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Replacement hydraulic cylinders

Discussion in 'Western Plows Discussion' started by mini_blaine, Feb 3, 2014.

  1. mini_blaine

    mini_blaine Junior Member
    Messages: 15


    Was wondering where everyone gets their replacement cylinders?

    Either oem or aftermarket.

    Looking for the angle cylinders for a Mvp plus 9'6"

    The sticker on it says it's a 1 3/4"x11"da.

    Does it need to be that size as I have seen some 2x11 and 2x10?

  2. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    I wouldn't recommend substituting anything but OEM on an MVP because they use what they call "regenerative" hydraulics on them. That means that fluid from on ram is displaced directly into the other to make the blade move faster than filling them with fresh oil from the pump every time. If the ram displacement doesn't match it could cause problems. I know guys who use aftermarket but they are still the same specs as original, just not as much money, and theoretically not as high quality. sometimes I wonder...
  3. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    You can't possibly be thinking that oem hydraulic cylinders are any different than any aftermarket units, can you? I can assure you, that plow manufacturers don't use particularly high quality parts. Frankly, plow hydraulics don't really need to be able to take the kind of pressure that other hydraulic equipment does.

    The key isn't so much that you don't replace them with something different, its that you make sure that the two sides *match*. I.e., if you want to put something slightly different on one side, do the same for the other side.

    You also don't want to be changing the length of the cylinders. A cylinder with a longer stroke will have a longer minimum length, so at full angle, the cylinder may stop before the plow actually hits its angle stop. You don't want this because it will move the stress from the angle stop onto the hydraulic cylinder AND it will limit the angle you can achieve.

    A cylinder with a larger diameter will move more slowly, and has the potential to overstress components. A cylinder with a smaller diameter will move fast, but be weak. Adding stress will increase the pressure in the lines, and it will be mode difficult to keep it angled.

    My suggestion is to make sure that the replacement cylinders match *as closely as possible* all of the measurements of the originals.

    This is all, of course, REGARDLESS of the specific plow. Applies to all.
  4. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    You are correct that plows are not "precision" hydraulics and you can get away with a lot on a basic plow. It's the MVP + that concerns me with the regenerative hydraulics that is sensitive because fluid from one ram is passed into the other to make them move fast. The displacement could be an issue. In my experience I have found that saving a buck buying aftermarket parts costs money down the road. All too often after people have tried substituting things they destroy something and then they learn why what they did caused it. The engineers at Western go to school a long time to design these new systems. I only sub in parts when the original is causing the problem. When I am getting paid to do a repair I always use original parts unless the owner provides me with the pieces they want me to use. And in that case they need to understand that if it fails or causes other problems it is their loss, not my problem.... The choice is yours.
    To answer you question, NO I don't think a ram designed and built in China for a specific application on a specific plow is any different in specs than some of the junk make in North America. My point is that you shouldn't jerry rig a bailer part for a plow ram just because you can make it fit. Put a lift cylinder where a lift cylinder belongs and put an angle cylinder where an angle cylinder belongs. Made in China or Iowa, who cares, same junk both places.
  5. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    The "regenerative" part is not a function of the cylinders (they're plain old hydraulic cylinders), rather it is of the pump itself. So really nothing to worry about.

    Here's an animation;

    Actually, I think its easier to understand when explained in words;
    On a dual acting cylinder (i.e., one that pressurizes in both directions), there is a higher fluid volume in the cylinder when it is fully extended than when it is fully compressed. The volume difference is equal to the volume of the ROD that extended out.

    When you are extending the cylinder, if you tee together the supply with BOTH the inlet and outlet of the hydraulic cylinder, then to extend it fully, you only need to input the amount of fluid equal to the volume of the rod. If you only supply the pressure to the inlet and release the outlet into the reservoir, then you need to fill the entire volume of the cylinder.

    So 10 inch stroke 2 inch piston diameter, 1.5 inch rod diameter.
    Normal volume to extend the cylinder is 10x(2/1^2)x3.14 = 31.4 cubic inches.
    Regenerative volume to extend the cylinder is 10x(1.5/2^2)x3.14 = 17.66 cubic inches.
    Because it takes half the volume, it moves twice as fast.

    Note that the force on the piston is proportional to the surface area exposed to the fluid. The surface area of one side of the piston is greater than the other by the cross sectional area of the rod, this means that with equal pressure applied to both, one side will win over the other. The fluid being pushed out of the outlet will be added to the volume being pushed out of the pump, and into the inlet.
    Last edited: Feb 5, 2014
  6. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    In Western's MVP+ the regenerative hydraulics (in one application) applies fluid to and fills only the base end of one angle ram. That forces the fluid out of the piston end, then the valves redirect the fluid coming out of that into the piston end of the second angle ram, not the base of the same cylinder as your example does. Finally the fluid from the base end of the second ram is allowed back to the reservoir by the valves. This requires the pump to fill only one ram base end to achieve simulated "straight blade" action. In other words one cavity is filled and four cavities are effected. It is not even close to a function of the pump, the pump has nothing to do with regenerative hydraulics other than to provide fluid flow and pressure.
    To answer the original question (which we have gone far away from) Changing the displacement, stroke or anything else can have an effect on the performance of the plow and or cause damage. Extending beyond the designed travel of the device it is pushing, applying too much force to what it pushes or applying too much fluid force to the relief valves that protect the unit are just a few of the problems putting the wrong size ram on a plow could cause. Aftermarket rams that are the same size as the originals are fine.
    As for OEM Vs aftermarket... They are, after all, virtual copies of the original be they a copyright infringement or not. An angle ram for a Western plow made in China is no different in it's operational dimensions than an angle ram made for the same application in North America, expect perhaps the quality, and I won't say which is better because that is debatable these days after seeing some of the junk that comes of our production lines....
    Last edited: Feb 5, 2014