On-Demand Limited Slip Differential

[Phoxtane]

Sorry about the delay, I've been busy!

To clarify: What I was thinking of was a device that would act like a standard Lego differential when in one mode, and act like a LSD in another mode.

[Dans lego]

Why not use a torsion diff ?

[Doc_Brown]

You could try my limited slip idea. I used 4 of these on the Patria I made and had no problems!

[Rockbrick]

love the rubber band idea - and the adjustable tension one thats just geniusly simple... perfect for crawlers and the like.

...however all these are just to improve torque to both wheels for off road use and overcoming one wheel getting stuck = almost lockable diffs

they are still not true L.S.D. which will transmit all the torque the the wheel on the ground when one wheel is in the air (which will normally spin)

mechanically we are limited to how this can be done with modern electronics and abs and pulse-breaking this is achieved on modern cars...

for me the rubber band is as close as functionally / useable we need it to be - no point over-engineering for little further gain.

[SNIPE]

for me the rubber band is as close as functionally / useable we need it to be - no point over-engineering for little further gain.

Sounds hard to do with lego but I'm sure somebody will do it, there's over 65,000 videos on lego so somebody has probably did it

I did see a video on somebody using pins connected to lift arms with pins or you can use the pinholes of a 24 tooth gear, there is not much give here to drive one wheel with the other, maybe a work gear can be used where when it rotates a spur gear so far it connects one wheel's drive to the other but I couldn't put this idea down into lego myself.

http://www.youtube.com/watch?v=EtJtRCvUjaE

[Johnny P]

This last idea is the most usefull imo.

Agread it takes up some space, but when needed it really locks. And if you want to have more free play before it locks,just gear the "lock" down. The Solutions with the clutch gear and rubber bands is not so good imo .

when you take turns there allready is some friction to overcome,so power loss and diff working loss. Also when enough power is used , you can still stop one wheel .

Edited January 15, 2014 by Johnny P

[andythenorth]

Some mindstorms thing, measure the rotation speed on each output of the diff, with motor-driven axle brakes on each side?

It's not a trivial problem to solve with mechanical means alone.

Edited January 15, 2014 by andythenorth

[Johnny P]

Or Sariels pneumatique difflock.

When the mindstorm detects to much difference , it automaticaly locks the dif pneumaticaly.

This would be so real.

Great idea Andythenord

[jesse66058]

It is technically not a LSD, but i thought i might share it aswell here.

It works very nice and noticed no wear to any part in the period i used the idea. The only negative side-effect is that the axle's are not perfectly horizontal aligned anymore.

[Splat]

Why not use a torsion diff ?

I agree!

It may not be 'on-demand', but it doesn't need to be. As soon as one wheel loses traction, the diff locks up, effectively transferring all torque to the wheel that still has traction. The other benefit is that it doesn't have bands or clutches that reduce the efficiency of the system, and it can also allow the vehicle to go around in circles without locking up (which some of the ones in this thread will do).

There are a few different designs, but this is my favourite one:

If you replace the large turntable with the new smaller turntable (99009 and 99010), you can get this even smaller.

Edited January 16, 2014 by Splat

[Rockbrick]

in all these fine lego non-minstroms solutions the diff locks up transfering all torque to BOTH wheels hence this is why not entirely a proper LSD as found in cars with traction control etc...

the torsion diff is the closest and most elegant we're going to get with non-minstorms / pneumatic solutions

[rm8]

It is technically not a LSD, but i thought i might share it aswell here.

It works very nice and noticed no wear to any part in the period i used the idea. The only negative side-effect is that the axle's are not perfectly horizontal aligned anymore.

Done. Works well enough.

Edited January 16, 2014 by Blakbird
: Removed quoted images.

[GBC Master]

Hi everyone,

Some time ago, I made this limited slip differential:

In the video, it acts as a LSD and open differential. It should be easy to have it fully locked as well.

The two differentials on top maximize the speed of the wheels. If a wheel goes faster than the control speed, the differential changes direction and is blocked by the ratchet.

Another design is this one (Work in progress for too long already):

http://www.brickshelf.com/gallery/severgonzalez/RavsenLSD/steering_axle1.png

The difference between the speed of the wheels is measured. Another differential should be added to maximize this difference.

As I'm writing this, I just realized you don't really need a differential to limit the output speed:

http://www.brickshelf.com/gallery/severgonzalez/RavsenLSD/ratchet1.png

The red axle won't go faster than the green one. If you apply this system to both wheels, it should make an LSD of the differential.

Notice whenever the driving motor changes direction, the ratchet should go on the other side of the gear in order to work properly.

[locoworks]

why not just drive each wheel with it's own motor and forget all about LSD's?? if you're not trying to turn on the spot one motor should load up slightly and the other spin easier?? that said there may not be enough mass to create a load large enough to tax the power output of the motors.

[SNIPE]

Perhaps something like this can be used as an automatic switch to drive the other wheel, when the diff kicks in as a closed diff the change in direction can drive the worm gear which goes to another gear that drives the opposite wheel

Here is a mock-up of the idea:

If this doesnt work try the older diff and put the worm gear onto the gears on the diff.

I recon this has massive implementations not just for diffs.

Regards, Snipe

Edited January 26, 2014 by SNIPE

[Zerobricks]

Here's an idea for a limited slip, just replace the center 12 tooth gear in the new 3L differential with the old 14 tooth one. Works great.