Posted by Michael Hernke (MO) [162.158.75.181] on Monday, April 16, 2018 at 06:49:28 :
In Reply to: I should clarify my question posted by Andrew in MI [172.68.58.206] on Sunday, April 15, 2018 at 21:50:10 :
I have always thought of a Torsen limited slip as a super inefficient gearbox. Imagine a conventional 2 or 4 pinion differential with the case fixed. It is basically a reversing gearbox. One axle is the input and the output is 1:1 but in the reverse rotation. With straight cut bevel gears the standard differential would probably have a measured efficiency (power out/ power in) in the high 90% range. The Torsen would be maybe something like 20% (just a guess). The video shows force vectors and mentions force but I believe with a Torsen it is truly a function of power (force x displacement or in this case rotation speed) Because of this I know they don't really have much static torque proportioning and usually require a little wheel speed to work. Doesn't work well in low speed rock crawling but works okay in mud or sand. A clutch type has higher static torque proportioning and depending on the design, wheel speed won't increase the ability to route power to the opposite wheel.
I remember in college we talked about planetary geartrains there were some equations we used for efficiency. On a homework assignment he gave us a geartrain that had a calculated efficiency of something like 5%. Everyone in the class worked on that problem for hours thinking they did it wrong but he added to make the point that you can make a really inefficient planetary geartrain. My career has gone a very different path than gear design and that was 20ish years ago so I don't remember the equations just spending a late night working on it.
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