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The working of Torsen differential is elaborately explained in this video with help of animation.
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It’s quite simple really, the engine applies torque to the input; *’witchcraft happens’*, and the wheels turn. See very simple.
😂😂😂😂😂🤦
Glad you understand
You had me in the first half
This !!
i thought it was voodoo? darn, im all mixed up
It is totally false to state (as this video does) that a Torsen diff will "lock" when one side has traction and the other does not. This has caused much confusion. As many of the commenters who actually have Torsen (also known as torque biasing) diffs have confirmed, it still acts like an open diff when the traction on the low traction side approaches zero. A Torsen diff *never* locks. The angle of the teeth on the worm gear and wheel establish a torque multiplier (torque bias ratio) greater than 1. In a conventional open diff, the multiplier is 1 (torque bias ratio of 1:1). This means the high traction side always gets exactly the same amount of torque as the low traction side. When traction on one side drops to zero, it takes effectively zero torque to spin that tire, so the open diff sends zero torque to to the high traction side, and you go nowhere. A Torsen diff may have, for example, a TBR of 3 to 1. In a low (but not zero) traction situation, the higher traction side gets 3 times the torque of the low traction side. If it takes 200 N*m to break loose the tire on the low traction side, the Torsen will send 600 N*m to the high traction side, giving you a total of 800 N*m to the ground. But being a multiplier, if the low traction side takes close to zero torque to induce wheelspin, then the high traction side gets 3 time 0 = 0, and you still go nowhere, just like an open diff.
The above is the primary reason why Torsen differentials are not used for all applications. They are *not* noisy (as was claimed by +Learn Engineering), but they are non-adjustable (can't change torque bias ratio on the fly), can't disengage when used in the center to reduce drivetrain losses and they never actually lock at all, making them mostly unusable for extreme offroad use.
The original Hummer uses Torsen diffs because they're mechanically strong and zero maintenance and the vehicle was designed for desert and other off highway usage, while keeping all four tires on the ground, not rock crawling (where you may loft a tire off the ground). When you do loft a single tire off the ground on the Hummer, it can get stuck. The trick is, while continuing to apply power, to lightly apply the brakes which increases the load on the previously zero traction side of the diff, and the Torsen diff then multiplies the torque required to overcome that braking force by its torque biasing ratio to give you more torque to the high traction side as explained above. This same trick works a little bit with an open diff.
Any Audi quattro made in the last 15-20 years or so does the same trick electronically by selectively applying the ABS brakes only to the spinning tire on the zero traction side and Torsen then sends that torque times the TBR ratio to the high traction side. It's quite effective.
On a side note. Understanding torque transfer can be extremely confusing. For instance, it is quite common to state that when a locking diff is locked, that it has a 50/50 torque split, but that is not true. An open diff has a 50/50 torque split, 100% of the time. A locked diff, where one side has no load (zero traction) and the other side has traction, now has a 100/0 torque split. 100% of the available torque goes to the high traction side, and virtually nothing to the zero traction side, despite the fact that both sides of the diff are rotating at the same speed. Relative rotation rates have almost nothing to do with applied torque.
+techdaemon Great follow up/explanation on it. Them calling it a worm gear is definitely misleading, its more of a helical gear, where it can be backdriven, but if the angle determines how easy that is, (and presumably the torque ratio in the torsen)
And the HMMWV example is good too. Where I'm from, rock crawling is the main form of offroading, so jeeps and just about anything with a beefy solid front axle and lockers remains 'supreme' Anywhere with more open space, for mudding, driving in dunes, etc newer/more advanced stuff makes more sense.
+techdaemon This is the most cogent explanation I've read about anything anywhere. Thanks. Your explanation also helps explain why early Quatro's (c1990) disabled the ABS when the center diff was locked. I remember a review where the author(s) did not understand why this was done.
+techdaemon Brilliant explanation, sir !
+techdaemon Thanks for the clarification brother, a few months back I almost installed a Torsen on my Bronco because I thought it was pretty bulletproof all around, and your explanation LITERALLY prevented me from continuing that idea =D.
*Definitely sticking with a heavy duty clutch pack, I've driven both types, and clutches feel MUCH more natural and *consistent (most importantly)*. I understand everything thanks to your explanation, but I've never driven a Torsen in extreme conditions, so I was wondering if you know *HOW DO TORSENS ACT WHEN SLIGHTLY **_ABOVE_** ABSOLUTE 0 TRACTION? (If your still getting say *20%* traction on the slipping side, *that means the other side would only be getting an equal 20% correct?* Assuming it's a 1:1 TBR of course.
+cybertree No. Again, by definition a torque biasing diff never has a TBR of 1:1. That's what an open diff has. If you're getting 20% traction on one side (meaning it you can spin that tire with only 20% of the torque required to spin the tire on the high traction side), then a torque biasing diff, will give you up to that much times the TBR to the other side. If it takes say.. 100Nm of torque to break the tire loose on the 20% side, then a torque biasing diff with a TBR of 3:1 will send up to 100x3 = 300Nm to the high traction side, for a total of 400Nm going to the ground. Any more than that, is lost to wheelspin on the low traction side. Torque biasing diffs work pretty well if the low traction side has a little traction, and very poorly when that side drops to zero, such as when a tire is in the air, or you've got no-season tires on pure ice.
"here comes the tricky part" I was struggling long before we got to that point lol
OMG! I'm glad I'm not the only one lol
They should give this to Chevrolet film makers in the 1950s they make it easy to learn about
Lol sometimes you have to watch it a few times to understand everything. It's common 😎
me: why do i hear boss music?
I'm mechanical and I do follow this but this video makes my brain hurt. There's a better explanation somewhere.
The graphics made to explain this are amazing, something like this would be impossible to explain otherwise. Great Work!
That is the best explanation I've seen so far in the last 20 years. I would recommend this video to anyone who did not fully understand the locking or the correspondence of the worm wheels with the worm gears.
Fabolous grafics, and without any distrubing musical background...much better.
Thanks for sharing.
nice graphics yes, but the content is wrong, a Torsen does not lock as this video states.
This is the clearest explanation I have seen about the principle of the Torsen differential. You only need 5 minutes to fully understand.👍👍👍👍👍👍
Truly genius. I always was mechanically inclined, but gears (and rope knots) was something I still can't comprehend fully.
