More torque for my Power trac?

[stray]

Woodlandfarms, I just do these drawings in windows paint. I have used this program ever since I had a 286 computer so I am used to it.

And Thanks kentT for coming with the information. I kept track of your project with much interest and have had the same thoughts as to whether the motors would handle the pressure or not. I would like you to think and comment on this.
While pushing a load. Say with the bucket against a dirt pile with the back wheels off the ground or any time you are giving the Pt all it can do in forward movement with the back wheels in the air would the full pressure be in force to the front wheels? Pretty much as in this low speed higher torque set up. Now I did break that wheel motor (shaft broke into) with the wheels were reversed. But never have I blown a wheel motor.
I believe I would really like your set up. It is just in my case I do not want to give up the speed. I travel long distances most times I use the PT. Any where form a mile to a couple hundred yards. Then two I believe the motors will handle the occasional use of this set up. I have been wrong before but I am willing to try it and take the chance. Like I said I bought one wheel motor as a consequence of seeing just how much they could take. Now I know.
I would also like for you to look at this drawing and see if I have the valve drawn right. Maybe someone knows where a valve like it can be purchased.

 

[KentT]

I would like you to think and comment on this.
While pushing a load. Say with the bucket against a dirt pile with the back wheels off the ground or any time you are giving the Pt all it can do in forward movement with the back wheels in the air would the full pressure be in force to the front wheels? Pretty much as in this low speed higher torque set up.

I don't think so, because the rear wheels would still spin while up in the air, functioning somewhat like a pressure relief valve... the pressure might spike at the front wheelmotor, rising beyond the normal operating pressure, but I don't think it would be the same as if all four wheel motors were plumbed independently...

I would also like for you to look at this drawing and see if I have the valve drawn right. Maybe someone knows where a valve like it can be purchased.

Sorry, but I don't know the correct symbology for hydraulic circuits so I'm of no help here. I'd think that a custom mainfold and solenoid valves would allow you to make the circuits function any way you'd like.

 

[woodlandfarms]

If it was me, I would go ahead and plumb this, on the simplest cheapest plan. Then hopefully blow the motors, then tell the wife the tractor is broke and I need new parts, then order the larger wheel motors.

Simple, effective, and maybe a bit out of the wifey radar.

 

[stray]

Oh yea of little faith, LOL

 

[Rip]

Stray, I am one of the ones who permanantly traded speed-for-torque by changing out all four wheel motors....not cheap, but did work as intended. I can understand what you are trying to do also.

Torque is a result of pressure acting on surface area and being unable to leak past due to warn motor componants or low oil viscosity. System pressure is limited by pump design (and wear), relief valve setting, by motor displacement & surface area, and bypass leakage by motor wear and oil type/temperature.

Speed is the result of the flow of oil, which is limited by the same parameters. A retrictive orifice will reduce the flow in a part of the circuit, but pressure will remain the same. For a given input, the system provides equal pressure to all 4 motors at all time, but the flow can shift from 50/50 up to maximum rated flow to one side only. Thus the speed of the left versus right side motors can change due to variation in load (traction or turning).

The variable displacment pump can not put out maximum rated pressure and flow at the same time; in fact it is an inverse relationship. The foot pedal changes the pressure/flow ratio such that at minimal input the pump is putting out maximum pressure (assuming full engine output power/RPM) and minimal flow. As one increases the pedal input, that ratio changes until the pump is at max flow, but at significantly reduced pressure.

One important thing to note here is engine speed/output. It is quite possible for the throttle cable to not be pushing the engine governor to maximum. Engine must be putting out full max power in order to get full hydraulic output.

Your idea of placing a restrictive orifice in line with the rear motors would only reduce the flow to them, yet not increase the pressure to the front motors for no torque gain.

I would thourghly check that:

Engine running at full rated RPM & HP (compression & valves)
Foot pedal providing full range of travel to hydro-back lever on pump
Operating technique - back off foot pedal to achieve maximum torque
Hydraulic oil not too hot or thin - cooler working, may try a higher viscosity/synthetic
Pump output at rated specs for pressure & flow (at hyd shop)
All wheel motors at full specs ( ie not excessivly warn - internal leakage)

Your solution may be bringing all aspects of machine back up to original specs. Some of the above items are quick & cheap to fix. Even replacing the hyd oil may not be too bad if you can filter and use it in another engine (OEM is 10W30 motor oil). Testing and possibly rebuilding the engine, pump, or motor(s) would be a bigger expense, but could well be the source of your lack-of-torque.

