# Weird Agricultural Conversion



## major (Apr 4, 2008)

Hi Blair,

Interesting project. First thing that comes to mind is why not use the pump motor? That is what it is designed for. Do you have the pump for it? Pump motors for forklifts often have similar power output to the traction motor, but rated on intermittent duty cycle.

The motor controller is needed for two primary reasons. One is to control the speed of the motor. Without the controller, the motor will run at a fixed RPM. This will vary with load, but you'll have no way to vary the RPM as desired. Second, the controller will limit current (amps). This is important on start up. Without a current limiting controller, the motor is likely to draw over 1000 amps when you first start it. This will last for a short time as the motor speeds up and current goes down. But the initial inrush is hard on the contactor (switch) and also produces large torque (or pressure in the pump) which can stress mechanical components.

Another thing that comes to mind is why use the variable displacement pump? If you use the pump motor and fixed displacement pump from the forklift, you can vary the flow by using a motor controller and varying the speed of the pump.

You might want to take a look at other equipment which use an electrohydraulic propulsion and auxiliary system and see how they do it. Like scissor lifts.

Regards,

major


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## sbgff (Nov 14, 2008)

The reason to keep the vaiable piston pump is simplicity. The cart design is very simplistic and works very well, to change this would mean completely redesigning the whole cart and setup.
The varible piston pump has a charge pump. The piston pump, pumps 12 gpm at 3000 psi @ 3600 rpm. This pump is what drives two wheel motors to drive the cart forward and reverse. The charge pump is bolted to the end of the piston pump, it feeds the piston pump with 100 psi to charge the pump, the remainder of this pump oil is used to drive a hyd. motor to drive the feed pump. Because the wheel motors require such high psi and gpm the forklift hyd. pump wouldn't be able to do the job. The piston pump has a rocker plate inside to allow a 0 gpm pumping and as you move it forward or backward it pumps from 0 gpm up to 12 gpm depending on rpm of pump and amount you move rocker plate.
So all I really need to do is couple an electric motor to pump instead of gas engine, and to be able to control rpm speed. I need to find a controler other than the forklift controler because if this works well i have 5 more to do so I would like to find a simple and inexpensive setup if possible.


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## major (Apr 4, 2008)

Hi Blair,

Please contact me off list, by PM (personal message), if you would. I might have a different approach.

Thanks,

major


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