Although this doesn't lock the wheels completely in a zero traction situation.
The simplicity and robustness is truly amazing.
Funny you say that... I love gears and knots but I can't wrap my brain around them.
@@Unhandled_Exception Check out some early videos from Corporals Corner or the Grey Bearded Green Beret.
Their knot tying instruction is excellent.
Just buy some lego gears and play with them. No, I'm serious. You can even make these differentials using the legos to model it and make it easier to understand.
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I've replaced the planetary differential with a Torsen differential in my classic 1/8th scale buggy. It improved the handling a lot.
Did the French Citroen have this type of differential?
Best Torsen dif explanation ever! Perhaps also mentioning the downsides would be great in the future.
Ruben Bauwens Thank you !
What are the downsides of a Torsen diff? I'm just curious.
***** Here are the main disadvantages of the Torsen,T-1 explained here.
1) Noisy
2) Costly
3) More difficult to assemble
Learn Engineering Ah, thank you! My truck has a Torsen dif on it, I haven't really heard any noise coming from it. Does it effect gas mileage at all?
The biggest disadvantage in "my book" is the fact that when one wheel is in the air or on "rollers"(no traction at all), there is no power send to the wheel with traction, because it is a torque biassing/torque multiplication dif.
This is why you see them on street cars (Audi Quattro being the most famous) and not on off roaders.
Look up some "Audi Quattro disadvantage" movies on YT, then you see that when one wheel is put on rollers the car doesn't move an inch... Tapping the brake manually or at the hand of an ESP system and the torque is multiplied to the other wheel, hence the car starts moving.
Costly they are, but i've never felt a noise disadvantage.
I need a desk model that I can put my fingers in and play with.
( ͡° ͜ʖ ͡°)
You can 3d print it
Me too.
or make it with legos
You'd cut yer fingers off, kid.
I have to say, when my university teacher tried to explain this with only technical CAD drawings and such, I had absolutely no idea how that thing worked. This was very clear explanation of a quite tricky subject! Thanks!
First patented in 1958 by Vernon Gleasman. He built them himself. He had to modify cutting machines to be able to make the gears. It was first marketed as the Dual Drive. It was later manufactured by Triple-D Inc of Detroit. Gleasman then went to Gleason Works in Rochester, NY when demand increased. Over the years there have been several owners of the patents.
Very nice
Good explanation. I understood the principal of operation long ago, however this graphic helps put it all in perspective as this video shows the theory in action. Thank you for the visual simulation. John, Australia.
They work great. Had them installed 30 years ago in a truck. You could have one tire in the air and the one on the ground would still pull you. Both tires will turn about the same speed and one won’t spin wildly. In turns on ice and snow you could still steer unlike a locker or most posi’s. An outside force (road) can cause the wheels to differentiate.
I love the animation! I learn by images and this really helps!
Things like the Torsen differential and VTEC and variable compression engines just make me in awe of how a person even thought of the idea, let alone implement it effectively
That's the most easy-to-understand presentation of an amazingly simple solution to a long time technical problem. I'd never be able to invent such a thing.
I think your explanation was just fine I completely understood you watching this for the first time. Good work bud thank you for your content
Read this and techdaemon's comment BEFORE watching the video. The Torsen does not work the way the video narrative suggests.
1. The video begins a worm gear can turn the worm wheel, but the worm wheel cannot turn the worm gear. That statement is correct. What is not correct, is that the Torsen uses worm gears and worm wheels. Next he calls his worm wheel, a spur gear, which cannot mesh with a worm gear. Then, notice how the gears magically transform from worm gears to 90 degree helical gears when the animation assembles them into the differential case. 90 degree helical gears work much like the ring and pinion gears on cars and transmit power in both directions. Moreover, with worm gears and worm wheels, the worm gear is always the much smaller gear. This shows the opposite. Since the differential pinions (which he calls the worm wheel) is smaller in diameter to the axle side gear (which he calls the worm gear), it is actually easier for them to turn the axle side gear than the reverse. This invalidates the basis of his worm-gear-based premise. However, the narrative continues based on the false worm gear premise, even though it is obvious to all there are no worm gears and worm wheels, and thus the remainder of his explanation of how it works is also false. I will prove in the following that differential pinion gears driving the axle side gears is central to how the Torsen works in a low-traction environment.
2. Gear types: Spur gears are the most efficient because all of the rotational thrust is applied between two gears in mesh is in their direction of rotation, which is 90 degrees to the shaft they spin on. Spur gears are never in contact with more than one tooth of the opposing gear at a time. The drawbacks are, since gears must have clearance to work, they generate noise and vibration when transferring from one tooth to the next. They are also not as strong because there is only one tooth in contact with the opposing gear. Helical gears are quieter and stronger because more than one tooth is engaged at all times as they slide in and out of contact, which is why they are used in transmissions. The downside of helix cut gears is gears sliding in and out of contact and the thrust vectors are not all in the direction of rotation of the gears, because the helix creates an inclined plane, thereby causing some thrust to be in line with the shaft, they rotate on. Optimizing this downside is what allows the Torsen bias its torque. One could argue that condition exists with 45 degree spur gears. That is true, but to a much smaller degree.
3. Open Differential: With a standard open differential, the axle side gears and the differential pinion gear that spans the distance between the two axle side gears is a highly efficient 45 degree bevel spur gear. The only time the differential pinion would turn relative to the differential case is if the axles were not going the same speed, either due to a turn, or loss of traction on one of the wheels. Therefore, when traction is good, and the vehicle is traveling straight down the road, the differential pinion gears are not rotating relative to the differential carrier, and since the differential pinion gears are in mesh with the axle shafts side gears, the teeth of the differential pinion gears simply push on the axle side gears through their teeth, with no movement between the the gear teeth of the gears. With no gears moving relative to each other, the effect is as though the axles were simply splined to the differential carrier because the axles rotate at the same speed as the differential carrier. Assume the differential carrier is rotating at 2 rpm, and you go around a corner that reduces the inner wheel speed to 1 rpm, then the outer wheel speed must turn at 3 rpm. Next, assume we have 100 rpm and 100 lbf of torque applied to the differential carrier. 50 lbf torque would go to each wheel when there is adequate traction at both wheels. Assume we are stopped, we add power, and the right-side tire starts to spin at 10 lbf of torque but the left tire doesn't move. As the carrier continues to turn at 100 rpm, the torque to the right-side wheel drops to 10 lbf of torque because that is all that it can do. However, because the carrier is still rotating about the stationary left-side axle, the left-side axle drives differential pinion gear, which in turn drives the right-side axle gear, thereby doubling the rpm of the right-side axle. The force generated to turn the additional 100 rpm cannot exceed the 10 lbf maximum imposed by the right-side axle, but the opposing force that drives the right-side axle through the differential pinion is on the left-side axle side gear, so 10 lbf is exerted added to the total tractive force for a total of 20 lbf, 10 lbf to each wheel, even though only right-side axle is turning. An open diff has a 50/50 torque split, 100% of the time.
