DOOM

JDM74

I looked up Audi's quattro crown gear center differential. I see what you mean by mind bending. It doesn't help that the input shaft and front output shaft are co-axial (one is hollow and the other passes through the center of it). That adds to the mind bendyness...haha.

Fabrik8

The coaxial part is fine, it's just two things on the same rotating axis that are different diameters so they don't interfere.

The bendy part is that you have two crown gears with the same tooth count, and are applying torque at a different radius on each gear while the two crown gears and the input shaft are all rotating the same speed (and therefore without any relative motion of the spider gears) and all three inputs/outputs share the same rotating axis. The shared rotating axis and difference in torque with no relative motion is what stalled me out the first time I saw it. It's easier to wrap your head around during wheel slip, when one of the crown gears is then rotating at a different speed than the other crown gear.

I think I remember that the key to the torque split is the ability of the spider gears (which can freely rotate about the cross shafts) to be in equilibrium on the two crown gears. I can't remember, I'll have to go look at it again. If they weren't in equilibrium, they'd rotate along the crown gears instead of just being a point of force application. So the spider gear transfers torque from the input shaft, but is also a gear that rotates at a distance from the center of the input shaft, and without that distance component you can't do the torque split. So the rotation of the spider gears make it possible to have different gear ratios from multiple shafts that share the same rotational axis.

You couldn't just have a flange on the input shaft (instead of the spider gears), and flanges on the two output shafts (instead of the crown gears) and bolt/rivet the flanges together at different diameters. You'd have no torque split if you did that, because you'd be transmitting torque at whatever flange attachment diameter into another flange with the same attachment diameter along the same axis. So you'd have a 1:1 ratio and the diameter therefore doesn't matter. You need an input gear (cross shaft and spider gears) driving two output gears for the concept to actually work at all.

Interestingly, just like an open rear diff in a RWD car, you have to have both output gears. If you don't have both, it will freewheel and you'll get no output torque at all. In this case though, if you break a front or rear shaft, the lockup ability from the clutch packs will still allow torque to be transmitted to the other shaft.

TATTRAT

Simply put: The angle of the dangle, needs to be in proportion to the heat of the beat.

Fabrik8

This is almost as fun as looking under a 5th Gen COPO this afternoon and pondering the multi-link strut (front) suspension.

Fabrik8

Too bad the OP doesn't seem to care about the thread he created...

Yardjass

That's because the OP just wants to see the classifieds. You should probably reset his post count.

Fabrik8

He has 164 posts, so the classifieds shouldn't be an issue. I think....

Yardjass

Oh, wow. No idea then.

JDM74

This is what helped me understand what as going on. Once I realized the input shaft and the front shaft were co-axial I was able to figure it out fairly quickly. I visually turned the input shaft 90 degrees and ran one of the crown gears (not by the same gear teeth that make the crown) with a piņon gear and then since you basically have spider gear running output gears on each side but the output gears are running on 2 different radii but with the same ratios because of the tooth count, it started to make sense. I think that works, but at any rate it helped me figure out what was going on.

Sometimes I wish I was a automotive engineer instead of a boat engineer...