New Holland SenseTrack and SuperSteer--Can someone explain how it works?

[AGRIMAN]

I'm still wondering, however, how the one way clutch driving the front wheels is able to sense the "driveline wrapup" when driving straight on a paved surface and thereby "declutch" the front drive. This is very useful for guys like myself who might forget to disengage FWD when roading.
Would sure appreciate anyone who can explain this automatic stuff for me.

Sorry npalen, I have been cutting/baling hay for the last two days and nights. I did not take your comments as being argumentative. The sensitrack is basically a clutch, but I think this would be an easier way to explain how it works.

Picture that inside the sensitrack there are two separate shafts. Shaft 1 has a gear that is splined on one end. Shaft 2 also has a splined gear on one end, but it has the ability to slide back and forth on the shaft. There is a large spring behind gear 2 that keeps it forced against gear 1. This is "basically" the setup.

Now let's say that you are driving alone with the lever in automatic and decide to make a turn. When the wrap up or "negative force" generated from the front axle becomes greater than the spring force holding gear 2 against gear 1, the spring pushes back and gear 2 slides back automatically disengaging the FWD. When the turn is complete and the "negative force" drops below the spring force, the spring pushes gear 2 back against gear 1 and automatically reengages the FWD.

So what about the full position. Picture the same setup, but now picture a shifter fork behind the spring on gear 2. When you shift the lever to full, the fork pushes the spring flat against gear 2 which locks it against gear 1. Since gear 2 can't slide, it doesn't matter how much "negative force" is applied by the front axle the FWD stays engaged.

 

[bigdeano]

I wonder if it makes a ratcheting noise when slipping. It sounds like it works like a Detroit locker differential from the above description.

 

[npalen]

Thanks for the explanation, AGRIMAN. I'm wondering what happens when driving straight on a dry paved surface. Is the FWD engaged at that time and scuffing the front tires?
I was under the impression that the FWD would be disengaged and would only engage on a slick surface that allowed the front wheel rotation to slow down because of rear wheel slip.
What actually happens in a turn situation? Do the front wheels slow down or speed up relative to the rear wheels?

Edit: After thinking more about the turn situation, I realize that it gets a bit complicated in that the "net" rotation speed of the inner and outer wheels is the differential speed.
The sharpness of the turn, of course, enters the picture relative to the front and rear wheels.

 

[Halftrack]

During any turn, the 2 front wheels travel a greater combined distance than the 2 rear wheels combined. So in any turn in the auto mode, the clutch allows the 2 front wheels to "freewheel", (travel farther than the rear wheels). In the locked mode the front wheels are forced to only travel as far as the rear wheels, so scuffing occurs from the front wheels traveling slower than they need to. Straight line traveling could become an issue if the front tires are worn a lot more that the rears, causing the clutch to remain locked and pushing the fronts down the road. (ask me how I know). Solution, new fronts. I would describe the clutch as being similar to an overrunning pto clutch, in that it allows the fronts to overrun the rears. The question that I can't answer is whether the clutch works at all in the auto mode, when backing. If it does, then there is a lot more to that clutch than meets the eye.

 

[boomer1025]

During any turn, the 2 front wheels travel a greater combined distance than the 2 rear wheels combined. So in any turn in the auto mode, the clutch allows the 2 front wheels to "freewheel", (travel farther than the rear wheels). In the locked mode the front wheels are forced to only travel as far as the rear wheels, so scuffing occurs from the front wheels traveling slower than they need to. Straight line traveling could become an issue if the front tires are worn a lot more that the rears, causing the clutch to remain locked and pushing the fronts down the road. (ask me how I know). Solution, new fronts. I would describe the clutch as being similar to an overrunning pto clutch, in that it allows the fronts to overrun the rears. The question that I can't answer is whether the clutch works at all in the auto mode, when backing. If it does, then there is a lot more to that clutch than meets the eye.

.
On my Boomer 1025 in Auto-Mode in reverse it will spin 1 rear wheel and 1 front wheel as it should. Think of the clutch unit as a limited slip diff unit in a car or truck.
The only time I Lock the front in is on snow, ice or in mud. When I get the front or rear down over a grade and the wheels start to spin I use the diff lock.
There is no need to run with the front locked in 99% of the time.

 

[dynasim]

I'm not sure that the front axle travels faster than the rear axle on the sensitrak installed systems. The front clearly does not bind when roading the tractor. The front axles do not brake in a down hill slide with the rears locked up. I have tested this. :0. They sensitrak clutch does not make any noise, and is oil filled.

Jinman has some drawings about this, I think.

Chris

 

[dynasim]

http://www.tractorbynet.com/forums/owning-operating/369738-new-holland-super-steer-sensitrack.html

 

[k0ua]

I definitely believe you are correct in your assessment. I had to see it for myself by making a sharp turn in both auto and full FWD. It's quite obvious that the front and rear are fighting each other when in full FWD but very smooth when in auto mode.
It's amazing in that the rear inside tire remains stationary during a slow sharp turn. I realize that any tractor with wheel brakes can do this but not without sliding the front tires "sideways" and doubling the speed of the outside rear tire due to differential action. It's also very hard to do a wheel brake turn with a hydrostat when the wheel brake pedals are on the same side as the HST foot pedal.:confused2:
I'm still wondering, however, how the one way clutch driving the front wheels is able to sense the "driveline wrapup" when driving straight on a paved surface and thereby "declutch" the front drive. This is very useful for guys like myself who might forget to disengage FWD when roading.
Would sure appreciate anyone who can explain this automatic stuff for me.

I can't really explain how it works, but the few years I had the tractor, I stayed in Auto most of the time and it worked very well. Supersteer took a bit of getting used to when hooking up the FEL as it is not entirely intuitive when getting lined up for the loader, but once learned, it was no big deal. I used the tractor for mainly a mowing tractor, and it was a great one.

 

[k0ua]

Sorry npalen, I have been cutting/baling hay for the last two days and nights. I did not take your comments as being argumentative. The sensitrack is basically a clutch, but I think this would be an easier way to explain how it works.

Picture that inside the sensitrack there are two separate shafts. Shaft 1 has a gear that is splined on one end. Shaft 2 also has a splined gear on one end, but it has the ability to slide back and forth on the shaft. There is a large spring behind gear 2 that keeps it forced against gear 1. This is "basically" the setup.

Now let's say that you are driving alone with the lever in automatic and decide to make a turn. When the wrap up or "negative force" generated from the front axle becomes greater than the spring force holding gear 2 against gear 1, the spring pushes back and gear 2 slides back automatically disengaging the FWD. When the turn is complete and the "negative force" drops below the spring force, the spring pushes gear 2 back against gear 1 and automatically reengages the FWD.

So what about the full position. Picture the same setup, but now picture a shifter fork behind the spring on gear 2. When you shift the lever to full, the fork pushes the spring flat against gear 2 which locks it against gear 1. Since gear 2 can't slide, it doesn't matter how much "negative force" is applied by the front axle the FWD stays engaged.

Thank you for that explanation.. I never understood how it worked. But it worked well for me..

 

[AGRIMAN]

Thanks for the explanation, AGRIMAN. I'm wondering what happens when driving straight on a dry paved surface. Is the FWD engaged at that time and scuffing the front tires?
I was under the impression that the FWD would be disengaged and would only engage on a slick surface that allowed the front wheel rotation to slow down because of rear wheel slip.
What actually happens in a turn situation? Do the front wheels slow down or speed up relative to the rear wheels?

Edit: After thinking more about the turn situation, I realize that it gets a bit complicated in that the "net" rotation speed of the inner and outer wheels is the differential speed.
The sharpness of the turn, of course, enters the picture relative to the front and rear wheels.

Good question. I don't believe that you will generate enough negative force to disengage the FWD by just driving straight on a dry paved surface, so you will remain in FWD. But in theory, if you did reach that point, it would disengage.

Let me do some checking.