Recently Sariel presented an idea for a Limited Slip Differential at his new website.
It is a simple adaptation usable into driving axles of vehicles, which automatically locks the differential whenever a slip situation occurs. It happens in vehicles for instance when a wheel from a axle, driven by a differential, loses contact with the ground or slips. In such situation the standard differential transfers all the torque to that wheel, making it turning free while the other keeps stopped. As result, the entire axle stops, which may easily stop the vehicle completely.
Sariel's automated solution, uses a second pair of semi-axles, attached to the main ones on the differential, which also connect to a pair of cams.
While the vehicle keeps both wheels rotating at the same speed the cams won't lock each other. If wheels speed differ, cams will lock after some time, the differential blocks and both wheels will run at equal speeds.
For a complete and detailed description of this mechanism in its own author words, please refer to the original description in the article linked above.
Below an image illustrating the mechanism and one video, where you may see the principles in action.
Because of its simple design, this locking mechanism may actuate after short periods of different wheel rotation speeds e.g. while the vehicle turns. However it shouldn't cause any problem since the wheels speed difference is very small, while you get safe from the slipping situations.
To improve this situation and reduce solutions sensitivity to small speed differences, BS user 'Memory' (Jacob) shown his own improvement suggestion where cams are geared to move slower.
He just added a third pair of semi-axles with an 1:3 gear reduction (8z to 24z gears), which would increase the tolerance to the speed differences caused by steering, to give the same example.
The only drawback is that while tolerance gets increased, it also takes longer for the cams to move apart after them to have engaged.
Learn more about, at HowStuffWorks:
- How Differentials Work
- Clutch-type Limited Slip Differential
Learn more about, at Wikipedia:
- Limited Slip Differential