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Wheel change
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Video Multi-cylinder Engine
Video Inl. 2-cyl. 4-stroke
Video Inl. 2-cyl. 2-stroke
Video Opp. 2-cylinder
Video 2-cyl. V-engine
Video Inl. 3-cylinder
Video Inl. 4-cylinder
Video Opp. 4-cyl. 1
Video Opp. 4-cyl. 2
Video Inl. 5-cylinder
Video 5-cyl. V-Engine
Video Inl. 6-cylinder
Video 6-cyl. V-inline-engine
Video 6-cyl. V-engine
Video Opp. 6-cylinder
Video 8-cyl. Firing Order
Video 8-cyl. V-engine
Video 8-cyl.-V-Classic
Video V-8 Cylinder Block
Video V8 Turbo Engine
Video W-8 Cylinder Block
Video V-10 Cylinder Block
Video V-10 Diesel Engine
Video V-10 Porsche Engine
Video V-12 Engine
Video V-12 Cylinder Block
Video V-12 Ferrari Engine
Video W-12 Cylinder Block
Video W-12 Engine
Video Radial Engine
Video Rotary Radial Engine

Video Multi-cylinder 1
Video Multi-cylinder 2

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Viscous Cooling Fan (additional


The housing of the viscous coupling, onto which the fan-blades are mounted, should, with increasing engine temperature, be more solidly connected to the wheel which, in this case, is driven by the crankshaft.

Engine cold

The air, that flows through the cooler, remains cold. A bimetal spring, which is connected with the ribbed aluminium through heat conduction, does not (yet) bend. Thereby, no viscuos fluid flows from the reservoir to the operations area (on the left). On the contrary, because of the big difference in RPMs, the wheel in the operations area pumps all the fluid out into the reservoir.

Engine warm

If you click on the figure, you'll see that the bimetal (two metals, each with a different heat expansion range) bends more strongly. The pressure plunger moves a little to the left and the (slightly sprung) intermediate disc opens the upper port between the reservoir and the operations area a little bit. The operations area is half-filled, from the outside edge, with viscous fluid.This provides for a certain amount of connection between the driven wheel and the housing. The cooler fan (in our example) runs at about half the RPMs of the crankshaft.

Engine hot

When the bimetal has reached it's maximum curvature, the port between the reservoir (left) and the operations area (right) is completely opened. The viscuos fluid completely fills the operations area. The RPMs are now, give or take a few hundred rotations per minute, roughly the same. 11/10               Top of page               Index
2001-2015 Copyright programs, texts, animations, pictures: H. Huppertz - E-Mail
Translator: Don Leslie - Email:

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