Good Luck, Rip

 

[stray]

Thanks Rip, I believe my pt is as powerful now as it has been since I did what you said about the gas motor. That did help it some. Other than that I do not think any amount of tweaking will give me the extra power I am wanting. What size wheel motors did you go with and were your old ones the 12.5 cu. Inch ones. I think Kent went with a somewhere around 24 cu in. I am sure that gave him plenty of low end power but would one need to go that far? I guess it would be a question of personal preference. In theory my set up would give the same power and slow speed but there is the question of more pressure to the wheel motors and of course the rear wheels spinning and robbing all the power. I really appreciate you and Kent sharing the information about the sizing of the hyd. motors and how they preformed. If I ever do get this project off the ground I will return the favor weather it turns out good or bad. In my mind I am still convinced it will work. I guess it is time to just try it and see.
Thanks again stray

 

[KentT]

Stray, just a couple more bits of info on the 400-series wheel motors.

The newer-style 425 wheel motors are White CE series, 14.2 ci. and yield a top speed of about 8 MPH.

The CharLynn S series I used are 22.7 ci. However, another TBNer has used the 18.2 ci ones.

Unless you need to work primarily on hillsides (which I do), I'd recommend new wheel motors in the 17 to 18 ci range. They would give you approximately 50% more torque, yet still operate in the 6 MPH range, or so, for mowing or transport...

The real limitation of upgrading wheelmotors on the old 425s and 422s are:

1. The physical shape of the wheelmotor box and space constraints -- they changed to a new "bolt-on" type for the new CE wheel motors on the newer 425s. With your ability to weld, I'd recommend you consider making all new wheel-motor boxes. Then, you could widen the stance of the PT (similar to reversing the wheels), without increasing the stress on the wheelmotors, only on the mounting boxes...

2. The one-inch hubs (tapered hubs on mine, though the other TBNer appeared to have simple keyed hubs) compared to the 1.25" tapered hubs on the newer 425s. You can readily find rear hubs, but the front hubs with parking brakes appeared to be a Tazewell-only part, based on my research.

 

[Rip]

Stray...... I have a 1845, so wheel motors are completely different series & size. Glad you feel your machine is "up to spec". In many cases though, such internal wear will be so gradual that it can be hard to detect from seat-of-pants perspective.

In any event, my point was that while you can play around with flow priorities and restrict part of the circuit, you really can not gain torque without increase in pump-side pressure or the displacement it is acting on. If your rear wheels are spinning when both fronts are not, then that flow is result of internal leakage within front wheel motors. While some is "normal", any above that level is robbing you of potential torque.

Once again, be sure you are backing-off the foot pedal when you want more torque rather than press it more. It is counter-intuitive to the habits we have all gotten into with the foot-feed as the "gas pedal", but has a completley different effect with hydro power equipment.

Others have mentioned smaller tires/wheels, but that presents ground clearance issues and would reduce real-world traction as well.

Good Luck, Rip

 

[J_J]

Does this make any sense?

If you put all motors in series, the motors will all run at the same speed w/ different torque - turning will be hard. If you put two motors in parallel, it will be like a differential - both motors will have the same torque, but different speeds. If you put the front two motors in parallel, and the back two as well, and then place both sets in series, you'll have the equiv. of a 4wd truck.

On my 1445. the front wheel motors are in parallel, and the back wheel motors are in parallel. All connected to one source.If one wheel is off the ground, then all the fluid will go to the wheel off the ground, which has the least resistance. If I raise both front wheels off the ground, engine not running, and turn the right front wheel, the left front will turn in reverse. Why, you say, because the one wheel motor is acting like a pump. If I raise the right front side, and the left rear side, I am betting that when I turn the right front wheel, the back left wheel will turn in reverse. Why again, because the turning front right motor is again acting like a pump and forcing fluid back to the left rear.

With engine running, if one could add a brake to the spinning wheel, the fluid would see the wheel motor as doing work and feed the rest of the wheel motors.

Does this sound logical to anybody else.

 

[ponytug]

The behaviour is the same as mine, although the plumbing is a little different. For some reason, PT has added a L/R equalizer hose on mine. But, yes, if you lock two wheels and raise two off the ground, turning one causes and an equal and opposite movement in the other wheel off the ground.

I guess you could get 4 solenoids and electronically "brake" wheels as needed...

