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I think they called that the "slick shift " Dave....didn't last long.
Because the ecu knows the gear you're in and the road speed it calculates the rpm needed for the next lower gear. With the engine on the overrun and the backlash dogs on the gears "loaded" due to driving the engine and foot pressure on the gear lever when the foot pressure threshold is reached the ecu simply blips the throttle to the required rpm. As the engine begins to accelerate to the desired rpm the split second the load comes off the gears the foot pressure on the already loaded shifter moves the drum and engages the next gear. On a bike it's not actually "blipping" the engine rpm in the manner a car with an H pattern gate is it's more "rev matching" and it all happens in a fraction of a second. The gear unloads and starts to disengage right at the start of the process of the revs increasing. The revs don't actually need to increase in reality to do this, the drive load just need to come off the gear with foot pressure applied on the gear lever. It's a similar reason a gearbox always shifts cleaner when you load the lever before you pull the clutch. As soon as the clutch has unloaded the drive dog faces the pressure that's already applied via the foot pressure drives the gear. It's also why the system works better with engines with light cranks and multi cylinders that rev quick and at high rpm. At low rpm/slow revving engines the shift action can be faster in elapsed time than the engine can bring the revs up. When the engine is really revving it catches additional revs a lot quicker.The lever extender mod I came up with and Chuck manufactured improved the shifting of the v11 gearbox because it reduced some of the leverage advantage your foot had over the shift mechanism so when the load came off the gear dogs and the detent spring released there was extra force already applied to the shift lever due to the reduced leverage which meant the shift action was faster and the shift cleaner. So faster cleaner shift action with reduced lever movement but with slightly heavier action. Gearbox shifting mechanics is an interesting subject and there are so many pieces that combine to make a clean shifting gearbox.Ciao
So you load the shifter and come off the throttle and at some point the gear box unloads enough to shift and at that point the ECU blips the throttle? Does sound brutal on the gear box internals ......... which brings us back to Huzo's opening post
you get a seamless down shift with the right revs for the lower gear.Ciao
How does the engine achieve “the right revs for the lower gear” when it it still connected by the gear it is about to exit ?It surely can only increase it’s revs to the target value, during the transition from the previous gear to the next. While any gear is engaged, it cannot alter it’s rpm if the road speed is constant (which it is) during the transition.eg..80 kph @ 3,500 rpm in 4 th to80 kph @ 3,000 rpm in 5th 0.2 seconds later.
Imagine the gear on the overrun with the dog faces loaded and as I've pointed out previously your foot is applying pressure on the shifter and the pressure switch (load cell) is approaching it's threshold for switching. The whole shifter mechanism is heavily loaded in the down shift position. The foot pressure now reaches the pressure sensor threshold and commands the engine to the new target rpm. Before the engine has even had the chance to increase the rpm by 10 rpm as an example the backdrive pressure is now released from the gear dogs and with the system already loaded by your foot the gearbox deselects the gear you're in and heads towards the lower gear and engages. The engine can't rev faster than you can "deselect" the gear partly because the deselection action happens immediately at the start of the engine acceleration process as soon as the increase in rpm has off loaded the gear dogs. In reality the engine rpm doesn't even need to raise for the foot pressure to deselect the gear the engine load just needs to be released same as "floating" the throttle manually. All this shifting action happens happens not in 10ths of a second but in Milliseconds. The adjustment range of my Techtronics unit is 20-120milliseconds of cut time. Ciao
This is where the slipper clutch on modern high performance motorbikes comes into play . Watch any Irish National roadrace , you can actually hear the engines over revving on downchanges as they enter corners . Dusty
You know all this stuff about quick shifters pretty much defeats the fun and satisfaction of executing a perfect downshift with your own hands and feet. I know a QS was an option on my Ducati. The unit has proven to be unreliable and occasionally causes ignition failure. The newer units are perfect but what fun is that? Anyway, I couldn't go an extra couple $ thou for a quick shift and some gold colored suspension pieces. The bike has a slipper clutch, I've felt it kick in a couple of times in pretty sedate situations. OK, just my opinion.
