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Seamless Gearboxes


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#451 saudoso

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Posted 12 March 2012 - 11:08

A gap in torque transfer, is a gap, is a gap, is a gap.
Cant see how that is difficult to understand.

I said AFAIK they were all ratchet types.
There are other methods of operation of which I am also aware.

If you know different please enlighten us.
Technology is the purpose of this thread.



There are gaps in torque transfer between cylinder burns. With a good enough magnifying glass there are gaps everywhere. Even on the gear's steel.

You just have to chose which one is small enough to let go. What's your number?

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#452 carlt

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Posted 12 March 2012 - 12:19

There are gaps in torque transfer between cylinder burns. With a good enough magnifying glass there are gaps everywhere. Even on the gear's steel.

You just have to chose which one is small enough to let go. What's your number?



:up:

as I said on in post 74
http://en.wikipedia.org/wiki/Semantics

#453 cheapracer

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Posted 12 March 2012 - 12:22

You just have to chose which one is small enough to let go. What's your number?




Relative post but there is no gap in the Zeroshift.


#454 24gerrard

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Posted 12 March 2012 - 12:37

There are gaps in torque transfer between cylinder burns. With a good enough magnifying glass there are gaps everywhere. Even on the gear's steel.

You just have to chose which one is small enough to let go. What's your number?


Well now, would you call the operation of a four stroke internal combustion engine seamless?

No?

So why try to call a stepped layshaft gearbox seamless?

An epicyclic transmission with clutch and or band overlap is seamless, a layshaft gearbox never can be.
A twin clutch layshaft gearbox gets closer but still a torque gap.


#455 cheapracer

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Posted 12 March 2012 - 13:15

So why try to call a stepped layshaft gearbox seamless?


No one is calling a "stepped layshaft gearbox" seamless, most intelligent people who can follow basic principles are agreeing that the claims made by 'Zeroshift' and other specific types of layshaft gearboxes are seamless when it applies to those specific gearboxes.



An epicyclic transmission with clutch and or band overlap is seamless, a layshaft gearbox never can be.


Bullshit and bullshit.



#456 NTSOS

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Posted 12 March 2012 - 16:36

It is but it is read at the propshaft and does not show the torque at the input and output parts of the shift mechanism.
The readings there are masked by the output damper.



If a zero torque drop was shown at the I/O parts of the shift mechanism, would you then attribute that to masking by rotational inertia?

John

#457 cheapracer

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Posted 12 March 2012 - 16:53

..... or that you believe that you are the one and only sole being in the entire universe who can design a seamless gearchange?

This 100+ year old seamless gear system that impossibly engages 2 gears on the same shaft at the same time probably doesn't exist either ...

Posted Image

http://en.wikipedia....r_gears#History

Edited by cheapracer, 12 March 2012 - 16:54.


#458 Tony Matthews

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Posted 12 March 2012 - 17:01

Ha! It occurred to me to post a picture of a Derailleur system, but this thread is so tedious I couldn't be bothered. However, it's nice to see an impossible rear set, all the sprockets occupying the same space...

#459 munks

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Posted 12 March 2012 - 17:31

This 100+ year old seamless gear system that impossibly engages 2 gears on the same shaft at the same time probably doesn't exist either ...


LOL, you bastard! You know they "are not both FULLY engaged!" (I might need to set up a hotkey for this response.)

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#460 cheapracer

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Posted 12 March 2012 - 18:03

LOL, you bastard!


I am not, my mother and uncle were married a clear 3 weeks before I was born thank you.


#461 desmo

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Posted 12 March 2012 - 19:38

Bravo with the derailleur example. Modern examples with ramped cogs allow full power shifts reliably.

#462 carlt

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Posted 12 March 2012 - 20:52

Bravo with the derailleur example. Modern examples with ramped cogs allow full power shifts reliably.


the torque graph will not show the seams in the spandex

#463 24gerrard

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Posted 12 March 2012 - 20:59

Bravo with the derailleur example. Modern examples with ramped cogs allow full power shifts reliably.


