Is it possible for a tractor to have limited slip?

[V1Rotate]

The small Terramite TLBs use a hydraulic motor driving an automotive type rear axle with what they call TRAC-LOCK which is a type of limited slip. The front wheels are driven by separate hydraulic motors.

 

[k0ua]

No, even if only one tire is spinning the speed of the tire does not double.
The speed of the tire (one or both) is limited by the engine rpm and gear ratio. Theoretical top speed of the car is the same as the max speed the one tire will spin. Actual top speed of course is less due to friction, air resistance, etc.

See I am not full of crap:laughing::laughing: Well actually I am full of crap most of the time.:laughing: but the twice speed thing is for real, if you one wheel is totally stopped and the other is spinning on an open diffy. that is why in your owners manual of your car, they caution against "excessive" wheel spin as it is hard on your spinning tires to go that fast, as you can easily go over the speed rating of your tire, and it can fly apart. I have never actually seen one fly apart from all that smoke rolling off of it, but I suppose it could happen. But I remember sitting perfectly still and seeing 120 MPH on the speedo. So I guess one tire was going about 240 mph, as there was only 1 black mark on the road.

James K0UA

 

[tcartwri]

K7LN is correct. Don't confuse a planetary unit with a differential. You might want to look into that a little more.

A typical open diff has four spider gears. The two splined onto the axles are considered sun gears and the two pinned to the carrier are the planetaries.

The planetaries are pinned to the case by the cross shaft, and when you abuse an open diff with one wheel peels, the gears will gall to the cross shaft, effectively locking the diff.

:thumbsup:

 

[Ford tractor]

See I am not full of crap:laughing::laughing: Well actually I am full of crap most of the time.:laughing: but the twice speed thing is for real, if you one wheel is totally stopped and the other is spinning on an open diffy. that is why in your owners manual of your car, they caution against "excessive" wheel spin as it is hard on your spinning tires to go that fast, as you can easily go over the speed rating of your tire, and it can fly apart. I have never actually seen one fly apart from all that smoke rolling off of it, but I suppose it could happen. But I remember sitting perfectly still and seeing 120 MPH on the speedo. So I guess one tire was going about 240 mph, as there was only 1 black mark on the road.

James K0UA

I hate to burst your bubble, but what you wrote makes no sense. The speedo is reading the speed of the tire, the spider gears are not multipliers. One wheel spinning is just that, one wheel spinning -- not spinning 2x the normal speed because only one is spinning. Watch the video, it will make it all clear.

Owners manuals tell you not to spin the wheels because "bad expensive things" happen when traction is found. You will also be much less in control of the vehicle while spinning and if stuck you will just dig down making it harder to get out.

 

[k0ua]

I hate to burst your bubble, but what you wrote makes no sense. The speedo is reading the speed of the tire, the spider gears are not multipliers. One wheel spinning is just that, one wheel spinning -- not spinning 2x the normal speed because only one is spinning. Watch the video, it will make it all clear.

Owners manuals tell you not to spin the wheels because "bad expensive things" happen when traction is found. You will also be much less in control of the vehicle while spinning and if stuck you will just dig down making it harder to get out.

Sorry, dont think so.. the speedo is reading the speed of the transmission, not the tire, the speedo gear is in the rear end of the transmission. so if it is reading 120, the transmission is running at the RPM that would make the tires go 120, after it goes thru the differential, and going in a straight line, now, the spyder gears are not turning, on their shafts, they are pushing the side bevel gears ok.. So now if you stop one wheel the spyder gears are now rotating on their shafts as well as still pushing "sideways" from the differential frame, which is attached to the main ring gear solidly by bolts. so you have the rotational speed of the differential frame pushing at 120 plus the spyder gears rotation against the now "dead" tire causing the speed to double.. the spinning tire is now going 240 MPH. thats my story and I am sticking to it.
James K0UA

 

[mjncad]

Here's the video on YouTube.

That's the video, thanks.

I'm sure that was a fake video. Not possible to create enough friction to catch a car on fire from an ice burn out.

I suspect the friction causing the fire was from something else on the car that wasn't kosher.

 

[RickB]

A typical open diff has four spider gears. The two splined onto the axles are considered sun gears and the two pinned to the carrier are the planetaries.

The planetaries are pinned to the case by the cross shaft, and when you abuse an open diff with one wheel peels, the gears will gall to the cross shaft, effectively locking the diff.

:thumbsup:

Sun gears, maybe. Spider gears, yes. Planetaries, no. A differential is not a planetary unit.

 

[k0ua]

To K7LN, Your are correct about limited slip differentials coming on the scene before 1965, I did a little research:

n the 1950s and 1960s many manufacturers began to apply brand names to their LSD units. While Packard pioneered the LSD under the brand name "Twin Traction" in 1956, the most famous of these in the USA was Chevrolet's "Positraction". Since then, Positraction (often shortened to "positrac" or merely "posi") has become a genericized trademark for LSDs in the USA.

Also found a reference to Porsche having one in the 1930's, and Torsen making one in 1958. So I stand corrected, on LSD's.. but the first Posi-Trac by Chevrolet I have ever seen, was in the 1965 model year. I cannot find out exactly when it appeared for sure, but that is the first one I know of.

James K0UA

 

[V1Rotate]

Sorry, dont think so.. the speedo is reading the speed of the transmission, not the tire, the speedo gear is in the rear end of the transmission. so if it is reading 120, the transmission is running at the RPM that would make the tires go 120, after it goes thru the differential, and going in a straight line, now, the spyder gears are not turning, on their shafts, they are pushing the side bevel gears ok.. So now if you stop one wheel the spyder gears are now rotating on their shafts as well as still pushing "sideways" from the differential frame, which is attached to the main ring gear solidly by bolts. so you have the rotational speed of the differential frame pushing at 120 plus the spyder gears rotation against the now "dead" tire causing the speed to double.. the spinning tire is now going 240 MPH. thats my story and I am sticking to it.
James K0UA

k0ua is absolutely correct and did a pretty good job of explaining how the differential works.

 

[TripleR]

This has been a fascinating thread with lots of good information by different posters. I now have a much better understanding of how these things work.

Funny that I have replaced a few "chunks" in cars/trucks over the years without ever knowing how they work.