About this detail of the Tiger
The original engine of the Tiger E, the HL 210 P45, had a drive shaft to power external cooling fans, but as far as I am aware it had no provision to declutch these fans. Later, the HL 210 P30 version was developed for the Panther. It addressed this problem by incorporating a gearbox with a clutch.
The Tiger E was later upgraded to a new engine, the HL 230 P45. As well as other improvements, this engine incorporated the new gearbox almost exactly as designed for the Panther.
This view of the rear of a HL 230 P45 shows the filters, the mounting frame, and between them the gearbox for the fans. The gearbox has two drive shafts, one at each side.
(Dimensions drawn in green are precise figures taken from German plans.)
This is the gearbox on a Panther engine. The original paint is gone.
The engine in this photograph has its air filters removed. The handle of the control rod is indicated. When pulled forwards it declutched the fans; this was necessary for underwater travel. It was pushed back during normal operation. Notice that the end of the rod passes through a sheet-metal support that locks it into one of these two positions.
In later versions of the engines there is no clutch control rod. The Saumur museum tank is an example, shown above. The supporting lug on the impeller is now used for something else (the cold weather starter). I don't think these engines could declutch their fan drives.