Tires spinning

[Deano]

LOVE both videos!!:thumbsup::thumbsup::laughing::laughing:

 

[xtn]

Pretty simple, really. Differential splits up the power to both wheels, either wheel on the axle can get any % of the available power.

--->Paul

I think the way you worded that gives a clue about why some people get confused on this subject. And open differential splits the MOTION, not the power. Okay that's not technically accurate, but it's a good way to make my point. Even when one wheel is stuck and the other is spinning, both sides have a driving force applied to them. Therefore it is rightfully called two wheel drive. And a machine with two of them can rightfully be called four wheel drive.

 

[Coyote machine]

I look at it this way: its all about TRACTion!
What used to be the go to TRACTion 'machine'? The horse!:thumbsup: As in HORSEpower. As in applied HORSEpower = TRACTion of horse over ground.
Now we mostly use TRACTORs with different amounts of HORSEpower to apply TRACTion to the wheels, (used to be hoofs), and the result is in most instances at least two hoofs/wheels are pulling/ pushing /spinning. To aid in putting more HORSEpower to the hoofs that are spinning, and thus to make them pull or push instead of spinning, we use differentials, locking differentials, 4wd engaging switches, etc.

 

[Gary Fowler]

If you want to see truly how your drive train works, drive diagonally across a ditch that is deep enough that your front axle block wont let one wheel fall to the bottom of the ditch. IF done correctly at some point, the front left wheel and right rear (or vice versa) will be off the ground and both spinning with you not going anywhere. Diff. lock will get you on thru it if you have one, if not, sometimes gently applying the brake to the spinning wheel will let the differential give some power to the grounded wheel.
Remember the old remedy for stuck in the mud prior to limited slip differentials, lightly apply the emergency brake to make both wheels turn.

 

[savageactor7]

Tim on occasion for a quick fix for traction I'll load the FEL bucket with sand. Nice thing about sand is that if you want to unload it ASAP you to back-blade quickly so that it vanishes.

 

[k0ua]

I got "stuck" twice yesterday moving rock fill with one rear and one front spinning harmlessly in the air, by accidentally moving across the rock strewn work area in such a way as trying to back uphill and running over two high rocks on opposite sides of the tractor.. Of course I was not really "stuck", once I just pressed the differential lock and the other I just moved forward for a couple of feet and moved over a inch or two. But I remembered this thread when it happened.

James K0UA

 

[shortthrow50]

Curious why you would say that? Then what would you call it?

I would call it 4 wheel drive. If it was all wheel drive I would call it all wheel drive

 

[PHILIP8N]

I was reading an article in Diesel Progress or Off Highway Equipment about a new Fendt tractor. The tractor is 4wd, 4wd with rear locking diff, or 4wd with rear and front locking diff. They called the 4wd with rear and front locking diffs something like 'permanent 4wd'. This is a larger tractor, 150hp+ or so range. The 'permanent 4wd' is computer controlled, and if you exceed 12.5 mph or 25 degrees past steering angle, the front diff automatically unlocks. Of course this takes an ecm, automatic locker, and steering angle measuring devices, so this is a little too much for our little scut's. Think hst+ is expensive and complicated, think about adding this technology to a Grand Lxx40. Philip.

 

[k0ua]

I was reading an article in Diesel Progress or Off Highway Equipment about a new Fendt tractor. The tractor is 4wd, 4wd with rear locking diff, or 4wd with rear and front locking diff. They called the 4wd with rear and front locking diffs something like 'permanent 4wd'. This is a larger tractor, 150hp+ or so range. The 'permanent 4wd' is computer controlled, and if you exceed 12.5 mph or 25 degrees past steering angle, the front diff automatically unlocks. Of course this takes an ecm, automatic locker, and steering angle measuring devices, so this is a little too much for our little scut's. Think hst+ is expensive and complicated, think about adding this technology to a Grand Lxx40. Philip.

Expensive.. yeah probably so, but it would be way cool:thumbsup: or how about equipping it with and air/electric locker for the fronts you could just press a button and lock for a second to get you unstuck and then you have brains enough to immediately unlock it before you turn the wheels. Eh.. I see some warranty claims on that one...

James K0UA

 

[SPYDERLK]

Well, a 2wd cor or tractor really only has as much traction as the lowest traction of one wheel.

A 4wd tractor has the traction of the 2 lowest value wheels.

A diff lock will add one more wheel to the above.

Pretty simple, really. Differential splits up the power to both wheels, either wheel on the axle can get any % of the available power.

--->Paul

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

 

[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