1. Stray, as far as I can tell, the amount of pressure available will automatically double the way you'd be plumbing it. You'd be trading volume (speed) for pressure (torque). It may climb that hill slowly, but it would climb the hill... I am interested in how much the PT will push and pull -- for boxblade, bucket and blade work... I've had my PT with a VERY big load of brush/trees in the grapple bucket, raised slightly off the ground for transport, stall on a slope -- when the oil is VERY hot -- and had to waggle to get it over a hump of dirt. Traction was such that it would not spin a wheel, and if I tried to simply back up over it with treadle pressure, it would begin to bog the engine down, with the wheel motors whining loudly. This is after switching to 20W50 Amsoil also... Once I made it over that hump, it handled it fine. IMO, this is a "gearing problem" and not a lack of power.... I'd use the analogy of trying to take off with a manual transmission in 3rd or 4th gear. It may feel like there's no power -- but it is really a matter of the gearing, i.e. torque available, not HP...
2. As I understand it, in a parallel system, the pressure will still be there, doubled, as long as the engine doesn't bog down -- and it is pressure that creates torque, not volume of flow. Volume creates speed (i.e. RPM of the wheels). See point #4 below for more on the "bogging down" issue.
3. As I stated earlier, according to the performance charts for the wheel motors, as currently "plumbed" each of the wheel motors could receive a maximum potential of 8 GPM at 1500 PSI. That yields 2691 in lbs of torgue. This is assuming all engine power is being used to power the tram pump, which it obviously is not.
In a parallel circuit, the maximum potential is 4 GPM at 3000 PSI, which would yield 5395 in lbs of torque. Even if using of the PTO, consuming HP, cuts both the pressure and the volume in half , to 2GPM at 1500 PSI, you'd still get 2902 in lbs of torque... 8% more torque than the theoretical maximum (full pressure, full volume -- i.e. no PTO use) as currently plumbed.... That "worst case" is better than the "best case" as currently plumbed.
4. One bit of data from those performance charts that I haven't mentioned -- Stall Torque -- becomes relevant here also. Stall torque is the maximum amount of torque the motor can apply when it is not turning. White, the manufacturer, actually rates these wheel motors at 1 RPM -- not zero. Stall torque is what moves the tractor from a stopped position, such as climbing over the hump that I mentioned above. Stall torque is what's required to initially push or pull an object to get it moving. Insufficient stall torque is what "kills the engine" in this circumstance. See how that stall torque figure also goes up with increases in pressure in the circuit:
1000 PSI = 1722 in lbs torque
1500 PSI = 2573 in lbs torque
2000 PSI = 3275 in lbs torque
2500 PSI = 4081 in lbs torque
3000 PSI = 4740 in lbs torque
As currently plumbed, 2573 in lbs (at 1500 PSI) is the maximum potential torque available to start the tractor moving -- even if no engine power is being used for steering, PTO, or lift cylinders. With parallel circuits that increases to potentially 4740 in lbs (at 3000 PSI).
Note that Stall Torque has NO relationship to volume, since the starting point is theoreticaly zero fluid going through the system. So, essentially all the available engine power is available to produce pressure in the system -- however, as currently plumbed, only half that pressure can get to any individual wheel motor...
So, parallel circuits should significantly reduce the potential of stalling the engine when pushing or pulling something from a dead stop. It will significantly increase the potential for spinning a tire, however, since it should feel like it has twice the power when it first starts moving....
This experiment could be fun -- especially since it's Stray's $$$ /forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif
