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How a diff works
Posted: Wed Jun 03, 2015 7:08 pm
by Buzz
For some of you (probably many) this will be a big "duh". For me, it was really a remarkable illustration even though it was done in 1937! See if you agree. Stay with it for the first few minutes, they chose a novel way to open the film!
http://www.popularmechanics.com/cars/a1 ... ial-works/
Re: How a diff works
Posted: Wed Jun 03, 2015 9:10 pm
by TechMOGogy
Great video!,
Thanks for posting
Re: How a diff works
Posted: Wed Jun 03, 2015 10:35 pm
by pcolette
Very nice!
Thanks for the link.
Re: How a diff works
Posted: Thu Jun 04, 2015 11:48 am
by Jimm391730
A very good explanation.
I like to think of it this way: a fixed, straight axle between both wheels makes the speed of both wheels the same, but the torque can be different: if one wheel is up in the air (as Pinzgauers are likely to do!) then it can have zero torque; the wheel in the air cannot push against anything. The other wheel, however, gets all the torque to push the vehicle along. This is what our diff locks do - effectively connect the left wheel to the right. But the wheels cannot turn at different speeds which is what is required in a curve, where the outer wheel must turn faster than the inner wheel.
But a differential makes the torque the same on both wheels, but the speed can be different: if one wheel is up in the air and has zero torque, the opposite wheel also has zero torque (to push the vehicle) but the wheel in the air can spin at crazy speeds while the other does not turn at all. So you are stuck and can't move. But in a turn (with both wheels on the ground) the outer wheel can turn faster, but both wheels have the same torque - they both push with the same force. As long as they both have reasonable traction, they share that traction (torque) despite different speeds.
Which is why our trucks have the choice of equal torque (diff levers up) or equal speed (diff levers down). Good drivers change between the two modes often, depending on the conditions.