Clutchless shifting?

[p.dath]

From a machinist point of view, a clutch is made to gradually apply power to a system, equalising speeds between driving and driven sides of a system, also reducing shock loading on wearing surfaces, it only makes sense that not using your clutch WILL wear out your box faster than without..

Ahh, but if the time to wear out the box when not using the clutch is longer than the life of the bike, then it's just a technical point.

Even it it shortened the servicing time from 200k to 100k - that's still a lot of use.

[gatch]

Ahh, but if the time to wear out the box when not using the clutch is longer than the life of the bike, then it's just a technical point.

Even it it shortened the servicing time from 200k to 100k - that's still a lot of use.

Yer fair enough, I wouldn't like to estimate the life of a bike though, I'd rather everything stay in as good a condition as I can for the sake of an extra 1/4 second while shifting gears..

[onearmedbandit]

I must admit that the only real reason I don't use the clutch for every change is purely down to only having one arm. The clutch set up is fine, albeit a new lever/perch and cable will help, but I find that on the track especially it is simply easier to change without the clutch.

[Dropped]

it doesn't matter when i change gear without the clutch it goes perfect.

[onearmedbandit]

From a machinist point of view, a clutch is made to gradually apply power to a system, equalising speeds between driving and driven sides of a system, also reducing shock loading on wearing surfaces, it only makes sense that not using your clutch WILL wear out your box faster than without..

Correct me if I'm wrong, but I'd argue that. Using the clutch reduces the load on the gearbox by disengaging the drive from the box. Having the throttle at the correct point also does the same, granted it doesn't disengage but it does reduce the load. So how can that damage the box? Using either the clutch or throttle application, the bike changes gear as lightly and sweetly as each other method. Opening the throttle after the gear is selected matters nothing, because the gear is already home, in fact no different from opening the throttle from a closed position at any time during the ride.

[bogan]

Correct me if I'm wrong, but I'd argue that. Using the clutch reduces the load on the gearbox by disengaging the drive from the box. Having the throttle at the correct point also does the same, granted it doesn't disengage but it does reduce the load. So how can that damage the box? Using either the clutch or throttle application, the bike changes gear as lightly and sweetly as each other method. Opening the throttle after the gear is selected matters nothing, because the gear is already home, in fact no different from opening the throttle from a closed position at any time during the ride.

ill add an engineerist's point of view, with clutchless shifting, the engine revs (roatitional inertia) changes very quickly, clutched shifting it can change slower. Gearbox must supply this changing force, so there is more force on the box during clutchless shifts. Of course this force could very well be less than it is under full throttle acceleratuion anyways so (as always) my point could be null

[gatch]

Correct me if I'm wrong, but I'd argue that. Using the clutch reduces the load on the gearbox by disengaging the drive from the box. Having the throttle at the correct point also does the same, granted it doesn't disengage but it does reduce the load. So how can that damage the box? Using either the clutch or throttle application, the bike changes gear as lightly and sweetly as each other method. Opening the throttle after the gear is selected matters nothing, because the gear is already home, in fact no different from opening the throttle from a closed position at any time during the ride.

Reducing the load by backing off the throttle is not the same as completing removing load by disengaging the clutch.

When you instantly shift gears something has to change speeds very quickly, with the engines internals being lighter than the rest of the bike, engine rpm will jump or fall. Using the clutch the only part that has to slow down/speed up is the input shaft of the box and gears that sit on it..

Less rotating mass to accelerate/decelerate, less stress on parts.

I think...

[onearmedbandit]

Yeah you're probably right.

[YellowDog]

Well I just stopped doing it after a few scares on the Tiger 1050 forum.

I still believe that if you get the engine speed right and do it smoothly, then it is puttling less stress and wear on the bike however............................
(I could be wrong)

[huff3r]

Well I just stopped doing it after a few scares on the Tiger 1050 forum.

I still believe that if you get the engine speed right and do it smoothly, then it is puttling less stress and wear on the bike however............................
(I could be wrong)

In a synchromesh box it is less stress if done right, because thats how the synchros are designed to work...

In a dog-type box, it could be slightly more damaging, depending wether you got a gap or not, its all guesswork with them

[gatch]

In a synchromesh box it is less stress if done right, because thats how the synchros are designed to work...

