Determining motor/pump size

[dodge85rc]

Here is the overall design of the machine.

The drive on the machine is hydrostatic. There are two complete cub cadet hydro units connected via driveshaft to the engine. Because of the weight I will probably end up running duals on all 4 tires. I suspect this will be about 1000 lbs when completed. Steering is also hydraulic, this is an articulating tractor so it steers in the center of the machine. No FEL, but there is a implement lift on the front for a snow plow and to hook the mower deck to, and will be a 3 point on the rear with an additional hydraulic remote front and rear. This machine is defintily a hodge podge of parts, using what I had or could aquire for next to nothing. I have parts from cub cadet, john deere, international, massey ferguson, toro, dodge, subaru and probably a couple more I forgot already. It isn't going to be pretty when its done, but that is not what I am going for. I know there are already several things that I wish I would have done differently, but finaces don't allow spending a lot so I do the best with what I have. If finances weren't an issue I wouldn't be building this and would have just bought a small kubota or something.

 

[J_J]

dodge85rc ,

Many years ago, I did the same thing, gathering all the parts to build a hyd driven unit with features of a tractor and skidsteer. As time progressed and with money already spent, I came upon a lightly used Power-Trac, that was too good a deal not to turn down, which would do all that I was trying to build, except for the tracks. So, I bit the bullet and purchased the PT with 8 implement, for $6000, and if purchased to day would cost me about $35,000. This saved me a lot of time and money, and trying to figure out all the mechanics of everything working together.

I applaud your efforts, and wish you success in the coming year.

 

[dodge85rc]

Well I picked up some components for the hydraulic system for this tractor. So time for some more questions. The steering valve I have is only a 4 port unit. So no power beyond. Am I correct then in my understanding that I won't be able to run anything off of the return port before it returns to the tank? And also am I correct that you can T into the return line but not the pressure lines? With hydraulic valves, when the valve is operated is all fluid diverted to the "output" of the valve or does the excess continue on through the valve and to the "return"? Or are all valves different?

 

[J_J]

With a steering valve, you would not want to tee in to the pressure line, because the steering must have priority. When steering is light, the fluid used by the cyl, and the supply fluid flows out the return port. I have the 6 port steering valve, and another three lever valve downstream. When not steering, all the fluid goes to the second valve for lift and tilt on the FEL.

So on your steering valve, I believe you could add another valve downstream, and use it if the steering valve is not using the fluid, maybe half and half. You are not steering or lifting all the time, so the fluid is used accordingly, with the steering taking priority.

With OC valves, and no PB, all fluid goes through the return port. With PB, if the valve is feathered a little, the fluid used by the cyl is passed through the return port, and the rest of the fluid is sent downstream for the next valve, and so on. If the lever is pushed to max, all the fluid is used by the cyl and is sent out through the return port.

You might check with the manufacturer of your steering valve and see if the IN port and Out port has same pressure rating.