I seem to see a GAP between the last tooth the chain engages with on the small gear and the tooth on the next largest gear it re-engages with, after the mechanism has moved all the links other than the last from one to the other using the slack in the chain.
Hmmm, interesting, built in mechanical modulation and torque control (mostly in the right leg in this diagram).
Now that is as good as it gets.
Still a GAP though.

Edited by 24gerrard, 12 March 2012 - 21:04.


#464 gruntguru

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Posted 12 March 2012 - 22:53

I can't see how that is possible , as munks posted , with the clutch slip , damping and drive train elasticity I would assume that torque would modulate

If the zeroshift mechanism is operated without any torque modification devices, the output torque for a 1->2 shift would look like the first gear torque curve, transitioning instantly to the second gear torque curve with no drop in torque whatsoever. There would be an additional torque "spike" superimposed at the shift point due to inertial effects.

The addition of torque controlling devices is firstly to remove the torque spike and secondly to smooth the torque transition from first gear level down to second gear level.

Edited by gruntguru, 12 March 2012 - 22:56.


#465 gruntguru

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Posted 12 March 2012 - 22:59

Torque has to be reduced at input to disengage the low gear bullets and with modulation there is a point after this where no torque from input is reaching output.

This is absolute nonsense. Engaging the second gear dogs/bullets unloads the first gear dogs automatically. The input torque does not need to be reduced.

#466 gruntguru

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Posted 12 March 2012 - 23:10

any mechanism that switches the power path from one to the other would seem to require some finite amount of time to operate, Zeroshift included.

Incorrect. Study the operation of Zeroshift.

Perhaps imagine a railcar propelled by a continuous cable with hooks at regular intervals. As the car progresses it comes to a section of track where there is a second cable with hooks travelling at a higher speed. When the next hook on this second cable catches up to the car it engages the car and accelerates it. This acceleration causes the car to outpace the first cable and it unhooks from it and continues at the higher speed drawn by the second cable. Note that for a brief time (depending on the elasticity of each mechanism involved) the car is drawn by both cables. Note also that there is no "gap" in propulsion.

#467 gruntguru

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Posted 12 March 2012 - 23:14

An epicyclic transmission with clutch and or band overlap is seamless, a layshaft gearbox never can be.

:rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl:
They are both stepped ratio transmissions with the ability to engage two gears simultaneously. There is no difference! One is a railcar with friction clamps on the cable, the other has hooks plus dampers and slipping devices to modulate the handover.
:rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl:

Edited by gruntguru, 12 March 2012 - 23:17.


#468 gruntguru

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Posted 12 March 2012 - 23:27

I seem to see a GAP between the last tooth the chain engages with on the small gear and the tooth on the next largest gear it re-engages with, after the mechanism has moved all the links other than the last from one to the other using the slack in the chain.
Hmmm, interesting, built in mechanical modulation and torque control (mostly in the right leg in this diagram).
Now that is as good as it gets.
Still a GAP though.

No, the "perfect shift" (it doesn't happen every time) on a derailleur system sees the chain engaging 2 (or more) sprockets simultaneously. The chain can maintain full tension throughout and the change in ratio occurs when the "jump" in the chain reaches the point where it unwraps from the sprockets. Note that the ratio change is not instant - it begins to change when the "jump" starts to unwrap and changes continuously until the "jump" is fully clear of the sprockets.

#469 desmo

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Posted 12 March 2012 - 23:38

No, the "perfect shift" (it doesn't happen every time) on a derailleur system sees the chain engaging 2 (or more) sprockets simultaneously. The chain can maintain full tension throughout and the change in ratio occurs when the "jump" in the chain reaches the point where it unwraps from the sprockets. Note that the ratio change is not instant - it begins to change when the "jump" starts to unwrap and changes continuously until the "jump" is fully clear of the sprockets.


Actually with any modern rear derailleur system in good repair downshifts at least happen pretty much perfectly seamlessly every time, the ramps machined into the rear cogs essentially guarantee that, albeit occasionally at the cost of a slight delay until one of the ramped sections comes round to the chain. As you say the chain is engaged on both cogs at the transition. For whatever reason upshifts don't have the same continuous "seamless" quality to my legs although they are certainly absolutely fine. I feel a slight discontinuity in the top run chain tension there.


