dual clutches? What is wrong with sequential dogs?

[tjts1]

Not misinformation. Nobody sells a car with a dog box to the public even on performance cars because they know that 99.99% wouldn't never want to drive that contraption day in and day out. If its on some race car and you're into that kind of thing, great. But there is absolutely no excuse for driving that thing on the street. DPK or the synchronized gearbox are much better solutions in the real world.

[dcb]

squawk!!

[some_other_dave]

Originally Posted by tjts1

Dogleg gearboxes are useless on the street.

Hmm, I've usually heard "dog-leg" only refer to the shift pattern. Some older German cars (Porsches and BMWs) have first gear to the left and down, with 2nd being middle/up, 3rd middle/down, etc. The type of transmission we're talking about here is one I've heard called "dog box". The sliders for gear engagement have "dogs" or "dog teeth" on them. Uhh, anyway.

In the video, you can see that someone with (presumably) quite a lot of experience driving this particular car and gearbox setup still gets a clunk pretty frequently. That is not acceptable to most of the drivers out there. It might be OK in a car that is primarily intended to be a track car, but my mom won't want that in her grocery-getter.

Heck, these days most Americans don't even know how to drive a regular manual transmission! If they won't even learn that, what makes you think that they'll be willing to put up with clunking and grinding noises in some or all gear changes? Or willing to put forth the thought and effort of actually shifting with a good enough technique not to have the grind?

The dual-clutch transmissions are much easier to operate automatically, without the NVH of a dog-box.

If they make a dog-box transaxle that fits my car that lasts for 100K miles, though, I would be quite interested. (But not enough to pay the undoubtedly-large amount of money required to buy one.)


The "why" in this case, as in so many, is "Because the carmakers think they won't make enough money to be worthwhile."

-soD

[dcb]

Appeals to popularity are not synonymous with reason imho. A minor knock when shifting into first (hell, put a synchro on first if you must) does not detract from the abuse taking ability or durability or smoothness of the other gears, or the reduced complexity or cost if done on the same scale. The point of this is not an exercise in despair about already being trapped into over-complicated solutions, it is to think about the possibilities. So you get a minor clunk going into first.

Couple magnets on the tranny side of the clutch to slow it down (or even as Bob hinted, control the speed of that half of the clutch precisely) and you get your nvm "concerns" back, but the are not showstoppers to me, plenty of vehicles have a clunk or two in their operation, i.e. trains, etc, don't know why folks should lose sleep over that. I'm not here to make excuses for people. If you bottom line it, it would be less expensive en mass. And since you only have one clutch, I don't know that dual clutch is "easier" to automate.

I have to wonder if the dog box longevity is a concern in low power applications, I know they use them in high power apps because they can handle the abuse better, and that of course has a direct effect on longevity if you hammer on the dogs. I'm not talking about that.

And recall we are talking about automating shifting, so with a few speed/position sensors it should be conceivable to robotically snick it into each gear if the driver can't.

So, do these fail when folks are not constantly putting 500hp through them? Does an occasional tap going into first need to be remedied?

Driving a dog box everyday and for countless miles, I know this is doable, and regularly driving a busted Dual mass flywheel TDI, I know what a pain synchros are to fast clutchless shifting first hand. Not only would the auto dog box have less parts, but it would need to move the parts it has less as well.

[mnmarcus]

dcb
You said you drove one everyday, what is it and what is it in? Maybe a lot of drivers couldn't handle learning some technique but I think there are a lot who could.
Thanks

[dcb]

it was my 81 gs250, but I am riding a 74 cb125 while I sort out fuel injection on the 250.

[Neddy Seagoon]

My Kawasaki W650 goes clunk when going into first from a stop, I hardly use the clutch at all, it now has 30,000 kms on it with no problems.
I learned how to drive on cars with no syncros in the gear box at all, so it was double de-clutch every gear shift. Both myself and my wife hardly use the clutch while driving around except for starting off, my wife's car is a 03 Cooper S six speed. We have never replaced a clutch or gearbox that was worn out in our lives and we have been driving for 30+ years.
If a driver does not understand how a gearbox or a slushbox works then they can cause untold damage in the long run by misusing it.
Neddy Seagoon.

[dcb]

Here is another experienced commentator:
Shifting a Dog Ring Transmission - RX7Club.com
Sounds like he prefers automating the actual shift event (i.e. air shifter/kill circuit coordinator)
"Automated (semi automated). The movement of the dog ring is powered and the engine is cut / re-instated in a co-ordinated manner. Gear-shifts take milliseconds. This system produces zero dog wear when set up well. It is not applicable to most cars, but it illustrates that speed of shift is a good thing. "

main thing is shifting quickly. Other options have "built in" kill switch when you yank on the shifter, and of course the coordinate your right foot with your shifter hand approach which is the most risky especially with lots of horsepower.

But it has to be the most efficient way to shift also, there is no opportunity for slippage, which may be viewed as a nvh concern as the acceleration drops off in small steps instead of slipping between gears, but I'm more interested in efficiency and simplicity personally. If that is an nvh concern, you might as well argue which hand lotion is best at that point...

[cleanspeed1]

Originally Posted by mnmarcus

dcb
You said you drove one everyday, what is it and what is it in? Maybe a lot of drivers couldn't handle learning some technique but I think there are a lot who could.
Thanks

Can't be that bad, I've driven 9-15 speeds in my trucks several thousand miles a week without using the clutch except to start and stop. Just practice that's all. No synchros to get in the way.

[some_other_dave]

Originally Posted by dcb

Appeals to popularity are not synonymous with reason imho.

They are if you're a manufacturer trying to move hundreds of thousands of units. Especially when each "unit" is priced in the tens of thousands of dollars.

It would be neat to see this offered as an option from a major carmaker. I would be interested, though since I have never bought a new car my interest wouldn't really be relevant. But I would bet that the option would sell very few units.

-soD