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roma3112

Putting Additional hydraulic circuit on a Sunstar

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roma3112
I was wondering if any of you folks have ever attempted to add another circuit to a sunstar hydrolic system. I was thinking about using this additional circuit to power a dump piston for a jbjr and a power angle for a dozer blade I want to put on this machine in the summer. I was thinking i could tee off at the supply lines for the existing valve for the source for the fluid. I was looking online for the various control valves ect. I think it is feasable cost effective is another thing. I guess i was looking for any cautions, suggestions that you guys may have.??:D

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HubbardRA
John, One of the major problems, that you would incur with the setup that you are considering, is a lack of oil reserve in the hydrostatic transmission. First of all, if all the cylinders were in a position at maximum stroke, the fluid level would likely be drawn extremely low. Second of all, even though there may be sufficient fluid remaining in the reservoir to fill the cylinders, there also needs to be excess capacity to allow for foam dissipation. The oil will foam to a certain extent as it moves through the transmission and in and out of the cylinders. If foam is drawn directly into the pump, it will cause cavitation and eventually destroy the pump. Most hydraulic systems that are designed to power front end loaders and other hydraulicly powered equipment have a significantly oversized reservoir of fluid, for foam dissipation, and to provide for a means of cooling the fluid. If you have noticed on automobiles with power steering, that when the fluid gets low in the reservoir there is a squeeling sound that comes from under the hood when the wheels are turned. This is because foam is being drawn into the pump which causes a high frequency oscillation within the pump (hence the sound). If a person continues to drive a car with this happening, he will soon have to replace that power steering pump. The hydrolift can be added directly to a Sunstrand tranny because of the small size of the cylinder and the fact that is is usually not in constant motion. Each additional cylinder that you add requires more reserve volume. The additional volume required is the diameter of the rod in the cylinder times the length of stroke, for each additional cylinder. The only other unit that is added at the factory is the power steering cylinder (as was shown in a recent post by MDB), these cylinders have a relatively small rod and do not produce significant volume variations. This also indicates that the factory engineers have computed the necessary volume of fluid and it is sufficient to work with these two additional cylinders. I would be very concerned that the Sunstrand transmission will not likely contain enough reserve volume to support the two additional cylinders that you propose. This would be especially true if all the cylinders are at their fully extended positions at the same time. That is when maximum volume is needed. Remember that if my suspicions are correct about insufficient fluid reserve volume, the part that will be damaged is the charge pump on the Sunstrand transmission. I hope this explanation was at least halfway understandable.

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roma3112
Rodney Thanks for the detailed explanation! The last think I would want to do is fry the hydro pump [B). The only reason I thought that the question was resonable (albeit a difficult project) was that reading through the manuals for the sunstar i seem to recall an additional hydrolic circuit for the front of the machine. The control mechanism of which was mounted side by side with the lever for the standard hydro lift. I will try to locate that info, I bet that that option has some kind of additional capacity and that the factory option is just more than another valve and some hose. Thank you for taking the time to write such a detailed post.

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MikeES
I have seen a SunStar (DA 1920H) with the factory aux. hydraulic kit. It was used to power the angle on the sweepster brush. There is also an aux. hydraulic kit for the Legacys (#1693274), maybe it will work on the Sun Star.

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ambler
The Sunstar was designed for an auxilary circuit. Thats what the front hydraulics are. Get the sunatar attachment parts manual. Its expensive though. My 1920 has it and it runs my power tilt blade. There are two levers side by sidewith the lift. From what I have seen control valve is the same with the lift, then its tees and lines.

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D-17_Dave
I have not seen the hydraulic schematics for the aux circut on the Sunstars so I'm somewhat ignorant on the details, but, the front extra's must be either a tee in the lines to an existing remote or there is a provision for adding a secound valve. To have accurate flow and pressure on any additional valve on any hyd. circut you must have whats called "power beyond" on the first valve. If you were to just TEE into the supply line to the exsisting valve and pull a lever the flow would simply go to the other valve since it would be unrestricted. I won't go much deeper now, but it can be done with the proper components.

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HubbardRA
What I said earlier was geared to the Sunstrands in the large frame tractors, but should also apply to the Sunstar, with the exception that the hydro on the Sunstar may have been built with a larger fluid reserve to accomodate the dual hydraulic circuits.

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