Hydraulic motor and pump help

[MossRoad]

Here's a picture of my VVP on the front of the engine.


and the two PTO pumps on an adapter on the rear of my engine...

 

[Metalburner]

Thanks for the link and visuals. From reading on Power Trac's site, these have somewhere around 35hp or more and weigh about 3600lbs, that's insane. But this does help out. Right now I'm searching for a kit that was sold on Surplus Center a couple years ago. It came with pumps and wheel motors, plus most of the lines to hook them up. They were from Parker and no longer sold from Surplus Center, so I'm trying to locate something of equivalent.

 

[MossRoad]

Power Tracs come in several sizes and configurations. Mine is tiny. 1500# with me on it. It'll fit between the wheel wells in the bed of a standard pickup truck without a tailgate. :laughing:

Anyhow, they are full time all wheel drive. 4 wheel motors hooked up in a series/parallel configuration to allow for turning, reversing direction and no turf scalping. You don't need that for your project. I turn with articulation. You need to be able to steer by different speeds/directions to each side.

 

[MossRoad]

How are the magnatracs (struck) set up?

Struck Corp - Power Solutions for Today

 

[Metalburner]

So basically the smaller Rs1000 and the kit RS196K use a series of v-belts and pulleys to travel forward and back as well as left to right. As doable as that is, it's more complicated than I'd like. The RS1000 by their measure puts out 1500ft/lbs of torque to the ground. It turns like a normal zturn mower, but with v-belts. They have an owner's manual PDF on the RS1000 that gives an idea how the belt system works.

Can't post the PDF from my phone unfortunately.

 

[MossRoad]

So they're belt drive, not hydraulic. Bummer. I guess I'd stick with a setup similar to a hydraulic drive zero turn mower, but geared down for lower speed/higher torque. I think you'd accomplish that by using higher displacement (larger) wheel motors. Several Power Trac owners wanted more low-end power and less top speed, so they did just that; swapped out the wheel motors for larger ones. It cut down the top end, and increased the available power at the low end.

 

[Metalburner]

Yeah plus the hydro drive would be more durable for the long haul. Probably would get two in the 16CIR then two variable pumps that would work.

 

[MossRoad]

There's some good calculators on the Surplus Center website...

Surplus Center

 

[aczlan]

If your uses are for ground engagement, pulling a cart around, plowing snow, etc. I looked at the JD lawn mower specs and the 300 series run around 5.5 MPH and the 500 series around 7.5 MPH. Average person walks at 3 MPH or more.

I would suspect that plowing snow and pulling your trailer at 2 -3 MPH will be disappointingly slow.

Based on your usage I would look hardest at two variable displacement closed loop pumps and two motors. This would give you the capabilities of traveling faster under low power situations and then slowing down as the load demands like running a zero turn or skid steer.

using 10" sprocket I get 168 RPM at 5 MPH You could possibly use a wheel motor to directly drive your tracks Vs the jack shaft and chain reduction. I believe some of the track type skid steers are driven this way. Might save some space. You would have to check bearing loads and possibly seal protection since this will be in the dirt and mud.

travel speed formula: MPH = (RPM x d)/ 336
RPM of drive sprocket or wheel
d = diameter of drive sprocket or wheel in inches

I found this formulae for converting axle torque to drawbar pull.
T = F x r
T = torque in inch lbs.
F = draw bar in lbs.
r = wheel or drive sprocket radius

Here are my suggestions:
Pump, 1.1ci 15gpm piston variable displacement pump, 1425PSI @3600RPM input shaft speed: Hydraulic-Pumps/Piston-Hydraulic-Pumps/1-10-cu-in-WHITE-HYD-PISTON-PUMP-101018000012
Motor, 19.6ci drive motor direct driving each track, rated at 16GPM and 1750PSI continuous: 19.6 cu in WHITE DRIVE PRODUCTS 25532A172AAAAA HYDRAULIC MOTOR
One of each of those for each side. Then scale them back by limiting the control lever stroke to what your engine will handle. Those will put out 10ish HP on each track, so you would need a 24+ hp engine to max them out.
That should give you a top speed a little over 5 MPH.
That puts you at $270ish/side in pumps and motors, I would put a cooler on the return line from each one to make sure they don't get too hot.
Not sure if you have found the hydraulics calculators on the Surplus Center site, but they are good to play with combinations of motors, pumps, etc: Surplus Center

Aaron Z

 

[Metalburner]

I was going to ask if I should put a cooler in and possibly get a small electric pusher fan to help cool it even more. Looking at the motor it seems like the shaft has large splines on it. Not a problem, would just need to have the drive sprockets machined to fit it directly or find a hub that'll fit and bolt on that way.