#470 kikiturbo2

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Posted 13 March 2012 - 07:29

Seamless means without any gap in torque transfer at any point along the torque path.
Reading the torque at the propshaft does not show the whole torque path from the crankshaft to the rear wheels.

It is a simple matter to build a gearshift to achieve an increase in the torque read at the propshaft.
In fact you could easily modify the shift graph shown to achieve it with a different rating of damper.
This still does not make the gearbox seamless on its own.



in all honesty, it is the torque at the wheels that does the job, and that "seamlessness" is what is important..

#471 cheapracer

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Posted 13 March 2012 - 07:50

It is a simple matter to build a gearshift to achieve an increase in the torque read at the propshaft.


Indeed, in fact I changed down from 3rd to 2nd to go up a steep'ish ramp just before.




#472 24gerrard

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Posted 13 March 2012 - 14:44

:rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl:
They are both stepped ratio transmissions with the ability to engage two gears simultaneously. There is no difference! One is a railcar with friction clamps on the cable, the other has hooks plus dampers and slipping devices to modulate the handover.
:rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl:


Automatic gearboxes using epicyclic gearing DO NOT use two 'gears' at once.
I suggest you study for a while grunt. :rotfl:

#473 24gerrard

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Posted 13 March 2012 - 14:46

in all honesty, it is the torque at the wheels that does the job, and that "seamlessness" is what is important..


Of coursae the smooth effect is what the system achieves and it does it well.

At the expense of shift efficiency.

There is still a gap.

#474 24gerrard

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Posted 13 March 2012 - 14:49

No, the "perfect shift" (it doesn't happen every time) on a derailleur system sees the chain engaging 2 (or more) sprockets simultaneously. The chain can maintain full tension throughout and the change in ratio occurs when the "jump" in the chain reaches the point where it unwraps from the sprockets. Note that the ratio change is not instant - it begins to change when the "jump" starts to unwrap and changes continuously until the "jump" is fully clear of the sprockets.


Still a gap.
An efficient CV shift overlap though.
The gap is in the muscle contractions in the leg at the ratio change.

Edited by 24gerrard, 13 March 2012 - 14:51.


#475 24gerrard

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Posted 13 March 2012 - 14:52

Indeed, in fact I changed down from 3rd to 2nd to go up a steep'ish ramp just before.


Insufficient information.

#476 24gerrard

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Posted 13 March 2012 - 14:54

This is absolute nonsense. Engaging the second gear dogs/bullets unloads the first gear dogs automatically. The input torque does not need to be reduced.


Only if the shift is attempted without input torque reduction and modulation.
In which case the effect is comparable to hitting the gears with a sledge hammer.

#477 24gerrard

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Posted 13 March 2012 - 14:56

If the zeroshift mechanism is operated without any torque modification devices, the output torque for a 1->2 shift would look like the first gear torque curve, transitioning instantly to the second gear torque curve with no drop in torque whatsoever. There would be an additional torque "spike" superimposed at the shift point due to inertial effects.

The addition of torque controlling devices is firstly to remove the torque spike and secondly to smooth the torque transition from first gear level down to second gear level.


I can recommend a good seller of sledge hammers for you to contact grunt.
You can then carry one with you to hit the gears with when your system changes gear.
Cheaper than a zeroshift mechanism without input torque reduction and modulation.

#478 24gerrard

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Posted 13 March 2012 - 23:52

This is absolute nonsense. Engaging the second gear dogs/bullets unloads the first gear dogs automatically. The input torque does not need to be reduced.


OK, so why is the input torque reduced if it does not need to be? Simple question.
It is shown in the graph marked 'zeroshift power on shift' and I have yet to see one without modulation and torque reduction for this mechanism.
If input torque is reduced to the levels shown on the graph with the near vertical disengagement of the clutch with no increase in torque as a direct result of engine torque output control, the 1st gear bullets will disengage at any time the 1st selector fork is moved into neutral.
There is no longer any need to 'wait' for the 2nd gear bullets to start engageing 2nd gear.
Why wait?
If you allow the timing of the 1st gear buttons disengageing to occur at or near the point the 2nd gear buttons engage, you will create a huge jolt, why would you want this?



