I had tinkered in the year 2006 from a jack and a hydraulic cylinder a manual booster. He is well proven, but if the storage bottles are empty very much pumping work is needed. As i buy a strong 12V wiper motor, I began to experiment and see with some modifications it works fairly well.
The original piston of the hydraulic pump had to be replaced with a smaller piston. The torque was not enough for the original. Unfortunately, I have not made too many pictures, but do never try this, the maschine explodes and all fingers be squeezed or cut off!
A little Video is here font> p>