[Vanisle]

I dont know anything about making a Bruder screwdrive model but I did briefly have a working Hanomag loader that used screwdrives. In regards to speed, the threaded rods (that drove the lift arms, bucket and to turn) were nice and fast. If I recall correctly, they were 10-32 thread and took approx one second to move one inch. If I understand the math correctly, that equates to approx 480 RPM ((60 seconds for RPM/4 seconds to move one inch) x 32TPI = 480 rpm). Of course, it used 380 sized motors so perhaps would not be practical for a hydraulic cylinder. A metric equivalent would be M5 threaded rod which is approx 31.75 TPI (25.4 mm/inch / .8 thread pitch = 31.75).