dual clutches? What is wrong with sequential dogs?

[dcb]

As many a motorcyclist (and many racers) have learned, with the right transmission and technique you do not need a clutch to change gears smoothly when accelerating, with a nearly imperceptible interruption in applied torque (yes clutch-less shifts are that smooth and fast in a dog box).

This "technology" has been around for decades, and doesn't seem terribly hard to automate to me if that is even necessary, so why do we need all the complications of dual clutches with the usual associated fear of "wearing out synchros" and all those other moving parts, extra clutch,layshaft and gears?

Apparently I'm not the first to wonder about it, dual clutch is about making a better automatic, but with a few solenoids why couldn't you automate a dog box plus have an overriding clutch and shifter lever and have a seriously kick-ass manual in the same car?

(Add some more neutral detents and sort out reverse of course)

view this engine is it running seamless shift - Forum - F1technical.net

So, dual clutch, over-engineered/over-complicated or not? Is this some goofy patent and/or marketing thing involved here?

[dcb]

And if you are stuck in h-pattern synchro mentality, or rpm matching mentality, and don't know what I am talking about, have a look at this starting at about 0:13 (sounds like straight cut gears except for top gear too, which is an interesting compromise). He has a h-pattern shifter here, which takes a bit more skill than sequential, but also doable, sequential would be easier to automate though.

http://www.youtube.com/watch?v=asFwD...tailpage#t=13s

EDIT: here is another vid from a manufacturer, talks about clutchless upshifts at 2:24

http://www.youtube.com/watch?v=n_1jO...ailpage#t=145s

[BLSTIC]

The issue with dox boxes in terms of using them in a car is the speed of the clutch (and flywheel and engine if the clutch is engaged) changes instantly. And a clutch/flywheel/engine on a car weighs a LOT more than a motorbike. I can't see that being good for drivetrain longevity (and face it, cars are bigger, heavier, and generally do 5x the mileage of the average bike before being crushed).

That said, if someone were to design an ultra-agressive synchro ring (that still allowed some slip), it could be do-able.

Ok so my next dumb idea is to modify syncro rings for more bite. Something like a button clutch...

[cleanspeed1]

I ride also, and have wondered the same thing. To me, the OEMs do a lot of things to "have something to do" , so to speak, to justify the paycheck. They don't like doing the strong, simple, most effective solution. We have had automated manual transmissions for a long time now, and I know on the bike side ( I think it's Walker ) has had an electric quick shifter for years ( someone correct me about whether it just interupts the power and does the shift or just kills the power so you can upshift ).

I've been desiring a sequential style box for Class 8 trucks.

With the current sequential transmissions available, it would be just a matter of changing from straight cut gears to something with a helix on them so that they can run quieter ( probably one of the reasons that they don't run them, that whole NVH thing ).

[Ryland]

The Honda N600 has more or less a motorcycle engine and transmission and you have to double clutch to get it to shift gears because it's just to heavy to force it in to gear, or to try to shift quickly like you've talked about, it just doesn't work.

[dcb]

re: hard to shift, the pfitzner video (I know, text is better) he shifts with one finger to demonstrate how easy it is.

re: wear/size concerns, again these are in large vehicles today, the dogs might have to be larger/etc, but it seems like that "issue" has already been surmounted.

[some_other_dave]

I've driven cars with dog-boxes before. Clutchless upshifts are fun and cool; come halfway off the throttle and apply a little pressure to the lever, and POP it goes into the next gear! You have to double-clutch the downshifts, though. The clutch was required for starting in first gear, and it ALWAYS went CLUNK into first gear at a stop.

And this was in a formula car, with a lot of compromises we would never accept in a street car.

They wear faster than transmissions with synchros, particularly when driven without paying attention. (And really, how many drivers out there do you think actually are paying attention to driving?) And they still do require clutches for initial launch and, apparently except for in motorcycles, for downshifting. And that vile noise and feel you get when you don't match revs (as you cannot do when at a standstill) is something that very few people would be willing to put up with.

-soD

[tjts1]

Dogleg gearboxes are useless on the street.

[bwilson4web]

Ok, consider this project:

• Honda IMA with manual transmission.
• Let the IMA control the ICE shaft speed to match either up-shift or down-shift requirements.
• Solenoid actuators to shift the gears.

You might still need the clutch to handle take-off from a dead start or up a hill. But once moving, everything else could be automatic with no further clutch plate wear. This is not an original idea I came up with but something I remember reading about in the past six years.

Bob Wilson

[dcb]

Originally Posted by tjts1

Dogleg gearboxes are useless on the street.

You are parroting misinformation. I drive a dogleg every single day, watch the pfitzner video. Besides I'm sure a computer could be taught to make it smooth if you don't have the skillz.