Limited Slip Differential

[Storext]

(Sorry for mistakes (I'm not from Britain / America))
I was thinking about LSD (Limited Slip Differential) in lego. Because all I saw yet were just differentials with locking mechanism that engages after few turns of axle. And only thing it was limitting was main function of differential. So I came out with this solution - I know it isn't great, but it is very simple and compact (actually you add one rubber band inside differential (under spider gear)). What that does ? - When axles want to spin at different speeds (while cornering) more power is required (so you lose some speed if you don't have powferful motor) but, if one wheel lose traction the other one gets more power (compared to open differential) and you can also set how much additional friction you wat (by adding different number of rubber bands inside). Here is one picture of it : https://imgur.com/a/JTjgdBn
I just want to know what do you think about it, and if there is possibility to create a real LSD in lego. 

[MxWinters]

I made a LSD a few years ago when I was prototyping for an off-road Morris C8 field artillery tractor. I ended up not fitted a centre differential so I never used it in the final model. This version worked quite well and applies a good amount of torque to the side that is free or lifted up but still allows the axles to spin at different speeds when cornering. It isn't as compact as your version so its more suited for centre differentials instead of axle differentials.


The pink belts go onto pink pulleys (I do this when LDD doesn't allow for part adjustment or manipulation).
LDD version here: https://drive.google.com/open?id=1E_1AwQ_ixsdeD1Bnowy41epDdgkuo5Bn

[Didumos69]

A real LSD is open by default and only 'closes' when one output axle starts consuming practically all power. Both attempts in this thread show differentials that are not open by default. In fact they are closed by default and only 'open' with enough torque difference. This will never work in real life: Assume one wheel on a surface with full grip and the other wheel on ice. Now imagine the level of friction the rubber bands would have to induce to avoid slipping of the wheel on ice. The level of friction would need to be so high that the engine won't be able to overcome that friction. You would need so much friction that you can hardly speak of an open differential at all. The result will be that in turns, with both wheels having grip, you get wind-up etc. Not good.

Edited October 9, 2018 by Didumos69

[JayDee96]

1 hour ago, Didumos69 said:

A real LSD is open by default and only 'closes' when one output axle starts consuming practically all power. Both attempts in this thread show differentials that are not open by default. In fact they are closed by default and only 'open' with enough torque difference. This will never work in real life: Assume one wheel on a surface with full grip and the other wheel on ice. Now imagine the level of friction the rubber bands would have to induce to avoid slipping of the wheel on ice. The level of friction would need to be so high that the engine won't be able to overcome that friction. You would need so much friction that you can hardly speak of an open differential at all. The result will be that in turns, with both wheels having grip, you get wind-up etc. Not good.

Typical mass produced LSD actually have clutch packs under heavy spring tension holding the centre gears to the centre casing, giving them the limited slip quality. This is why OEM limited slip diffs require special friction modifiers in the diff oil to stop the clutch packs "sticking" (causing a clicking or jumping while cornering), the friction modifiers actually reduce the LSDs effectiveness. So typical LSDs are never actually completely open, its engine torque that's helps the diff lock (as best it can), however if one wheel is in free air, no torque can actually be applied to the diff because there is no traction to apply it to. This is where the spring tension helps apply some torque to the non lifted wheel.

 

I have built a makeshift LSD by inserting a thin rubber shim behind the three centre gears in a LEGO diff. However this virtually locked the diff and makes cornering as hard as with locked diffs, but will let the diff distribute torque enough to not break parts. I think the idea is sound if more effort is put into finding the correct thickness and friction of rubber used. 

[TeamThrifty]

without electronics, lsd's are tricky, especially in lego. Torsen diffs are the best compromise.. they never lock, but are a nice solution.

[Imanol BB]

Something i would really like to see is a lunchbox or lock-right differential locker, they work like ratchets which drive the wheels, when going straight both wheels turn together like a normal axle, when cornering the outer wheel has a "free-wheeling" motion and it is able to turn faster than the inner one, in this case all the power goes to the inner wheel so this type of locker can affect the handling of the vehicle in some cases, but that's worth when using it for off-roading, when a wheel loses traction the locker engages and both wheels turn together like a normal locked differential, and it still lets the vehicle steer without the tires rubbing or the axle winding like a fully locked differential.