#479 gruntguru

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Posted 14 March 2012 - 00:10

Automatic gearboxes using epicyclic gearing DO NOT use two 'gears' at once.
I suggest you study for a while grunt. :rotfl:

Perhaps you tell me what happens during the shift?

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#480 gruntguru

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Posted 14 March 2012 - 00:11

Still a gap.
An efficient CV shift overlap though.
The gap is in the muscle contractions in the leg at the ratio change.

Nonsense. If there was an electric motor driving, it would be the same - and no gap.

#481 gruntguru

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Posted 14 March 2012 - 00:20

OK, so why is the input torque reduced if it does not need to be? Simple question.

Simple answer (and it is contained in a dozen posts already in this thread)

The input torque is reduced to remove the inertial spike - for comfort and durability. The graph is for a road box with added systems that are not part of the Zero-Gap Zeroshift mechanism.

#482 bigleagueslider

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Posted 14 March 2012 - 03:03

You are correct munks.
Nothing has changed.
The zeroshift components shown are not capable of sustained shifting without modulation to the levels shown.
The operation has to be modulated to a point where there is no torque transfer from input to output.
Torque has to be reduced at input to disengage the low gear bullets and with modulation there is a point after this where no torque from input is reaching output.
Without modulation the mechanism might work a couple of times and create a shift impact like a sledge hammer, that would shake the car enough the make the drivers teeth rattle.
There would still be a seam at the point of overlap caused by the impact.
It would be a result of the drive train winding up as engine torque came on with a sledge hammer bang at the high revs it was turning in low gear and letting go as the engine was dragged down to the lower revs required for the new high gear.


24gerrard,

Your points are very valid with regards to durability. With any type of positive engagement shift device, the relative speeds at the coupling interface of the engaging gear must be synchronized and/or unloaded. Otherwise the impact loads would quickly cause structural failure of the coupling device. Hard shifts can be tolerated with race transmissions as long as they don't destroy the gearbox. The Zeroshift concept is not immune from this basic condition. It relies on the selected gear overrunning the previous gear, thus the bullets on the selected gear are subjected to load the instant they engage.

slider

slider

#483 bigleagueslider

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Posted 14 March 2012 - 03:31

..... or that you believe that you are the one and only sole being in the entire universe who can design a seamless gearchange?

This 100+ year old seamless gear system that impossibly engages 2 gears on the same shaft at the same time probably doesn't exist either ...


cheapracer,

Your example of the bicycle chain derailleur is not completely valid with that of a manual gearbox. First, the bike chain only drives in one direction between the front & rear sprockets, and there is a ratchet between the rear sprocket and wheel. Second, there are not two discrete "gear ratios" engaged at the same time. Instead, during a shift the chain acts more like a CVT. The actual "gear ratio" during a shift is the variable/irregular distance the chain travels around the rear sprockets versus the front sprocket.

The bike chain example is more akin to a manual gearbox that uses overrun clutches, and it has the same basic drawback. That is they cannot both drive and backdrive (engine brake) in one given gear mesh.

slider


#484 cheapracer

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Posted 14 March 2012 - 03:49

The zeroshift components shown are not capable of sustained shifting without modulation to the levels shown.


You have no way to prove that statement.



The operation has to be modulated to a point where there is no torque transfer from input to output.


If you believe for an instant that race cars don't take advantage of 'banging it into the next gear' and the moment of extra torque the driveline windup offers to launch forward you are mistaken - again. When people dump the clutch in a drag race they do not dump it at idle to "modulate" the torque transfer.





#485 cheapracer

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Posted 14 March 2012 - 03:56

Your example of the bicycle chain derailleur ... That is they cannot both drive in one given gear mesh.


Not only they can, I was looking today and I can tranverse 5 gears at once, front and rear while applying torque/drive.

Your points are very valid with regards to durability.



Not relevant, has nothing to do if the box is seamless or not - everything breaks at a point, it's engineering 101.


