All wheel drive transfer case

[Ozymandias]

Here is the basics of torsen. While this is a different design using spur gears to merry the axles into equal power division the one im using does the same thing where the worm gears are engaged into each other in the center.

At first I demanded the type in this video but after more education came to realize this is for smaller vehicles such as the Toyota. This is a much more cost effective design as well but they simply can not deal with the torque we are talking about in low range on pavement with a loaded gooseneck hooked up and you decide to pull the Honda civic up the side of the mountain it drove off and is now on its lid. Lol

That is partly true because the Torsen needs a feedback (load) from 5he Wheels to divert torque to the other wheels, as soon as there is no load on any wheel it will stop working.
Torsen have a torque bias like 1:2 in an AAM axle or up to 1:4 in TrueTrac aftermarket units. If the demand is higher it will spin the wheel with the lower traction. On normal usage this is never a problem, but in a demanding offroad situation like climbing over rocks, steep uphill, that can turn into a problem. I think it should be possible to add a dog clutch to the unit for locking.

Side note to it, Eaton makes a TrueTrac for Jeep front axle application that uses a PRELOAD design, so even if a tire goes airborne it still diverts torque to the other wheel as the preload simulates a road feedback.

 

[Charlie Lawhon]

That is partly true because the Torsen needs a feedback (load) from 5he Wheels to divert torque to the other wheels, as soon as there is no load on any wheel it will stop working.
Torsen have a torque bias like 1:2 in an AAM axle or up to 1:4 in TrueTrac aftermarket units. If the demand is higher it will spin the wheel with the lower traction. On normal usage this is never a problem, but in a demanding offroad situation like climbing over rocks, steep uphill, that can turn into a problem. I think it should be possible to add a dog clutch to the unit for locking.

Side note to it, Eaton makes a TrueTrac for Jeep front axle application that uses a PRELOAD design, so even if a tire goes airborne it still diverts torque to the other wheel as the preload simulates a road feedback.

I think you are misunderstanding how torsen works. It will not allow a single side to turn by itself. That is the actual principal of the design. When a wheel becomes unloaded and begins to spin freely and the ratio allotted by worm gear angle is reached(which happens instantaneously) the unit becomes locked due to fact the physical worm gear action only works when the worm gear turns the worm wheel. A worm wheel can not turn the worm gear which is what happens when 1 tire tries to spin.

I design mechanical stuff for a living and it took me a min to build the gear set in my head and solve the problem in reverse which is how it makes sense. Thinking of it working from the power input to the tire beginning at the pinion it doesn't make sense. But when you think of it from the spinning tire backward to the pinion THEN you see how it locks.

In the split of a rotational speed difference the gears are ignorant of forward and reverse. To them where there is a speed difference one goes 1 way and the other goes the opposite way, not 1 goes faster than the other the way we perceive motion of travel and slip/spin. The speed difference becomes too great to split and the entire unit binds up in a totally free wheeling 1 side situation.

 

[fest3er]

If I understand the video, there can *never* be any free spin when one tire is on dry pavement and the other is on ice (or in the air). This is because the ring turns the case and the case moves the worm wheels around. Because the worm wheel cannot turn the worm gear (on the axle), the worm wheels don't turn and both worm gears turn at the same rate. This is exactly the same as driving in a straight line: both worm wheels are 'locked' because the one is locked. In the case of a turn, one wheel turns a little faster than the ring and t'other turns a little slower than the ring. The worm wheels keep the difference (between worm gears and ring) equal (but opposite).

What I haven't pictured yet is what happens during deceleration when the vehicle is at speed with the left tire on dry pavement and the right on ice. Apply the exhaust brake. If I'm picturing it right, now the left worm gear is driving (or can drive) its worm wheel faster than the ring. This *should* result in the right worm wheel driving the right worm gear faster than the ring, resulting in no engine/exhaust braking. Am I missing something in the concept?

 

[Ozymandias]

Not really....

Behaviour of Torsen differentials
The Torsen differential works just like a conventional differential, but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR).[2] When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric traction conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the angular acceleration of the faster output side of the differential.

The TBR should not be confused with the uneven torque-split feature in the planetary-type Torsen III. The planetary gearset allows a Torsen III center differential to distribute torque unevenly between front and rear axles during normal (full traction) operation without inducing wind-up in the drivetrain. This feature is independent of the Torque Bias Ratio.

Torsens in front and/or rear axles
When a vehicle is in a turn, the outer wheel will rotate faster than the inner wheel. Friction in the differential will oppose motion, and that will work to slow the faster side and speed up the slower/inner side. This leads to asymmetric torque distributions in drive wheels, matching the TBR. Cornering in this manner will reduce the torque applied to the outer tire, leading to possibly greater cornering power, unless the inner wheel is overpowered (which is easier to do than with an open differential). When the inner tire (which has less traction due to weight transfer from lateral acceleration) is overpowered, it angularly accelerates up to the outer wheel speed (small percent wheel spin) and the differential locks, and if the traction difference does not exceed the TBR, the outer wheel will then have a higher torque applied to it. If the traction difference exceeds the TBR, the outer tire gets the tractive torque of the inner wheel multiplied by the TBR, and the remaining applied torque to the differential contributes to wheel spin up.

