Clutchless gear shifting?

[The Stranger:Me]

Nope. You do it as you go through the gearchange. Takes a bit of practice but once you can it becomes second nature, although I suspect what gearbox ratios you are running can either help or hinder the situation.
I rarely use the clutch in either direction (depending on speed) and after 45,000kms the gearbox changes sweet as ever (bit of a surprise for a Triumph.....).
I cut my teeth (excuse the bad pun) on racecar straight cut "dog" boxes which helped but, like anything else, it's just practice, practice, practice...

Fark, ok. Learn something new every day. Don't anticipate I will be trying it as I will have about a milisecond in which to blip the throttle and for the engine to respond. Beside the XT slips through smooth as silk without clutch in either direction.

[Max Preload]

O....K.... this is a piss take right.
You are coming up to a corner and want a smooth entry and you are going to blip the throttle with the bike in gear and the clutch engaged?

Nope. You do it as you go through the gearchange.

Correct-a-mundo - I should have been a bit clearer on that.

[ckai]

Hi guys

I have a mate with a Hyosung GT250R who wants to give me a drag for $100 some time soon, somebody recommened I shouldn't bother with the clutch as It will make shifting faster.

My question is:

Is that a good idea? I.E is it bad for the bike if not done properly?

Please help out a newbie

Thanks

So who won???? Do you get to shout with your cool winnings?

Personally because the ninny is about .3 seconds faster to 100km/h I would have said change normal and make it a good close race. And, unless you have fat man syndrome, your bike is lighter.

[GaZBur]

Im with svr in holding the throttle wide open flick the clutch and gear lever simultaneously as I believe you are fractionally faster on the power and less likely to stuff up the change than clutchless and adjusting the throttle on the change. Try both ways yourself and see which works best for you and your bike. I wouldn't downshift without the clutch unless i am going straight as a rough change can really unsettle your bike particularly with bikes that have heavy engine breaking.

[mattathm]

If your bike isnt a hyo 250, then you have probably won the race already, hehehehee

[Leseid]

Ok I'm only a noob as a motorcyclist, but I've somehow (by mistake) learnt how to change gear using throttle and left foot.

But as a qualified mechanical engineer I've naturally analysed this technique of changing gear and what effect it would have on the bike.

So here's where my thinking is at the moment (by all means correct me if I've gone down the wrong train of thought).

Suddenly backing off the throttle just a little slackens the chain, removing the load from the teeth in the gear box. Or more specificatively the backlash in the dog teeth, that engage drive from the shaft to the gear. A pre loaded gear shifts in like silk.

Now here is where I think motorcycle gear boxes might be really cleaver. The gear ratios between gears are matched so that the revs you've just dropped it to slacken the drivetrain, so the dog teeth of the next gear slide right in. The reason for this thinking is it's only possible on my cbr125 to flat shift from gear 3 upwards, but there's no reason a race bike could do this for all gears. I also assume the dog teeth won't be straight cut, so with a bit of taper you can flat shift with some tolerance.

If any one is qualified to confirm or deny this I would be really interested in learning more about this.

[Maki]

I used to have a Kawasaki 250R and the only way I could keep up with others on certain KB group rides was by shifting clutchless. If you want to race the hyo practice shifting up through the box a few times before the actual race. When the shifts feel silky and effortless you have it nailed...

[p.dath]

This is way beyond my knowledge Leseid, but I found this info that looks related to your question:

http://www.eng-tips.com/viewthread.c...142609&page=11

In a motorcycle dog-clutch transmission the drivetrain provides a cushion for the change in speed of the clutch /and engine if reqd. The rubber damper in both the clutch inner hub and the rear wheel hub provide lots of cushion. The dogs also have a lot of slack in rotation to increase the likelihood of a clean engagement. The ratios tend to be close which helps a lot.

Just apply simple kinematics. You need to look at how many degrees engine rotation you can get from the flex you have in all the parts from the clutch disk to the tires, and assume it all acts like a torsion spring. Estimate the engine inertia. Calculate the resultant torque (T = I x angular accel) required to decelerate the engine speed from one gear to the next over that many degress.