Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Must be Valentines day,

Marc

Hi Bob how r u?

Sry been busy.  Yes there is a little bit of axil twist involved, and I am very glad you brought that up. Seriously I am not kidding you.  Shows you are a thinker and have much more understanding than someone who more or less just reads brochuiors. Tells me you are somewhere in between a rocket scientist mechanic and an above average mechanical person.  Point you are quite capable of understanding practical application, and have fun with it as two heads are better than one etc. 

So it may at times sound like I am disputing you, however you understand that is the way it is with mechanical processes, it is not as surface level as some may think.

You were dabbling in something like conventional rear ends.  So lets clarify that.  Limited slip diffs were not put on any production cars till the late 50,s  Therefore cars were being made with rear ends in them for 50 prev years.  Their rear ends I would thus call them the conventional ones.  They were called single action, or ring and pinion yada yada.  Then to the consumer (not the race enthusiast as there were LSD's and full lock units avail there) came the advent of the Limited slip diff.  A device that was suppose to transfer power at torque sensitive applications/speeds and different driving conditions, with slippage between two wheels that have to travel different distances around bends.   on the same axil plane.    That is why they named it  "differential. "

At the same time they started calling the older style rear ends,  simple diff's. which can just confuse everybody cause everybody just started calling every rear end a differential.

Then there was an enhancement made to LSD's and for an example we will use GM's Positive traction.  Then everyone started calling them posi and also calling the LSD's posi.  To boot, two of the three are very complicted mechanical applications, that are suppose And the key word here is suppose to do a lot of the same type things. Truth they all try and some succeed and some don't. Basically because there are differences in their design.     

Positraction, works well The GM Version.  It primarily, not secondarily now, it primarily splits the torque between the two wheels.  Then it allows for differential in turns,  and under low torque situations it can and does at times transfer the entire 100 percent of power to one wheel or the other.  It's primary function is 50 50 split.

Limited slip  Is named well , it is limited and it slips.  Now keep this in mind when I make the statement of LDS having a primary dependency on the righr rear wheel when going forward.

When you raise both rear wheels on both type vehicles, and put the car in neutral no brake etc and you by hand turn lets first say the posi unit one of the wheels, you can look under the car and see the other wheel spinning the same speed in the same direction,in relation to forward or reverse. You go to the car with the limited slip diff and turn one of the rear tires, lets say to simulate the direction it would turn when traveling forward, you look under at the other wheel and  the funny thing is it will be turning opposite direction.

That is also a quick test to see if you actually got posi on your vehicle.  They are different systems.

Where is this all going is here the posi units work well .. the production limited slips hardly work at all when driving the car.  They are little better if any better at all than a simple diff.  They are a very cheap version of a true differential. 

It gets complicated  there are I believe they break them into classes,  like class1  and class 1.5 and class2  etc.  ,Clutch strength  and torque applications,  LSD's are very sensitive to torque applications, posi's are not , only low torque conditions low revolutions, like in up hill snow driving.  Other than that they are primarily 50 50.

Most people I know will tell you they never found a LSD that actually worked except for an aftermarket one. 

Every one I owned , and I live in a very hilly environment, actually at the start of the Allegheny mountains. When you go up a hill in the snow the only wheel that will spin is the right rear,  How can I tell cause when the car will not go up anymore or I am going at a crawl I can feel it and hear it number one, but I can also open my door and look at the tire, and I have never found one of them spinning,  Different engine rpm's feather the gas on and off etc.  It is almost always a dead wheel.  Now the right one is spinning it is suppose to transfer power to the left,  never had it happen,  never knew anyone who had it happen, and never saw it happen , and tried many times to make it happen.  It was always a constant gripe by everyone who ever had them in these hilly environments, It has been written about in the standard auto magazines for years and the articles on them are often titled  the Myth of LSD.  Except if you are reading something that is basically trying to sell or not knock the manufacturer, then you get a blurb like it comes standard with LDS.

It also has a limited factor to it by it's design where someone may think well if I spin the rear wheel faster then I might be able to get some more power from the other.  Under those conditions it transfers all the power to the spinning wheel, thus nothing left over for the otherside.

Front wheel drive.  I never saw any of them spin any more than one wheel in the snow.

Had to push a guy out of an establishment after a Monday N NFL game, in an adjacentlot half paved half cinders, partially snow covered. LF wheel only spinning, it's in the muck  Right f wheel on solid dry surface,  No matter which way he turned that wheel, or any other thing he did was there any sign at all from the dead wheel..  How do I know cause I knew it was gonna happen that way so that was the side I was pushin on and the other fellows were really swearing as they were getting covered with muck.

I have never found one or knew of anyone who found one that works with any amount of appreciable. force

The only time I have seen the Left tire grab is on a sudden High speed burn out, like a neutral to drive or a high rpm clutch dump. 

