buickanddeere
Super Member
JJ if a pair of 1500psi motors are placed in series in a 3000psi system. The first motor in particular will fail when it hits 3000psi as it stalls against something .
Help with PTO pump selection
- Thread starter dgarrett
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J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
I would think you would have a crossover relief on each motor set at 1450 psi to protect the motor which has a continuous pressure of 1500 psi.
Excerpt:
Series circuit.
Connecting two fluid motors in series minimizes pump size and eliminates the need for a flow divider. Line sizes are also smaller than in a comparable parallel circuit, and piping is usually simpler, with only one pressure line and one return line required. Maximum torque at each motor is adjustable with the relief valves. The speed of motor A is controlled by the bleed-off flow control valve. Direction of motor B is controlled by the 4-way valve, which has an integral 2-way valve, which vents the relief valve when the motor is stopped. Total system pressure is then available at motor A.
Parallel connection (right)
Pump pressure can be lower in a parallel circuit because in a series circuit the pressure at the pump must be the sum of the pressure drops across the motors. However, where motor pressures vary widely, there is a loss of efficiency in supplying the motors requiring lower pressures. This circuit is most efficient where the load on each motor is the same. Raising the pressure on one motor renders the others less efficient and may disrupt the speed relationship. In parallel circuits, the only way to increase torque of the highest-pressure motor is to increase system pressure.
On our Power-Tacs, we use a series parallel combination to drive the wheel motors.
Excerpt:
Series circuit.
Connecting two fluid motors in series minimizes pump size and eliminates the need for a flow divider. Line sizes are also smaller than in a comparable parallel circuit, and piping is usually simpler, with only one pressure line and one return line required. Maximum torque at each motor is adjustable with the relief valves. The speed of motor A is controlled by the bleed-off flow control valve. Direction of motor B is controlled by the 4-way valve, which has an integral 2-way valve, which vents the relief valve when the motor is stopped. Total system pressure is then available at motor A.
Parallel connection (right)
Pump pressure can be lower in a parallel circuit because in a series circuit the pressure at the pump must be the sum of the pressure drops across the motors. However, where motor pressures vary widely, there is a loss of efficiency in supplying the motors requiring lower pressures. This circuit is most efficient where the load on each motor is the same. Raising the pressure on one motor renders the others less efficient and may disrupt the speed relationship. In parallel circuits, the only way to increase torque of the highest-pressure motor is to increase system pressure.
On our Power-Tacs, we use a series parallel combination to drive the wheel motors.
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Would the tractor motor stall if it was only commanded to output half it's HP? The pump spec says you need close to the max PTO HP to support the psi of the hyd motor. The reason I ask is you mentioned the hyd device will always operate at it's designed psi.
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
That is not what I said.
A hyd cyl or motor will develop the pressure based on the load.
For instance, a hyd motor with light load might develop only 1200 psi, and under full load might be around 2500 psi.
You can half the HP by using half GPM's or limiting the pressure to half.
If you reduce both pressure and GPM by half you reduce the HP to 1/4
A hyd cyl or motor will develop the pressure based on the load.
For instance, a hyd motor with light load might develop only 1200 psi, and under full load might be around 2500 psi.
You can half the HP by using half GPM's or limiting the pressure to half.
If you reduce both pressure and GPM by half you reduce the HP to 1/4
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