#486 gruntguru

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Posted 14 March 2012 - 05:27

If input torque is reduced to the levels shown on the graph with the near vertical disengagement of the clutch with no increase in torque as a direct result of engine torque output control, the 1st gear bullets will disengage at any time the 1st selector fork is moved into neutral.

Rubbish. Read the descriptions, watch the video, the first gear bullets never disengage before second gear engages - always after.

#487 gruntguru

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Posted 14 March 2012 - 05:37

The actual "gear ratio" during a shift is the variable/irregular distance the chain travels around the rear sprockets versus the front sprocket.

The "actual ratio" will remain unchanged until the ratio "jump" (fed onto the cluster by the derailleur at the beginning of the shift) rotates around to the tensioned section of the chain. As the "angled" or "jump" links begin to feed off the cluster and straighten the ratio progressively varies up or down to the new ratio. In other words it is a stepped ratio transmission but the steps are smooth transitions - not instant. (they are pretty sudden I will admit)

#488 24gerrard

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Posted 14 March 2012 - 09:24

Rubbish. Read the descriptions, watch the video, the first gear bullets never disengage before second gear engages - always after.


Sorry grunt but I do not see any confirmation of this from a source close to the system.
Are you saying it is 'not possible' for the 1st gear bullets to disengage with reduced input torque before the 2nd gear bullets fully engage?
With the mechanism shown and the shift sequence, it is possible.
Hardly justification for 'rubbish', makes you look bad when proved wrong.

Edited by 24gerrard, 14 March 2012 - 09:28.


#489 24gerrard

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Posted 14 March 2012 - 09:27

The "actual ratio" will remain unchanged until the ratio "jump" (fed onto the cluster by the derailleur at the beginning of the shift) rotates around to the tensioned section of the chain. As the "angled" or "jump" links begin to feed off the cluster and straighten the ratio progressively varies up or down to the new ratio. In other words it is a stepped ratio transmission but the steps are smooth transitions - not instant. (they are pretty sudden I will admit)


It is a stepped ratio transmission but it also has constantly variable shifting.
It is the closest mechanism there is to my ESERU.
That also is a stepped gearbox with CV shifting, in this case by using electronic induction from an energy recovery system.

#490 24gerrard

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Posted 14 March 2012 - 09:31

Not relevant, has nothing to do if the box is seamless or not - everything breaks at a point, it's engineering 101.


What kind of answer is that Cheapy?
You have just discounted every technical innovation in engineering for the last 200 years at least.

#491 24gerrard

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Posted 14 March 2012 - 09:45

You have no way to prove that statement.

If you believe for an instant that race cars don't take advantage of 'banging it into the next gear' and the moment of extra torque the driveline windup offers to launch forward you are mistaken - again. When people dump the clutch in a drag race they do not dump it at idle to "modulate" the torque transfer.


I dont choose to prove the statement at this time.

You are mixing up completely different parts of the drive train and completely different operational requirements.

#492 24gerrard

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Posted 14 March 2012 - 10:38

Simple answer (and it is contained in a dozen posts already in this thread)

The input torque is reduced to remove the inertial spike - for comfort and durability. The graph is for a road box with added systems that are not part of the Zero-Gap Zeroshift mechanism.


So where is the graph for the non modulated shift using this mechanism?
So far all we have is marketing hype.
I cant see the zip on my jeans, I think I will call them seamless.

#493 24gerrard

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Posted 14 March 2012 - 10:58

Perhaps you tell me what happens during the shift?


In conventional automatic transmissionsThe gear system uses planetary gear sets not seperate gears.
Shifts use wet friction clutches and brake bands to connect or brake components in the geartrain.
The 'components' change the torque path from input to output.
Often the path is changed through the 'same' planetary set using the 'same' gears with a different input to output torque path.
The shift overlap is achieved by the slip in the wet friction components.
Modulation is mainly from the torque converter fluid 'slip' range, these days at high torque low gear shifts.
At higher ratios the converter is usualy locked by an internal clutch.