4. Torsen Differential: While going straight down the road and axles turning the same speed, the Torsen differential behaves similarly to the open differential. If you simply go around a corner, and one wheel is going proportionately faster than the other, there is no torque being applied through the turning differential pinions because their axle side gears and rotating differential carrier are both perfectly coordinated. If the left-side wheel is on dry pavement, and the right-side wheel is off the ground, the differential carrier revolves around the left-side fixed axle side gear, and as with the open differential, transfers the left-side rpm through the differential pinions to the right-side axle side gear. Because the wheel is off the ground, very little additional torque against the left-side axle side gear is required to transfer the rpm from the left-side axle to the right-side, and thus negligible torque on the left-side axle gear is available to move the vehicle. If the right-hand wheel is on ice, and it can generate 10 lbf of torque, the differential carrier again revolves around the left-side fixed axle side gear, but this time it requires significantly more than 10 lbf of torque is required due to the thrust vectors of the helical gears to transfer the the rpm through the differential pinions to the right-side axle side gear, and arrive with 10 lbf of torque. The extra effort of torque as a ratio required at the left-side axle side gear is the design Torque Bias Ratio (TBR). If the designed TBR can achieve 3:1, then there will be can be up to 30 lbf applied to the left-side axle side gear, 10 lbf to the right-side axle side gear for a total of 40 lbf. If 40 lbf, is not sufficient to move the vehicle, the left wheel will remain stationary, and the right wheel will continue spinning at twice the differential carrier rpm, just like with an open differential. If there were a worm gear and worm wheel used here, it would be instant lockup, and there could be no TBR.
5. Torsen Implications:
- When turning a corner, it is not effectively different than an open differential.
- When the differential carrier rpm is not perfectly coordinated between the axles, as is the case when there is a traction problem, it biases torque to the wheel with the lowest rpm.
- If there is 0 lbf required to turn one wheel, there is 3 x 0 = 0 lbf transferred to the stationary wheel.
- If there is 10 lbf force on the spinning wheel, with a TBR of 3:1, there is a maximum of tractive force of 40 lbf available. If that is not enough to move the vehicle, it will still behave like an open differential with one wheels spinning
- If 40 lbf was not available to move the vehicle, you could drag the brakes. By adding 10 lbf to both wheels, you would increase the tractive lbf at the stationary wheels to. (10) + (30 + 30 - 10 = 50) = 60 lbf of total tractive force. Of course with one wheel off the ground being at 0 lbf for one wheel, you could also get moving by applying the brakes and gas.
- If I can drag the brakes on a Torsen and gain more traction, then why doesn't that work with an open differential with its 45 degree spur gears? It does to a lesser degree. Computers and traction control these days can also apply the brakes to the spinning wheel to bias torque perfectly to meet conditions.
Again, techdaemon's comment explains accurately how this device functions, which is critical to its application and usage.
Might want to use Nm instead of lbf to be taken a little more serious in the automotive industry
@@timbroski4487 The automotive industry in the US uses lbf unless it is in foreign literature. We also use horsepower rather than kilowatts. Fuel is sold by the gallon not liter, and speed and distance is measured in miles not kilometers.
@@jackt6112 sure but the American automotive industry isn't exactly the most respected in the world
Who is, is just someone's opinion. They were the earliest and most aggressive at developing the technology and engineering. The Torsen was invented by American. Our measurement system came from Great Britain, partially which came from the Romans. Great Britain started the industrial revolution and number one in technology for a very long time. Both beat Germany and Japan technologically in the last world war. English is the technology language of the world for a reason. I would bet far more people on this thread relate better to lbf than Nm and are from the US. Using Nm would be like leaving a response in Chinese.
Thank you for your comment, i learned a lot.
There is an issue at 0:56. The left wheel is helical and the right one is spur. But in fact they both are helical, so they both can rotate each other, but depending on the angle of teeth it will be more or less easily.
If my Mechanical Engineering degree is worth any salt, the blue component should be the worm wheel, and the orange should be the worm gear (helical). This should be the correct interpretation because the blue component turns the orange component, and not the other way around (unless the system is non-locking).
I had a Torsen T2 installed in my 2004 Mercury Marauder and could not be more pleased. It cost me $2500 and has been worth every penny.
For street driving, HARD driving, there is no better solution. Many times before the upgrade I would have places where I would be negotiating a tight turn while applying high torque to the drive wheels, such as a 4-2 downshift coming out of the turn. Before, with the stock Traction-Loc differential, the two rear wheels would lock together and I would lose traction on the inside wheel because it would be spinning at the same speed as the outside wheel. But with the T2 that never happens and I can make those 4-2 downshifts coming out of the turns with confidence and full traction on both rear wheels. She's like a roller skate on a rail!
Just watched 90 seconds , and I located my car blend door and just tapped it, it started working . You saved me 300$ just today . Thank you .
I’ve installed an aftermarket (quaife) one on my sports car and it greatly enhanced the driving experience. You can put more power through corners, when you reach the limit the rear starts to slip gradually but the limit is higher. Before it would not do anything then snap suddenly because it would spin the inner wheel with the other not spinning then it would suddenly spin the other wheel if pushed further.
The video describes only the Torsen T-1 (or Type A) design. The Quaife ATB (automatic torque biasing) differential is a different design, similar to the Torsen T-2 (Type B).
This was still confusing at first but I got it. Here’s why.
1. Despite appearances, the orange gear is the worm, and the blue gear is the wheel. Worms can drive wheels easily, but wheels struggle to turn worms.
