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IRA11Y
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Location:
sydney
Registered:
May 2002

Re: DOUBLE CLUTCHING the low down

Sat, 29 November 2003 22:36

firstly sorry to everyone for the length...

Bayka

urmmm No! you diddnt ask about syncromesh you asked about double clutching

Quote:

Hi ppl, did a search and didnt' find much in the way of this topic.
There are 2 stories i have heard
1. clutch in -> change gear -> clutch out -> kick clutch in/out again

2. clutch in -> shift to neutral -> clutch out -> clutch in -> shift to gear -> clutch out

Im pretty sure number 2 is rite, but don't know much in the way of why or reason. Ive heard its to avoid the synchro's or some shit.

Whats the deal??

this subject has been covered previously, and a search "should" have answered your INITIAL question (I have to admit i couldnt find the old thread in the search but i did find this where there is a link to an old Twincam16 thread asking the same question,

http://forums.toymods.org.au/index.php?t=msg&t h=978&rid=2&S=6e81f544eabfa252f97d1f7138be 8368&pl_view=&start=0#msg_7894msg_7894 )

however the people without knowledge (or those that have heard something and assume that they now have knowledge without any application to back up what comes out of thier mouth/keyboard) responding to this thread wont/arent taking on board what more experienced people have posted, in this thread ive seen the same responses posted over and over

eg

Quote:

You double clutch when you drive a truck etc.. This is because the gearbox is not synchronous. I think this is where the confusion is getting set in.

Quote:

Just to summarise:

- Double-clutching is mostly used on non-synchromesh gearboxes (eg big trucks) although as mentioned above it's sometimes necessary with worn-out synchromesh boxes. It's also used in autocross-type events when you need to select first gear at speed -

Quote:

Double clutching is so not needed for any modern cars

Quote:

As explained earlier, it synchronises the speeds of the input shaft and output shaft in the gearbox to allow a smooth shift. This is only necessary in non-synchromesh boxes, and since all cars built in the last 40 years or so have synchromesh, there's no need to do it.

Quote:

but as norbie says, all the recent cars have syncromesh, so its actually a lot quicker to change gears normally!

hmm not much there to answer what you asked i spose Rolling Eyes

if anything you should take this quote on board, its what all Dog/Crash gear-box drivers do ( except as previously quoted after initial momentum a clutch is generally no longer used )

( I drive HC so if you want to tell me im full of shit please feel free, ive only been driving heavy vehicles since i was 12 so not much experience there Smile

)

and WILL improve performance in terms of reduced lost change time and IS a benefit but takes practice to do well, the hardest bit is timing the depression of the clutch to when it hits the gate of the next gear. an ideal way is to put a slight amount of pressure on the lever just before you are about to change ( not enough to pull it out of the gate), this way when you back off the throttle and start depressing the clutch ( you can do the same in a flat shift) it will slide out of gear in time with depression of the plate and should hit the new gate at the critical depression point of the clutch.

Quote:

Usually means pulling gear into neutral while still pushing clutch in so that by the time I'm going back into the next gear the clutch is fully in.

next question

Quote:

Like for instance why it is difficult to get 1st gear in at speeds of around 40-50.

this is primarily due to the large gear step between first and second, the synchro's need to match between the two gears but the step is so big compared to other gears they neeed to be rotating a lot slower to engage thru the gate

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