Electric clutch for mechanical fan?
 

I read that electric fans are less efficient at cooling than mechanical fans. Converting motion to electricity & back to motion again.

Has anyone with a mechanical fan thought about making an electric clutch instead of using the thermal clutch? It could use the same controls as a single speed electric fan.

I think you would want to use a light weight fan blade to control the weight & accelleration. I have never taken an AC pump apart to know how much the clutch wieghs, or if the clutch could handle the instant torque it will see.

What are your thoughts?

Don

For as much as a radiator fan is on, I'd say electric is fine.

the rotating mass of the clutch system and the drag present even when the clutch is disengaged would probably negate any savings one would make from converting an electric fan to an electro-mechanical one as you suggest, since the electric fan operates during a smaller percentage of the operating time.

best bet is to improve air flow over the radiator to the point of not needing to use the fan.

Fans are mostly needed for low speed operations so improving the airflow enough to eliminate the need for them is tough.

That said, my F150 has no fan, but then again it sees virtually no stop-n-go town traffic either.

Building one now
 

Hi, I have a Toyota Landcruiser which uses 30 litres of LPG to the 100 k's so I am building a remote electric clutch for the existing fan. I am useing an old Ford air con compressor clutch which I believe will handle the torque as these compressors use about 3 to 5 hp and start under full load. My fan although spinning free on 6003 2rs bearings will probably be spinning anyway when engaged as the air flowing past it will most likely turn it. The electric clutch pulls 2 amps and is designed to cycle often. Modern cars disengage this clutch at certain speeds automatically. Steve :)

Check out a Mercedes 190e 2.3 or a 90s C220. These cars had a mechanical fan with electric clutch from the factory. There are many others. I replaced mine with a normal puller electric fan because it's more efficient and cheaper to replace. The electric coil is fixed on the water pump behind the fan pulley (doesn't spin).
http://www.autohausaz.com/secure/Par...1022000677.jpg

Thanks looks good, I am setting the cluch up in place of an existing idler pulley and will make provision for it to be locked together mechanically with a couple of set screws in the case of an electrical fault in the clutch whilst in the middle of nowhere.

Since I've totally removed the mechanical fan on my pickup and seen how little the fan is actually needed, I'd vote for a simple electric fan install just for the fact that- at least for my usage patterns- the fan is barely needed at all thus whatever inefficiency penalty there may be from the mech-elec-mech conversion losses is more than offset by the removal of all mechanical fan losses. Now, if there is a usage pattern that requires much more fan use- like on a tractor- I can see where the clutched mechanical fan would be the more efficient choice.

...ah-h-h, but that same "clutch" would work great on an alternator!

Would it?

:confused: