Simviation Forum - clutchless shifting

May 30^th, 2008 at 6:29pm

Craig. Offline
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Birmingham

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two topics in one really so help always appreciated.
Firstly, Watching some videos of a both a V8 car being driven and a Nascar being driven by Montoya, on both cases on the upshifts niether used the clutch with the exception of pulling away. Now I know you can change gear without a clutch but everything I have read suggests you need to drop the rev's then steady them before doing it. But in both cases these guys had their foot flat to the floor when upshifting. Any idea's?

Secondly just watching an old top gear with Clarkson testing the ascari A10 with its sequential gear box. It appears on the upshifts he's just pulling the stick as you would in most, but on the down shifts it appears he's using a clutch pedal. Again, is this one of the standards of this type of gear box or is it just a trick of the light and maybe he's just reacting to the braking or something?

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Reply #1 - May 31^st, 2008 at 4:51am

expat Offline
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As for the Ascari A10 with its sequential gear box, you need to look no further than motorbikes (though Fozzer would be a better person on this subject), they have aways had sequential gearboxes. The top racers never use the clutch to change up, it is time lost in the power train and that translated to lost time in a lap. If you watch them, they only use the clutch to change down. In my bike days................before I got married, I use to change up without the clutch, not so often, it was a road machine and not a racer. I see no reason why a sequential box in a car could also not be used in such a fashion. Also, you have no idea what come CPU is doing in the back ground. Foot flat to the floor, reach a set RPM and a computer controlled clutch does in a millionth of an eye blink what would in comparison take a driver three days to do. Just watching what the driver does today no longer gives you a complete picture to how one of these cars operate (unfortunately)

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Reply #2 - May 31^st, 2008 at 5:09am

Fozzer Offline
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In my old Brooklands 1931 Riley 9 Car with its "crash-type" silent 3rd. gearbox, where each toothed gear had to be physically meshed with the next gear, it was necessary to carry out what is referred to as "Double De-clutching" between changing gears.

This necessitated depressing the clutch, changing into neutral, releasing the clutch, allowing the revs to settle and the gears to slow down, depressing the clutch again, and changing into the next gear.

This was necessary in both upward and downward gear changes.

The practice was also common on old Lorries (Trucks).

Modern gearboxes contain syncro-mesh gears using "dog clutches", (where the gear teeth are constantly in mesh), rendering this practice unnecessary nowadays.

A definite technique, and loads of fun...especially under racing conditions...in old cars.........and old Lorries!.. Grin

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Reply #3 - May 31^st, 2008 at 5:18am

eno Offline
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You don't need a clutch to change up or down.

In the dim and distant past when gearboxes didn't have syncromesh, double clutching was the norm, it's too hard to describe in words but in essence it's all about matching engine revs to gear speed.

To change up you let the engine revs drop to those of the next gear and slip the gear in. To change down you blip the gas to match the revs of the lower gear. To get an accurate match takes practice and requires a slight pause in neutral, modern sequential gearboxes do this automatically and very fast because they are computer controlled.
I've successfully driven many vehicles without using the clutch, apart from pulling away and stopping. However it's becoming more difficult as cars get more sophisticated and engine management gets more complicated.

Edited:

Just what Paul said ..... but in more detail !!

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Reply #4 - May 31^st, 2008 at 6:34am

Fozzer Offline
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In my time in the British Army....long, long ago...thankfully...

My old Army petrol Scammell tractor unit, tank transporter, and my old Bedford QL and K3 3-ton Lorry, and my old Coventry-Climax 1/2 ton electrical generator Unit with its wooden cab and perspex windows, all required double de-clutching their gear boxes during gear changes.....

With central, cab mounted gear boxes, many of the gear-shift levers were located BEHIND the driver!

...Gear changing was a VERY long-winded, body twisting, and time consuming process...

...trust me... Wink

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(Quite good fun tho'...at the time!)

Paul....REME....BOAR....distant past... Wink

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Reply #5 - May 31^st, 2008 at 6:47am

Hagar Offline
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Fozzer wrote on May 31^st, 2008 at 6:34am:

In my time in the British Army....long, long ago...thankfully...

My old Army petrol Scammed tractor unit, tank transporter,

I think you mean Scammell. Scammed has a slightly different meaning. Tongue

Was it anything like this? http://www.youtube.com/watch?v=qFUurpWn3Gs&feature=related

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Reply #6 - May 31^st, 2008 at 7:07am

Fozzer Offline
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An elderly FS 2004 addict!
Hereford. England. EGBS.

Posts: 24861

Hagar wrote on May 31^st, 2008 at 6:47am:

Fozzer wrote on May 31^st, 2008 at 6:34am:

In my time in the British Army....long, long ago...thankfully...

My old Army petrol Scammed tractor unit, tank transporter,

I think you mean Scammell. Scammed has a slightly different meaning. Tongue

Was it anything like this? http://www.youtube.com/watch?v=qFUurpWn3Gs&feature=related

Sorry Doug....my Typo Error....

...distant memories and general confusion... Wink

...!

Yep...that's the one!....

...!

The "Petrol" Scammell engine/bonnet was much larger than the Diesel version...VERY inpressive... Smiley

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I loved it to bits....hauling Centurion Tanks down the German Autobahn!.... Kiss

...!

Paul....getting scammed, on occasions... Cry

...!

...

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Reply #7 - May 31^st, 2008 at 4:02pm

Mushroom_Farmer Offline
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To the Sooper-Coop Fred
Indiana, USA

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The Jerico transmission is used in NASCAR, also in drag racing. It is designed to allow shifts without clutching, although some old-timers like Mark Martin still clutch-shift.
I have an old 1975 C-10 pickup/ute which can be shifted up and down without clutching.

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Reply #8 - May 31^st, 2008 at 9:50pm

The Ruptured Duck Offline
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My advice to you: Stop watching NASCAR

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Reply #9 - Jun 1^st, 2008 at 4:21am

Mushroom_Farmer Offline
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To the Sooper-Coop Fred
Indiana, USA

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The Ruptured Duck wrote on May 31^st, 2008 at 9:50pm:

My advice to you: Stop watching NASCAR

I don't watch NASCAR, can't stand it. Wink

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