2. When driving normally, the wheel turning faster pushes from the orange worm end. Worms can turn wheels, so the axle can turn faster.
3. When wheelspinning, the engine is turning the wheel, which struggles to turn the worm. As a result the wheels bind together and drive both sides.
4. They are not completely worm and wheel like as the helical angles are different, so if there is light enough load or enough power the wheel can turn the worm, hence why it can only bias so much torque and doesn’t work when there is no grip on one side.
I see you watched the video too
problem is the orange gear looks like a wheel (helical gear) to me as well because the worm gear should look like a screw with one continuous ridge.
An ingenious video describing an ingenious piece of mechanical engineering! Kudos!
the science behind this is astonishing, great video, explained alot
This is a truly excellent video. As someone who has driven both viscous, open and torsen diff-ed versions of the same car and felt the differences between all three on the limit of grip, I am pleased I now understand what is actually going on. One of those things that is simple when someone explains it, but you can't imagine how clever the people must have been to come up with it in the first place!
at a bar one nite... u know telling engineering jokes & dreams
I’ll just go watch those old car videos.
WuzNab Torsen was patented in 1958
They explain it 10x better
Amen to that.
Good ole jam handy
Thank you for an outstanding explanation with mind blowing animation.
Excellent! The graphics are just right, and the animation is too. Now I understand.
The Torsen knows when its tires are slipping because it knows when the tires arent slipping...
Underrated comment
haha yes
"He can see things before they happen."
Remember Torsen differential works on the principle of the force between the slipping wheel and the ring gear in order to send more torque to the other wheel. If the wheel is completely free spinning or very little resistance means there is almost no resistance between the two, there will be no limited slipping action. Although, you can manually apply the limited slipping action by gently applying the brakes which applies resistance so there is a force difference between the ring gear and the slipping wheel axle.
thanks, didn't understand that either. 😂
Yup trying doing a burnout in a Toyota Soarer with a Torsen 🤣 only spins 1 wheel
AMAZING EXPLANATION! 10/10 I UNDERSTOOD EVERYTHING. EVEN MY DOG KNOWS NOW HOW IT WORKS! KEEP UP THE GOOD WORK. THANK YOU
So it’s pretty much a lsd and a standard differential in one... pretty smart. Thanks for the video it helped me understand how differentials work throughout the 3 videos you made on differentials. Definitely subscribing.
Nice explanation, thank you.
How well would it interface with a flux capacitor?
brain.exe has stopped working
Trust me, I'm an Engineer I have a better solution that torsen
eror 22 forgot to brain
Taifeng Jia Tell us
stroke.exe found
Then here's the easiest way.
If there are more moving parts in a engine. then worse it gets.
Excellent visualisation and comments🙏Thank you very much🍰
Just took one of these apart so freaking simple and so less to worry about setting it up
to make a Torsen differential perfect, we have to add an active locking mechanism. for situations where the auto-slip-compensative function of the torsen gears won't make sense (means where we actually need the same force on both wheels without any kind of balance or where we need simply hardconnected parallel traction together with another pair of wheels) . Therefor a mechanical locking option still makes sense.
this is genius. i feel dumb as a coconut after watching this.
Invented in 1930 by Walter Truck Company.
Unfortunately it is also wrong, a Torsen diff does NOT lock when one wheel has no traction.
😂
Superb comment! I feel the same way.
@@An.Individual thankyou for your comment,,,,,,,,,,,,this is first time i ever saw torsen diff.............i am used to truck rears such as rockwell and eaton heavy duty diffs.........the minute i heard that one wheel locks up when the other is on a slippery surface i said that this is like a power divider or and inter axle differential..........your comment says it's not so..........i agree although i don't quite know why , i need to become more familiar with this torsen concept. ,,,,,,,,thanks again.........i kinda thought i was nuts
THE most brilliant differential solution!
This has got to be the most elegant solution possible
Great video!
In my opinion this is a better design than the clutch LSD.
it is on one hand.. diff service is pretty much the same as conventional, less heat.. the clutch and viscous type give a smoother engagement especially if the surface traction is fluctuating from high to low.. plus the clutch type can be set up for a limited amount of power tranfer and different engagement parameters .. viscous smoothest engagement especially on the driveline but generates alot of heat..
Torsen in one sentence: the tendency of gears to push away from each other when under load is utilized to create large amounts of friction, which makes it hard for the gears to turn, making the differential seemingly “lock.”
The “Detroit TrueTrac” differential utilizes a much-simplified gear mechanism to the same effect. Gear type LSD differentials are awesome
ELSD as in zl1 1le
Wrong Sir.
TrueTrac causes the helicals to push out and jam the ends of the helicals into the case side to make the locking action.
Pure old metal to metal friction.
Thats why you do not use posi lube or synthetic oil in a Truetrac. Reduction of lock up friction.
@@hotrodray6802 That is literally what the first sentence says :D
You're describing an Auburn differential, (cone type limited slip). Truetrac doesn't function like that.
Thanks for these. I was wondering just what the heck a Torsen differential was and how it differed from other LSD's. This (and the other video) were just the right depth of explanation. I had been wondering about some odd sensations from the back end while driving and this certainly explains them. Now it's suggesting your brushless motor vid--I think you've got a new subscriber.
As a first year graduate of Automotive Technician, this is a great refresher 👍👍👍
ingenious design.
I'm missing something. How can the differential "tell" that one situation is spinning one wheel faster because of going around a turn from a situation of spinning a wheel faster because of lower traction ? Does it lock up after certain speed difference is encountered?
The only thing that I come up with is that during a turn some torque goes "around" that is "exit" thru slower wheel and drives faster wheel as both wheels maintain traction and it goes "back" to differential to spin the gears from the axle side. That way it would act as a weak friction LSD.
But when the wheel keeps spinning without traction there is no torque transfer thru road surface to drive slower wheel so now worm wheel tries to spin worm gear on lower speed axle side... But it can't because it doesn't work that way and whole thing spins as a single assemblty.
I think that I've figured it out while writing this comment :)
In the one scenario the power comes from the engine trying to spin the wheel, -not possible because the worm gear locks.