Dual clutch layshaft stepped gearboxes use this 'concept' but use 'dry' clutches (usualy for cost reasons and to allow one at least to be used for direct engagement). However these units do use seperate gears.
Because they use dry clutches and there is no fluid 'damper' in the form of an unlocked torque converter, the shifts have to be modulated and controlled on input torque otherwise the shifts would be sledge hammer like.
The same problem for a so called 'seamless' shift mechanisms in a single layshaft stepped gearbox.
The dual clutch boxes are faster for less judder than the single layshaft systems, however they suffer from higher windage and torque loss and a larger size and weight. Manufacturers choose them because they are cheaper than a 'proper' automatic gearbox.
The shift paddles, push buttons and any other space age gear shift gimmicks can be fitted to any of these gearboxes.
The result is the same, slower changes than from a dog ring manual gearbox less efficiency with torque transfer but with a smoother shift AND WITH THE RIGHT TORQUE TRANSFER CONTROL AND MODULATION less wear and potential damage.

Edited by 24gerrard, 14 March 2012 - 11:08.


#494 gruntguru

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Posted 14 March 2012 - 12:20

Sorry grunt but I do not see any confirmation of this from a source close to the system.
Are you saying it is 'not possible' for the 1st gear bullets to disengage with reduced input torque before the 2nd gear bullets fully engage?
With the mechanism shown and the shift sequence, it is possible.
Hardly justification for 'rubbish', makes you look bad when proved wrong.

Every description of the operation I can find says that the second gear bullets engage and then the first gear bullets are disengaged by second gear overdriving the shaft. If it is operated the way you describe, it cannot be called a Zeroshift.

If you can find any reference to the shift being operated the way you describe please post it here and I will retract.

#495 gruntguru

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Posted 14 March 2012 - 12:35

In conventional automatic transmissionsThe gear system uses planetary gear sets not seperate gears.
Shifts use wet friction clutches and brake bands to connect or brake components in the geartrain.
The 'components' change the torque path from input to output.
Often the path is changed through the 'same' planetary set using the 'same' gears with a different input to output torque path.
The shift overlap is achieved by the slip in the wet friction components.
Modulation is mainly from the torque converter fluid 'slip' range, these days at high torque low gear shifts.
At higher ratios the converter is usualy locked by an internal clutch.

Dual clutch layshaft stepped gearboxes use this 'concept' but use 'dry' clutches (usualy for cost reasons and to allow one at least to be used for direct engagement). However these units do use seperate gears.
Because they use dry clutches and there is no fluid 'damper' in the form of an unlocked torque converter, the shifts have to be modulated and controlled on input torque otherwise the shifts would be sledge hammer like.
The same problem for a so called 'seamless' shift mechanisms in a single layshaft stepped gearbox.
The dual clutch boxes are faster for less judder than the single layshaft systems, however they suffer from higher windage and torque loss and a larger size and weight. Manufacturers choose them because they are cheaper than a 'proper' automatic gearbox.
The shift paddles, push buttons and any other space age gear shift gimmicks can be fitted to any of these gearboxes.
The result is the same, slower changes than from a dog ring manual gearbox less efficiency with torque transfer but with a smoother shift AND WITH THE RIGHT TORQUE TRANSFER CONTROL AND MODULATION less wear and potential damage.

What a load of waffle! 99% of your post is irrelevant to the issue. eg torque converter - I have operated auto boxes with converter locked as has yourself. Shifts can be modulated to a very acceptable level of smoothness without the torque converter. The key facts are.
1. A planetary auto trans is a stepped ratio gearbox with a fixed number of ratios. How those ratios are achieved (whether by locking, driving or being driven from the sun, planets, annulus etc) is irrelevant to the topic.
2. A planetary auto trans achieves zero gap drive via its ability to drive through both ratios simultaneously during a handover period. Both gearsets are being partially driven through slipping clutches or brake bands. This is a cablecar with friction devices to grip either the slow or the fast cable. Zeroshift is a cablecar with selectable ratchets to grab each cable.

