The Honda tractor I want to add hydraulic cyliders to has two single acting cylinders. The manual says to not keep the valve handle in the raised position after the implement is at position. This is because the pump can be damaged. The handle has a spring return so letting go unloads the pump. My first thought was to just put a power steering pump on the front PTO to power my added cylinders. Looking at the pump in the tractor today I see that it is a gear pump. Since these are positrive displacement pumps there must be some sort of bypass that keeps things from breaking when the cylinder reaches end of travel. This, I think, is why keeping the pump pressuring a cylinder can cause damage. The bypass just bypasses internally and things can get hot fast. But when the pump is filling a cylider the oil is not bypassing and heating up. I think that if the pump was pumping into the reservoir it could do so for long periods of time without the oil getting too hot. Looking at the way the cylinders are actuated, where the valve is located, makes me think that this is what is happening. The pump is spinning all the time as near as I can tell and it is just recirculating the hydraulic oil. This makes me think that if I plumb the front cylinder oil port from the tractor's hydraulic valve into an open center valve I can use it to power my added hydraulic cylinders. I would need to somehow lock the tractor's valve handle in the on position and then use my added valve to control the added cylinders. Does this make sense? BTW, reading online about hydraulic valves I ran into some definition problems. Open center valves were described, in several references, as valves that when centered would have all the ports on the valve connected together and open to the reservoir return line. This means that this type of valve would not hold a cylinder in position when centered. Then, reading further I see that the kind of valve that holds the cylinder in place is called a Tandem Center valve. I think. But that they are commonly called Open Center valves in catalogs when the valve is manually controlled by a lever of some sort, instead of by a solenoid or similar. And typically used on mobile equipment. Is this correct? I can just order an open center valve with levers and expect it to hold the cylinders in place while at the same time returning oil from the pump to the reservoir? Thank for reading, Eric
- posted
5 years ago