All the best,

Peter

On my 1445. the front wheel motors are in parallel, and the back wheel motors are in parallel. All connected to one source.If one wheel is off the ground, then all the fluid will go to the wheel off the ground, which has the least resistance. If I raise both front wheels off the ground, engine not running, and turn the right front wheel, the left front will turn in reverse. Why, you say, because the one wheel motor is acting like a pump. If I raise the right front side, and the left rear side, I am betting that when I turn the right front wheel, the back left wheel will turn in reverse. Why again, because the turning front right motor is again acting like a pump and forcing fluid back to the left rear.

With engine running, if one could add a brake to the spinning wheel, the fluid would see the wheel motor as doing work and feed the rest of the wheel motors.

Does this sound logical to anybody else.

 

[KentT]

The behaviour is the same as mine, although the plumbing is a little different. For some reason, PT has added a L/R equalizer hose on mine. But, yes, if you lock two wheels and raise two off the ground, turning one causes and an equal and opposite movement in the other wheel off the ground.

I guess you could get 4 solenoids and electronically "brake" wheels as needed...

All the best,

Peter

The 425's are plumbed differently, as SnowRidge so aptly described.

On the 400 series machines, each side has the front and rear wheel motors in series. The two series coupled sides are in parallel.

You can lift both front wheels off the ground using the bucket, and the tires will spin slowly, yet the rears will continue to push the tractor. Similarly, you can pucker the rear of the tractor, lifting both rear wheels off the ground, and the front wheels will continue to push the tractor.

You'd only lose propulsion completely if both the front an rear wheel on the same side were off the ground, and that circuit would get all the flow. Luckily, with the oscillation of the PT, that's almost impossible, unless you're in the unfortunate process of tipping the PT over on its side....

 

[ponytug]

I wish the scenario below were true for the 1445 that I have, but since the plumbing all comes back to two ports on a single pump, it is possible to get diagonal wheels off the ground and spinning, with no tractive force.

I won't say that you don't get some traction, but even having a single wheel spin on a steep slope is a major loss, a loss that I have always attributed to the single port issue.

I find it interesting that the lower flow variable displacement pumps have two pairs of ports that are independent, which is a very useful feature.

I have learned, the hard way, that when working with a stationary tool on a slope, e.g. a trencher, that it is best to set the parking brake and deal with the slippage of the tires on the slope, rather than actively trying to keep a position, which often deteriorates into a wheel spinning a hole. But that could just be a feature of my soils and/or my ineptitude.

All the best,

Peter

The 425's are plumbed differently, as SnowRidge so aptly described.

You'd only lose propulsion completely if both the front an rear wheel on the same side were off the ground, and that circuit would get all the flow. Luckily, with the oscillation of the PT, that's almost impossible, unless you're in the unfortunate process of tipping the PT over on its side....

 

[stray]

Once again thanks guys for the information and the energy you all have shown to help on this project.
In my thinking if excessive leakage were causing me not to be able to climb hills with a load it would be in the variable speed motor. I am guessing that it is not slipping more than its design lets it. I understand about just getting used to it but the Pt seems to climbing places as it always has.
Let us say that theoretically the pump was not bypass leaking at all, even at low speeds. I would think that one could ease down on the peddle and the Pt would climb a trees till a hose or something bursts. But as it is I keep pushing the peddle down and the motor compensates with more flow to overcome the internal leakage in the Hyd motor. Now I get to the point where the gas motor starts to bog but the tractor is not moving up the hill. Playing around with the peddle (a little more a little less) I teeter on not having enough flow and pressure to move the Pt on up the hill or killing the motor.
If the problem was say leakage in the wheel motors then there would NOT be the tendency of Killing the Gas motor. You would just be setting there with the peddle on the floor, Full throttle, and all the power you could muster, fluid bypassing the wheel motors and not going on up the hill, the gas motor not trying to die.
Now does this seem right or have I got it all wrong? Mabe leakage in the wheel motors can cause the Hyd motor to need to pump a higher volume leaving the pump in (for lack of better words) a higher gear. This just takes it right back around to Rips recommendations and maybe me still thinking my Pt is still doing close to what it was designed to do. Wow!!!

