Tires spinning

[xtn]

Twice the lowest value in each case. ... Remember, the wheels not spinning are driving equal to their mate on the other side.
larry

Yes. That's why I said an open differential splits the MOTION, not the power.

 

[SPYDERLK]

Yes. That's why I said an open differential splits the MOTION, not the power.

However, that is not truly correct, but I know what you mean. Mechanical power requires motion. All power is going to the spinning wheel, but thrust force is matched by the stationary wheel. [Absent acceleration of the spin of course.]
larry

 

[xtn]

However, that is not truly correct, but I know what you mean. Mechanical power requires motion. All power is going to the spinning wheel, but thrust force is matched by the stationary wheel. [Absent acceleration of the spin of course.]
larry

Yes. That's why I also said it isn't technically accurate.

 

[Lefty7]

It's natural for someone to think that FOUR WHEEL DRIVE means that all four wheels are driving all the time. Of course, we all know: NOT!

There are differentials (and transfer cases) that are more highly evolved - and this is not real recent. These units sense the wheel that is NOT spinning, and apply power to that one. Much more effective. Can only guess that these aren't generally used because they are also much more expensive.:2cents:

 

[megaboz]

Wow, interesting read.

Wouldn't describing a typical 4WD be that all 4 wheels have the capability of pulling or applying power to the wheel? This just doesn't apply to just tractors, cars and trucks perform the same way.

All Wheel Drive is simply no button,switch or other means of engaging, it is always on, but still the differential is what decides where the power goes.

The differential simply splits the power (depending on the diff, it splits the power differently).

A "locker" simply lets you combine both wheels at once together (some off road vehicles run a locker in the front and rear).

If you have ever own a four-wheeler (or used the locker on tractor), you would know why you wouldn't want all 4 wheels trying to turn at one time, while one wheel is turning the other wheel is actually pushing the other wheel when turning. Net result is increased turning radius.

As one person example about getting two opposite wheels of the ground at the same time, unfortunately for me that happens way too often..

Depending on the situation, another approach when you are spinning the one wheel is to apply some break to that wheel (assuming you have steering break) and it will actually cause the other wheels to start to turn under power due to the resistance applied to the spinning tire. I often do that instead of locking the differential in, often very useful when you get your tractor in an off balance condition that is temporary.

 

[Ilikeurtractor]

Yes. That's why I said an open differential splits the MOTION, not the power.

An open differential sends equal torque to each wheel. That's why SPYDER is correct when he said twice the lowest traction tire since the other side has the same torque as the spining wheel (usually not much if it's on something like ice). Also, if you have the front axle on dry pavement and ther rear axle on ice, you won't only have the two lowest tires pulling, one of the front will be pulling for sure regardless of the traction of both rear tires.

Regarding power it would be a product of torque and speed (technically angular velocity), not sure how motion fits into the equation unless you are referring to torque.

 

[rambler]

It's natural for someone to think that FOUR WHEEL DRIVE means that all four wheels are driving all the time. Of course, we all know: NOT!

There are differentials (and transfer cases) that are more highly evolved - and this is not real recent. These units sense the wheel that is NOT spinning, and apply power to that one. Much more effective. Can only guess that these aren't generally used because they are also much more expensive.:2cents:

If you have a truck with a locker diff, in snow and ice sometimes you realize that isn't always a good idea, as all wheels spin and you start moving sideways, no control of your direction......

--->Paul

 

[Lefty7]

If you have a truck with a locker diff, ... sometimes you realize that isn't always a good idea

How true. It can also be a problem on a wet surface in the warm months of the year if you're pulling a trailer. (But it's usually when you forget about what kind of diffy you're running.) Gentle on the throttle, friend.

 

[crazyal]

My side by side has the option of 2wd with an open rear diff, 4wd with the rear diff locked, or every wheel driven where both diffs are locked. TBH the front diff lock really doesn't help much. If you are in deep mud it just digs deeper and gets you stuck even more. If you are on uneven ground then the rear tire with all the weight (because of the rear diff lock) almost always keeps it moving. On really steep hills with good traction it helps.

 

[My Hoe]

Here you go.. this old 1937 video explains how a differential works better than anything I have ever seen. Keep in mind you have 2 differentials a rear and a front. but If you can follow this you will understand. The first 2 minutes seem worthless, but there is a purpose stay with it.


[ame=http://www.youtube.com/watch?v=F9EPf8SJc2Q]Auto Mechanics: Differential: "Around the Corner" 1937 General Motors 9min - YouTube[/ame]


James K0UA

What a GREAT VIDEO!!!

Thank you for posting, K0ua!

It just further supports my contention that automotive text books, or even most any "how to" book, was better written (i.e., easier for me to GRASP) when it was written in the 1920's, '30's, '40's etc....

Why? I believe it's because they were written to be more easily "accessible" to the unsophisticated student, i.e., the "farmboy," fresh off the land. Eager to learn, but needing things to be K.I.S.S. And/or, EXPLAINED assuming ZERO knowledge on the student's part. In other words, they start from the beginning.

I have an automotive manual (not sure just where, or I'd list the title) for (I believe) all makes, generally, and it was written in 1925. It EXPLAINS HOW (and WHY) A COIL OPERATES, before it gets into troubleshooting and repair. Priceless!

I find modern manuals less "accessible," by comparison. And I was never even a "farmboy"!

Again, thanks for posting, K0oa. And, if I may, how did you find it? Do you know where there is a "treasure trove" of similar videos?

John Thomas--you mentioned seeing men get almost to the point of fighting over a "debate" about what is meant by the term "FWD." I too have seen that, albeit in web forums, re: pickup trucks. It is a testament to the HIGH QUALITY of the membership, here, that such topics to not devolve into such mayhem.

Now, I'll throw one out there: how many of you would believe that the front diff of my F-250 is geared "one-one hundredth" of a ratio higher, than my rear diff--from the factory? IIRC, (I don't feel like crawling under it right now) the rear "rear" is 3.50:1, while the front diff is 3.49:1.

To the engineers and mathematicians: if I've listed those values incorrectly, please school me--I'd rather look foolish and learn than just look foolish. :laughing:

Does anyone know why diffs vary by .01:1? I was told an answer, which made sense to me, and I'm sure many here already know it, but I'm throwing the question other there for fun, if nothing else.

And Kudos to Gary Fowler, for this:

By Gary Fowler:

Remember the old remedy for stuck in the mud prior to limited slip differentials, lightly apply the emergency brake to make both wheels turn.

I can't tell you how many times I've successfully used this trick, albeit on snow and ice, and with studded rear snows, only. Far more times, however, than I've been able to make people understand, and believe, that it works, I think! LOL

My Hoe