That's kinda what I said Phil . By allowing the engine to over rev it prevents wheel hop , ask Huzo if I didn't already tell him that . Dusty
Ok, I accept the premise of what you’re saying Phil, but I think it serves my point more than it does yours.In your (educated) opinion, can or has the flywheel had enough time time accelerate (or decelerate) by say 500 rpm, in the amount of time that the drivetrain is “between gears” ?There has to be a finite time that this “between gears” state exists, by virtue of the fact that it’s not in two gears at once, even though they are constantly meshed and what would you suggest that period of time is ?Now the “blip” of the throttle may (or may not) be able to accelerate the flywheel to the required rpm for the next ratio for a downshift, but it certainly would not “spin down” to the required figure in the case of an upshifting in the minuscule time you nominate. How then has it achieved the target value ?If you run your engine up to 5,000 rpm in neutral and chop the throttle, there is a clearly observable time required for the crank to drop the 500 rpm.In the real world of a clutchless shift, there is nothing slowing that crank other than the frictional drag and work being done, in the engine internals.I again suggest that the quick shifter will engage the next higher gear before the crank has FULLY dropped to the target figure and the gearbox dogs will mesh and the excess energy will be dissipated in the (INAUDIBLE) crash that the gearbox will feel.If I am provably incorrect in that assumption, then my argument is over.Now I routinely drive a truck with a 15 litre engine and an 18 speed Eaton Fuller Roadranger manual gearbox, almost all changes are clutchless and silent. That is because I can flip the box into neutral momentarily and match the rpm for the downshift of wait for the engine to spin down for the upshifting..(about 2 seconds typically).The input and output shafts need to be spinning at correct revs relative to each other for proper engagement.Same with the bike, whether the gears are constantly meshed, sequential.. or otherwise, it does not exclude the operator from that fact.ie The input shaft has to be spinning at the correct rate relative to the output shaft.I suggest that any torture that is being dished out, is either of low enough impact to be inaudible or indiscernible .ORThe operator does not keep the thing for long enough that his mechanical lack of sympathy is repaid in failed/prematurely worn, internals...(That’s for the next poor guy).I think that’s it unless I read something that targets my point.
You know all this stuff about quick shifters pretty much defeats the fun and satisfaction of executing a perfect downshift with your own hands and feet.
Remember Huzo these things are primarily for performance applications and their forte is on bikes that are in the upper areas of the rev range and have by Guzzi stands now flywheel effect at all. So rotating at 10,000rpm the engine can catch an extra 500rpm very fast. Add to this that its not about perfection in getting the engine and gearbox meshing speed absolutely perfect but close enough to get a clean smooth transfer of load.It probably also helps to picture the motorcycle drive system holistically from the crank to the tyre contact patch. An older dry clutch Ducati had a cush damper in the clutch hub, a chain and another cush damper in the rear wheel and a rubber tyre between the torque generator (crank) and the load (road surface). All these combine to reduce the shock loading on the transmission. Is that enough? Real world experience suggests it is adequate enough. Some shifting systems also use fuel cut to achieve the unloading of the transmission and a "staged" re introduction of the fuel to ease the shock loads. A motorcycle is also a fairly small mass in the grand scheme of things so if that shock load can also be accommodated by a jerk in acceleration an extending of the suspension etc and with a light crank a speeding up or slowing down of that component. it's a bit like an elastic band in some ways and helps mitigate the shock to the drive system. I know components are designed for their intended purpose but you get the idea when it's compared to a big diesel truck pulling a lot of weight. There the shock loading can only dissipate through any drive plate cushioning arrangements and enormous drive train and chassis movements and twisting. You're not going to get much help from a single tyre that can flex and deform to help. I've seen trucks on occasions pulling away from a standstill loaded up and then shifting gears and I always cringe at the thought of whats happening to the drive train.Ciao
Oh now I get it.The slipper clutch in my Norge, blends the sharp edges off my clutchless changes and smooths it all out with Italian fairy dust.How did I miss that...?
Indeed. It surely has taken the "art" out of it as well.
Not sure why you are being obdurate Huzo,due to the weight and centrifugal force of the flywheel
It’s because I’m trying to get the topic onto the flywheel and not what “some guys mate used to do back in the day on his Speed Twin”.Also, I’m trying to have a conversation about physics, with someone that confused centrifugal (which is actually centripetal) force, with angular momentum.See why I need to argue ?Should I just walk away ?
It’s because I’m trying to get the topic onto the flywheel and not what “some guys mate used to do back in the day on his Speed Twin”.Also, I’m trying to have a conversation about physics, with someone that confused centrifugal (which is actually centripetal) force, with angular momentum.See why I need to argue ?Should I just walk away ?Centrifugal or centripetal force, has no place in this conversation.It is irrelevant.The reason these conversations go on so long, is that more than half the time is spent ironing out wrinkles in basic terminology and principles...(sometimes it’s me I hasten to add), but I cannot address an issue that is constantly being dragged into a different sphere.
One question before you call it quits PhilIs the slipper set to some nominal value, or is it controlled, i.e. does it sense the the rear wheel speed and adjust the amount it slips to avoid any rear wheel lock up?TrisPS thanks everyone - every day's a school day