Are fans on air cooled cars repairable?

[rbuswell]

I was cleaning the fan for my SC and a chunk fell off. When I inspected it more closely, I noticed a barely discernible ding right where the aluminum fell off and another ding on the top of the blade in front of it. I'm guessing that a stone snuck into the engine compartment and did the deed. Hard to tell how long ago it happened. Here are some pictures:






Am I SOL or can someone who welds and works with aluminum fix this? A friend told me that guys who weld aluminum propellers for boats can do wonders with this kind of stuff. Of course, I'd be worried about balance. Can it be run as it is if it can't be fixed? Thanks for your input.

[Porsche_monkey]

I would smooth it off with a file and drive it. Just make sure there are no crack propagating from the damaged area and inspect it the next few weeks. If a crack develops drill a small hole to prevent it from spreading.

[Formerly Steve Wilkinson]

Hard to tell exactly how big that "ding" is, although I can guess. What we usta do with airplane propellers when something like that happened was grind the jagged break to a smoothly radiused loss-of-metal without stress risers. And if you were a bush pilot and had really taken a whack out of one blade, you cut off the equivalent amount from the opposite blade and restored balance.

I have a fairly large ding on my fan--though not quite as deep as that--that I smoothly radiused and let it go at that. I don't think balance is a huge problem at the speeds the fan is turning--it's not a turbine, after all--but you do want to get rid of the stress risers, which are jagged, sharp-edged corners from which cracks propagate.

Whether it can be welded, I dunno. It's not aluminum--which would be easy--it's a magnesium alloy, I believe. Magnesium burns.

[cgarr]

Just for fun I would try to build it up with some Alum epoxy, shape it in and run it, see how good the stuff really is, otherwise I would just clean up the sharpies and run it.

[rbuswell]

Originally Posted by Formerly Steve Wilkinson

Hard to tell exactly how big that "ding" is, although I can guess. What we usta do with airplane propellers when something like that happened was grind the jagged break to a smoothly radiused loss-of-metal without stress risers. And if you were a bush pilot and had really taken a whack out of one blade, you cut off the equivalent amount from the opposite blade and restored balance.

I have a fairly large ding on my fan--though not quite as deep as that--that I smoothly radiused and let it go at that. I don't think balance is a huge problem at the speeds the fan is turning--it's not a turbine, after all--but you do want to get rid of the stress risers, which are jagged, sharp-edged corners from which cracks propagate.

Whether it can be welded, I dunno. It's not aluminum--which would be easy--it's a magnesium alloy, I believe. Magnesium burns.

Originally Posted by cgarr

Just for fun I would try to build it up with some Alum epoxy, shape it in and run it, see how good the stuff really is, otherwise I would just clean up the sharpies and run it.

Boy, it really seems like aluminum although it may be an alloy. The ding on the top of the adjacent blade is small and flat and doesn't appear to have any radiating cracks so I hope that never amounts to a problem. Neither does the actual broken section have any obvious radiating cracks. I like the idea of rounding it out and running it. It's also good to know that balance won't be too big a problem. I've seen a new fan on evilBay for about $240 shipped but I obviously don't want to spend that if I can avoid it.

As for an aluminum epoxy product, is there a brand and source that you recommend?

[cgarr]

I have used the Devcon Liquid Alum before, its a 2 part system.

[rouxroux]

Originally Posted by Porsche_monkey

If a crack develops drill a small hole to prevent it from spreading.

Sounds like a drummer trying to save a favorite cymbal. BTDT.

[richde]

Originally Posted by rbuswell

Boy, it really seems like aluminum although it may be an alloy. The ding on the top of the adjacent blade is small and flat and doesn't appear to have any radiating cracks so I hope that never amounts to a problem. Neither does the actual broken section have any obvious radiating cracks. I like the idea of rounding it out and running it. It's also good to know that balance won't be too big a problem. I've seen a new fan on evilBay for about $240 shipped but I obviously don't want to spend that if I can avoid it.

As for an aluminum epoxy product, is there a brand and source that you recommend?

Jet engine compressor blades are repaired the same way. I'd skip on the epoxy though. It's either going to be ugly and not much more effective than the ding in the blade or snap off. Blend the blade and keep an eye on it for cracks.

[Formerly Steve Wilkinson]

Trust me, it's not aluminum.

[rbuswell]

Originally Posted by Formerly Steve Wilkinson

Trust me, it's not aluminum.

I'll take your word on that. By the way, I finally got around to reading your book and I couldn't put it down. Thanks for writing down what I'm feeling right now.

[Formerly Steve Wilkinson]

Hey, thank you for saying that! 'Preciate it.

[scarceller]

The fan is magnesium.

[scarceller]

Here is an aluminum one:
http://**********.com/ShowItem/208322%20Porsche%20911%20-%2011%20Blade%20Alternator%20Fan%20-%20Aluminum.aspx