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Hydraulic drive

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marcuswayne

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I am building a 4 wheel drive hydrostatic driven 4 wheeler. The question that I have is I would like to make sure that equal hydraulic fluid go's to the front hydraulic motor as the rear hydraulic motors. I have 4 hydraulic motors and a hydrostatic drive to power them. It looks like I will need a divider valve to make this work. Do I use a pressure divider valve or a gear divider valve? Also will the hydraulic fluid just pass through the return line. There will be a divider valve on the forward line and the reverse line.
Thanks
Marcus
 
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Delmer

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What are you trying to accomplish??? running the motors in series would do the trick...
 
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lantraxco

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Lots of ways to approach this, none of them particularly good. You could use a four section gear flow divider in the forward pressure line splitting flow out to four motors, it will run either way, but no slippage really to accommodate for turning.

Two section divider/combiner just split the flow front and back, but then you get two wheel drive basically when the other two spin.

Personally I would probably figure the max pump flow, divide that by 4 and put a pressure comp flow control with reverse check inline with each motor line set at about 5% more than that figure. When the flow gets above that the flow control restricts and pressure builds on the remaining motors. Poor man's positrac, YMMV Or a combination of choices off the left side of the menu.

Your motors do have case drains right, as their will be charge pressure on the low side line all the time?

Series would work in a way but the pressure adds in series also, your motors would have to be four times the displacement and able to take up to 100% of the max pressure on the outlet port at times.
 
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marcuswayne

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wheel loaders

lantraxco said:
Lots of ways to approach this, none of them particularly good. You could use a four section gear flow divider in the forward pressure line splitting flow out to four motors, it will run either way, but no slippage really to accommodate for turning.

Two section divider/combiner just split the flow front and back, but then you get two wheel drive basically when the other two spin.

Personally I would probably figure the max pump flow, divide that by 4 and put a pressure comp flow control with reverse check inline with each motor line set at about 5% more than that figure. When the flow gets above that the flow control restricts and pressure builds on the remaining motors. Poor man's positrac, YMMV Or a combination of choices off the left side of the menu.

Your motors do have case drains right, as their will be charge pressure on the low side line all the time?

Series would work in a way but the pressure adds in series also, your motors would have to be four times the displacement and able to take up to 100% of the max pressure on the outlet port at times.
Click to expand...

Having equel pressure between the front wheels and back wheels is what I was looking for. Its ok if one wheel spins on the front and one on the back. The motors do not have case drains on them. This unit originally was a golf corse bunker rake. It was a 3 wheel drive unit that had a hydraulic motor on each wheel. What ever wheel broke ground only that wheel would spin. I am building a new 4 wheel drive articulated machine and would like better traction.
Thank you for the info.
Marcus
 
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lantraxco

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You'll blow the shaft seals out on the motors running hydrostatic without case drains....

You can use a flow divider/combiner to split the flow but there again you'll have high pressure on the outlet in like reverse....
 
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Jim D

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lantraxco, if it is gear rotor motors, no case volume and any leakage leaks to the low side, so case drains aren't necessary. I've seen some golf course equipment that uses gear motors, open-loop, for traction motors. Very crude drive control... not really 'hydrostatic drive'.

For a bunker rake, what he needs is a four section (Northern Hydraulic equivalent) gear pump, four open center bang-bang directional control valves, and four gear motors. (Operate the valves in unison, or not... operating three motors skids the machine around the dead wheel. When Case sold Unimogs, they had steering brakes on the front wheels, to skid the rear wheels and turn the machine around the implement on the front of the machine.)
 
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Welder Dave

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I'm guessing it's a Toro Sand Pro with Ross wheel motors. Knew the mechanic that inspired Toro to add a faster transport speed to them. The first Sand Pro's were 3 wheel drive but had a very slow transport speed. He took a course and studied a bunch of hyd. circuits and came up with a way to disconnect the front wheel giving more flow to the rear wheels for a faster transport speed. Toro was impressed and later machines had a faster transport speed. Golf course machines have always been kind of pioneering with hyd. drives getting away from mostly complicated belt and chain drives.
 