 

[BobRip]

Once again thanks guys for the information and the energy you all have shown to help on this project.
In my thinking if excessive leakage were causing me not to be able to climb hills with a load it would be in the variable speed motor. I am guessing that it is not slipping more than its design lets it. I understand about just getting used to it but the Pt seems to climbing places as it always has.
Let us say that theoretically the pump was not bypass leaking at all, even at low speeds. I would think that one could ease down on the peddle and the Pt would climb a trees till a hose or something bursts. But as it is I keep pushing the peddle down and the motor compensates with more flow to overcome the internal leakage in the Hyd motor. Now I get to the point where the gas motor starts to bog but the tractor is not moving up the hill. Playing around with the peddle (a little more a little less) I teeter on not having enough flow and pressure to move the Pt on up the hill or killing the motor.
If the problem was say leakage in the wheel motors then there would NOT be the tendency of Killing the Gas motor. You would just be setting there with the peddle on the floor, Full throttle, and all the power you could muster, fluid bypassing the wheel motors and not going on up the hill, the gas motor not trying to die.
Now does this seem right or have I got it all wrong? Mabe leakage in the wheel motors can cause the Hyd motor to need to pump a higher volume leaving the pump in (for lack of better words) a higher gear. This just takes it right back around to Rips recommendations and maybe me still thinking my Pt is still doing close to what it was designed to do. Wow!!!

This behaves just like my 422. I sometimes walk my PT up a hill by steering left then right over and over. It helps some. I think your machine is working OK. I did go from 5w30 to 15w50 synthetic oil in the hydraulic system and this helped a fair amount.

 

[SpringHollow]

"But as it is I keep pushing the peddle down" You want to be letting up on the pedal, not pushing harder. Use the throttle for speed.

Or am i missing something?

I know i routinely push harder - hard habit to break.

Ken

 

[J_J]

Once again thanks guys for the information and the energy you all have shown to help on this project.
In my thinking if excessive leakage were causing me not to be able to climb hills with a load it would be in the variable speed motor. I am guessing that it is not slipping more than its design lets it. I understand about just getting used to it but the Pt seems to climbing places as it always has.
Let us say that theoretically the pump was not bypass leaking at all, even at low speeds. I would think that one could ease down on the peddle and the Pt would climb a trees till a hose or something bursts. But as it is I keep pushing the peddle down and the motor compensates with more flow to overcome the internal leakage in the Hyd motor. Now I get to the point where the gas motor starts to bog but the tractor is not moving up the hill. Playing around with the peddle (a little more a little less) I teeter on not having enough flow and pressure to move the Pt on up the hill or killing the motor.
If the problem was say leakage in the wheel motors then there would NOT be the tendency of Killing the Gas motor. You would just be setting there with the peddle on the floor, Full throttle, and all the power you could muster, fluid bypassing the wheel motors and not going on up the hill, the gas motor not trying to die.
Now does this seem right or have I got it all wrong? Mabe leakage in the wheel motors can cause the Hyd motor to need to pump a higher volume leaving the pump in (for lack of better words) a higher gear. This just takes it right back around to Rips recommendations and maybe me still thinking my Pt is still doing close to what it was designed to do. Wow!!!

Stray,

You can not forget about the relief circuits on the pump. When you exceed the torque limits of the wheel motors, you will maybe hear the relief circuits in the pump operating. When you hear the engine start to lose power, it is probably working at or near relief pressure. If the relief did not work, the engine would stall , or something would blow out, be it pump, hose, or wheel motors. If you want to climb hills or whatever, then you need larger wheel motors, or larger engine, or larger pump with a larger engine, and larger wheel motors. You have to simply overcome the energy available for the weight you are trying to get up the hill. Why are motorcycle fast, Hp to weight ratio. Look at the hydraulic winch. straight off the motor shaft, you have so much pull, but run that shaft through a gear box, and you increase torque.

You have to realize, that a larger PT might not be able to get up that slope, because even though it has a larger engine, it also weighs more.

Go into this web site and use the hydraulic calculators to work some figures. With the same engine, same pump, by doubling the cu in of the wheel motors, you will double the torque. but you will lose some speed, as has been stated before.

Burden Sales Surplus Center - Tech Help

 

[SnowRidge]

I find it interesting that the lower flow variable displacement pumps have two pairs of ports that are independent, which is a very useful feature.

If you are referring to the PT-425 series, they don't have two independent pairs of ports. The left and right series coupled wheel motor pairs are plumbed in parallel by way of T fittings screwed into the pump's wheel motor ports.

 

[SnowRidge]

I would think that one could ease down on the peddle and the Pt would climb a trees till a hose or something bursts. But as it is I keep pushing the peddle down and the motor compensates with more flow to overcome the internal leakage in the Hyd motor. Now I get to the point where the gas motor starts to bog but the tractor is not moving up the hill. Playing around with the peddle (a little more a little less) I teeter on not having enough flow and pressure to move the Pt on up the hill or killing the motor.

