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| rac3r |
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rac3r
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 Posted: 10:21 - 14 Oct 2012  Post subject: Gear shift speed |
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Was just thinking that performance cars now pretty much all have paddle shift twin clutch stuff so that they shift faster than you can blink, how long do you think before bikes go the same route?
I know you can get quickshifter's but how do they compare to the paddle shift stuff?
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Bikes : 2006 CBR125R - 2004 Monster 620ie - 2004 ZX-6R B1H - 2005 Monster S2R 800 - 2011 Street Triple - 2009 Streetfighter 1098 - 2014 ZX-6R 636
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| Dave McCool |
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Dave McCool
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| 0l0dom0l0 |
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0l0dom0l0
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| Posted: 11:33 - 14 Oct 2012 Post subject: |
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Quickshifters change gear in around 50-60ms.
The dual clutch boxes are slightly different in the way the work, but I'm pretty sure they don't change gear that quickly.
Also, more bikes are coming with the quick shifters fitted as standard now!
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CBT Passed: 30/08/2009, Theory Passed: 31/08/2010, Mod 1 Passed: 6/9/2010, Mod 2 Passed: 13/09/2010. Restriction ended 13/09/2012.
Bikes: 2007 Derbi GPR 50, 1998 Yamaha Fazer 600 (written off), 2002 Yamaha Fazer 600, 1994 CBR 600F, 2003 Triumph Daytona 600, Kawasaki ZX6R J1.....Current: 2006 Yamaha FZ6, 1998 Suzuki TL1000R and a Honda VFR 400 NC30. |
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| Blau Zedong |
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Blau Zedong
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| tahrey |
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tahrey
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| Posted: 13:31 - 15 Oct 2012 Post subject: |
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Depends on your views re: clutchless shifts, I suppose?  |
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| weasley |
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weasley
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| Dazbo666 |
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Dazbo666
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| tahrey |
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tahrey
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| Posted: 10:07 - 16 Oct 2012 Post subject: |
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The thing about the twin-clutch system is that it's smooth, fast, and doesn't actually have a break in the power delivery. Even when banging up clutchlessly through the gears on a dog-clutch sequential, you have to ease the throttle, there's a split second where the box is actually in neutral, and the affair isn't exactly what you'd call seamless. Can be quite jarring, even. Still a heck of a lot faster than clutch in/release throttle, click / move lever in a more considered manner, then pick up throttle and slide the clutch back into engagement, but the dual-clutch would beat it.
The question is whether the 100-200ms saved is worth the extra complexity, bulk and weight, plus the reduction in full driver/rider control, particularly at launch. I haven't seen many of these used in racing (I think a few F1 teams have them? that's about it? I could be out of touch though), especially not rallying, so that's at least one sector of the millisecond-shaving community who figure the weight and extra failure risk isn't compensated for by the slightly improved power delivery. (Drag racers, of course, use manually-braked epicyclic setups and to hell with the transmission weight...) |
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| mysterious_rider |
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mysterious_rider
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| Posted: 10:10 - 16 Oct 2012 Post subject: |
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Buy a more powerful bike and stop worrying about the half a second this clutchless stuff will save you in a 1/4 mile.  |
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| Alpha-9 |
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Alpha-9
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| recman |
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recman
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| Posted: 10:25 - 16 Oct 2012 Post subject: |
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I hope not, I do it between 3rd, 4th and 5th a lot.  |
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| Islander |
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Islander
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Islander
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Islander
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| weasley |
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weasley
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| stinkwheel |
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stinkwheel
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| Posted: 15:02 - 16 Oct 2012 Post subject: |
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bikertomm
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| tahrey |
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tahrey
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| Posted: 18:18 - 16 Oct 2012 Post subject: |
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| Islander wrote: |
Get the speed/revs matched properly, change gear. |
How the hell do you do that on a sequential constant-mesh box which doesn't have any "true" neutrals between any gears other than 1st and 2nd?
When I do it (not as much as one time, as I got bothered I might be hurting something, but didn't stop entirely), it's basically have foot in position ready to change as the appropriate speed approaches, then when the time feels right, put a moderate amount of upward toe pressure on the lever and ever-so-briefly dip the throttle closed.
The shift in load throughout the bike momentarily unloads the gearbox, the friction between the dogteeth releases, and it snicks out of the lower gear and usually more-or-less-instantly into the next, requiring only the next gear's dogs to rotate the necessary handful of degrees to line up with the selector ones that are now pushing against their crown and coming into better alignment as the revs drop ever so slightly
Very rarely dared do it shifting down though. Experience with either playing around at or being forced to "speed shift" a car box (e.g. when a clutch cable broke) has shown that, for whatever reason, all these bits mate up far more nicely and gracefully when you're going up the box, and the revs are falling with basically no power (other than what's in the flywheel) coming off the crank. Downshifting is a noisy, imprecise affair that feels like it's causing damage almost every time. Not for no reason does "double declutching" exist for downshifting old car and particularly unsynched truck boxes (which share some DNA with sequentials).