In the steering scenario the power comes from the wheels, in that direction the worm gear may move freely and allows adjustment
@@stefanritscher7868: 100% Correct, but now if you stand on accelerator during that turn you are then changing "where" the power and speed difference is coming from, the diff will then sync and both tires will spin (squeal on tar) at the same speed.
loved it.
Could you please share any information regarding dual clutch function in tractor applications.
This is great! This is what was used in the Audi Quattro, and what caused All Wheel Drive to work successfully. Amazing!
"LSD technology..."
I'm in.
What this explanation leaves out, or simply states as the law of the worm gear set, is that the inherent friction of the worm/worm wheel interface, coupled with the trigonometry of the tooth interface results in the gear set locking when the worm wheel tries to drive the worm. When the friction coefficient is greater than the tangent of the angle the interface won't slide. Just like the ladder on the wall problem from high school physics. As long as the worm is driving, this friction is just an inefficiency. So the torque bias is related to the ratio and related helix angle of the gears.
Jack Thompson Thank you for elaborating the physics behind worm gear-worm wheel such a detailed way :)
+Jack Thompson awesome, I was wonder why the worm wheel cannot spin the worm gear but it's a matter of how the friction interface is shaped.
Also, I notice that the cutaway section at 1:08 makes it apparent that the worm gear has symmetrical "teeth", whereas the worm wheel has assymetric teeth. Is this important in the function?
+Learn Engineering any advantage of the clutch pack limited slip differential?
No.
Clutch packs wear out.
So cool! I'd been baffled by these things for a while, this explains it really well. Granted I have most of an engineering degree by now, one year left. Makes me really want one for my old Slugbug - they are available, direct replacement for stock open diff. Just hella expensive. With enough money there are very few things you can't do on an old Bug.
Excellent graphics and explanation. Thank you.
Those worm wheels must be very strong to hold that shock /load,when slipping.
Yeah imagine if you got your shirt tail caught in there!😂
@@wesleycrouch2135 why would your shirt be anywhere near a Torsen differential?
@@alexnutcasio936 why comment on something that is obviously a joke with some stupid reply like that. Not everything has to be literal, my goodness man, grow a pair.
@@wesleycrouch2135 that was a joke Ms Wesley?
@@alexnutcasio936 first of all it’s MR. Wesley. Second of all it wasn’t meant to just be a gut buster, just a little hehe. Get a clue of how humans work and interact you windpipey robot.
"As you might be aware"
*Stops*
*Let's the clutch out slowly*
This was somehow recommended to me even tho I'm a computer MTec student. It was actually quite interesting!
Going to uni soon and if my teachers explain things that way I'm sure I will learn. A lot. Amazing video!
0:49.... hey wait a minute! The worm wheel is not a SPUR gear!!.
But it is operating like one.
No its not!. Its operating like a HELICAL gear!.
Marek Sumguy True, my bad :-) I meant to say that it has the same effect - I was trying to say that I saw what he was saying. I'm not a mechanical engineer.
The "teeth" (splines) follow a helical profile. Spur gears are straight cut... like the gears on the ends of the worm wheels, in this video.
dude litterally nobody gives a shit.
I kind of understood how the right worm wheel is spining in the opposite direction due to the relative motion, but I can't see hoe is the situation different when a wheel needs to spin faster because of a turn or when the wheel is spinning faster because of a slippery floor. How does the system know the difference? From how I see it, in both cases the system should lock.
you can kinda see it at 3:50 where the left wheel isnt moving and this is why they lock. in the case of a turn, both wheels are turning so the worm gear is able to compensate for the speed difference
The outside tire is being speed up by the road itself, just as the inside tire is being slowed down by the road itself. All the worm wheels and the spur gears connecting them do is balance the action between the two.
If you floor it with one tire on ice, because the road is not pushing one tire faster then the engine is driving it - they have no choice but to spin the same speed.
The way they explain that the inner (worm gear) can only be the input, and the outside worm wheels can only be driven as output. there is just no way for a tire to spin faster then the diff unless the tire itself spins it faster and not the diff.
h82fail but I mean how is the situation different from when the one wheel is spinnig fastwr than the other and when one wheel is spinning excessively fastwr than the other. If you answered this I could not understand it. Looking back in the video when the car is negotiating a turn, how is there the worm wheel not trying to rotate the worm gear and lock the system as it is not possible.
There is no difference. @ 2:24 the different speeds are accounted for by the spur gears ontop of the worm gear, it doesnt matter the speed at which they go because the slower one is traveling proportional to the faster one seen @ 2:35 - 2:50. the blue spur gears make sure they're proportional no matter what speed they travel, faster or slower, as long as they're both 'freely' turning @ 3:05.
taking this into account, imagine the left wheel is stuck, and the right wants to rotate, what happens is the right wheel rotates the worm wheel, spins the worm gear connected to the other set of worm gears and is forced through the differential frame to rotate the left wheel because of the principle @ 1:00
this video was EXTREMELY well explained as well as every other video ive see by you. fantastic work.
Amazing video. This is the only video on youtube which explains torsen so effectively. I would like to know which CAD software do you use for this gear animations?
"
Excessively"...needs a definition, like 10% more slip....
so why diffrential are not locked during turn?
+Raju Yadav if they are locked during turns the tires are going to wear out very fast
+Raju Yadav When the transmission shaft(TS) is driving the whole axis, a Torsen dif allows one of the wheels to spin faster but NEITHER of them can slow down. Therefore, say as the vehicle's turning left, the right wheel is free to spin faster to make the turn; even if one wheel is slipping, the other one is still being driven (CANNOT slow down), so that the vehicle could pass through. Unlike Torsen, early models of differential can't always drive both the wheels, which means one side may rotate slower than the TS does as the other side goes faster. Once the wheel on the one side is slipping or hanging in the air, it will spin as twice fast as the TS does, drawing all the power from the other wheel. Then the entire axis fails.
