Hydraulics/wheel motor question

[curtjeep]

Theoritically speaking, I'm not saying that I am planning to attempt to build an articulating tractor with a 3 pt and FEL... could a single pump run 4 wheel motors, a 3 point hitch and a FEL? If I were to do this I would have a 26 hp gas engine and would probably intend on a 23in tire. With potentially these wheel motors? Not exactly sure yet. https://m.northerntool.com/products...ors + Mounting Brackets&utm_source=Google_PLA

Honestly, hydraulics are somewhat black magic for me. I know the pump provides pressure... the flow rate is the deciding factor as to what can be powered, correct? Just trying to get more information and google is not giving me the answers I need.

 

[oldnslo]

Simple answer is yes with a bunch of valving and you probably would not be happy with how it operated.

You would need a priority flow control to provide flow for steering & breaks if required. This flow would then return to tank.

Balance of flow could be used for drive, FEL, 3 pt. Here again you might need some flow controls so that you can drive and use the FEL at the same time.

I would suggest looking at a double pump or spending some more money and using a true hydrostatic drive like Ventrac does for travel and and an auxiliary pump for the other functions.

 

[curtjeep]

Ok, I had an idea of using 2 k66's out of the husky garden tractors and then a separate pump for 3 pt. And FEL. And steering.

 

[texasranger556]

Agree with oldnslo. I can't think of any commercially built machines that run a single pump for traction and auxiliary flow. It could be done, but with many drawbacks. At minimum you'd want a dedicated pump for traction, and another for other things. You'll find most hydrostatic tractors run 3 or more pumps. A piston pump and motor for forward motion, and 2 gear pumps for steering and auxiliary hydraulics (loader, 3 point hitch, etc). For example my 4400 Deere has a dedicated gear pump for the steering and charging the hydrostatic pump. The third pump runs the loader and three point hitch (or backhoe).

 

[MossRoad]

Theoritically speaking, I'm not saying that I am planning to attempt to build an articulating tractor with a 3 pt and FEL... could a single pump run 4 wheel motors, a 3 point hitch and a FEL? If I were to do this I would have a 26 hp gas engine and would probably intend on a 23in tire. With potentially these wheel motors? Not exactly sure yet. https://m.northerntool.com/products...ors + Mounting Brackets&utm_source=Google_PLA

Honestly, hydraulics are somewhat black magic for me. I know the pump provides pressure... the flow rate is the deciding factor as to what can be powered, correct? Just trying to get more information and google is not giving me the answers I need.

Simple answer.... check out a Power Trac in the Power Trac forum here on TBN.

I have similar the machine you are considered building.

It's articulated.
It has a 25hp gas engine.
It has three pumps.
1st pump is a variable volume pump. That is used for moving the machine by means of 4 wheel motors. One at each wheel. They are connected in a series parallel configuration.

2nd pump is for the steering/FEL and aux function, such as a grapple claw, power angle of a snow blade, and the quick attach cylinder that allows me to change implements in 15 seconds without getting off the machine (about 30 seconds if its a powered implement, like a mower, because I have to get off and connect the hydraulic mower motor).

3rd pump is a higher output section than the 2nd pump, that provides flow to the mower motor, tillers, trenchers, brush cutters, stump grinders, etc...

Besides articulating between the front and rear sections, the machine also oscillates between the front and rear section. This will be your biggest engineering challenge. The oscillation goes up to 12 degrees on mine. It has to oscillate for a couple reasons. One being it prevents 3 wheeling. All 4 wheels stay on the ground more often. This helps with traction. More importantly, it relieves stress from the center pivot joint and the areas on each side of the joint at the front and rear sections.

Anyhow, go to Power Trac and check them out.

Then go to the Power Trac forum here on TBN.
http://www.tractorbynet.com/forums/power-trac/

 

[MossRoad]

As to the FEL/steering pump/circuit, the pump goes to the steering valve first. The steering valve has a power beyond port that feeds a 3 spool valve.

Spool 1 goes to FEL up/down.
Spool 2 goes to FEL curl/dump.
Spools 1 and 2 are connected to a 2-axis joystick to control the 4 FEL functions (up/down/dump/curl).
Spool 3 is an auxiliary circuit to control the quick attach cylinder. The hoses for that can be disconnected and connected to an implement cylinder to provide implement cylinder functions like the power angle snow plow, grapple, 4-in-1 bucket, etc... anything that needs a cylinder to operate. Not a motor.

 

[MossRoad]

This setup allows for steering priority over the FEL functions. If you lock the steering wheel to one side or the other, it can affect FEL operation. Just release the steering wheel a small fraction from lock and FEL functions return to normal.

 

[MossRoad]

The drive section is more complicated.

On an articulated machine, you don't want the wheel motors on the same side to be in series.

Think of it this way.... if you are on an articulated machine, sitting still, not moving forward or backward, and you crank the steering wheel to the left, the left tires will roll TOWARD each other as the right tires will roll AWAY from each other. And vice versa if you turn right. If the motors on the same side were in series together, they could not roll towards or away from each other.

And think of this... as you turn left, the front left wheel rolls backwards and the rear left rolls forward, while the right front rolls forward and the right rear rolls backwards.

And if you think about it some more, as you turn left, the left front rolls backwards and the right rear rolls backwards, while the left rear rolls forward and the right front rolls forward. This is the one that makes you realize the left front and right rear are always rotating in the same direction, while the left rear and right front are rotating in the opposite direction.

So, you put the left front wheel motor in series with the right rear wheel motor, and you put the right front wheel motor in series with the left rear wheel motor. That keeps them happy. Call them drive circuit 1 and drive circuit 2.

Then you put drive circuit 1 in parallel with drive circuit 2 by connection the forward ports with a T and the backwards ports with a T off of the forward and backward ports on the variable volume drive pump.

And there you have it.

 

[MossRoad]

As to why in heavens you would ever want a 3pt hitch.... that's another story. Unless you are going to be doing ground engaging tasks like plowing a field or stump pulling, you'll rarely require a 3pt hitch on a machine like this.

All implements are up front, mounted on the FEL arms. Loader buckets, pallet forks, mowers, brush cutters, snow plows, stump grinders, earth augers (3pt hitch doesn't have power down, as the FEL on these does), trenchers, etc....

A traditional tractor has much better pulling power than one of these. If that's your gig, than that's what you should be looking at.

One note about this setup, though, is that you have only one range of gearing. There is no hi/lo or hi/medium/lo as on a traditional tractor. So, when you plan it out, you have to make some compromises.

You can make a tug boat with huge wheel motors that will have tons of power, but no ground speed. Or you can make a speed boat with tons of speed and no low end grunt. Or you can make a happy medium that can accomplish most of your tasks well.

Mine has a top speed of 8 mph. I can move around my property at a pretty good clip. I mow about 4-5 MPH. And I have no problems dragging logs out of the woods, plowing snow, FEL work, etc... If I installed larger wheel motors, it would cut down the top speed, but would improve low-end pulling power, say, for something like ripping earth. I don't need that task.

Anyhow, go over to the Power Trac forum and read, read, read.

And welcome to TBN, by the way! :thumbsup:

 

[curtjeep]

Actually MossRoad. I joined this forum because I ran into your website about your power trac. I then researched power tracs as a potential to own, but I am thinking I may want a new (extremely large and difficult) project. After looking into them I decides I wanted to build my own power trac like tractor that is smaller... The 3 point may or may not come to fruition. I will be building a FEL on it. Thanks for the information guys. I think I will start with building the basic articulating tractor once I iron out all the kinks, then move to the FEL. I don't think I will need a pto.