was the 'assisted' box's changes 'slow and inefficient' - they might not have been as sharp as the Fazza, but they were quick.

Carl, I find that meditating on Tony Matthews' aphorism is helpful  ;) .

#135 cheapracer

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Posted 27 February 2012 - 06:33

As I suspected, you do not understand the operation.

1. The instant the bullets fully engage the higher gear, it is still not transmitting any torque, but the lower gear is still transmitting 100% torque.

2. An instant later the higher gear is transmitting a tiny amount of torque and the lower gear is transmitting a tiny amount less than 100% torque.

3. This "handover" process continues until the higher gear is fully loaded and only then is the lower gear fully unloaded. This is the crucial point - THE LOWER GEAR CAN ONLY UNLOAD TO THE EXTENT THAT THE HIGHER GEAR HAS TAKEN OVER THE TORQUE LOAD.

4. At this point the lower gear begins to "over-run" and the bullets disengage from the lower gear.

5. Shift completed and NO GAP in torque delivery.


The moment it's engaged it's driving man ...

The moment the higher gear is driving the lower gear is not, it's an instantaneous changeover - how do you judge that time, it's like you are carrying a bag and I'm a bag snatcher running past and grabbing it instantly moving the bag faster forward.

Those bullets must take a hell of a hiding.


#136 cheapracer

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Posted 27 February 2012 - 06:36

I spent a lot of yesterday just listening to gearchanges


I have heard many a race car over the years but was surprised when I heard a Nissan GTR change gears recently, maybe just because it was on the street environment rather than a track.


#137 carlt

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Posted 27 February 2012 - 08:26

Carl, I find that meditating on Tony Matthews' aphorism is helpful ;) .



You make it sound like I Need help

Stop feeding my paranoia ........ :eek:

#138 carlt

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Posted 27 February 2012 - 08:29

it's like you are carrying a bag and I'm a bag snatcher running past and grabbing it instantly moving the bag faster forward.


excellent analogy ..

A 'seamless' transfer of wealth

#139 Tony Matthews

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Posted 27 February 2012 - 08:49

Oi! Has someone been meditating on my aphorism?

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#140 24gerrard

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Posted 27 February 2012 - 09:49

1. The instant the bullets fully engage the higher gear, it is still not transmitting any torque, but the lower gear is still transmitting 100% torque


Not possible.

2. An instant later the higher gear is transmitting a tiny amount of torque and the lower gear is transmitting a tiny amount less than 100% torque.


The high gear bullets rub on the faces of the high gear dog, this overruns the bullets engaged to the lower gear dog.

The lower gear bullets spring out of engagement with the lower gear dog. AN INSTANT LATER the high gear bullets fully engage with the high gear dog producing a spike.

3. This "handover" process continues until the higher gear is fully loaded and only then is the lower gear fully unloaded. This is the crucial point - THE LOWER GEAR CAN ONLY UNLOAD TO THE EXTENT THAT THE HIGHER GEAR HAS TAKEN OVER THE TORQUE LOAD.


You are suggesting that two sets of sprung loaded bullets undertaking angular movement while attached by friction to a non locked surface at each end and working with only sprung ring energy in one direction, can transfer 100% of input torque between them. Think again. The shift is very fast but the lack of a gap is an illusion .

4. At this point the lower gear begins to "over-run" and the bullets disengage from the lower gear.


If you waited this long to disengage the lower gear, you would have a lock up or bind up followed by broken bits in the gear case.

5. Shift completed and NO GAP in torque delivery.


Incorrect

Edited by 24gerrard, 27 February 2012 - 10:00.


#141 24gerrard

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Posted 27 February 2012 - 10:05

excellent analogy ..

A 'seamless' transfer of wealth


Big difference, you are not trying to snatch two components rotating at different speed with a snatcher set at a fixed speed.
You will either drop the bag or break it and drop the bits in it on the floor.

#142 24gerrard

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Posted 27 February 2012 - 10:11

name=]']]

Those bullets most certainly do take a hiding.
When we tested the idea (and others similar) way back in 1979 there were neither the materials or the computer technology to perfect the ideas.
I must dig out some of the patents I was involved with. I dont usualy bother but this case is interesting.

I see there are road gearbox conversions of 'zeroshift'.
The bullets and mechanism definitely work well in F1 and other competition where the engines have light components and the requirement is not for long distance use.
I am not sure how such shift systems on single layshaft boxes will last in a heavy road car.
I would need a lot of convincing but then you all know that already.

Edited by 24gerrard, 27 February 2012 - 10:13.


