How a differential works

#1

http://www.youtube.com/watch?v=K4JhruinbWc&feature=player_embedded

This video is from the late 30’s. Watching this I kind of had to marvel just how well they illustrated how a diff works, without any kind of fancy BS that would be all over the video today.

Note how much custom work they did to create the models, and the cars that had the driveshafts in different places. At the very end where they are showing rear wheels moving at different speeds, consider how they choose to illustrate those different speeds and how well it got the idea across.

Listen to the vocal inflections of the narrator…they can’t help but make you grin.

This video would have been made by my grandfather’s generation. Those guys had their act together.

#2

that is cool - you might say it is jam handy to have…

the biggest difference with a video of today is that the corporate legal beagles wouldn’t allow them to show those motorcycle drivers doing all those irresponsible things at the beginning!
cheers,
bruce

#3

What a great video…so how is limited slip added to the mechanical workings of the differential?

#4

So THAT’S what’s inside that big metal box. {I liked the motorcycles too} :woohoo:

#5

GCP wrote:

Well, I was hoping someone else would weigh in on this.

I should probably go look this up before I embarass myself, but I can’t be bothered.

As I understand it…

The open diff forces a wheel to turn and it doesn’t care which one. So if one wheel wants to turn, (in the snow or it’s gone 110% of traction budget due to cornering forces) then it will turn. Meanwhile the wheel with traction does nothing. Everyone has seen the car stuck in the mud where the wheel with no traction is the only one turning.

And LSD diff can be imagined like a locked diff with a clutch that provides a fixed friction coefficient. The design has clutch pads and preload the pads to some spec such that there is a designed resistance to one wheel spinning faster then the other. With an LSD diff, the wheel that’s easiest to turn won’t spin freely. If the clutch plates provide enough friction to support 50ftlbs of torque, then the “other” wheel won’t just sit there doing nothing, it will have 50ftlbs applied to it.

Don’t take the “imagined like a fixed diff” analogy too far tho. The LSD diff allows wheels to spin at different rates like an open diff. It’s just that it’s hard to imagine an open diff with clutch plates.