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SHIFTING without Clutch Explained

Discussion in 'New Riders and Riding Tips' at netrider.net.au started by bonox, Jun 1, 2006.

  1. As a further to the thread attached to this one

    https://netrider.net.au/forums/viewtopic.php?t=20532

    I thought i'd put together some pictures to help understanding.


    synchro-box1.
    The first picture here shows your average engagement mechanism for a SYNCHROMESH gearbox such as you might find in a car - note that the synchromesh system is not included because it hides what i'm trying to show you.

    The gear (dark blue) is free to rotate on bearings on the shaft (light blue). The gear does NOT move at all along this shaft in a constant mesh gearbox (practically everything these days except most reverse and some first gears). Neither does the gear on a parallel shaft that mates with the gear I have shown you.

    The engagement ring (red) is fixed to rotate with the shaft and has a large number of small sharp teeth (yellow). To engage a gear, the shifter mechanism (light blue fork) pulls this ring that slides along the shaft until the teeth enter the slots in the gear (light brown). This is how the shaft from the clutch drives each gear in turn depending on which dog ring is engaged with which gear. Take note of how little relative motion you have to make sure that the teeth engage in their slots.



    The next picture shows the arrangement of a NON-Synchromesh gear

    dog-box1.

    The same system is in place, but the engagement dogs are much bigger, but there are only perhaps 3 or 4 of them. Their corresponding slots in the gear (light brown) are huge and allow a great deal more relative motion between selector ring and gear compared to a synchro box.

    It is this behaviour that makes a non synchro box so easy to shift without the clutch compared to a synchro box. Note that the relative speeds of the input shaft that drives the dog, and the output shaft (wheels) the turn the gears must be as close together as possible in both cases for a nice smooth shift.



    Crunching sounds that you get from a poor shift are from the little teeth (the dogs - yellow in both cases) crashing against the edge of the slots in the gear but not actually going in. Over time, you will wear away the bearing surface of these dogs (the part that presses against the side of the slot and turns the gear). Instead of a nice parallel slot, you get a slope on it - if you apply enough force or the slope is big enough, the dog ring will be forced out (ie back into neutral or no gear engaged) without you doing anything - obviously this is bad.


    I should probably also add that I have depicted, say, the input shaft of the gearbox.

    The output shaft runs parallel to the input and looks the same EXCEPT all gears are fixed to the shaft and turn with it, and there are no selector rings.

    EDIT: Have a look at the difference in the designs of the little pins (the dogs - in yellow) and their respective slots above.

    The chance you have of seating those dogs fully home in their slots is directly proportional to how easy a box is to shift without the clutch.

    The problem for a driver/rider lies in how close you can get the relative speed of the dog ring and the gear slots - obviously, the bigger the margin for error, the easier the process is for the user.

    In the given example, you have about 10 degrees of relative motion for the synchro (car) box, but you have about 80 degrees of relative motion for the dog (bike) box to seat the dogs BEFORE THE LOAD COMES ON.

    Granted, if the differences in speed are great, then you get a big jerk as road speed and engine speed are suddenly forced to be the same - but this is NOT the same as ease of shifting as far as getting the next ratio engaged.



    gearbox.
    (multiple gears exist on the same shafts, and all are meshed together all the time - this arrangement I have drawn is a constant mesh type - only the selector rings lock a gear to the input shaft so that it drives it mate on the other shaft. The rest of the gears in the train that are not being used just spin on the input shaft at a speed proportional to the numbers of teeth they have compared to their mate.
     
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  3. How do diagrams of a car gearbox advance the argument with reference to a bike gearbox???
     
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  4. Only in explaining that bike gearboxes are sequential......
     
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  5. :applause: That should explain things a bit better for those here that already know everything. :LOL:
     
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  6. EDIT:

    First synchro = car

    Second DOG box = BIKES, roadranger trucks etc.

    what's the problem hornet/inci?

    The shift mechanism is different between a truck and a bike (i explained that in the other thread - ie H gates vs sequential drums) but that only affects the movement of the selector rings, not the design of selector ring dogs that makes shiftless changes in a bike easy for a bike compared to a car - answering those comments about how "all my car driving friends say it doesn't work and when i try it in my car it crunches" type arguments.
     
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  7. have a look at the difference in the designs of the little pins (the dogs - in yellow) and their respective slots above.

    The chance you have of seating those dogs fully home in their slots is directly proportional to how easy a box is to shift without the clutch.

    The problem for a driver/rider lies in how close you can get the relative speed of the dog ring and the gear slots - obviously, the bigger the margin for error, the easier the process is for the user.

    In the given example, you have about 10 degrees of relative motion for the synchro (car) box, but you have about 80 degrees of relative motion for the dog (bike) box to seat the dogs BEFORE THE LOAD COMES ON.

    Granted, if the differences in speed are great, then you get a big jerk as road speed and engine speed are suddenly forced to be the same - but this is NOT the same as ease of shifting as far as getting the next ratio engaged.
     
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  8. None, except maybe communication. I believe Hornet's comment referred to the link FALCON-LORD posted, and it's relevance to bike boxes. I merely replied that it explained the concept of a sequential box as opposed to a 'spread H', and bike boxes are sequential. Your explanation is crystal clear to all but those who will not see, and already was, even before the diagrams.
     
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  9. on that link that Falcon-Lord provided, click next and check out the animation at the bottom.
     
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  10. righto then - that was a waste of an hour or two!
     
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  12. If you believe the guy who gets money from you when you fcuk your bike, over the guys at ape, you're beyond help.

    Thanks bonox, incitatus and falcon-lord for taking the time to try to drum some knowledge into these unwilling minds. But I fear our efforts are wasted.
     
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  13. Bonox - for those of us who are mechanically challenged (I make no secret of not knowing 1 iota about how my bike actually works and frankly, I don't care. I just want to ride it!), can you confirm whether clutchless shifts are a good thing or a bad thing for the bike. I find 4th - 5th and 5th - 6th barely noticable (clutchless) but I always use the clutch going down gears and from 1st to 2nd to 3rd.
     
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  14. If you can change smoothly and decisively without the clutch, you will not damage anything and your clutch probably will last longer.

    I personally find it very hard to downshift without the clutch so i only clutchless upshift, but if you can do it comfortably both ways there is no mechanical reason why you need to use the clutch with a gearbox of this type except for starting.
     
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  15. Thanks.
     
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  16. In general, anything that does not cause loud noises, vibration or sudden loads (jerkiness for example) in a machine is not harmful to it.
     
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  17. So the moral of the story is dont be a jerk!!!
     
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  18. Im no bike tech and dont get any of that really, I always use my clutch and sometimes it gies a clunk on the way down but i have the revs higher now when changing down to stop this and it works better.

    Whats the difference in not using compared to using the clutch.
    Is it laziness ?
    Or maybe saves time in corner or tight section of road and NOT clutching gives you 500ms of powering on ?

    If the second one applies then shouldnt you have been in the right gear first ?

    I will always use my clutch as Ive been taught that, but i may start putting my feet down instead of using the brakes.
    That will only damage my boot and not the brakepads. :)
     
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  19. Bonox,
    Bolox to your efforts being a waste of time. The complex concrete is simpler to understand than the complex abstract and I really think I understood a lot of the concrete. In fact I showed my son your pics and he immediately started telling me about how he was doing clutchless changes on my car!! No way I'd have got that out of him without your input. Big thanks.
     
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  20. Followed by a clip around the ear :LOL:
     
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