How Does Lunchbox Locker Really Work?

[SirFuego]

I also asked this on a local board (where some people may not be familiar with a lunchbox locker), so please forgive the "noob-based" introduction. Please correct anything that may be wrong in this so I don't have any incorrect information here. The real meat of my question is at the end of this post...

Those familiar with locker terminology have undoubtedly heard of or have personal experience with lunchbox lockers. These are automatic lockers that lock up when you are applying torque to the axles (i.e. using the skinny pedal) and unlock when going around turns without applying torque (coasting around turns).

So what I am curious of is how they work -- in the context of the parts actually moving and what physically causes them to lock up. Here are some pictures from on 4x4xplor that may help.

So as you can see, there really are not many parts to a lunchbox locker (Aussie is used in this example, but LockRite is another commonly used lunchbox locker out there):

http://www.4x4xplor.com/images/aussi...cker-parts.jpg

Not shown in the above pic is that the pins are held in place my springs, but you can see that from the following pic of it installed in a carrier:

http://www.4x4xplor.com/images/aussi...0/DSC01186.jpg

Please correct me if any of following is incorrect:

So from what it looks like, the carrier is "locked" when the teeth of the cam gears and axle gears are interlocked. And it is "open" when the axle gear is able to rotate independently of the cam gear (which causes the ratcheting sound?).

Now here is where I am lost:
Assuming the above is correct, the only thing I could see that could control that would be the springs. It looks like that if the spring compresses, it would allow that ratcheting action. So if the spring decompresses, it forces the teeth to interlock when lined up and locks the axle.

So, what I don't understand is how torque applied to the ring gear causes the springs to decompress and lock the gears. Is it perhaps just from the centrifugal force of the carrier spinning?

[SirFuego]

So yeah, I was having a hard time understanding how the springs could be strong enough to lock the axle, and I was definitely wrong about the role the springs play. Here is the answer I got from a reputable friend.

Let me give you the short and understandable answer.

The torque is applied through the pinion to the ring gear. Since the carrier is attached ring gear it also sees the torque forces. The torque is then transfered through the center pin from the carrier into the locker.

Now on to how the locker works, Jared you are correct in your thinking, however you missed one small part. The hole where the pin goes through the locker is the shape of an oval. When throttle is applied forward or reverse the pin moves toward the "pointed" ends of the oval applying pressure to the inside gears and forcing them toward the outer gears and "locking" the teeth together.

And to visualize it, imagine the center pin applying a force to the two areas I have circled (and the bottom of the "oval" hole on the opposite side).

[AgitatedPancake]

that is exactly it. I actually starting writing a response almost identical to that one before I read it. as torque is applied, the cross shaft presses those cogs apart, so the teeth cannot slip. You let off the gas, the shaft stops putting torque on those peices, and allows them to seperate enough for the gears to spin against each other.

[J B]

You got it. Now, note that those teeth are ramped so that they can ratchet, and as they wear and get rounded, they'll tend to not hold, even under some pretty serious torque.

Every lunchbox that I have had first time knowledge of that has had lots of miles eventually will slip and not hold out on the trail.

So, they WILL eventually wear out, and that's the downside of their simplicity.

[AgitatedPancake]

True, which is what happened to my buddies lockright, he'd get one tire in the air and it would let loose and ratchet like crazy till he let off and let it catch again. I have a couple of years on my aussie and it's still doin good, just as predictable as the day I got it so I'm not worried yet.

[SirFuego]

Great points, guys.

Seeing as the center pin "rubs" on that hole to get the cam gears to close, does this put extra stress on the center pin and cause it to wear over a long period of time, too?

[AgitatedPancake]

I wouldnt worry about it, that thing is damn thick. Also i've never heard of it having issues.

[novacayne75]

if u get one go aussie little more aggresive but at least i know its working

[JBN311]

Nice.....never knew exactly how it worked.

Thanks for bringing this up SirFeugo