I am searching for a practical factory-made hydraulic cylinder (actuator) that can provide an axial push of 140 kN against the shaft of the rotor of an electric generator and also transmit the 90 kNm torque from the motor to the shaft of the generator (see Fig. 1).

Electric generator rotated by a motor and pushed by a hydraulic cylinder

Fig. 1. Electric generator rotated by a motor and pushed by a hydraulic cylinder.

Explanations: The generator is an experimental submerged electric machine of a special construction supposed to be rotated by an underwater turbine mounted on its shaft, in front of the generator. This turbine rotates at about 60 RPM providing a 90 kNm useful torque. Unfortunately, it also pushes against the generator with 140 kN. For testing purposes, the generator will be rotated first with an electric motor which I found. However, it only simulates the torque of the turbine. The thrust has to be generated with a hydraulic cylinder that I have not found.

Question: Are there hydraulic cylinders (like the one in Fig. 1 or of a different construction) that provide thrust and at the same time transmit rotary motion from a motor to a generator?

Even cylinders that can generate 14 or 7 kN of thrust would be useful for the beginning.

Remark: I have found rotating hydraulic cylinders (pistons), like in Fig. 2, but they can provide push to the motor itself if mounted in front of it. They can also supply thrust to the generator but in this case the shaft between the generator and the hydraulic cylinder needs a cogged wheel on it that has to be rotated by another one on the shaft of the motor. The setup is complicated.

Rotating Cylinder

Fig. 2. Rotating Cylinder.

  • $\begingroup$ The sensible thing to do is duplicate the thrust bearing assembly in the generator and use it to apply the test thrust to the generator. You get double the data that way. A Timken 32022x has a 50k + pounds dynamic load rating at 1800 rpm and costs about $75. So you put a stop collar on the shaft, slide a bearing and carrier over the shaft against the stop collar, and use a hydraulic cylinder to push on the carrier. $\endgroup$
    – Phil Sweet
    Oct 16, 2022 at 3:29
  • $\begingroup$ vevor.com/hydraulic-cylinder-jack-c_10090/… $\endgroup$
    – Phil Sweet
    Oct 16, 2022 at 3:32
  • $\begingroup$ Apparently these exist. Who knew. laser-chuck.com/… $\endgroup$
    – Phil Sweet
    Oct 16, 2022 at 3:41
  • $\begingroup$ @PhilSweet , You suggested a nice and cheap configuration for applying thrust to the rotating shaft of the electric generator just by using a thrust bearing and an ordinary hydraulic cylinder. However (maybe I missed something in your explanation) how do I also rotate the generator with the motor of ((2 * pi * 60) / min) * 90 kN * m = 565.48 kW? $\endgroup$ Oct 16, 2022 at 4:32
  • $\begingroup$ the cylinders are hollow. You need a jackshaft to connect the motor and generator. It will need support bearings. You need a shaft connector at the generator side that is axially rigid and able to support the axial and torque loads. The thrust block goes on the jackshaft. The shaft connector between the motor and jackshaft needs to be axially free, probably a splined connector. You also have to realize that the thrust needs to be supplied continuously for a long time. The hydraulics will cost a couple thousand dollars. The mounting bed for all this will cost $10,000 and weigh a couple tons. $\endgroup$
    – Phil Sweet
    Oct 16, 2022 at 13:34


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