Hi Shaft A has variable RPM, getting input from some rotating element (say X), ranging from 0 to 2000. The RPM of X cannot be adjusted or controlled. A has to transfer the rotation with limiting RPM of upto 400 to Shaft B. Is there a way to limit the RPM using a mechanism such that at particular RPM, Shaft B have constant RPM irrespective of Shaft A RPM. Example: Shaft A RPM= 350 Shaft B RPM= 350 Shaft A RPM= 400 Shaft B RPM= 400 Shaft A RPM= 1200 Shaft B RPM= 400 Shaft A RPM= 2000 Shaft B RPM=400 Also I would like to mention that due to space constraint a bulky system/mechanism cannot be accommodated. Thus I want a small system of nearly or less then 6 inches(LBH) size.