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Changing gears without clutch

fgclark123
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Changing gears without clutch Empty Changing gears without clutch

Post by fgclark123 on Sun 10 Dec 2017, 7:35 pm

Hi guys,

This is something I've just cottoned on to - can you let me know the deal? Is changing gear without clutch possible without damaging the gear box? Is it only at higher or lower revs, with or without giving it throttle?

Thanks, interested to hear more.
louis_sutton
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by louis_sutton on Sun 10 Dec 2017, 10:11 pm

Only up the gears mate. Clutchless upshift for me involves a decent lift up the rev range, then backing off just a touch, when the gear will effortlessly snick up.
skyrider
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by skyrider on Mon 11 Dec 2017, 6:41 pm

usually I only use the clutch when changing down
fgclark123
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by fgclark123 on Sat 16 Dec 2017, 10:57 pm

just tryiung this today. don't know why i was ever taught to use the clutch to upshift... works a treat clutchless.
Jameshambleton
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by Jameshambleton on Sun 17 Dec 2017, 12:05 am

@fgclark123 wrote:just tryiung this today. don't know why i was ever taught to use the clutch to upshift... works a treat clutchless.
If you hold the throttle in the same position as you do when you upshift you can also downshift too.
fgclark123
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by fgclark123 on Tue 19 Dec 2017, 11:38 pm

Is there a short answer as to why this is? How does the engine revs interact with the gearbox???
skyerae
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by skyerae on Wed 20 Dec 2017, 6:16 am

I used to do this in my wife's car, a Peugeot 306 and then it started to drop out of fifth gear quite happily. I learnt an expensive lesson as the car was taken to a metal scrap merchants as it wasn't worth repairing - many things were going wrong as french cars like to do................I now own an automatic car and that does all the thinking and changing for you - much better in my humble opinion, and it is NOT french.
motofan
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by motofan on Thu 21 Dec 2017, 5:29 pm

If you're going to change gear without using the clutch you must match the engine speed to the rear wheel road speed, therefore to change up, dip the throttle as you press the gear lever, this lowers the engine revs to match the higher gear. To down change you must "blip" the throttle as you press the gear lever to raise the revs for the given road speed, that is to say from a closed throttle as you slow down you open the throttle to raise the revs and press the gear lever.
Changing up is more natural and thus smoother at first than changing down which takes a bit more learning. If you do it gently but firmly it should go easily, don't use too many revs at first and if you mismatch the speeds it'll let you know! It shouldn't do any damage (unlike the poor Peugeot of Skyrae) bike gearboxes are different to car ones.
I don't clutchless change between 1&2 normally as neutral gets in the way and makes things really crunchy but on my BM the top three gears are smoother clutchless!
Skyrae, with you all the way on automatics, my artic was heaven to not have to piss about with 16 gears!

Merry Christmas santa and Hiccuppy New Year to one and all.  rendeer
skyerae
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by skyerae on Thu 21 Dec 2017, 7:30 pm

I only have 5 gears to worry about Shocked
motofan
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by motofan on Thu 21 Dec 2017, 8:26 pm

Lucky!
skyrider
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by skyrider on Thu 21 Dec 2017, 8:33 pm

anybody who has more than six gears is being greedy Laughing
motofan
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by motofan on Thu 21 Dec 2017, 11:43 pm

40 tons say 400hp = 10hp/ton. If your 1ton car had a 10hp engine how many gears would you need to get up to 55mph? I don't know but I bet you'd wish you had more than 6! I think six gears in a bike over 250 is 1 too many but I don't like changing gear and these new cars with six gears, what's all that about. Give me a naughtymatic any day! Very Happy
skyrider
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Post by skyrider on Fri 22 Dec 2017, 10:04 am

the two stroke tractor units the drivers never stop changing gear Neutral
stormbringer
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by stormbringer on Mon 25 Dec 2017, 10:55 am

Reverting to subject, I would recommend you to have a google for 'dog box'.

As mentioned, motorcycles and household cars do not use the same kind of gearbox. Rally cars, however, oftentimes use a design similar to the motorcycle version - a dog box.

The thing is, a dog box is faster! It's also mechanically smaller, which is the primary reason our CB's sport this type - cramming six gears into little space and little weight is important. As a nice side effect we get handed - free of charge - the gear changing speed.

So, a dog box it is. Youtube has several good videos on the subject, but in essence the difference to a household car engine is the absence of synchronisation mechanisms, helping parts not banging into each other when you operate the gear lever.
In the olden days, car drivers had to assist the internals of the gearbox synchronising by 'double-clutching' on shifts. That didn't go down well with buyers as the car became a commodity, sold to less mechanically proficient consumers. So, someone invented a mechanism to simplify gear changes. No KLONK! at the cost of switching speed.

Switching our attention back to motorcycle- and racecar-users, speed, size and weight remain essential, meaning the dog box is simple and rugged, designed to withstand the mechanical shock caused by sudden changes in rotational speed of internal components. It does away with the complex and slow bronze synchromesh mechanisms, replacing them with simple, compact and resilient interlocking mechanisms. Klonk is unavoidable, but with the help of a clutch and/or practice in operating throttle + gearlever it can be minimised to the point where you really don't notice.
skyrider
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by skyrider on Mon 25 Dec 2017, 11:06 am

is that sometimes called a crash box
stormbringer
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Changing gears without clutch Empty Re: Changing gears without clutch

Post by stormbringer on Mon 25 Dec 2017, 11:50 am

@skyrider wrote:is that sometimes called a crash box
It is.

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