+Yiming Liang I won a bet once regarding the feature of the spinning side spinning twice as fast as it would if both wheels were on the ground going forward with identical traction. This is a not-well-known feature of differential action. It was a complicated bet involving a semi-tractor with tandem driving axles with the front unit containing what is known as a "power divider". There is a serious misunderstanding among truck drivers as to what this "PD" does, with the majority believing that this "turns on" the back rear end when you switch the "lockout" feature on the dash into engagement, which is way-far from the truth. They don't seem to understand the nature of "full-time 4-wheel drive" which is what it actually is, considering 4 wheels (8 actually!) on the back end. All 4 hubs drive against the road all the time, through this "PD" which is no more than a small differential set located in the front unit or "pig". The "lockout" feature actually locks the 2 rear ends together, like welding the spider gears up in a demo derby car. The individual rear ends still have differential action but as a pair they now no longer do. 2 wheels now have to break loose before you're stuck instead of just one. WELL, on to the bet! I said I knew a way to get a rig to double its highway speed in any gear with a modification that would take one hour. Since we were among mechanics, we agreed to use a dyno at a truck repair center to prove this point. With the truck normal as it sat, it could do say 60 MPH. Since we didn't want to try to spin a dyno at 120 MPH, we settled on being able to hit 60 MPH in, I think it was 6th gear, instead of 10th. 6th was able to do 30 MPH on the road. So in theory this truck could do 120 MPH, and the dyno was a safe way to prove the point, all agreed. NOW, I pulled into the parking lot, and took all 4 wheels off the rear tandem, and hung the axle from a chain, completely off the ground. I pinned the Maxis on the 2 front brake chambers so I could leave the brakes set (by leaving the red button out) so only the brakes on the rear tandem were set, effectively locking the rear tandem from being able to turn and forcing all driving force to run through the front one. NOW, without activating the "lockout" feature on the dash, the differential action in the PD would take place. I parked the truck on the dyno like a single-axle tractor (on the front half of the 2-part dyno rollers) and showed them what I could do. I won the bet! They argued violently against paying me, but I held fast on the fact that I did what I said I could do, and the modification, as hokey as it was, happened in less than one hour! So trick bet or not, I did get paid!
+Raju Yadav this is because the power needs to be split perfectly at all times. If the left is turning at -20% then right will turn at +20%
This is the case of turns. but in slippery situations one wheel is turning at 0% , so to balance the equation, other must turn at 0% hence both wheels will receive same amount of power.
The locking of turn ratio is because of the spur gears that mechanically bind the who half shafts together. since if they turn they must turn in opposite directions, the power is split like the way explained.
you missed the point of the question.
Hey this interesting information and I like the you combined the visual with your explanations.
These are almost as good as having lockers. Brilliant. There are some very clever engineers out there!
Except when you get one wheel at zero traction it will not transfer torque to the traction side. Its not a auto locker.
i dont understand one thing. when making a turn, 1 worm gear spins faster then the other but the worm wheels drive each other and run at the same rate. how does this not cause a binding issue??
Carbon Ronin Worm-gears always spin at the same ratio but in different directions, one doesn't turn faster than the other. Remember that the whole differential system is spinning. that allows wheels to turn at different speeds, while the relative speeds of the worm-gears are the same. its because one worm-gear is adding to the relative speed on the whole system but the other one is subtracting from it
Joey Grip, I totally agree with you! It is really questionable how the Worm Wheel (That is suppose to be called WORM GEAR, and here the Worm Gear they say is suppose to me called WORM) on the Left side rotate faster than the Worm Wheel on the Right side because they are mating or meshed?! This is ridiculous! They have the same Pitch diameter (or Pitch circle) plus they are meshed therefore they will have exactly the same RPM!
Aris Taukulis, sorry Dude I totally disagree with you. Don't you see that the two Worm Wheels (as they call it here in this video) are meshing with each other through the two sets of spur gears integrated at both ends? Plus they are both driven by the Left and Right Worm Gears (as they call it here in this video) of the same size. I can say "This is totally Impossible"! You guys review the video well, and you will realize that to solve the problem, you need to eliminate those two sets of Spur Gears, and you will have a very good differential assembly applicable in a straight path driving as well as in a curved path driving! And further more, in this video's explanation, you do not need to let the Worm Gears (as they call it here in this video) rotate in opposite direction when making the vehicle turn either left or right. That is another ridiculous analysis. If both axle needs to turn in opposite direction, does that mean the vehicle will turn pivoting at the middle point of the differential (because one wheel is turning opposite direction to the other wheel at the same speed in this video)? How in the world could you achieve that?! It is like turning the way a Fighter Tank turns, and cars or trucks do not turn that way. Plus another thing, turning in a curved path does not mean both axles should turn the opposite way! They both should turn in "The same way" only that one spin faster than the other! That is very simple to understand. This video has misleading explanation, plus there is a redundant part in the assembly (The Spur Gears integrated to the Worm Wheel as they call it here in this video). Totally misleading video!
Pretty much every word of this explanation is wrong.
First off there are no "worm gears" in a torsen, they use crossed helical gear sets, which leads to the second problem;
The differential action of the torsen is highly dependent on the tangent gearsets being able to be driven by the slower moving axle, as this is the exact method of differential action.
Then theres the part where the narrator doesn't appear to understand that, even if it were the case that these were worm gear sets, the fact that you can't backdrive SOME worm gear sets is solely down to the worm gear helix angle and the contact friction in the back drive direction being different to the primary drive path.
Then theres the fact that torsen differentials DO NOT ACHIEVE LOCKUP EVER which is why they spin a wheel if its in the air, because they only achieve torque ratioing, not wheelspeed management, which is the method that, for instance, clutch pack differentials operate on (and detroit lockers and haldex, etc).
The actual explanation for how torsen differentials work is, ironically, so much simpler than this garbage... in the primary drive path (through the tangent gear axles to the output shaft gears) there is no movement and therefore no friction and no internal losses. When a speed differential occurs between the wheels there is a secondary drive path which occurs from the slower moving wheel to the faster. In low drive difference circumstances, where torque delivered is nowhere near the limit of grip, the ratioing is very limited and therefore torque transfer across the tangent gear set is low and the losses are low (although its worth noting that according to the video explanation any speed different should lead to a lockup, effectively making the drive system a spool). In high load applications where the inner wheel is unable to transmit full torque to the ground, the differential begins ratioing more and more torque to the outer wheel, in which case the gearset friction climbs and the torque ratio climbs with it, delivering a torque ratio of up to 4 to 1 (from memory) for this style of gearset, although that can be dependent on incorporating thrust clutches and similar devices to increase the tangent gearset friction.
