Limited Slip Differential

[Vr5fx]

I just tried out the "tape" fix thanks to Jaggerbombs

Stock diffs

http://youtu.be/kiKkZIDvM2s

Tape diffs

http://youtu.be/VdDubK9pFwo

Approximately 6-8 tight wraps per diff.

[locoworks]

instead of trying to get limited slip diffs, why not just use 4 small motors wired in parallel and drive each wheel independently? any motor getting more or less strain will speed up or bog down accordingly and if a wheel spins or gets air it won't stop the other ones turning it will just rev harder cos of no load on it. this set up will use a little more current from the battery but the weight of the vehicle only needs a specific amount of energy to move it at a given speed whether that is one big motor or 4 little ones shouldn't make a lot of difference to the power needed?? there will just be more heat loss at a guess???

[DLuders]

...why not....?

1. More weight

2. More expense

3. Less ground clearance

[Doc_Brown]

Nice work with the tape diffs, but wouldn't that make the Lego sticky after you remove it?

[Someonenamedjon]

The performance on the tape diffs are very impressive!

[Doc_Brown]

1. More weight

2. More expense

3. Less ground clearance

DLuders is right, and after doing all that it really wouldn't be 9398 anymore would it!

But your ideas are cool and remind me of this beast!

Perhaps it could be done, and that would be too awesome.

[N-4K0]

DLuders is right, and after doing all that it really wouldn't be 9398 anymore would it!

But your ideas are cool and remind me of this beast!

Perhaps it could be done, and that would be too awesome.

That's really cool!

[Ralf]

Hi,

here is my easy, small and good working LSD solution.

Today i have tested it and the slip i can change with different rubber bands.

Also i have tested two 60c01 clutch 24 tooth gears but there it is not possible to change the slip further the sound (it sounds like "crack") is not really nice.

But look yourself:

[Junpei]

Cool solution! I tried with 24t clutch gears as well, but I don't hear a cracking noise. Is it just not enough torque to make the gear slip causing the gears to click?

[Ralf]

Hi,

@TwentyLeggedHen, yes you are right, i´ve checked my clutch gears and one is broken inside and noisy!

And here is my final solution and it´s working great, i´ve tested it today.

Now i have to build two new axles, front and rear.

Further with the gear of the steering portal axle (92908) the LSD is four up to six times stronger like now.

Here is my testpart from today:

[Boxerlego]

That is a very clever solution and nicely built too I must say. Great job!

[Junpei]

Well built, what a great way to use rubber bands! I wish I had that many old-style half-bushings, they're better than the new ones in every way...

[kevman]

wonderful LSD, gotta try it on my 41999 crawler and future MOC's

[DrJB]

Well built, what a great way to use rubber bands! I wish I had that many old-style half-bushings, they're better than the new ones in every way...

Not sure you need the old style bushings for this. The new ones will do the trick as we'll ... Unless I am missing something here ...

Edited November 4, 2013 by DrJB

[Lipko]

Are these Lego LSD.s really working? I mean when a wheel is lifted, can the motor actually drive the whole car with only one wheel on the ground? Or does it only work (does something useful) with 4wd cars?

[Ralf]

Yes, it´s working good...... test it yourself.

I´ve only used the "old" half bushings because i´ve to many of them.

The new bushings are the same.

For example, i turn one wheel and the motor shaft turns but the second wheel stops.

I´ll do a small video next time to show it.

Further i´ve build it in the SAME dimensions as the 9398, so it´s easier to change between some cars or crawlers.

And look at the pics, it´s certainly possible to use as an rear axle for 2WD cars.

P.S. A differential is only a gear with an inverse function, if you want to have an LSD you have to "brake" the inverse function..........i hope i explained it understandable.

Edited November 4, 2013 by Ralf

[Junpei]

Yeah, I know for this the new bushings are the same, however the old ones have more clutch power, and can lock toggle joints, plates, etc. at different angles.

P.S. A differential is only a gear with an inverse function, if you want to have an LSD you have to "brake" the inverse function..........i hope i explained it understandable.

Aren't you talking about a diff-lock here? That's the only thing I can think of that matches your description, it locks the inverse function so both axles turn at the same speed.

Maybe I'm interpreting this wrong?

[kevman]

i dont know how to adapt this to my 9398- any one try yet? there are two gears on the sides of the diff since it is a portal axle

[Ralf]

@TwentyLeggedHen,

yes that´s the way it is working, but not really a lock of 100% the rubber bands have slip and so the diff is working also.

Now i´m working on a way to implement it in the 9398 with the original gear this is not really difficult.

I have to change some fixing points and to go a little outside with the gear than it´s possible to realise.

The next days i post a picture here.

[kevman]

@TwentyLeggedHen,

yes that´s the way it is working, but not really a lock of 100% the rubber bands have slip and so the diff is working also.

Now i´m working on a way to implement it in the 9398 with the original gear this is not really difficult.

I have to change some fixing points and to go a little outside with the gear than it´s possible to realise.

The next days i post a picture here.

Cool! looking forward to the picture.

[Rockbrick]

What about the small rubber/card disc under the middle bevel gear of the diff? probably slips a bit too much

(i know, I know not lego purist enough)

[Ralf]

The slip of the rubber band is OK (i think a limited slip of around 40-50%), if i use the portal axle (92908) the LSD is much more stronger because there is a gear inside 2-3:1.

But i can say it sure after the tests with the first car (hope at the weekend with my 9398).

[Ralf]

Hi all,

now i´ve used the 9398 of my daughter to test the LSD inside (in the moment only one LSD at the rear axle).

But unfortunatly i must build the axle 10mm more track width but it looks also good.

To show that it works i´ve removed the transmission gears of the right wheels, front and rear (look at the pictures and the small video).

Unfortunatly i have to wait for parts i´ve not enough parts to change the 2nd axle.

Further i want to build it to switch on and off (on 50-60% / on 100% lock / off).

But to construct it to switch is not really easy, i want to have a small solution!

No transmission to the wheels (right side)

Transmission only the left side.

Video: http://www.vidup.de/v/S4lMl/

But unfortunatly you must turn your head to the left........ i´ve filmed with my smartphone

[Junpei]

Awesome job on fitting the LSD into the 9398, it seems to work very well!

Slightly off topic, but does the 9398 have ackermann geometry?

[Ralf]

Thanks,

yes i think it´s ackermann, there are different angles at the outer and inner wheels if you´re steering.

But ackermann is not really need at Lego, there is so many backlash in the parts........