Water Pump to Fan Anti-Cease Compound?

[Dennisfly]

There have been several instances in our club where it was extremely difficult to separate the newer aluminum two blade fan from the stainless steel water pump shaft. I found this information on the Albany Fasteners web site:


"For the rest of our post, instead of referring to anode and cathode, we will be using the example of aluminum (anode) and stainless steel (cathode). When aluminum and stainless steel are used in an assembly together, the electrons from the aluminum will begin to transfer into the stainless steel. This results in the aluminum weakening. This weakened aluminum causes it to deteriorate at a much faster rate. This can lead to an extended life of the stainless steel. Note: Aluminum, if left on its own with the electrolyte, will still lose its electrons eventually, but having stainless steel present will significantly speed up this process.
The galvanic corrosion practice is actually commonly used in plating to create a sacrificial layer on top of another material. Zinc plated steel and black oxide are commonly used examples."


While there is much more discussion and many more variables involved, my question is: Would it be prudent to use some anti-cease compound when installing the fan on the water pump shaft?

[Synchro909]

I've had an aluminium fan on a stainless steel shaft for about 10 years and when I came to repair the water pump, the fan pulled off with no trouble. I'd put the fan on as is and drive happily off into the sunset.

[Dennisfly]

I have been informed that aluminum paste is a major component in most anti-cease compounds. Therefore, it would be counterproductive to use it in this application.

[Joe K]

A lot of the difficulties with removal of the fan was issues both with the fan (i.e. wasp-waisted hole caused by "as cast" taper) and the shafts (many repop shafts appear to have TWO different tapers.)

The mating of these two seem to result in a "line" contact of high contact pressure. Many report the fans "coming loose" after a short period of driving (and wiping of the interior surface of the radiator by the fan blade) The usual recommended prevention against this is to "re-torque" the fan on the shaft.

What you're doing is creating an "interference fit" between mis-matched parts. The line contact by virtue of brute force becomes spread out - galling the aluminum and possibly the shaft and "stretching" the fan hub over the barrel shaped taper of the shaft.

Removal of an interference fit usually requires a "puller." Hence the issue with removing a fan.

This would have been more common 10 years ago. Today, the complaints are still there but the issues between mating parts have been somewhat answered to by the manufacturers. The quality is a lot better.

BUT - you're still "stretching" an aluminum hub over a steel taper - and there still may be a requirement to use a puller. Or gentle tapping. Or heating lightly with a hair dryer or boiling hot water.

And - a galvanic mis-match CAN occur and add to the mechanical requirement.

I think given where we're at in the design we're about as good as you can get - so maybe yes, put it together with some common grease to exclude water and call it a day.

I see there is now an actual "fan puller" available from the parts dealers. Not that you can't figure out and implement a "bridge puller" of your own design.

Try not to pein over the threads of your pump shaft. I just restored the threads of a pump shaft so damaged on my lathe. It's been a while since I put change gears on the lathe for 7/16-20 fine thread.

Joe K.

[katy]

On a Model A w/an aluminum fan on a stainless steel shaft there is no electrolyte present to cause galvanic action.

[rotorwrench]

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A person has to be careful using anti-seize on a tapered shaft. Torque would have to be reduced due to the lubricant or it is possible to crack the aluminum casting. I use either nickel or copper based anti-seize but I don't get carried away with it on a tapered shaft.

[Keith True]

Tapered shafts,clean and dry.I've had that drilled into me since the 70's,I did screw a few things up.Anti seize has solids in it,be it copper,aluminum,nickel,or lead.You can tighten it all you want,at some point that stuff will flatten out a little more.A few years ago I was assembling some drive hubs to vacuum pumps for a braze furnace.They wanted the white glove test on both the hub and shaft.Make sure the tapers match up,make sure you don't dislodge the key when sliding on the fan,tighten it up clean and dry.It won't go anywhere.

[rotorwrench]

A lot depends on the amount of torque it takes to turn the shaft. TCM/Bendix recommends it on magneto drives but they aren't torqued all that tight and torque to turn isn't excessive. Now for an axle taper, no way. The taper is designed to hold the torque and the key is a back up/alignment feature. Use no lubricant of any kind on a high torque application.

[old ugly]

an FYI

if you have an aluminum fan that is giving you grief to remove, warm it up hot with your electric hot air heat gun.
as mentioned in a previous post i have had good success with warming the aluminum up as it expands quickly and will come off of the shaft easier.

as far as corrosion i would imagine if you were worried about that, as stated above a sacrificial component like never-seize may help. i have never done that.