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.