Terry on using the Treadle

[SnowRidge]

If I forget to take the parking brake off, the motor bogs. Nothing spins or moves. If I make a sharp uphill turn on wet grass while mowing, I can get a tiny bit of wheel spin on one side only. Both wheels spin.

If I am trying to crawl up a steep wet slope and I lose traction, all wheels spin. The last time that happened, I was on a trail coverd by wet leaves. I picked up the brush cutter, and the machine clawed its way up the trail.

 

[SnowRidge]

RegL, your wheel motors must have some sort of pressure relief valve in order for one to stall and the other to spin if they are plumbed in series. Have you looked up the specs for your wheel motors?

 

[MossRoad]

I use that technique often on one particular trail on our property. That extra traction on the front wheels really makes a difference.

 

[RegL]

RegL, your wheel motors must have some sort of pressure relief valve in order for one to stall and the other to spin if they are plumbed in series. Have you looked up the specs for your wheel motors?

I haven't looked up any specs. I don't think it's a pressure relief valve in the motors. I think at a certain amount of load, oil just leaks past through the motor. It's much worse when the oil is hot. That's been talked about a lot in the past. It appears from these discussions that, at the point of stall, The 1430's week link is wheel motors and the 425's is the engine. If my wheel motors all kept spinning like you describe, I think I could go anywhere.

 

[SnowRidge]

I haven't looked up any specs. I don't think it's a pressure relief valve in the motors. I think at a certain amount of load, oil just leaks past through the motor. It's much worse when the oil is hot. That's been talked about a lot in the past. It appears from these discussions that, at the point of stall, The 1430's week link is wheel motors and the 425's is the engine. If my wheel motors all kept spinning like you describe, I think I could go anywhere.

If you have Char-Lynn motors, they mention an internal poppet valve. I find it hard to believe there would be that much leakage.

 

[BobRip]

If you have Char-Lynn motors, they mention an internal poppet valve. I find it hard to believe there would be that much leakage.

Even if they do have an internal poppet valve, if the wheels are spinning or off the ground then there is low torque or no torque and no back pressure so the poppet valve would not open. I think it is leakage.

 

[SnowRidge]

Even if they do have an internal poppet valve, if the wheels are spinning or off the ground then there is low torque or no torque and no back pressure so the poppet valve would not open. I think it is leakage.

The valve, if it exists, would be open on the stalled wheels, not the spinning wheels.

 

[KentT]

The valve, if it exists, would be open on the stalled wheels, not the spinning wheels.

With the old-style wheel-motors, I've gotten into situations in the woods (with hot hydraulic oil) where the wheels would not spin and the tractor would not climb out of the hole it was in -- the wheel motors would just whine at any treadle position up to about half-treadle. If you pressed down past about half-treadle, the engine would start bogging down, still without spinning a tire or moving the PT. The only way out was to give very little treadle, and waggle the PT back and forth. The steering cylinders moved a front wheel a foot or so at a time, and the treadle position served as a "brake" so that you didn't lose that forward progress when you steered to the other side... I've had to use the same technique a few times when climbing steep slopes heavily loaded.

As far as I can tell, there is no by-pass valve in the White RS series motors -- they just have significant leakage when the fluid is hot. There may be a relief valve on the tram pump, but I don't think there's any on the wheel motors, nor are there case drains on mine at least...

 

[J_J]

RegL, your wheel motors must have some sort of pressure relief valve in order for one to stall and the other to spin if they are plumbed in series. Have you looked up the specs for your wheel motors?

According to some data that I have read, some hydraulic wheel motors have built in pressure relief valves.

As you know, oil from the charge pump is pumped into the closed loop hydraulic circuit, and fluid not required to replenish the closed loop system, flows either into the pump housing through a cooling orifice, or back to the charge pump inlet through the charge pump pressure relief valve.

So if the wheel motors are relieving the pressure, you will not be at top performance, and if the charge pump is relieving pressure, you will have degraded performance.

So the trick is to go easy on the treadle. and if the motors are not worn, they should turn.

I know one of my hydraulic pumps was not pumping to full capacity, and gave me decrease performance on my steering and lift circuit. My PTO pump was also bypassing internally, and gave decreased performance.

There appears to be some difference in the hydraulic plumbing of the different machines. On my 1445, all four wheels turn the same but if one of them is off the ground, I lose traction, because the hydraulic fluid goes to the path of least resistance. It would be nice to have posi-trac, but is not available.

 

[BobRip]

The valve, if it exists, would be open on the stalled wheels, not the spinning wheels.

You are correct and I am wrong. Sorry for the error.

 

[SnowRidge]

There appears to be some difference in the hydraulic plumbing of the different machines. On my 1445, all four wheels turn the same but if one of them is off the ground, I lose traction, because the hydraulic fluid goes to the path of least resistance. It would be nice to have posi-trac, but is not available.

Can you replumb it so that the front and rear wheels on each side are fed in series, while the two sides are fed in parallel? That's how the PT-425 is plumbed, and it works well.

 

[BobRip]

There appears to be some difference in the hydraulic plumbing of the different machines. On my 1445, all four wheels turn the same but if one of them is off the ground, I lose traction, because the hydraulic fluid goes to the path of least resistance. It would be nice to have posi-trac, but is not available.

Do you loose all traction when one wheel is off the ground? This happens often if the ground is real uneven.

 

[J_J]

Can you replumb it so that the front and rear wheels on each side are fed in series, while the two sides are fed in parallel? That's how the PT-425 is plumbed, and it works well.

Some time ago, someone had considered changing the flow. I think they gave up due to the excessive plumbing that would be required. I would think a better solution would be to limit the spinning tires with , say a built in brake that you could activate independently. I remember when if one of your car tires were spinning, you could apply some brake, and that would limit some slip, probably enough to get out of a situation.

I believe there are some new systems out there that monitor and will limit slip automatically, but the system would be expensive.

Now, if each wheel motor had electric brakes, you could just activate the brake on the spinning tire to achieve traction.

I am not sure if a bypass circuit would be required to bypass the fluid in the wheel motor.

 

[MossRoad]

On our 1970 Nova we had that setup. If one tire started spinning, most of the power would go to the spinning tire. If you just stepped on the brakes lightly while giving it gentle gas, that was usually enough to keep the tire from spinning wildly and you could make it off the ice or out of the mud.

 

[SnowRidge]

On our 1970 Nova we had that setup. If one tire started spinning, most of the power would go to the spinning tire. If you just stepped on the brakes lightly while giving it gentle gas, that was usually enough to keep the tire from spinning wildly and you could make it off the ice or out of the mud.

That's the standard technique with any vehicle with a plain differential.

 

[BobRip]

That's the standard technique with any vehicle with a plain differential.

I have seen a dune buggy where they split control of the parking brake, so you could have two handles and could apply parking brake to only the wheel that is spinning.

 

[MossRoad]

I have seen a dune buggy where they split control of the parking brake, so you could have two handles and could apply parking brake to only the wheel that is spinning.

One of the main uses for a split parking brake setup is similar to a tractor... turning brakes.

 

[FOURTEEN]

On my PT-425, the wheel motors will not stall before the engine.

How old is your PT425?

My PT425, since new, built in 2/2004, has always stalled the wheels, the lift arms, or the PTO without noticably reducing engine speed, and certainly never stalling the Kohler engine!!

If I try to push too hard, lift too much, or stump grind too hard, the PT425 will just not move, not lift, or not grind! The engine runs about the same with only a slight drop in RPM!!