When a Torsen differential is employed, the slower-moving wheel always receives more torque than the faster-moving wheel. The Torsen T-2R RaceMaster is the only Torsen to have a preload clutch. So, even if a wheel is airborne, torque is applied to the other side. If one wheel were raised in the air, the regular Torsen units would act like an open differential, and no torque would be transferred to the other wheel. This is where the parking brake "trick" can help out. If the parking brake is applied, assuming that the parking brake applies even resistance to each side, then the drag to the airborne side is "multiplied" through the differential, and TBR times the drag torque is applied to the other side. So, the ground side would see (TBR X drag torque) minus drag torque, and that may restore motion either forward or in reverse. In Hummer/HMMWV applications, there are both front and rear Torsen differentials, so the use of the main brakes will operate this "trick" on both axles simultaneously.

 

[Charlie Lawhon]

Not really....

Behaviour of Torsen differentials
The Torsen differential works just like a conventional differential, but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR).[2] When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric traction conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the angular acceleration of the faster output side of the differential.

The TBR should not be confused with the uneven torque-split feature in the planetary-type Torsen III. The planetary gearset allows a Torsen III center differential to distribute torque unevenly between front and rear axles during normal (full traction) operation without inducing wind-up in the drivetrain. This feature is independent of the Torque Bias Ratio.

Torsens in front and/or rear axles
When a vehicle is in a turn, the outer wheel will rotate faster than the inner wheel. Friction in the differential will oppose motion, and that will work to slow the faster side and speed up the slower/inner side. This leads to asymmetric torque distributions in drive wheels, matching the TBR. Cornering in this manner will reduce the torque applied to the outer tire, leading to possibly greater cornering power, unless the inner wheel is overpowered (which is easier to do than with an open differential). When the inner tire (which has less traction due to weight transfer from lateral acceleration) is overpowered, it angularly accelerates up to the outer wheel speed (small percent wheel spin) and the differential locks, and if the traction difference does not exceed the TBR, the outer wheel will then have a higher torque applied to it. If the traction difference exceeds the TBR, the outer tire gets the tractive torque of the inner wheel multiplied by the TBR, and the remaining applied torque to the differential contributes to wheel spin up.

When a Torsen differential is employed, the slower-moving wheel always receives more torque than the faster-moving wheel. The Torsen T-2R RaceMaster is the only Torsen to have a preload clutch. So, even if a wheel is airborne, torque is applied to the other side. If one wheel were raised in the air, the regular Torsen units would act like an open differential, and no torque would be transferred to the other wheel. This is where the parking brake "trick" can help out. If the parking brake is applied, assuming that the parking brake applies even resistance to each side, then the drag to the airborne side is "multiplied" through the differential, and TBR times the drag torque is applied to the other side. So, the ground side would see (TBR X drag torque) minus drag torque, and that may restore motion either forward or in reverse. In Hummer/HMMWV applications, there are both front and rear Torsen differentials, so the use of the main brakes will operate this "trick" on both axles simultaneously.

The part that I feel like you haven't factored in is where I mentioned the bias gears that will be more or less quick change for racing/off road application. That is where you're pre load comes from in the TC I'm building. You are discussing axle diff function. Im not building the diff to sell to be used in an axle.

 

[Ozymandias]

Seems i missed that part.
I thought you said your using a D80 Torsen - so you are building it from scratch and it will be a so called Torsen Type-3 Differential?
That sounds good!

 

[Charlie Lawhon]

The

Seems i missed that part.
I thought you said your using a D80 Torsen - so you are building it from scratch and it will be a so called Torsen Type-3 Differential?
That sounds good!

The TC I'm building is a complex device and I haven't really given enough information out yet to fully understand it. That is my fault not yours.

Im into road race where operating smoothly is critical especially in the rain when the outside temp is reading 32 deg F and the sun is passing the horizon on its way down.

I don't like the Borg auto 4 wheel in my eco diesel. It won't engage unless your applying power so as you come into a 25mph suggested speed 90 deg turn in the rain and go from dragging the chin of the front bumper on the brakes and start changing clock angle a slip begins as you enter and go from TPS reading of idol to WOT the rear has enough time to cause a moment of unloading the body roll weight transfer and right about the time the way of energy drifts across the body from the inside of the turn outward the BW acknowledges that A traction control is necessary and power is requested and instantly engages the front assist causing a second wave of body roll shock the suspension and tires need to deal with. HIGHLY undesirable!

The awd sports cars I've driven had a torsen center and very predictable and transfer of power that the suspension isn't burdened with while you're in the beginning of maximum request of lateral traction.

I will specifically make a video of 1 wheel off the ground front then rear with the truck tied to an excavator when we are testing it.