At the crudest level, you unload the transmission (in that case by briefly tapping the throttle open) to get it into neutral, then rev up just beyond the point where the engine speed matches what it would be if in the next lowest gear, then slide the stick home whilst coming back off the pedal... the balance of forces being much like it would be if you were changing UP from TWO gears down. Bit harder to do that on the bike. Closest I tend to come is blipping the throttle whilst doing a clutched downshift so there's much less / no deceleration shock when you let the clutch back in.
| bikertomm, stinkwheel wrote: | (pictures etc) |
...why is the shift control on the bars and not under the rider's left foot? Surely you could have it set up to basically act as clutchless manual (C90 Cub style), and all that goes in place of the clutch lever is a mode switch? (Neutral, Drive/Cruise, Drive/Sport, Manual)
Also that thing looks massive.
edit: oh wait it's got the engine in it as well :p
| weasley wrote: | All you do when you pull the clutch is releasing pressure from the gearbox |
Well no there's a bit more to it than that, and that's not 100% right.
What you're doing is disconnecting it from the engine, and therefore both allowing the input shaft to run free, and releasing whatever forces may be being transmitted between engine and road via the box. It's still connected to the rear wheel (the output shaft is still hard-connected to it even when in neutral), so it's not completely unloaded or non-spinning. It's just there's no longer a conflict between two bits going at a different speed when you try to mesh a gear into engagement.
It's maybe a bit more important in a synchro box, though, where one of the main things the sync/baulk rings do is spin the input shaft (and clutch output plate) up to speed by acting as mini clutches, driven by the roadwheel(s) rather than the engine, so reducing noise and roughness by preventing full engagement of stick into slot (and selector onto dog teeth) until the shaft and the gear spinning freely upon it are much closer in rotational speed and locking one to the other creates no grinding or jolting sensation.
That done, you can then reconnect the engine.
Or maybe I'm wrong. Maybe it's more important in an unsynched box like on a bike, because the clutch then becomes your primary method of preventing that grinding conflict. Or at least minimising it. There's no baulk ring or synchro to bring the input shaft into harmony with the output shaft, so the selector teeth have to slip into a gap between the cog dogs a lot more quickly and forcefully in order to be successful, and then transmit a fair bit more load when they do so.
With the clutch disengaged, there's relatively little inertia in the parts that have to be brought up to speed, and they do so without much complaint.
With the clutch engaged, they have the full weight of the engine behind them, so there's more of a thump, potential damage etc. However if you've unloaded the system anyway, there's not much difference for that split second (where you've preloaded the pedal so the change happens as quickly as possible, in that brief gap where it's effectively like you've declutched), and the shift happens in the blink of an eye. There's a bit more of a jolt, as you're asking the engine speed to reduce much, much more rapidly than you would with even the sharpest approach to handling the clutch (which is, thankfully, absorbed through the springs, chain, tyre...), but as you were on the power immediately before, and are back on it immediately after, this is also not too bad.
And I'm in danger of confusing myself if I go much further so I'm gonna quit now. |
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| stinkwheel |
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stinkwheel
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| Posted: 19:41 - 16 Oct 2012 Post subject: |
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There are many, many threads on this forum dealing with clutchless gearchanges.
If you have good throttle control, it is smoother than using the clutch. I'll often clutchless change when carrying a pillion to make the ride more comfortable for them.
I have also done a daily commute for up to 2 weeks at a time with a broken clutch cable.
In terms of damage, I had to replace the primary gear selector on my GPZ500 at about 60,000 miles because the "hook" that pulls the selector drum round had become slightly rounded and didn't always engage. I strongly suspect this was little to do with clutchless changes and more to do with it being flimsy and me repeatedly going for a non-existant 7th gear.
Suffice it to say. If you do it right, it's very smooth. It's harder to do neatly on the way down the box though.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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| Noxious89123 |
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Noxious89123
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| Posted: 22:35 - 16 Oct 2012 Post subject: |
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What I dislike about the look of those DCTs on the VFR1200 / Crosstourer is that the gear change is on the bars. Why not just have a normal gear lever, but instead of a linkage, have it attached to a sensor? Would be far more natural. Think I would miss having a normal clutch lever though tbh.
Would like a flappy paddle box on the car... Or just a standard one that doesn't have 118k on it and is crunchy when "pressing on".
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'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless 
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| tahrey |
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tahrey
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| Posted: 13:02 - 17 Oct 2012 Post subject: |
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SW, how did you deal with standing starts? Run-and-jump or something else?
When the cable went on the car, I was able to carefully time my approaches to lights and islands to minimise the requirement to do less than 1st gear idle speed (or even what the engine would tolerate of me riding the brake in 1st), but there were still a couple points where I had to kill the ignition and quickly yank it into neutral.
Luckily the vehicle was light, had a powerful starter motor and fresh battery, and no start-in-gear lockout, so it could always be bumped into motion on the starter and then driven away on its own power as soon as the engine began firing properly again. Plus it was only for the one journey, albeit a long one, on fairly quiet roads.
Two weeks of it, on a bike, in traffic? Heroic  |
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| stinkwheel |
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stinkwheel
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| tahrey |
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tahrey
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| Posted: 09:28 - 22 Oct 2012 Post subject: |
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Dropping into Honda dealer to pick up spare bits, what do I see on my way out? Pile of brochures... have a quick leaf through...
...and part of this year's new line-up is a 1200 with a dual clutch box. Huh. How about that.  |
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Old Thread Alert!
The last post was made 13 years, 350 days ago. Instead of replying here, would creating a new thread be more useful? |
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