PT AL-629 ( can it be done ? )

[J_J]

Kent, Three ways that will increase torque. Larger wheel motors, larger hyd pump, but only if the hyd motors can handle the higher pressure.and smaller diameter tires.

Stray, please restate why you were going to make this mod, and were you concerned about pressure? As I understand your post, it was about series and parallel circuits.

As David said, we already have a good arrangement.

Kent, Do you know for a fact that your 425 is operating at full potential. Your tram pump might not be. putting out the advertised pressure and gpm's

 

[Bob999]

I really don't know how steep that hill is -- I've never tried to measure it.

It is very difficult, if not impossible to determine slope from casual pictures. That said my impression is that your slope is less then 20 degrees (not percent) and should be well within the capabilities of the PT.

I have to wonder if there is some mechanical issue with your tractor--be it wear, a mis adjusted pressure relief valve, or some other problem that is preventing the tractor from doing what it is supposed to do.

Do you run out of engine power or do the hydraulic motors simply stall? The answer to that question should point you in the correct direction for further exploration.

If the issue is hydraulic then JJ's suggestion of getting some pressure guages and checking out the pressure in the drive system might be time and money will spent.

 

[MossRoad]

One other analogy I thought of regarding the loss of "posi-traction"... I should be no worse off than a normal 4WD CUT/SCUT without diff-lock engaged. How limiting is that for most things you'd be doing? IMO, though limiting, it is not "catastrophic"...

A locked rear differential is one thing. A locked rear + locked front differential on a 4x4 truck makes turning very difficult without getting tire spin or skid. Have you ever driven a 4x4 truck with the front diff locked and tried to turn on pavement? With very little steering wheel motion you can get the front tires to plow, push, hop all over the place. This puts tremedous forces on the steering linkage.

With all four wheels in series with each other, they will be essentially locked together. If a motor starts to spin, it won't spin much, because the fluid will bypass to the next motor, which has traction, which will increase back pressure on the spinning motor, keeping it from taking off wildly, is my guess.

The way the Power Trac is currently set up the wheels on opposite corners are in series with each other. So if you use my turning example:

1. Turn the wheel all the way to the left.
2. As you turn the wheel to the right, the left front tire rolls forward and so does the right rear tire. At the same time, the right front tire rolls backwards and the left rear rolls backwards.

That's why there is no turf tear or skidding when turning. If you connect all four wheels in series, how are you going to turn without skidding a tire?

Now, if you can get a valve in a location that is convenient for the operator, or perhaps an electric diverter valve, where you can switch the circuit from the current setup to a full series setup, it will probably help you climb hills when you are going straight. But if the wheels are not aligned straight, as in steering up a curved slope, my guess is as soon as you engage the full series circuit, all four wheels will start turning at the same speed. You tractor will either crab up the hill spinning the inside whees faster than the outside wheels, or they will overcome the reliefs on the steering circuit and straighten the unit out. Or, they will bust the tabs that hold the steering rams to the unit or the motor mounts or put crazy side loads on the motor shafts. Of course, that is my prediction, not any fact to back it up with and no real experience with hydraulics to speak of. It just looks that way logically, to me. Hey, a Rubic's cube looked like it would be easy to solve to, until I tried it.

 

[MossRoad]

I really don't know how steep that hill is -- I've never tried to measure it. Here's a few other views of it.

Oh, man, that is beautiful property. Very nice.

 

[MossRoad]

I have to agree with Kent that the PT425 model that we have is no hill climbing beast. As the hydraulics heat up, the hill climbing ability goes down. That is a real-world fact. We go up hills nicely. A half hour of hard work later and we return to the hill and have a difficult time going up. That's why I was happy to see that PT increased the torque on the new model's wheel motors.

While the Kohler engine is rated for a 20 or 25 degree angle (I can't remember right now) that doesn't mean the machine will perform on that angle. The engine runs fine. The hydraulics lose power. That is a characteristic of the machine and does not surprise me.

So how can we owners with weeny wheel motors improve performance without spending $$$$$ ??

 

[BobRip]

.

With all four wheels in series with each other, they will be essentially locked together.

Moss, the wheels will be in parallel, not series. As such there will be less tendency to lock together than now. Which ever wheel needs to go faster will automatically get more flow. The problem is if one wheel slips, it will get all of the flow and the others will get none. Of course, unless a wheel is in the air, the others wheels will still get some torque. Here a valving mechanism would allow you to back the flow down on the slipping motor, Actually you could put a solenoid valve in series with each motor and close that valve when the wheel slipped, or perhaps have the valve partially open when solenoid is engaged. A diverter still sounds like a better choice. But what the heck, try it and see.

