[MOC] Trial Truck with Auto-lock Differentials

[JoKo]

Lately I experimented a bit with differentials, trying to create a self locking system.

I used a secondary diff beside the main open diff. It works "backward" with two input axles and the diff gear as output.

the left wheel is linked with left input 1:1 gear ratio and the right wheel is linked with right output with 1:1 chain ratio.

With this configuration the secondary diff output doesn't rotate when the car runs straight and rotates slowly when steering.

When a wheel loose traction, the other one stops and the secondary diff output rotates fast. I use this output to rotate a centrifugal device with two arms. when the device rotates fast enough the arms step aside and lock against a well-placed obstacle. (yeah... I know... that's obscure. see the video! )

 

The tuck is 4WD with one XL motor and auto lock diff for each axle.

Full independent suspension, wheel hubs with planetary reduction.

L motor for steering, functional steering wheel

Dimentions : 40 x 23 x 20 cm 

Weight with batteries : 1.6kg  (the motorcycle boots used for traction test in the video are 1.6 kg each)

It still has some flaws I want to fix. The weak point of the self lock diff is the chain, I want a 100% gear system. The steering radius is not great. Front suspention is too soft.

 

 

 

Rear axle system:

 

FRont axle system

 

 

What do you think about this system?

 

[Davidz90]

Amazing idea with the locking system!

[Arie]

This is just brilliant. And from the video it seems to work very well! Nice job

[2GodBDGlory]

That differential lock is genius! I'm itching to try it out, but left my Lego at college for the holidays :(

It reminds me of the automatic differential lock I made a while back:

Spoiler

 

My design was similar to yours in that it would only engage the lock if the speed difference was actually as high as in a slip situation, but had way, way more complexity involved, and would work far worse in practice.

Your design is very clever, though, and looks like the most practical true auto-locking differential I've seen in Lego.

Nice work!

[gyenesvi]

Wow, really cool idea for the diff locking! Too bad it needs a lot of space for the centrifugal device and cannot really be mounted on floating axles.. But still, it's genius!

[9v system]

interesting diff mechanism, my only concern is the chains may snap under high loads, i experienced this myself with the akiyuki ball factory, i suggest upgrading to 2 sets of chains incase 1 snaps .

[JoKo]

18 hours ago, Davidz90 said:

Amazing idea with the locking system!

 

15 hours ago, Arie said:

This is just brilliant. And from the video it seems to work very well! Nice job

 

 

13 hours ago, 2GodBDGlory said:

 

Thanks, There is still some improvement needed but for sure it has some potential.

[Zerobricks]

That's a really good idea. I think there is potential to improve it further, maybe using a centrigual clutches on both sides of the differential outputs which would engage with the casing directly?

[JoKo]

3 hours ago, gyenesvi said:

Wow, really cool idea for the diff locking! Too bad it needs a lot of space for the centrifugal device and cannot really be mounted on floating axles.. But still, it's genius!

 

3 hours ago, 9v system said:

interesting diff mechanism, my only concern is the chains may snap under high loads, i experienced this myself with the akiyuki ball factory, i suggest upgrading to 2 sets of chains incase 1 snaps .

 

3 hours ago, gyenesvi said:

 

 

Here is my next try, with your ideas in mind

- I used 24t gears for the chain, to give it a better mechanical advantage. (I had problems with chain snapping on the truck) and the perfect tension is provided with two red free gears.

- I tried to fit the centrifugal system in the smallest place possible.

[2GodBDGlory]

Nice upgrade!

If you want to get rid of the chain, isn't the spacing now perfect to just delete it and put a third 24T gear in between the other two? I would think that would be stronger if braced properly.

[JoKo]

5 minutes ago, 2GodBDGlory said:

Nice upgrade!

If you want to get rid of the chain, isn't the spacing now perfect to just delete it and put a third 24T gear in between the other two? I would think that would be stronger if braced properly.

How did I not see that?

Yeah thanks. it's even better of course. I fixed that.

 

[vascolp]

This is pretty cool! Its a subtractor used in a different way.

You can try it like this, which I used as a subtractor, its compact:

[JoKo]

1 minute ago, vascolp said:

 

Thanks! It's nice and compact, i will give it a try. I don't have much 7x11 frame.

I don't like using gears just beside the diff. with high loads. It's a weakness in my truck.

[JoKo]

There are some more!

I built a 2WD rover with live axle

And thanks to

7 hours ago, vascolp said:

 

I now have a new more compact and study configuration:

Edited December 23, 2022 by JoKo
photos

[vascolp]

Very cool! And no gears next to diff.

[aeh5040]

Wow, this is an amazing idea! Is it perhaps an entirely new approach to a limited-slip diff, Lego or otherwise? That would be surprising, but certainly I have never heard of one like this.

Does the centrifugal clutch still work if it is not horizontal, or does it automatically lock? (Not necessarily a bad thing, if your vehicle is at some crazy angle!)

Edited December 27, 2022 by aeh5040

[JoKo]

9 hours ago, aeh5040 said:

Wow, this is an amazing idea! Is it perhaps an entirely new approach to a limited-slip diff, Lego or otherwise? That would be surprising, but certainly I have never heard of one like this.

Does the centrifugal clutch still work if it is not horizontal, or does it automatically lock? (Not necessarily a bad thing, if your vehicle is at some crazy angle!)

Thanks, I don't know if something similar existed or if it's even doable for a real vehicle. I came with this idea without exterior inspiration and I'm really happy with how it works.

The system still works with small angles and locks past 25-30° and it's a good thing indeed!

 

[2GodBDGlory]

15 hours ago, aeh5040 said:

Wow, this is an amazing idea! Is it perhaps an entirely new approach to a limited-slip diff, Lego or otherwise? That would be surprising, but certainly I have never heard of one like this.

As far as I know it's new!

[HectorMB]

This is just brilliant. In a fair comparison with a differential lock, I don't think that is too bulky. 

[1980SomethingSpaceGuy]

Really nice idea and realization! 
What I enjoy the most is that it indeed works when put in practice. Good job!

Edited January 1, 2023 by 1980SomethingSpaceGuy

[JoKo]

27 minutes ago, 1980SomethingSpaceGuy said:

Really nice idea and realization! 
What I enjoy the most is that it indeed works when put in practice. Good job!

Thank you. Yeah it works but this version was not strong enough for max torque. Some cracking noises when pushing it too hard. I meanwhile rebuilt it 100% with bulletproof mechanism. It can handle the torque until the XL motor stall.

Coming soon on Eurobricks!