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Thread: Hydraulic balancing control for two cylinders

  1. #1
    Associate Engineer
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    Hydraulic balancing control for two cylinders

    Hello all, first time poster here. I am a EE nerd and fulltime farmer. I think there is a valve that will do what I need but I do not know what they are called and hoped someone can help me source them. It is on a "V" style hay rake that has two hydraulic cylinders that have a common fluid power source from the tractor. It is a simple supply/return circuit with the supply hoses splitting to each cylinder. I have three rakes that all have the same problem. The load/weight that the cylinders control (raising & lowering of the wheels) is the same on each side of the machine but the forces applied due to terrain will cause one side to come up without the other side raising equally or at all sometimes. In other words the two loads do not raise equally unless you are on level terrain. Is there a valve that will control the pressure/flow to two cylinders when the load is varying from cylinder to cylinder so that they will move the same?

  2. #2
    Technical Fellow jboggs's Avatar
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    You are looking for a flow divider. There are two types that I know of: proportional and gear or rotary. My experience with the proportional types has not been good. (They were probably mis-applied.) The gear type has saved our manufacturing plant many thousands of dollars in repairs over the last few years. They synchronize the motion of two or more cylinders so that they both (or all) move exactly the same amount. Neither moves without the other moving simultaneously, regardless of loading. I'm talking about an industrial heavy duty application. Our unit costs $835 each. The mobile hydraulics world seems to be an industry unto itself and I'm not very familiar with it, but I would think a similar device might be available for a mobile application. Anyway - flow divider, that's what you're looking for.

  3. #3
    Associate Engineer
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    Thanks for replying. Here is a link from Northern Tool. Does this sound like what I need?

    flow-divider.png

  4. #4
    Technical Fellow jboggs's Avatar
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    Well you're in the right neighborhood, but wrong address I think. The ONLY review on that item is not pretty. The product itself might be fine but there are no guiding instructions etc to help a newbie figure it out. I would avoid it if I were you.
    As I said there are two types. One operates by sensing internal flows and pressures and balancing an internal spool to affect the flow one way or the other. I'm sure they work well in the right application for people that know how to adjust them, especially if the two desired flows are not equal. But I'm a simple guy and the gear type is simple. An internal shaft with two gears on it absolutely controls the flows in two separate ports and forces them to be equal, regardless of direction of flow, flow rate, pressure, etc.

    Grainger has some gear type flow dividers (https://www.grainger.com/category/hy...veElement=true) and there are other low cost sources too. Just read up what you can before you purchase and try to get a good understanding how the device works, what fittings you will need, where and how to mount it, etc. As far the plumbing, that's simple: you just replace one of the two existing tees with this device.
    my only successful experience is with gear type dividers

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