Near Intersection of I-35 & I-90 Southern Mn. | co2shaun - 1/28/2025 18:40
Not sure on getting a rawson repaired anymore. I don't think I would have real high hopes of trying to repurpose that module either. The way I understand a rawson motor is that it has an electric motor and a hydraulic motor. The electric motor sets the speed and the hydraulic motor provides the torque. The electric portion can't be very high amperage with that size of wires. Even if you were able to get it to run a small electric motor it would be too small to be useful and would most likely trigger a much of other errors.
I messed with the Rawson drives many years ago as a Tech. Your description agrees with my thinking as to how they work. I believe the electronics runs what I think of as a "pace motor that turns the speed that the seed shaft should turn. The speed is calculated based on the desired population for the current ground speed, row width, gearing etc. There is no seed shaft speed sensor as such. The pace motor does not directly turn the seed shaft but only sets the pace that the seed shaft should turn given the current inputs.
By use of some clever mechanical linkage, the hydraulic valve inside the drive adjusts the hydraulic flow in an attempt to get the seed shaft to turn at the pace set by the pace motor. So for example if the operator should increase the target population, the pace motor would turn a bit faster, the linkage would increase the oil flow slightly until the seed shaft speed again matched the pac motor speed.
Since the Pace Motor is not directly carrying the load of turning the seed shaft, it does not need to be a heavy duty motor and light duty wires are sufficient to handle the very small load.
I agree with the above reply in that trying to repurpose the pace motor or pace motor circuitry for another task might be possible but probably isn't worth the effort. Modern Microcontrollers that are unbelievably cheap are able to handle such tasks quite easily with the proper programming.
Edited by tedbear 1/29/2025 09:39
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