The other instance.  Is the one that comes into play with your realization of the axil twist.  The left one will spin on a left turn burn out in reverse,  (weight slitly shifted off that wheel in reverse torque of the drive shaft. )

Oh forgot have seem many people brake torque them to the limit,  Not my personal preference so I don't like to go to an extreme in that situation.  You would think that the added effect of brake pressure on the system would further enhance some of that power to the left wheel.  Seen it I don't know how many times, with an lsd only the right rear spinning

Now there is a lot of different type stuff out there that work, I believe Jeep is suppose to have one, it might be called full lock-up  One that I know that worked for sure was the VW bug, and most of the all wheel drives with the Viscus joints and few posi type"s, Tranfer torque, but don't know of any LSS's doin the job

Which reminds me How do the diff's work on the snowblowers, like the ariens,  I would have to think that under those conditions they could have to be able to make a differential that gives you power to both wheels,  I never tested one, but I constantly see owners saying that they really have to lock the mechanism in deeper snow or up hills,  I just cring, and say I hope they are not as bad as the automobile LSD myth

Ben07

Hi Bob,

Richie you are throwing a lot of correct applications in to the pot.  Lets just touch on them as one of em may just slightly get turned around.  The reason is your example is great  but even better if you turn it around and put it on the front of a car, a front wheel drive one where it does not have what is a term"a live axil plain" more commenly reffered to as a live axil.  In the FrontWD it has two independant Constant velocity joint axils.(two axils independently each side not housed therefore trued up with a CV joint.  There is no overall one piece casting connecting both axil's together., and the physics of these axils are pulling the car not pushing it which would further eliminates the aspect down to null. That is why the front example enhances your thoughts better as some will argue  that the rigidity of the system in the rear would nulify any type of independant suspension aspect. So just to leave a possable gray area out, I am gonna turn it around to the front where the slight axil twist of a conventional system don't come even close to coming into play. That's where you insight on independent suspension on the whole comes into play in a state of the art situation.  .   You know how this goes, you don't dot an eye and cross a tee, people pick on one slight gray area and try an make themselves an expert an you a fool,  even if you set up the whole thing as I did and specifically said I was taking all aspects of LDS out of my explanation. One because it is too complicated and 2 because they don't really work in production models.    And I got countered even when doing that,  by saying I was saying misconceptions and the misconceptions were trying to be countered by using the  Limited Slip Diff Applications (talk about seeing the punch coming ahead of time)   I don't mind I will go there, take a lot of key strokes,  getting countered there and someone saying, misconceptions is getting hit below the belt,  so ok let's discuss the falacy of Limited slip. So you are 100 percent right no axil twist there on front drive and the suspension further rules it out , however on Front wheel drive models they offer the option of traction control to try and help the so called automatic transfer from side to side.  Well why would they offer it if it worked in the first place, obvious answer is  It really don't work in the real world. And the small references I made to the burn being longer on the right side, is not responsable because of axil twist.  Your  example is a much better way of showing it rather than me saying there is axil twist but it don't come into play, and that the twist would actually cause the opposite and the left tire strip would actually be longer due to the less weight condition he reffered to in the first place.  Thanks for the further/better/sharper point Richie..       Back to your touching the break a lil when starting out on the snow.  That is a perfect example of probably one of the only applications where you can get a little amount of Limited slip to help you.  Reason being it is a slow start and the vehicle is not under load(remember torque sensative, had to reinforce that as I can see another punch coming here, so I will just pre type the answer and have it ready) , Same with the application of traction control, slow start vehicle not under load. LDS is torque range sensitive, that don't mean it has slow overall application to the process, it means it does completely different things at different speeds/ torques.  It is so full of not working more that working ,mechanics will not even try to understand them as the general consensus is they just don't work.  Thus the general consensus of if you have front wheel drive you actually only got one wheel pulling and on conventional 4x4 to be actually only two wheels pulling.

Very Thorough in your points R.  here is another example of the snow thingy.  I had an LSD car, that nomatter how perfect you kept the Emergency brake system and rear brakes, I mean in the condition of a well oiled shotgun,  In the slush and snow and freeze, it would  freeze up.  Consequently someone would use the car, tell them not to use the E-brake unless you have to.  What the car would do to them is they would be parked with all four wheels on snow, they would release the brake and try to move, the brakes would be hung , the right rear would break because the LDS put the power there.   However the left brake shoe would be hung up, so the person cannot move the car. Cause the right wheel and note only the right wheel., is spinning on slippery surface and the left one has the brake on, and the LSD will not transfer any power over there. (naturally they would say I took the emergency brake off and the car still won't go, kinda like some accusations here when the real issus is I told you not to put it on in the first place.)  So I would go get them or over the phone to just start the wheel spinning and slowly press on the brake and pop it would trans enough over to break the lock.

If it worked the way it was suppose to one would never have to do that

Ben,   I suspect  we still disagree somewhat on how differentials work but it's been a lively discussion anyway.      -Bob

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Ben,   I suspect  we still disagree somewhat on how differentials work but it's been a lively discussion anyway.      -Bob

Thx Bob I appreciate your comments.  I'd be willing to bet if we were talking in person over a couple of beers, we would be able to explain each others aspects much better,  and not disagree as much as it appears. ,, and learn more in the process.  Two heads are better than one etc. 

Hard to do some of that in the forum , typing on a computer, context, emphasis gets confusing etc. 

If you can ever help me out  feel free to step in. I'll do the same.

Regards Ben07   

I believe it came out that the person who looked at it said all four wheels turned, as they were directly hooked up to the drive line.  They said there was a trigger on each handle that lets use the example if you wanted to turn left you would activate the left trigger and it would in essence disconnect  the left two wheels from the system, and they would then be free wheeling.

I think it may be similar to what toro has, on their high end models, so you could research there.  IWill PM someone whom I think has that sys and see if he will post here as I wanted to ask him how it worked anyway

Ben 07