KentT, correct me if I am wrong about this.

 

[KentT]

KentT, correct me if I am wrong about this.

Bob,

I believe you are 100% correct. MR's two major points are contradictory, IMO.

1. All the pressure will go to the wheel with least resistance (i.e. spinning) when you lose the "posi-traction" of a series circuit

2. All four wheels will be "locked" and it will crab...

IMO, point 1 is correct and point 2 is not.

As I've said, it is a relatively cheap experiment for me to find out for sure, as long as I don't damage the expensive tram pump...

 

[KentT]

Oh, man, that is beautiful property. Very nice.

Thanks, Moss! I'm quite "tickled" with it... the best thing is it's location, with about 450' of frontage on a 6 acre pond (they call it a "lake" of course) and across the road from another 4 acre one. All this, about 5 miles (by air) from the Great Smoky Mountains National Park. Waterfront property in the mountains, what more can you ask for?

Here's an old aerial view that I've edited to show the general location of the driveway (white), the clearing (light green), the planned building locations (salmon), and the property lines (red).

There's a lot more pictures and maps and such on this site I put up so that my family can track the progress, if you're interested:

Loon Landing: Our Own Golden Pond

Right now, I'm getting bids on Phase 1, building the 2-car garage with in-law apartment/guest quarters above it... Hope to get that built this summer.

LOL. I just realized that I may have turned this into the biggest threadjack in TBN history... Sorry folks!

 

[BobRip]

Bob,

I believe you are 100% correct. MR's two major points are contradictory, IMO.

1. All the pressure will go to the wheel with least resistance (i.e. spinning) when you lose the "posi-traction" of a series circuit

2. All four wheels will be "locked" and it will crab...

IMO, point 1 is correct and point 2 is not.

As I've said, it is a relatively cheap experiment for me to find out for sure, as long as I don't damage the expensive tram pump...

Just a word of caution on the tram pump. When I took the class at PT, they stated that the tram hydraulics were a very clean area which was required by the variable displacement pump. They also stated that if you went into that area (replaced a motor, hose, etc.) you should filter it with a three micro filter prior to use. They sold such a kit for $700 (year 2000). I believe they hooked the filter between the PTO outlet on the front and returned it to the tank. Its been a long time so I am not sure of the details. There has been discussion of putting a super filter driven by an electric pump in the system, and that sounds even better. On the other hand, PT had never sold one of these, so maybe it is overkill. The did show me the plate that does the displacement change and how it had been damaged by dirt. Personally I am leaning towards the two speed motors. $2000 sound cheap compared to a new PT. I also like have the short 422 PT. Will I have the courage to do this? I just don't know.

 

[KentT]

I just realized there were questions here that I had not answered:

JJ -- I am not sure that the tram pump is pumping to spec, for two reasons (1) I don't know what those specs are, and (2) this machine only had 250 hours use on it when I got it, and is up to about 370 hours or so now, and I've never considered/had the need to hook up gauges to it...

Bob999 -- It exhibits some symptoms of both descriptions you gave. It will bog the engine down to the point that it will actually kill the engine when the oil is cooler. The only way to avoid this is to back off on the treadle, and ease back down on the treadle, trying to strike a balance that doesn't choke the engine. When the oil gets hotter, it doesn't bog the engine down to the point of killing it quite so easily, but it just loses torque. As I've said, I've had to combine "feathering the treadle up and down" with waggling the PT to climb up that back driveway more than once when loaded pretty heavily. I have gotten it into situations in the woods, when hot, where all it would do is whine, and I'd have to waggle my way out of the predicament... So, I think I'm seeing some symptoms of both. I'm hoping that by replumbing it to parallel, that I shift the torque curve enough that it will not be as prone to bogging the engine down, and I can then maintain enough RPM, speed and momentum to climb these hills and not get into situations where the wheel motors are bypassing -- if that is what the whine is coming from....

Note also that if the part number that SnowRidge provided for these White wheel motors (400230W31222AAA) is correct, then it is 14.2 ci motor WITHOUT relief valves. So, if it is bypassing, where is it bypassing?

http://www.whitehydraulics.com/pdf/catalog/UScat04_ce.pdf