Editing Dynamometer (section)

===Force lubricated oil shear brake===
An oil shear brake has a series of friction discs and steel plates similar to the clutches in an automobile automatic transmission. The shaft carrying the friction discs is attached to the load through a coupling. A piston pushes the stack of friction discs and steel plates together creating shear in the oil between the discs and plates applying a torque. Torque can be controlled pneumatically or hydraulically. Force lubrication maintains a film of oil between the surfaces to eliminate wear. Reaction is smooth down to zero RPM without stick-slip. Loads up to hundreds of thermal horsepower can be absorbed through the required force lubrication and cooling unit.  Most often, the brake is kinetically grounded through a torque arm anchored by a strain gauge which produces a current under load fed to the dynamometer control. Proportional or servo control valves are generally used to allow the dynamometer control to apply pressure to provide the program torque load with feedback from the strain gauge closing the loop. As torque requirements go up there are speed limitations.<ref name=shear>{{cite web |url=http://www.ien.com/article/slashing-test-time/187285 |title=Slashing Test Time with Oil Shear Brake |work=Industrial Equipment News |access-date=22 July 2015 |archive-url=https://web.archive.org/web/20150924032918/http://www.ien.com/article/slashing-test-time/187285 |archive-date=24 September 2015 |url-status=dead }}</ref>