Fan clutch

[Zedrally]

Just a couple of points.

The clutch is split as I write [had a siezed bearing which I've tried to press out, managed to loosen up, but still unsatisfactory]. There are no blades or vanes which make it operate in one direction only. My experiance with any item of machinary which is intended to be driven in one direction only, is that an arrow indicating direction is always cast into the body. This is not

Internally, there is a disc with 6 * 13mm holes [actualy 1/2 inch so this one may not be an OEM]. Note there is no rotor or stator which would make it turn in one direction only. [i haven't actually worked out how it operates yet, perhaps someone else has an indepth explanation as to how and why it can only operate in one direction]?

Second point and most important is which engines are counter-rotating that these other fan clutchs are made for?

[JZM]

I see. I really don't want to say this word on this site but HONDA civic D15B engines run counter clockwise but do not req. fans due to being transverse

mounted.I beleive some earlier small bock FORDS also ran counter clockwise too.I'm sure there are some others as well.but back to the revearse rotation fan clutch,I thought you had to run a serpintine belt system for those.I have not delt with serp systems that much.

JZM

[Bambikiller240]

Mike:

This is the way it was explained to me & as I understand it.

I'm open to correction.

See this page http://www.pbase.com/bronte/image/20486859 It shows a picture of a 280Z Fan Clutch disassembled. Near the outer circumferance there are two rivit heads (for lack of a better term) each is located in a arcing slot. My understanding is that when the bi-metallic switch on the front of the fan clutch is in the off (closed) position, and the "valve" that will eventually allow the fluid to move (activating the "coupling" action) is also closed, the rivit(s) are at or near one end of the arc. The fan will free wheel at this time. When the bi-metallic switch reaches a certain temperature, it "activates" and allows movement (it doesn't "push") of the plate that the rivits are attached to, and the rivits get closer to the other end of the arc, the rotation of the plate allows the valve to open and fluid to move and "couple" the mechanism, engaging the fan. The arcs cut into the plate serve to limit the travel of the other plate (the one with the valve) relative to the one with the arcs..

If what I understand is true, then operating the fan (and fan clutch) in the opposite direction would seem likely to create sufficient rotational force (in the opposite direction from normal rotation) to prevent the plate with the rivits (and valve) from rotating to the point where the valve opens.

Said another way, The bi-metallic switch isn't strong enough to "push" the plate with the valve to the open position against the counter rotating forces.

Here's a link to other pictures of this system:

http://www.pbase.com/bronte/fan_clutch

Also, here is a link to an article I prepared on rebuilding the fan clutch. There are links at the bottom of my post to other websites which have info on fan clutches (in general, not specific to Z cars)

http://www.classiczcars.com/forums/showthread.php?t=10441

[Zedrally]

Thanks Carl,

I had only just recently re-read your article on fan clutchs. hoping that it may have included instructions on re-buiding siezed units.

I would only add to your explanation that the direction or rotation of the fan unit is only due to the orientation of the bi-metal spring.

To alter the direction, one would only need to invert/flip the bi-metal strip 180 degrees to achieve harmony of the fluid coupling.

This is of course unproven and may remain so........

Now back to these counter-rotating engines, with matched counter-rotating gearboxes and matching diffs....have to of French origin, wouldn't they????

MOM

[Bambikiller240]

Sorry, I only covered the replentishment of viscous fluid in that article. No one that I could find had info on replacing bearings and such.

I didn't think about reversing the bi-metallic spring. I don't know if that would work or not. If someone has the time to disassemble, it might be worth trying (should someone need a reverse fan clutch).

EDIT: On further reflection I *think* that reversing the bi-metallic strip would result in the valve being open when it should be closed, and vice versa

Regarding the engines, . That's funny.