why diffential causes different wheels direction?

[jasonyw]

While waiting for the MOT to complete today, I noted this many times but couldn't comprehend why the rear wheels moved in opposite direction with the rear diffential.

The MOT mechanic raised both rear wheels and started to inspect the offside tyre by spinning it clockwise. The nearside wheel spins by itself clockwise in the opposite direction. I asked the mechanic, if the engine is on and drive the car forward surely the offside rear wheel will turn clockwise and the nearside would turn anti-clockwise in unison. He said no, because of the diffential, the nearside wheel turns clockwise is correct.

Anyone got any see through simulation link to prove the case.

 

[whitenemesis]

http://en.wikipedia.org/wiki/Differential_(mechanical_device)

HowStuffWorks "Open Differentials"

 

[jasonyw]

No one solve this puzzle yet.

 

[Mactech]

Yep! Where's the problem?
The drive line will be locked or stiff, therefore the rotation of one rear wheel is resolved through the planet wheels as the opposie rotation of the other side
Simples!

Now if it is an LSD (no not that stuff!) then you will find the wheels both rotate the same way....unless the prop shaft is locked (ie It's in Park) depending on the preload on the plates.....to much information

 

[Frank O' Phile]

http://en.wikipedia.org/wiki/Differential_(mechanical_device)

HowStuffWorks "Open Differentials"

No one solve this puzzle yet.

I think the link does explain how it works. Look at the first animated diagram. Propshaft is the input (car is being driven), driveshafts are the output (forward motion).

Imagine the effect if the nearest driveshaft was the input (mechanic turning the wheel) and the propshaft was locked (stationary car). It would make the other wheel turn in the opposite direction.

 

[joshmerc]

it defo explains it in the link

 

[jefrs]

When prop shaft rotates it drives pinion wheel which drives crown bendix which drives pinion shafts which drives axles: clear as mud. Look at moving pictures in 'ow stuff works. Now when pinion wheel rotates the crown goes round which turns the shafts causing the axles to gyrate together, their pinions rotate not, yet if one wheel is retarded then the axle pinions shall rotate causing the other wheel to rotate the faster: conversely if the prop shaft halted it is then if one wheel spinneth then the other must also but in opposite direction. Simple it is.
Unless you have a limited-slip diff that is.

Other little known facts about differential gears: EP90 stinks.

Imagine that you take hold of the tow bar of a two wheel trailer and walk it around in a circle on the spot: one wheel rotates one way and the other goes contrariwise. A car that is turning rotates about its back axle: the wheels have to go at different speeds, yet still both be powered.

 

[oldcro]

A similar thing happens when there is no differential, as demonstrated by the wagon wheels in many old western films.
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