What this video should say is that the benefits of torsen are;
Extremely progressive and instantaneous ratioing results in very predictable handling and benign characteristics (limited understeer moment development even under full action etc)
Limited torque transfer characteristics result in the system not actually functioning at all where a wheel is in the air, as, when a wheel is in the air the torque that the wheel can support is zero, therefore the highest drive wheel is able to support 4 times that load, which is still zero.
And finally that consistent high load operation of a Torsen will result in the gear oil becoming very hot and reducing the effectiveness of the locking action, then, if continued hard driving occurs will finally result in the breakdown of the oil and potential failure of either the tangent gearset or alternately of the ring and pinion gears, as there is limited lubrication for them due to the breakdown of the gear oil.
Anyway, find someone who can explain how one of these things works to you before making a video about how one of these things work, that explanation was wrong in every conceivable way, from the method of operation all the way to the description of basic construction, the only thing that was correct was how the system works when the vehicle is driving in a straight line.
+Drew You're a complete idiot.
6strings1pickup Of course you'll be able to back that up by... you know... identifying an error in what I've said, right?...
Drew, You are *not* an idiot but YOU ARE ABSOLUTELY RIGHT. As you say from the outset how this video explains the action, and subsequently what happens, is *completely wrong*. Yet this video is quoted like a rash all over the internet.
This video needs to be banned.
how long do those oils typically last? in vehicles such as 86/brzs?
I haven't read all you say, but, I am certain a Torsen diff does NOT lock as this video states.
The first time I watched this (maybe a year ago) I did not really understand it. This time, it made more sense. What a brilliant and simple (thus brilliant) system.
Really well done animations/explanations. You have a subscriber.
Let me help explain this because this video isn't too simple.
When the car is turning, the road is pushing the axles at different speeds, so the worm gear turns the spur gears, which turn the worm gear. The worm gear of the faster axle rides along the spur gear differently than the worm gear to the slower axle. The way the worm gear compensates for the different speeds is that the worm gear of the slower axle "rides along" the spur gear. The Worm gear of the faster axle sort of pushes the spur gear, rather than riding along it.
Now pay attention to the way they are spinning and how the threads of the gear look.
Image the worm gear was in place and couldn't travel in a circle. The LEFT FASTER SIDE worm gear, spins so that the spur gear can move as fast as it wants to, if the spur gear wanted to spin faster, so would the worm gear.
Remember we are thinking if the worm gear was stuck in place. On the slower side, the worm gear spins so that the the spur gear must go in reverse. So in order for this right worm gear to spin and the spur gear turn and make the car go forward, what would have to happen? Well, the worm gear must ride along in circles around the spur gear, it can't be in place.
So basically, the worm gear on the slower right side is spinning backwards so that it is traveling along the spur gear, while the left one is spinning so that it lets the spur gear go as fast as it wants to.
From left to right, the left spur gear speeds up, it makes the left worm gear speed up. The left worm gear makes the right worm gear speed up, which makes the right worm gear travel along the spur gear in circles rather than speed up the right spur gear.
Thanks man!
Ismael Pintley No problem, just glad I helped someone.
i have to pause many many times and rewind many many times. which gear can't move which gear?
+not_a_russian
One that look like a gear cannot turn the one that looks like lolipop cane.
Don't worry about it. This explanation is very wrong anyway so it doesn't matter.
On more than one occasion my Torsen Differential made a life saving difference when driving on Black Ice, in the winter here in Alberta.
Having driven with other differentials under the same conditions I ended up in the rhubarb, which is very unpleasant at -20 C to -40 C.
Incredible demonstration.
Man...I need a nap now.
Is it just me or did the differential just loose all its teeth at 3:10? The right worm wheel spinning at the same speed as the on to the left, while the axles are at different speeds, means mayhem. The fact that the worm wheel can't spin the worm gear, means that the fast axle is "bracing" against the slow axle. That is the reason for the differential action and torque multiplication through the smaller gears. AFAIK
That’s what I was thinking. Something seems off about that part…
@@jonathanburke6255 unfortunately it's wrong. I have one of them in my truck and was just looking for locking options to add to it, but yeah, this is not how it works.
Let’s take a moment and appreciate all this technology in our vehicles. It’s amazing people have come to figure all this out.
these videos are excellent, thank you!
Every time I watch this video, which I’ve seen at least 3 times in the last few years, I leave still confused
This is a bit complex, I would have to see it in person to fully understand it.
It helps to picture that you're looking at the rear of the vehicle looking forward, the left side is the left axle and the right side is the right axle.
It's like a combination of a regular differential and a posi-traction differential, not a limited slip differential and no clutches just gears, it's a great idea.
I thought whoever invented the differential (regular spider-gear type) was a genius. Then comes this one..LOL.
They start off telling us that the worm gear can not spin the worm wheel. , then in the example the worm gear seems top spin the worm wheel.
How the heck can those Spur gears turn at the same speed and yet the axles turn at different speeds. I know the system works , but these geniuses better get a new PR firm to demonstrate how this system works because the narrator says one thing while the gears do another thing.
At the 03:20 mark it show how one gear goes backwards, but it doesn't, it's like our Moon going slower that our 24 hours in a day so it looks like it is rising in the east to go west .
I had several Teacher like this in High school that taught in this manner and expected us to know how something worked and yet they them self didn't fully understand it . I need to see the path of energy from the pinion gear where only the parts doing work will light up , plus, all the fixed pieces should be in one color since I can't tell if something is free floating or driven by another part.
Gary wood
The spur gears will turn at the same speed because they are locked together. The axles (or worm gears to be exact) are turning at different speeds because relative to each other they are going opposite ways. In fact, the reason why their spur gears are turning at all is because the worm gears (or axles) are relatively going the opposite ways. And this is where I think your confusion is coming from, how could they be going the opposite ways when in fact they are both rotating forwards. The answer to that is found in basing your frame of reference on the carrier.
It's the same thing when you're at a light and somehow your frame of reference gets focused on the relative position of your car against the car beside you. If the car beside you rolls backward, you will instantly try and stomp on your brakes thinking that your car had somehow moved forward, when in fact it was just sitting still.
So from what the video shows, the left axle is turning fastest, the carrier is turning slower relative to it, and the right axle is turning the slowest. From the carrier's point of view, the left axle is going forward and the right axle is going backwards (at the same speed but opposite direction), and hence the spur gears need to rotate to accomodate their relative movement between each other.
