Self-locking differential

[TheMindGarage]

After a little tinkering, I managed to create this self-locking differential. It locks when the car goes straight and unlocks when turning:

A set of 12t gears are connected to the steering rack. When the rack is in the middle (and the car going straight), the two halfshafts are coupled together, locking the differential. When the rack moves to the left or right to steer the car, the 12t gears disengage with the 20t gears and let the differential act like an open diff:

The main downsides I see with this setup are that the differential may stay locked during wide turns with small rack movement and the width of the axle is increased. A standard independent suspension with a differential and 68.8x36 ZR wheels (the combination I usually use) is 25 studs wide; with this feature it increases to 27.

[Imanol BB]

That is a very nice idea, it could be really useful for large trucks, and it is very compact also.

[JJ2]

I have had a few ideas like this but all of them were to complicated, good job.

[BusterHaus]

Nice idea, but since the wheels rotate at different speeds in a turn, I would expect the 20 tooth tan gears to be misaligned when the two 12 tooth black gears (attached to the gear rack) come back into place. Looks like a recipe for grinding gears, unless I'm missing something.

[Jurss]

Instead of this

You could use

[TheMindGarage]

Nice idea, but since the wheels rotate at different speeds in a turn, I would expect the 20 tooth tan gears to be misaligned when the two 12 tooth black gears (attached to the gear rack) come back into place. Looks like a recipe for grinding gears, unless I'm missing something.

Haven't tested that fully. Seems like it'll work OK - bevel gears are much better for this kind of thing than regular spur gears (like 8t and 16t). I was considering using a transmission driving ring, but that proved to be much more difficult.

[Alex Ilea]

great idea !

[2LegoOrNot2Lego...]

This seems like a very good and interesting idea! :thumbup:

What I wonder though, or what I would even argue about is when steering only a little the lock is still engaged right? Only at a certain angle of the wheels it stops locking... Or am I wrong...?

[TheMindGarage]

This seems like a very good and interesting idea! :thumbup:

What I wonder though, or what I would even argue about is when steering only a little the lock is still engaged right? Only at a certain angle of the wheels it stops locking... Or am I wrong...?

True - it take about 1/2 a stud of steering rack movement to make the differential unlock (I did say that this may be an issue in wide turns). But the rack's maximum movement is 2 studs each way, so the differential will be unlocked with anything more than 1/4 of the steering lock applied, assuming that the rack is the limiting factor in steering and not the steering linkage.

[2LegoOrNot2Lego...]

...(I did say that this may be an issue in wide turns)...

Sorry, missed that... ...even more thanks for your reply then! Looks like a useable design! After all in wide turns the friction is less...so lets assume it is excellent!