Trying to clean up the 3.2 before installation. I wont tear it down, but I have it stripped to the long block. Apparently new alternator but attached was this
Click to view attachment

It really is grey, I forgot to change the light color. I know that magnesium loves to oxidize back to mother earth, and this is no exception. But it can be sanded smooth pretty easily. There is one large chip and a very small nick as though something went through at one point, and hit two blades in succession.

These conversions seem to cost in $500 bills (if they made them), because every time you want something it is several hundred dollars. Believe it or not it adds up.

So - I can smooth it out and get rid of all the stress risers, put a balancing nick on the other side. Or buy a new one. I think I know the answer to this one already. If I go new I have the choice of apparently decent aluminum Chinese or used.

Sand/smooth it away. That small amount of material should not affect balance to a detrimental level. I doubt those fans are balanced to that small an increment to begin with.
There are type 4 fans running with entire blades missing. Look at any aircraft in service and you will see blends on blade edges all the time. The rotors are balanced but not to the micron level. You will be fine.

I'm sure someone has written a masters thesis about the effect of the distance from center of rotation to the missing chip causing variances in the centrifugal force exerted. .I'd personally only be concerned with the blade with the larger missing portion. .
Yep, they are balanced for a reason, so you have a few choices.
<li> Leave it alone
<li> file smooth and re balance
<li> take off a corresponding amount in exactly the same place 180 degrees away . .
<li> bead blast, build a backing mold on one side of the big chip, and fill with JB Weld, sand to shape. If you do this , be sure and use wax or something as a mold release on the mold side.

I think you can find a good used one a lot cheaper than the $500 you estimated. .

Two options, get a used OEM one or as suggested, smooth it out and rebalance....since these are mostly toys for us.I would get a good used one.

I'd just smooth it a bit and run it.



no need for wax, JB won't stick to most smooth plastic or clear tape.

You are right - used or repros go at about $350 with shipping. But OK, lets say I want a Setrab cooler next, and then some oil lines. My point is I am finding that it adds up in chunks.

Thanks for the ideas.

I think JB Weld would be a pretty good option if you can ensure that the metal is superclean before attempting to fill it in. If it doesn't stick, no harm no fowl.

Sell it as a "lightened" racing fan for $600 and buy a new one.

I might disagree.....anything coming off at high rpm....not a good thing or sounding.

I would clean it up...check for cracks and run it.

with most of the others. You'll probably never notice anything. Run it.

This just calls the whole engine into question. I'm just south of you....lemme come up and get the whole mess and you can start fresh...no disposal fee even...

Check it for cracks, smooth it a bit and then run it man, run it.

Good enough for AA

I have to get the brown volume out to check. I remember a certain number of vanes per sector is stated as OK. Probably true to. I still bought a complete used one from RhodyGuy when I built the 4.

Thanks everyone, and no. I want to try to start it before anyone can have the engine.

The 917's when first under development used a fiberglass fan hard mounted to a bevel gear driven take off. Some experienced separation at the fan center from vibration alone and became airborne. All others broke at the shaft/hub connection on sudden deacceleration and helicoptered off into the sunset. Porsche changed to a rubber mounted fan. That fan weighed in ounces!

The metal fans on 911 motors are balanced just like any rotating assembly. They won't fly off but they will take out alternator bearings or the alternator itself. You could remove some material on 2 other blades to balance it but I still don't advise using a damaged blade.

Hmmm, and they say there is no coincidence between that phenomenon in the 917 and Odd Job's hat in Goldfinger. I am not quite sure which is earliest. Still would have liked to see the fans shooting up.

I will sand into it and see what I have and how far the cracks extend. If it looks salvageable I will definitely balance it. If I do use JB weld it will have glass fibers in it, and it will be feathered onto a knife edge grind to give it shear grip. Not sure I trust it at speed. I actually almost always drive the limit. So why am I building this?

Call E.A.S.Y in CA
Call LA Dismantlers

Call around and see just how much a used fan would cost.
If it was me, I would at least look into the cost of a replacement with no chips before I took the time to attempt a fix.

rich

Thanks Rich,
I will give the calling around a try. Probably after Christmas, so I don't feel bad about spending more on my own presents to myself than on the entire family. In the mean time I will probably do some exploratory cleaning.
It looks about $300 from an ebay listing from one of the dismantlers, and also I think the price will now be stabilized somewhat by the new aluminum fans. It is silly, but I cannot say that bling has no appeal to me, and you can sort of see the fan (on a 911).

I have seen pieces missing in those fans 12x bigger and run for many Many MANY years, with no noticeable vibrations or adverse cooling effects.

The way those things corrode, it would not surprise me if many of these, are already out of balance by now.

The only thing I would worry about, is if there are any cracks extending from the chipped area or other part of the fan. Inspect it with a 10x optic or higher. Other than that run it and keep an eye out for a good deal at your leisure. It is a very small amount of weight you are missing there, even after blending it smooth.

I will bring it to the lab and have a look at it under the dissecting scope. No one will be surprised. Like when I accidentally had a 914 seat delivered to the stock room.

for that much, I would fix it.

How thick is the area?
I would drill it with a 1/16 inch bit and put a few pin in there with epoxy, then build it up with some more epoxy or JB weld type material.

Then glass bead the whole thing and have it powder coated, and balanced.
Done.

Rich

I work on F/A18s in the Navy and we have nicks in the first stage blades on our engins, No biggie.

Exactly! And those turbine tip speeds / g forces are a lot faster / bigger due to the much larger diameter, even though the 10k ish rotor rpm of the turbine is only about 30% more than the magnesium fan. In other words, double the diameter of a given rotor and you double the tip speed / g forces, assuming all other things are equal.