#496 24gerrard

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Posted 14 March 2012 - 14:27

What a load of waffle! 99% of your post is irrelevant to the issue. eg torque converter - I have operated auto boxes with converter locked as has yourself. Shifts can be modulated to a very acceptable level of smoothness without the torque converter. The key facts are.
1. A planetary auto trans is a stepped ratio gearbox with a fixed number of ratios. How those ratios are achieved (whether by locking, driving or being driven from the sun, planets, annulus etc) is irrelevant to the topic.
2. A planetary auto trans achieves zero gap drive via its ability to drive through both ratios simultaneously during a handover period. Both gearsets are being partially driven through slipping clutches or brake bands. This is a cablecar with friction devices to grip either the slow or the fast cable. Zeroshift is a cablecar with selectable ratchets to grab each cable.


In the valve chest of an automatic gearbox, you will find valves called 'modulation valves'.
Guess what they are for.

How the torque is transfered from input to output is of the utmost relevence.
You said two gears were driving at the same time.
That is not correct.
A planetary auto trans does not achieve zero torque gap on shift overlap.
It comes much closer than a zeroshift mechanism but no cigar.

#497 24gerrard

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Posted 14 March 2012 - 14:31

Every description of the operation I can find says that the second gear bullets engage and then the first gear bullets are disengaged by second gear overdriving the shaft. If it is operated the way you describe, it cannot be called a Zeroshift.

If you can find any reference to the shift being operated the way you describe please post it here and I will retract.


You can start by taking a closer look at the video of the operating mechanism.
Ask yourself why the 2nd gear selector fork has to move closer to the 1st gear after the 1st selector has selected 1st.

To engage 1st gear, the second gear selector fork then disengages 1st gear before the 2nd gear selector fork moves towards second gear.

Then ask why the 1st gear selector fork moves close to 2nd gear after the second gear selector fork has selected 2nd gear.
To engage 2nd gear.

Apart from torque control and modulation, you are missing half of the actuation.

Edited by 24gerrard, 14 March 2012 - 14:38.


#498 hogits2

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Posted 14 March 2012 - 15:59

As I see it….
1st gear ‘drive’ selector moves toward 1st gear. The gear is turning and the ‘socket’ catches up with the dog on the bullet and drives the hub. Then the 2nd selector/bullet moves towards 1st gear to fill up the backlash space.
So 1st gear is driving and there is minimal backlash if it goes into overrun.
When it is time for 2nd gear, the 2nd gear selector moves towards 2nd gear, leaving the backlash zone from 1st gear and the drive end of the bullet moves into the socket in 2nd gear. This leaves the 1st gear dog still driving. As the 2nd gear is moving slightly faster, its ‘socket’ soon catches up with the dog on the bullet and starts to take up the load.
As 2nd overruns 1st the socket in 1st gear rotates away from the drive dog and so it unloads the dog and the bullet can be withdrawn or if the ‘overrun’ side of the socket catches up it will push it out of the way.
At this point 2nd is now driving but there is still a ‘backlash’ hole. When there is alignment, the bullet (which carries the 1st gear drive and 2nd gear backlash dogs) moves in to the space, taking up the backlash.
The load changes from 1st to 2nd second gear while both ‘drive’ dogs are engaged but no ‘backlash’ dogs are in place. This takes place over a few degrees of rotation.

Am I being thick? I can’t see any point in the cycle when there is no drive. There will be a change which can be sudden or gentle depending on dampers etc.
If I stand on my left leg with right foot off the ground and then gradually transfer my weight to the right leg and lift my left foot off the ground, at what point do I become weightless? I may be a bit light headed due to this thread but I shall now put on my helmet and flack jacket and see who starts shooting. Apologies if I’ve confused anyone by blurring the meanings of dogs/sockets/selectors/bullets etc.

Edited by hogits2, 14 March 2012 - 16:15.


#499 saudoso

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Posted 14 March 2012 - 16:10

It's like arguing with a woman: pretty much one minute into the discussion and it's not about the original matter anymore, but who will get the last word.

In the man X woman case, we all know it's the man: "Yes Madam".

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#500 Tony Matthews

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Posted 14 March 2012 - 16:19

Apologies if I’ve confused anyone by blurring the meanings of dogs/sockets/selectors/bullets etc.

There's only one person confused here, and it's not you. Or me...