I think you may have a bad tram pump. Your description sounds similar to that of Central_PA_Chris when his brand new machine couldn't climb up onto his trailer. His was obviously worse than yours, but there are certainly similarities. PT finally fixed the problem under warranty.

There should be an implement (wheel motor) relief valve that screws into the pump body. It may be bad, partially bypassing some fluid. It is located on the bottom of the pump, directly opposite the trunnion shaft.

For what its worth, I can tow my 2,400# trailer around with my PT, even up a mild incline. I also towed a small trailer with 60 gallons of water and a bunch of tools (roughly 1,000#) up my hillsides when I was planting Xmas trees. What you are experiencing just doesn't seem right.

 

[ponytug]

Thanks for being the straight man!

This is my point: the hydraulic fluid will always flow to the the wheel with the least resistance, if it is plumbed in common. And, apparently, all of our tractors are plumbed in common. Powertrac would have had to install some rather expensive flow matching devices to create separate circuits.

SO, the tractors will climb the best when all four wheels are on the ground, and in good contact with the earth. Slippage of any one wheel will unload all of the wheels.

All the best,

Peter

If you are referring to the PT-425 series, they don't have two independent pairs of ports. The left and right series coupled wheel motor pairs are plumbed in parallel by way of T fittings screwed into the pump's wheel motor ports.

 

[ponytug]

Stray,

I don't think you have a leaking motor or pump by your description. I would have to say that you are close on your description below, but not quite totally on the money.

I would like to clarify one point, which has been extensively discussed elsewhere. The drive pump for power-tracs is a Variable Displacement Pump. (Check out the animation, I think it will help explain the action of the pump.) These are special pumps that can vary the amount of oil pump from 100% to 0% to -100%. (i.e. full forward to stop to full backward). This means that if the engine is going at full speed (Wide open throttle, WOT), all of the peak horsepower can be applied to pumping 0-100% of the flow. If you are creeping up a hill, with only a little bit of hydraulic flow, then the pump needs only to be pumping that limited volume plus whatever gets lost in the pump or drive motors. If you try to pump more oil that the required amount, then either the reliefs will open and dump oil, or the engine will start to slow down. With extra load on the engine, the engine speed slow more, you loose horsepower, and the engine slows more, until the vicious cycle stalls the engine, or you let up on the treadle.

So, the best strategy on hill climbing with a PT (or anything else with a similar drive) is to have the engine at peak horsepower, (WOT), and just enough pedal pressure to just barely slow the engine, keeping the engine running at peak horsepower.

Oh one other thing-you want to keep all four wheels on the ground.

I hope that this helps.

All the best,

Peter

P.S. My limit on hill climbing is loss of traction; my soils just break loose, and the wheels spin. Somewhere around 20 degrees, I have to shut down the draft control to get up the hill, adding another five degreees, and I have to shut the PTO down as well. If I could keep the wheels from slipping, I probably wouldn't have to shut anything down... I need to upgrade to either duallies or chains, but so far, I haven't done it, as both are expensive (about the same cost, funnily enough).

Once again thanks guys for the information and the energy you all have shown to help on this project.
In my thinking if excessive leakage were causing me not to be able to climb hills with a load it would be in the variable speed motor. I am guessing that it is not slipping more than its design lets it. I understand about just getting used to it but the Pt seems to climbing places as it always has.
Let us say that theoretically the pump was not bypass leaking at all, even at low speeds. I would think that one could ease down on the peddle and the Pt would climb a trees till a hose or something bursts. But as it is I keep pushing the peddle down and the motor compensates with more flow to overcome the internal leakage in the Hyd motor. Now I get to the point where the gas motor starts to bog but the tractor is not moving up the hill. Playing around with the peddle (a little more a little less) I teeter on not having enough flow and pressure to move the Pt on up the hill or killing the motor.
If the problem was say leakage in the wheel motors then there would NOT be the tendency of Killing the Gas motor. You would just be setting there with the peddle on the floor, Full throttle, and all the power you could muster, fluid bypassing the wheel motors and not going on up the hill, the gas motor not trying to die.
Now does this seem right or have I got it all wrong? Mabe leakage in the wheel motors can cause the Hyd motor to need to pump a higher volume leaving the pump in (for lack of better words) a higher gear. This just takes it right back around to Rips recommendations and maybe me still thinking my Pt is still doing close to what it was designed to do. Wow!!!