Differential with light slip clutch

[Didumos69]

I turned my simple 90° indexer into a light slip clutch and to me it seemed very suitable for application in a limited slip differential. I replaced the angle element with square mid-section with a 2L axle connector so it has 8 preferred positions (45° steps) instead of the 4 in the 90° indexer.

I played a little with it and even in a small light-weight push-along car you can sense the straight-line-stability and the clutch actually starts slipping when pushing the car through turns. The white silicon band can be replaced with a red one wrapped around the limiters (2L liftarms) twice to make the clutch tighter. I think this approach gives a very realistic effect, or at least an effect that is realisticly proportional to Lego vehicles, also motorized vehicles. But you will have to find out that for yourself.

EDIT: As has been pointed out below this does not really qualify as LSD. The friction clutch is always engaged and for it to be a LSD the clutch should only be engaged when one of the output axles slips.

LXF-file here.

Edited December 9, 2017 by Didumos69

[2LegoOrNot2Lego...]

Very nice...! :-)

[doug72]

Nice simple idea.

I,m going to try and see if this can be adapted to provide a snap action for driving ring change over.

[MaxSupercars]

Didumos69. It's not a LSD. LSD works as open differential and locks by difference of halfaxles rotations.

Your solution makes opposite. It works as closed differential and opens by rotation difference...

But interesting solution...

Max

Edited June 10, 2016 by MaxSupercars

[Didumos69]

Didumos69. It's not a LSD. LSD works as open differential and locks by difference of halfaxles rotations.

Your solution makes opposite. It works as closed differential and opens by rotation difference...

But interesting solution...

Max

Max, I don't understand what you mean, could you pleae clarify? It could very well be that I'm not completely correct with the terms that I use, but after some googling around I arrive at the conclusion that the essence of a LSD boils down to "some sort of mechanism that applies a torque (internal to the differential) that resists the relative motion of the output shafts. In simple terms, this means they have some mechanism which resists a speed difference between the outputs, by creating a resisting torque between either the two outputs, or the outputs and the differential housing" (source Wikipedia). You could argue that the mechanism is not internal to the diff, but applying a torque that resists the relative motion of the output shafts is exactly what my solution does. Or am I missing something?

Edited June 10, 2016 by Didumos69

[Tommy Styrvoky]

Max, I don't understand what you mean, could you pleae clarify? It could very well be that I'm not completely correct with the terms that I use, but after some googling around I arrive at the conclusion that the essence of a LSD boils down to "some sort of mechanism that applies a torque (internal to the differential) that resists the relative motion of the output shafts. In simple terms, this means they have some mechanism which resists a speed difference between the outputs, by creating a resisting torque between either the two outputs, or the outputs and the differential housing" (source Wikipedia). You could argue that the mechanism is not internal to the diff, but applying a torque that resists the relative motion of the output shafts is exactly what my solution does. Or am I missing something?

This is more of a semi-solid axle with differential or maybe better used as a friction induced power transfer mechanism( say you have two output shafts, one is the differential side, and the other is mounted on the ratchet, when the ratchet is overcome, the power gets transferred to the differential.)A real LSD will only slip on one side for some duration, then transfer power from the slipping side, hence the term limited slip. As with your version, when the differential starts slipping, there isn't anything to stop it from slipping or allocate some power from the slipping side to the immobile side. While with the ratchet in your version makes the whole axle behave like a solid axle without a differential, but when slip occurs it will behave like a traditional open differential.

Edited June 10, 2016 by Tommy Styrvoky

[Victor Imaginator]

Didumos69, i like things that you do, clever fresh ideas) Some cars use that type of differential, locked by default, but opened when turning/slipping. I think, that it works similar way. I "build" LSD some time ago - just put two 2L axles between tan gears in differential. Works perfect but only at low torque or low difference in speed between right and left. If you try it - you will notice the difference with your differential.

Edited June 10, 2016 by Victor Imaginator

[Didumos69]

Didumos69, i like things that you do, clever fresh ideas) Some cars use that type of differential, locked by default, but opened when turning/slipping. I think, that it works similar way. I "build" LSD some time ago - just put two 2L axles between tan gears in differential. Works perfect but only at low torque or low difference in speed between right and left. If you try it - you will notice the difference with your differential.

Thanks Victor, appreciate it.

I would like to get out of this more competent than I was, so let me try to summarize what some of you are trying to tell me: The part that I call clutch is actually behaving as a lock until it starts slipping, from that point on it will no longer create resisting torque between the two output axles, until it no longer slips. Is that what you mean? So this is also not a LSD, or is it?:

I intended to see the rattling clutch (it's not a ratchet because it allows motion in two directions) as something that also creates resisting torque while slipping. When I deliberately rotate the output axles in opposite direction, it also feels like it still provides substantial resistance. Would it make any difference when two smooth rubber surfaces created the resistance, or would that still not count as LSD?

Edited June 11, 2016 by Didumos69

[Didumos69]

I have been reasoning about this approach a little more and have come to the understanding that when a setup like this - with a simple friction clutch between the output axles - gets confronted with one of the output axles spinning, it will never be able to transfer more torque to the non-spinning wheel than the amount of torque created by the friction clutch. Given that a light slip - or low friction - clutch will never live up to the torque needed to get a car moving, a setup like this will never resolve a spinning wheel. In that sense my approach is indeed not realy diferent from inserting 2 2L axles between the tan gears in the differential.

I know about Torsen diffs and active diffs and I know my simple clutch is absolutely not an advanced principle, but I thought it would qualify for LSD. But I've learned my lesson about LSD now, also after seeing this video: https://youtu.be/WeLm7wHvdxQ. And to come back to my approach, the practical value of my type of differential (locked by default, but opened when turning/slipping) could be that it avoids windup in turns (diff open) and adds to straight line-stability when driving straight (diff closed). So lets call it a straight-line-stability-diff .

Edited June 10, 2016 by Didumos69

[MaxSupercars]

Didumos69,

I have found this accidentaly... Maybe it's interesting for you... :)

Max

[Didumos69]

Didumos69,

I have found this accidentaly... Maybe it's interesting for you... :)

Max

Thanks! Interesting idea! I wasn't really looking for a limited slip diff or a friction clutch. I just thought of another application of the simple 90° indexer I built as a possible improvement of the Porsche gearbox.

It would be nice to built a clutch that is only engaged when an axle starts slipping someday, but I'm affraid my focus will be the Porsche untiI I have actually built it

Edited June 11, 2016 by Didumos69

[Victor Imaginator]

I know about Torsen diffs and active diffs and I know my simple clutch is absolutely not an advanced principle, but I thought it would qualify for LSD.

Yes, sure. I just used all my rubber bands already and start to thinking, instead of building and trying) Torsen doing the same thing, it's not so advanced.