Concept of dual clutch 4 speed gearbox

[falconluan]

Not sure if this has been discussed before(did a quick search and didn't find exactly same stuff though)

Trying to build a dual clutch gearbox with "real" dual clutches and this is what I've got so far. 

The red(right) end is input while the yellow(left) end is output. The right half is the "dual clutch" part, the output speed of the clutches are different, then the output of clutches are connected with two identical 2-speed gearbox thus makes it a 4 speed gearbox.

 

1st gear, ratio is 12:20 then16:16 = 0.6

 

2nd gear, ratio is 16:16 then 16:16 = 1.0

 

3rd gear, ratio is 12:20 then 24:8 = 1.8

 

4th gear, ratio is 16:16 then 24:8 = 3

 

As a 4 speed gearbox, it is not as practical as the "standard" type gearboxes, where only 2 gear selectors are enough. It is more a demo of the dual clutch concept. It will only out perform the standard one if the right 2 gear selectors can be "real" clutches which can engage/disengage more smoothly than the left 2 gear selectors.

Also the gear change mechnism will be more complex of it. As you can see, the right 2 gear selectors are easy to drive since they have the standard 4 position transition during the gear change process. One 35188 orange shifter will work if one of the clutch is placed "above" the input axle. 

However, the left 2 gear selectors are hard to drive. Yes, it will be easy if they are allowed to have 4 positions during transition as well, but by doing that way, the gearbox will lose the "dual clutch" advantage and demo purpose completely, since the "pre-select gear" function will be lost.

As indicated in the pictures above, ideally the left 2 gear selectors don't stay at neutral postion during gear change. Only one of them will change postion during one gear change process. I'm still in progress of figuring out a working driving mechnism for that.

 

What do you think of this type of gearbox? Please share your thoughts 

 

[BusterHaus]

Flat gear boxes like this one should be the standard in Technic sets. They show much better what happens when gears change, as the whole path of power is visible for each gear.  Instead, we get "magic" gearboxes hidden deep within a car, with two layers of gears. Very little is visible and the user is left to guess what's happening inside.

Hardcore Technic fans would probably complain about the lack of realism, but we complain about the current gear boxes. Each supercar has its own improvement thread and could be modified from a flat gearbox to a more realistic one.

You have a nice experiment here, and it's still a mix of realism with a flat layout. 

 

[Divitis]

Maybe I'm reading the schematic wrong, but my expectation was to see the load divided between two axles/ gear couples and I don't see this happening here.

 

For example in the case of the first gear: the axle at the bottom doesn't spin, and movement to the one above is transmitted through one pair of 12:20 only. The other 20t gear spins freely as it's not connected to the axle.

 

Am I missing something?

[Lego Tom]

4 hours ago, Divitis said:

Maybe I'm reading the schematic wrong, but my expectation was to see the load divided between two axles/ gear couples and I don't see this happening here.

 

For example in the case of the first gear: the axle at the bottom doesn't spin, and movement to the one above is transmitted through one pair of 12:20 only. The other 20t gear spins freely as it's not connected to the axle.

 

Am I missing something?

As I see it, here is the flow in 1st gear:

 

[falconluan]

12 hours ago, Divitis said:

Maybe I'm reading the schematic wrong, but my expectation was to see the load divided between two axles/ gear couples and I don't see this happening here.

 

For example in the case of the first gear: the axle at the bottom doesn't spin, and movement to the one above is transmitted through one pair of 12:20 only. The other 20t gear spins freely as it's not connected to the axle.

 

Am I missing something?

As @Lego Tom's pic above, the bottom axle will also turn since the lower left gear selector is engaged(for pre-selecting the 2nd gear) . Only to note that the flow of the picture should be reversed since the right side is input.

 

[Divitis]

Thanks for visualizing the flow, @Lego Tom, that's what I had figured as well.

 

@falconluan the lower axle might spin, but it doesn't carry any load. It spins freely - I'm sorry but I still fail to see the utility of this. 

[falconluan]

1 minute ago, Divitis said:

the lower axle might spin, but it doesn't carry any load. It spins freely - I'm sorry but I still fail to see the utility of this. 

No worries 

Yes, only one axle carries load in one gear. Maybe I am wrong but I think the less gear involved in transferring load, the less friction will be there. 

I think the main reason of split axles here is for pre-selecting next gears. Although still figuring out how to synchronize the left two gear selectors to make the upper one move "Left, Right, Right, Left" while make the lower one "Left, Left, Right, Right"...