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Old 29 Apr 2007, 01:50   #1
karimbo
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How does a seamless shift gearbox work?

In Formula 1 this year every competitive team is running a seamless shift gearbox. I would like to know how it works. Could anyone explain me what is the difference between a seamless shift gearbox and an automatic gearbox.

I know that John Barnard introduced the semi-automatic box on the Ferrari with the shifters in the early '90s. Then, a few years later came a gearbox shifted all by itself: it allowed the driver to race the car like a kart. Then the rules brought back the shifters on the steering wheel. So today I would like to know:

1) Is a seamless shift gearbox the same as a CVT (continously variable transmission?

2) Do drivers have to shift gears themself.

3) How many gears do these transmission have?

4) Do they have discreet ratios?

Thanks in advance
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Old 29 Apr 2007, 02:02   #2
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Karimbo you might find this to be of some help?

http://www.zeroshift.com/pdf/RcarN6V15_Zeroshift.pdf
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Old 29 Apr 2007, 04:18   #3
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Theyre a development of the current gearboxes, in short. Still 7 speed, semi auto, driver shift controlled. Theyve just been modified so that the power isnt cut during shifts.
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Old 29 Apr 2007, 05:26   #4
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Quote:
Originally Posted by karimbo
1) Is a seamless shift gearbox the same as a CVT (continously variable transmission?
No, it is'nt , because if it was it would be illegal, it has been banned ever since Williams tested it in 1994(it was to fast), now the car is in the VDT factory.


http://www.cke-tech.com/graphics/CVPST/CVT-test_car.jpg
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Old 29 Apr 2007, 16:35   #5
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Quote:
Originally Posted by karimbo
In Formula 1 this year every competitive team is running a seamless shift gearbox. I would like to know how it works. Could anyone explain me what is the difference between a seamless shift gearbox and an automatic gearbox.
These are called sequential gearbox. Which also have electronic shifting no mechanical linkage.

BMW calls it thier SMG gear box. Porsche has their triptronic sequential gear box.

Many ppl call them "paddle shifters"

Info on differnt transmission:

http://www.autozine.org/technical_sc...ear_manual.htm


1) Is a seamless shift gearbox the same as a CVT (continously variable transmission? SEQUENTIAL

2) Do drivers have to shift gears themself. YES, right paddle UPshift, Left Paddle downshift

3) How many gears do these transmission have? 6 for road cars, 7 for F1 cars

4) Do they have discreet ratios? Road cars, yes, for the most part. Race cars the gear ratio is depended on the race circuit.

Last edited by AU N EGL; 29 Apr 2007 at 16:38.
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Old 29 Apr 2007, 19:10   #6
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Originally Posted by steve nielsen
No, it is'nt , because if it was it would be illegal, it has been banned ever since Williams tested it in 1994(it was to fast), now the car is in the VDT factory.
]
Actually it was tested in 1993...by David Coulthard

http://www.youtube.com/watch?v=x3UpBKXMRto

The seamless shift works in a very simply way...there is a point where 2 gears are selected at the same time....but one of them is ratcheting (the one to be selected) and when the driver clicks on the paddle the gear to be selected locks and the previous gear ratchets when the torque is applied to the selected gear.
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Old 29 Apr 2007, 19:50   #7
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Quote:
Originally Posted by AU N EGL
These are called sequential gearbox. Which also have electronic shifting no mechanical linkage.

BMW calls it thier SMG gear box. Porsche has their triptronic sequential gear box.

Many ppl call them "paddle shifters"

Info on differnt transmission:

http://www.autozine.org/technical_sc...ear_manual.htm


1) Is a seamless shift gearbox the same as a CVT (continously variable transmission? SEQUENTIAL

2) Do drivers have to shift gears themself. YES, right paddle UPshift, Left Paddle downshift

3) How many gears do these transmission have? 6 for road cars, 7 for F1 cars

4) Do they have discreet ratios? Road cars, yes, for the most part. Race cars the gear ratio is depended on the race circuit.
Karimbo

