open differential

Are Nascars running open diffs ?

Two different times I saw when one wheel had no traction, no tire, that wheel would spin and the car would not move.  

Torsen could do the same

In reply to iceracer :

Could be a broken axle. All sorts of tricks are being used to change camber on rear axle. 

Where was this at?  I've heard they use lockers on most tracks, but open on the long high-speed tracks for increased (power) efficiency.

By Nascars do you mean NASCAR stock cars?  If so what series?  The top three series use a Detroit locker style rear.

First thought on first was axle but after new tire all was good.

First time was Pocono and second was Bristol as I recall.

So, does a locker allow one wheel spin ?

Talking about Clint Boyer on the last restart at Bristol?  Looked like his locker failed, because he sure did leave one big black stripe behind the left rear while half a dozen cars passed him.  Can't have spit an axle, because he never would have kept the car under him on corner exit afterwards.

In reply to iceracer :

Traditional lockers are either completely locked (no differential action), or totally open. There are a host of newer ones that are controllable, or soften the locking action. I'm not sure what type of locker is currently used in NASCAR, but I'd guess a traditional one.

Most tracks they run Detroit Lockers. We ran an open diff at Daytona for less drag because traction isn't an issue. Sometimes with a locker if the springs get weak they will occasionally fail to lock giving you the one wheel peel.

If you watch TV coverage of the races when the cars are leaving their pit box there are two distinct lines of rubber as the wheels spin until they get up to pit road speed. That would indicate they are running some type of locking differential. 

This was my thought too,but the spinning wheels and no movement got me curious.

 The locker only works when in a straight and both tires have traction.  So that would explain the spinning wheel.

 At least that is how the internet explains it.

Appleseed said:

In reply to iceracer :

Traditional lockers are either completely locked (no differential action), or totally open. There are a host of newer ones that are controllable, or soften the locking action. I'm not sure what type of locker is currently used in NASCAR, but I'd guess a traditional one.

Lockers are never "open" in the sense of an open differential.... they are either locked, or one wheel drive.  They have no gears, they have a kind of bi-directional ratchet mechanism that allows one of the outputs to overrun the carrier.  So if you are going around a tight corner and accelerating gently, the power will be going to the inside wheel and the outside wheel can overrun the carrier.  Never the other way around.

Basically a spool that won't break axles.  (The action is  pretty noticeable when it's ratcheting, too... and sometimes on the highway it will do a little side-dance when going from coasting to accelerating as the pawls on either side meet at slightly different times)

Now, there are CHEATER "lockers" that will always drive the right wheel no matter what, basically the right side never unlocks...  I am not sure of the benefit, but they do exist.  And I would imagine that if it broke, it might result in NO power to the right wheel. 

I had a locker fail in my 150hp 4Runner, I knew something was wrong when it laid a stripe with 31” tires.

The installer claimed it was defective, then I brought it back with all of the bolts loose, the ones that they never tightened.

Streetwiseguy said:

Talking about Clint Boyer on the last restart at Bristol?  Looked like his locker failed, because he sure did leave one big black stripe behind the left rear while half a dozen cars passed him.  Can't have spit an axle, because he never would have kept the car under him on corner exit afterwards.

I watched the rerun of that a couple of times this morning.  I think what happened is that he was still turning when he got on the gas so the locker was unlocked and when the inside spun so violently it didn't lock up right away.

In reply to APEowner :

That shouldn't be possible, since it is only ever unlocked for long enough for it to skip teeth and then it is engaged again.

I am curious to see the video now.

I do know that you can "confuse" it if driving at neutral throttle in a very tight turn, since both sides will be trying to override the carrier and the shuttle doesn't really allow that.  That is generally a parking lot maneuver issue.

The genuine Detroit Locker unit I have, and the unknown "NASCAR takeout" race unit I have, are definitely different in internal construction though, so who knows what other designs are out there...

Knurled. said:

Now, there are CHEATER "lockers" that will always drive the right wheel no matter what, basically the right side never unlocks...  I am not sure of the benefit, but they do exist.

I'd guess the benefit is vectoring torque in a way that's beneficial in circle/oval track racing.

Knurled. said:

In reply to APEowner :

That shouldn't be possible, since it is only ever unlocked for long enough for it to skip teeth and then it is engaged again.

 

I am curious to see the video now.

 

I do know that you can "confuse" it if driving at neutral throttle in a very tight turn, since both sides will be trying to override the carrier and the shuttle doesn't really allow that.  That is generally a parking lot maneuver issue.

 

The genuine Detroit Locker unit I have, and the unknown "NASCAR takeout" race unit I have, are definitely different in internal construction though, so who knows what other designs are out there...

I agree that it shouldn't happen if everything is working like its supposed to.  I have an impression from somewhere that the NASCAR units are modified for a little softer or later lockup to reduce push on corner exit.  I don't remember who I got that from and, as always, I may be wrong.

You can adjust their unlocking characteristics with springs.  Ron Sutton's website has a bunch of info on this.

It's my understanding (and somewhat experience) that under power, they drive like spools, unless you have so much grip/so little cornering force that you can drive entirely off of the inside tire.  Which makes the car push.  When you overpower the inside tire, it makes the car dive to the inside of the corner just like you had a spool.  (Not back end sliding out, it feels like someone inside the corner has a rope on your front bumper and they are pulling you in)

On the other hand, I'm not driving a two ton car with 700hp and 12" wide slicks, so YMMV,