But which teeth are the Drivers and which are Driven because I can't see any notations for the Fixed parts . I understand how the Moon seems to revolve around the Earth from east to West by the obit speed being slower than Earths rotation.
The big question I have is for how the unit works when the car is in Reverse or the Engine-Breaking is use on a Hill and the wheels cause drag to get the gears to go slow down .
The Pinion Gear is also adjusts for Lash and Lag which is where the actual Teeth rub and can cause excessive wear in one spot. All of these contact points must be pretty exact to achieve even wear , and cost big bucks to fix if something goes wrong .
I'l keep watching it and see if if someone points out the free spinning teeth or fixed teeth on splines so i can follow the energy path and understand how those planet gears work one way to Drive a gear but can become the Driven gear.
Techdaemon said it much more thoroughly, but to say it quickly, the slipping wheel doesn't steal most of the engine power. The same power that's sent to it is also sent to the other tire, but since that tire is on a non-slip surface, that amount of power isn't enough to make it spin. Watching the 1936 Jam Handy film on differentials will fill you in on the details quite well.
Thank you for all the great videos! Could you please enable the closed captions for this video too???
This seems to better than a limited slip differential. Why is this not standard yet?
Gray Man It is a limited slip diff.
Qasim Mir No I would not consider this to be an LSD
Gray Man Well it is classed as one.
All those helical gears cost a lot more than a clutch pack LSD and torsens are no better than an open differential when a wheel has no grip at all, while a clutch pack LSD will still drive the car forwards. This is also why dragging the brake slightly on a Torsen based 4WD vehicle can allow it to get moving while one wheel is off the ground.
This is a differential that allows for a limited amount of slip between the wheels, so it's definitely a limited slip differential, but it really isn't as good as a clutch LSD.
*WTF* that makes no sense. You say that the differential will lock when traction is only on one side, but by that logic it should always lock. When the vehicle is truning the "worm wheel" from one side will not be able to transfer its power to the other because as you stated "the rotating wheel can't spin the worm gear".
while turning. one tire is slowed down and the other sped up externally! so the worm gears are applying the differential torque and the spur gears spin in a speed related to the speed difference but if just one wheel wanna speed up by the torque of the engine that's a force coming from the drive train not the wheels so that's the case when the spur gears are trying to turn the worm gears. but the real magic happens when you are turning while on a slippery surface with one wheel cos a torsen diff can be kinda close and kinda open at the same time.
It’s totally wrong in this video and waste of time
@@vmark1111 What you describe only works while rolling, then you get the „perfect differential“ by external force, but if you follow the rules of the video, whenever you would accelerate in a corner, you should lock the diff in an instant, which is bad and actually not true.
@@laser_simon922 I don’t think you understand how the gearing works. When there is no external driving force accelerating the outer wheel and slowing the inner wheel the differential acts as a locked differential. The external force caused by turning forces the worm gears to turn in opposite directions at exactly the same speed. (When turning the outer wheel speeds up the exact same amount the inner wheel slows down) in this situation the torque applied to both wheels is identical despite the fact that the speed each axle is rotating is different. If the inner wheel loses traction, the spur gears prevent it from spinning up any faster because the outer worm gear is tied to the outer output ring.
Torsen differentials can have only really one state and that is the sum of the wheel speed percentage between the two wheels has to add up to 100%. So, while rolling torque is always applied where there is traction. The only place this breaks down is when one wheel is lifted and the lifted wheel can spin at 100% while the other does not spin at all.
Dude, you know what relative motion means?, that's all in there, If you know how relative motion works then you'll understand. I was lost too until I've realized that
appreciation is the least i can do; you are awesome keep it up.
what a science. im so happy to understand these things. these are treasure
Well I'm off to watch Scooby Doo solving some mysteries not more mysterious than this mystery going on here
I watched this 10 times. Still over my head. Nobody comment to try and explain. I still won't get it..
So you see whats going on is pretty simple let me break it down for you
Jk jk i dont understand shit either
This is the best explanation yet of the torsen diff. Thanks!!
If anyone was wondering if you can drift with a torsen, I can confirm they are very drift friendly. I can also confirm that it will behave like an open diff if you lift a wheel off the ground, but this is not an issue when drifting. It can become an issue in snow. Over all, I prefer the torsen over my Tomei T-trax(2 way clutch type) in my 350Z and the welded diff in my other miata. The T-trax is actually quite harsh for daily use. Great for drifting though. The torsen is silent and smooth.
Just weld the whole thing.
Tire wear is another problem, let's say you take a turn, since both wheels move at the same rate while the ground is angled/curved and not straight relative to travel a wheel has to slip, reducing availible grip and wearing down a tire, with complete loss of grip you cannot steer properly and can slide, good for rock crawling and drifting, bad for traction.
Noice.... Don't get the whole car welded
Drifter spotted ^^
Can you imagine getting your finger stuck in between two of those gears.
no
Thank you for the video, borrowing this to use as a demonstration :D
To me this is one of the best methods, it seems like it's complicated to some but wow I'd go with this differential anyday
"The worm gear rotating on it's own access." Axis isn't pronounced the same as access.
Not quite the whole story. If the worm gears were truly irreversible, as in the worm can turn the wheel but the wheel cannot turn the worm, then the Torsen diff will supply zero torque to which ever wheel turns slowest. This is not the best way of distributing torque for best handling and will give the CV joints on the driven axle a very hard time.
But the worm and gear pairs are not totally irreversible. If you look even in the video the helix angle is nearly 45 degrees, making them crossed helical gears which are reversible. By very careful choice of helix angle the gears become nearly irreversible, that is, one way is easy the other way is hard. Hence the Torsen diff can be engineered to give varying amounts of torque split to the slipping and gripping wheels and is much less violent than the proposed mode of action.
I cannot help but feel that there is a better way of making a limited slip' other than running gears at inefficient pressure angles and relying on a good extreme pressure oil to give an acceptable service life.
Techdaemon below gives a similar explanation.
+Donald Sayers
It may not be better in all aspects, but you can have a computer detect the spinning wheel and selectively brake it.
My car does that.
Great explaination so is this most effective than other types
This...This is making so much sense right now!!!!!