#143 24gerrard

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Posted 27 February 2012 - 10:17

Its gone quiet , I think he's stopped digging


You guys realy should study these systems you are nearly down to China.
Hmm, you could then at least talk to Cheapy 'face to face' like the bullets rubbing in a so called 'seamless' shift.

#144 24gerrard

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Posted 27 February 2012 - 10:31

Oi! Has someone been meditating on my aphorism?


They should Tony it is a very useful one for the modern age of illusions.

#145 24gerrard

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Posted 27 February 2012 - 11:48

I can't see the graphs big enough to read clearly on your link
but from the written word there is no break in torque transfer to the rear wheels

On the graph - does the 'torque spike' go to zero ?


That depends on whether the marketing men allow the graph to be big enough and the time line opened up enough to see it!

#146 carlt

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Posted 27 February 2012 - 12:18

That depends on whether the marketing men allow the graph to be big enough and the time line opened up enough to see it!



The question was to you --

do they show the spike going to Zero ?

if the spike does go to zero , then you are correct , there is a seam [by definition]

if the spike doesn't go to zero , then you are incorrect and there is No Seam


You need to have a look at their torque graph and get back to us with a definitive answer , otherwise arguments about seams should [ as you pointed out ] be confined to the Tailors shop

#147 cheapracer

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Posted 27 February 2012 - 12:45

The lower gear bullets spring out of engagement with the lower gear dog. AN INSTANT LATER the high gear bullets fully engage with the high gear dog producing a spike.


Actually it's an instant before, the gears are NOT fixed to the mainshaft and can rotate independently of the mainshaft, the power flow goes from the gear through the dogs to the mainshaft (as with any common synchromesh gearbox).

One gear of each pair in a typical gearbox must be able to free spin on it's shaft ... you need to stop thinking dog box power flow and think common synchromesh box power flow as it would be impossible with a dog box.

Remember that in a dog box one gear is a fixed drive (splined) to the mainshaft then the next one along might spin freely, then the next one is fixed and the next one spins freely ect (loose example only and not always that 1-2, 1-2 pattern) and the same for it's layshaft partner.

In a common synchromesh box all the gears on the mainshaft spin freely and the layshaft are all fixed.

Big difference ...

Edited by cheapracer, 27 February 2012 - 12:51.


#148 TC3000

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Posted 27 February 2012 - 12:46

for a better readable version of the graphic - torque goes to zero or not
http://www.zeroshift.com/68.html

some general info:
http://www.ret-monit...-transmissions/

Posted Image

Posted Image

#149 cheapracer

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Posted 27 February 2012 - 13:02


Posted Image


Notice synchromesh style splined hub and smooth bore free to spin spline'less gears...


Oi! Has someone been meditating on my aphorism?


Was that in the bag that was snatched?

Edited by cheapracer, 27 February 2012 - 13:08.


#150 24gerrard

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Posted 27 February 2012 - 14:24

Actually it's an instant before, the gears are NOT fixed to the mainshaft and can rotate independently of the mainshaft, the power flow goes from the gear through the dogs to the mainshaft (as with any common synchromesh gearbox).

One gear of each pair in a typical gearbox must be able to free spin on it's shaft ... you need to stop thinking dog box power flow and think common synchromesh box power flow as it would be impossible with a dog box.

Remember that in a dog box one gear is a fixed drive (splined) to the mainshaft then the next one along might spin freely, then the next one is fixed and the next one spins freely ect (loose example only and not always that 1-2, 1-2 pattern) and the same for it's layshaft partner.

In a common synchromesh box all the gears on the mainshaft spin freely and the layshaft are all fixed.

Big difference ...


I am well aware that the gears are free to rotate on the mainshaft Cheapy.
I have been working with such gears for over 30 years.
The systems work in exactly the same way as a dog ring syncromesh (a baulk ring box has slip rings instead of dog rings and cone contact areas as part of the gear)
In the 'seamless' systems the dog ring hub (splined to the shaft) is replaced by a splined hub with a sprung mechanism with bullets instead of dog rings.
The bullets engage with the cut out teeth in the gears.
During the shift the ends of the bullets 'slide' along the gaps between these cut outs.
There has to be a gap in torque to allow the lower gear driving bullets to disengage.
This has GOT to happen before the higher gear is FULLY engaged, otherwise you would be trying to put max torque through two gear sets rotating at different speeds.
During this friction contact, torque is only used for gear shift actuation not to drive the vehicle.
It is a very very smal time period but it has got to exist.
Also, if it did not there would not be a spike as the next higher gear FULLY engages.

The graph you show is nice Cheapy, mainly for what it does not show rather than what it does.

Edited by 24gerrard, 27 February 2012 - 14:52.