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lantraxco

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Open loop is fine, if it's a hydrostat the charge pressure and reversals will almost certainly blow the shaft seals, the pressure has nowhere to go. Typical shaft seal is only good for about 35 psi
 
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Scrub Puller

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Yair . . .

lantraxco and others who may be interested.

As mentioned up thread by Jim D Jacobsen have been using Gerotor traction motors and gearmotor cutting cylinder drives (no case drains) for the best part of fifty years.

They also use a simple four section gear pump and miscellaneous control systems to give two speed and reverse plus lift and lower of the cutting units, a backlap function and, on later units power steering. According to a couple of hydraulic folks I've spoken too it shouldn't really work . . . and it all functions with no oil cooler.

I could not believe the complexity and extra plumbing on the John Deere that replaced it and is no where near as controllable and user friendly.

This mower design has been essentially unchanged since the 'sixties and is still available with cable steering.

Cheers.
 
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Delmer

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Is this going to be a four wheel drive articulated bunker rake? or some other purpose?

Basic redneck engineering, if you don't change the function, you don't have to change the parts. If we're trying to make a golf course machine into a logging machine, we need to think about this a little more.
 
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Jim D

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lantraxco said:
Open loop is fine, if it's a hydrostat the charge pressure and reversals will almost certainly blow the shaft seals, the pressure has nowhere to go. Typical shaft seal is only good for about 35 psi
Click to expand...

The shaft seal *can* be good for much more pressure; I've seen a couple of bent-shaft axial motors where the cases were blown apart, by case pressure, when they were plumbed incorrectly. The shaft seals held to a lot more pressure than 35 psi... it probably takes hundreds, or even a thousand, of psi to blow apart the steel motor cases. ;^)
 
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mikebramel

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You'll get about 1000-1500 hours running with no drain line for the shaft depending on the charge pressure maybe more maybe less.

As for piston motor cases pressurized. What do you think the surface area of the seal is compared to the end cap?
 
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Jim D

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yes. I have a straight axial piston motor that runs the case at charge pressure and vents the case to the low pressure side of the circuit, Eaton Series 1 fixed displacement, I've never had one apart to see what the shaft seals are... No flush valve either, it really shouldn't work.

The motors I mentioned that I saw that failed, the cases split longitudinally, from the 'hoop' stress.
 
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Welder Dave

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Scrub Puller said:
Yair . . .

lantraxco and others who may be interested.

As mentioned up thread by Jim D Jacobsen have been using Gerotor traction motors and gearmotor cutting cylinder drives (no case drains) for the best part of fifty years.

They also use a simple four section gear pump and miscellaneous control systems to give two speed and reverse plus lift and lower of the cutting units, a backlap function and, on later units power steering. According to a couple of hydraulic folks I've spoken too it shouldn't really work . . . and it all functions with no oil cooler.

I could not believe the complexity and extra plumbing on the John Deere that replaced it and is no where near as controllable and user friendly.

This mower design has been essentially unchanged since the 'sixties and is still available with cable steering.

Cheers.
Click to expand...

You're thinking about a Greens mower not a sand trap rake. The Jacobsen Greensking came out in 1968. It was kind of crude but paved the way for better machines. The Greensking II used a 4 section Webster pump and the basic design I think is still used but much improved with hydrostatic drive. Toro came out with the hydraulic drive Sand Pro in the 70's. My dad sold turf equipment from the mid/late 50's till the late 90's. Started with Toro then Jake from about 63-83 and then back to Toro. In that time he sold a lot of revolutionary machines. A lot of golf courses are going back to walk behind greens mowers for finer stripes. Odd thing is a ride on has less ground pressure than the person walking on the green behind the mower.
 
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