In a dog-type box, it could be slightly more damaging, depending wether you got a gap or not, its all guesswork with them

"Most" bike gearboxes are not synchro mesh.

[Juzz976]

I sometimes upshift without clutching and find its really smooth, however I just dont do clutchless downshifts.
I dont believe it causes anymore wear on the gearbox than closing the throttle at high revs.

My opinion is that once you've let off throttle sufficiently for the shift, the reduction in angular velocity required to "mesh" smoothly with the next gear is taken care of by compression and other losses within the reciprocation of your engine.
The inertia of a motorcycle engine is small so the energy difference between initial angular momentum to desired is pretty damn low and is very quickly absorbed by compression and friction.
The output side of the gearbox also has very little inertia and I would hazard a guess this excess energy is spread quickly to the slack in the chain, thus tensioning it and absorbing the residual energy.

I'm not saying that its perfect meshing without wear, because all parts are subject to wear. It's just not all that significant in the overall dynamics of a the type of craft we're dealing with.

anyhows thats my opinion and I ride a bike with 7,000kms on it, they dont last forever and I'm not "going to see how many k's I can get from a bike before something gives out" and "how can I make sure my bike will last 160,000k's" - I think I'd be more inclined to worry about the safety aspects of my bike and how I can enjoy myself more. (of course a gearbox lock up at high speed concerns me but thats a risk we all take.

[Juzz976]

oh yeh last bike I had I did 10,000k's on resulting in 72,000 overall.
I raped the box on that thing and she still runs mint now, it was one of the few things not replaced during my ownership.
I know for a fact the 2 previous owners did too, and most likely the 10 before that too.

Oh yeh did I mention that oil has a slight dampening effect, at high speed energy is absorbed by the reluctance of the fluid being displaced.

[bogan]

I sometimes upshift without clutching and find its really smooth, however I just dont do clutchless downshifts.
I dont believe it causes anymore wear on the gearbox than closing the throttle at high revs.

My opinion is that once you've let off throttle sufficiently for the shift, the reduction in angular velocity required to "mesh" smoothly with the next gear is taken care of by compression and other losses within the reciprocation of your engine.
The inertia of a motorcycle engine is small so the energy difference between initial angular momentum to desired is pretty damn low and is very quickly absorbed by compression and friction.
The output side of the gearbox also has very little inertia and I would hazard a guess this excess energy is spread quickly to the slack in the chain, thus tensioning it and absorbing the residual energy.

I'm not saying that its perfect meshing without wear, because all parts are subject to wear. It's just not all that significant in the overall dynamics of a the type of craft we're dealing with.

anyhows thats my opinion and I ride a bike with 7,000kms on it, they dont last forever and I'm not "going to see how many k's I can get from a bike before something gives out" and "how can I make sure my bike will last 160,000k's" - I think I'd be more inclined to worry about the safety aspects of my bike and how I can enjoy myself more. (of course a gearbox lock up at high speed concerns me but thats a risk we all take.

compression friction etc doesnt really come into play with the timescale we're talking here. Rev you engine in nuetral and see how long it takes to drop a couple of thousand rpm, half a second? clutchless shift times are milliseconds. So virtually all of this angluar momentum has to be absorbed by the driveline, generating large forces in the gearbox.

In saying that though, I havent seen actual figures for engine inertia, shift times, or comparative gearbox torque between clutchless shifting and full throttle acceleration.

[Juzz976]

I also think if the manufacturer didn't want us doin so they would make box's they dont shift nicely without clutching. like a car.

Totally agree with the time factor too and I'd like to investigate further.
my bike drops revs fairly quick, actually faster than the tacho needle can fall. I'll go hook up my ocillioscope later and maybe a vibration sensor and log some graphs for us.

Another consideration is how close your gear ratios are as I think thats a real important factor as I'm not dropping a couple of thousand revs on a shift and the response time of a tacho is pretty slow - most I think would be an analog output from the cdi which has DAC Latency coupled with the dampened effect incorporated into moving coil ammeter/voltmeters subjected to shock and vibration.
I always clutch to second btw. and really I think I can clutch change as fast as non clutch.

And yes to clarify it will be detrimental to the integrity or your gearbox but then who gives a toss. Get a new bike and rape that too. oh yeh and i rekon there ppl out there so shit at doin clutched changes that they put extra stress on their box's anyways.