The above statement is not correct AU N EGL is only talking about a sequential gearbox the Zeroshift is explained by Monstrobolaxm correctly. Basically 2 gears are selected together then I would think there are various way of changing to the second gear. There was talk of fitting 2 clutches in the gear box to select each engaged gear not sure if this was banned. Basically the Zeroshift means zero time that the gearbox is not driving the car. What has changed is the time it used to take for the selector ring to disengage from one gear and engage in the next gear.
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Old 29 Apr 2007, 21:11   #8
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Originally Posted by ChironWSC
Karimbo

The above statement is not correct AU N EGL is only talking about a sequential gearbox
HELLLOOOO????? That is what I said, Sequentials.
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Old 29 Apr 2007, 21:25   #9
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Quote:
Originally Posted by AU N EGL
HELLLOOOO????? That is what I said, Sequentials.
Except that the question wasn't about sequentials as such, but the particular sort of sequential called "seemless shift" or "Zeroshift". This type have no gap at all in power delivery while the gear is being changed. As I understand it F1 has banned a zero time lag, but the technology is still used with a deliberate pause of the minimum allowable gap (or maybe that was the rule and its changed. Expert help anyone? Adam?) Anyway, I seem to recall that the main problem with using the truely seemless gearboxes is that the near instantaneous change in rotational speed of the output shafts, and hence wheel rims, gives the tyre walls some serious grief.
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Old 30 Apr 2007, 08:46   #10
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Quote:
Originally Posted by ChironWSC
There was talk of fitting 2 clutches in the gear box to select each engaged gear not sure if this was banned.
I dont know if it was banned or not, but the function of having 2 clutches is basically the principle behind Volkswagens DSG gearboxes. The seamless gearboxes are different than the DSG boxes apparently, and the explainations already provided seem to back that up.
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Old 30 Apr 2007, 17:14   #11
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To try and answer this as succinctly as possible:

Quote:
Originally Posted by karimbo
1) Is a seamless shift gearbox the same as a CVT (continously variable transmission?
No. CVT's do not have discreet gear ratio's, F1 gearboxes all do.

Quote:
2) Do drivers have to shift gears themself.
Yep, they still have the paddles.

Quote:
3) How many gears do these transmission have?
I believe most, if not all, current F1 team use 7 forward gears in their transmissions.

Quote:
4) Do they have discreet ratios?
Yes.

As far as I know, the main difference between yesteryears "semi-automatic" and this years "seamless shift" gear boxes is about the use of the clutch, not the gears themselves.

In a normal semi, like with a normal gearbox, the clutch disengages whilst a new year is put into place, then re-engages the new year. This means there is a time (in an F1 car, a few milliseconds) where there is no power going directly to the wheels.

In a seamless shift box, there is no such time. I'm not entirely sure on the mechanism behind this, but I would imagine it could well be something like using two clutches (or more) so that for a period both gears could be engaged simultaneously, although only one would then be connected to the wheels. This would allow for there to be no momentary loss of power to the wheels when changing gear.

Hope that makes sense.
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Old 30 Apr 2007, 21:48   #12
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Quote:
Originally Posted by Sev
I'm not entirely sure on the mechanism behind this, but I would imagine it could well be something like using two clutches (or more) so that for a period both gears could be engaged simultaneously, although only one would then be connected to the wheels. This would allow for there to be no momentary loss of power to the wheels when changing gear.
No its entirely cleverer, and indeed simpler, than two clutches. It's all explained in the link from Jeremy in the second post
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Old 7 May 2007, 12:52   #13
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I'm not sure you are right dtype38
All evidence i've heard so far is that the type used in f1 are based on the twin clutch/twin shaft idea
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Old 7 May 2007, 18:58   #14
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Errr... ok, you got me there carlo. I "thought" that the seemless shifts used in F1 were a version of the Zeroshift, but I'm not prepared to put any money on it! Depends on your understanding of the terminology, but you could say that the dog engagement system of the Zeroshift is a twin clutch system.. sort of! Do you have any references for the system you refer to?
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Old 7 May 2007, 19:19   #15
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F1 is definitely not using Zeroshift boxes. I believe they are using Dual Clutch technology, which gives an upshift time of approximately 40ms, downshifts a little longer. The Zeroshift box, uses overunning clutches and doesn't have a viable shift quality yet.
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